How Geocells Provide Sustainable Solutions for Soil Stabilization and Erosion Control

Posted October 31, 2024 by Ashley Beyer

Innovative Site Solutions for Civil Engineering and Construction Projects

When faced with challenging site conditions—whether it’s weak soils, steep slopes, or erosion-prone channels—finding an efficient, long-term solution that minimizes maintenance is essential. Geocells offer just that. These innovative cellular confinement systems (CCS) are a proven solution for load support, retaining walls, slope stabilization, and channel protection applications. Geocells not only improve soil stability but also contribute to eco-friendly, sustainable project designs.

Geocells are three-dimensional, honeycomb-like structures typically made from high-density polyethylene (HDPE). By confining and reinforcing infill materials like soil/vegetation, sand, gravel or concrete, geocells create a stable, load-bearing surface. This cellular system prevents soil movement and erosion, making geocells a versatile solution for stabilizing weak soils and supporting structures such as roads, retaining walls, slopes, and channels.

How Geocells Work

The core function of geocells is to create a grid of interconnected cells that confine and stabilize infill materials. This CCS strengthens the underlying soil and distributes loads more evenly, preventing the movement of infill under pressure. In load support applications—such as roads, parking areas, or driveways—geocells act like a semi-rigid slab.

The geocell structure increases the load distribution angle and spreads vertical stresses over a larger area, which is commonly referred to as the mattress effect. This feature helps stabilize weak subgrades and prevents surface deformation, such as rutting or differential settlement, under heavy loads.

Key Benefits of Geocells

Soil Stabilization for Weak Subgrades: Geocells are designed to stabilize soils that would otherwise shift or settle under loading. By confining infill materials, geocells create a firm, stable base that can support the demands of roadways, heavy-duty parking lots, or other infrastructure projects. The mattress effect further enhances this stabilization, ensuring that vertical stresses are distributed across a wider area, reducing the likelihood of differential settlement or deformation over time.

Erosion Control for Slopes and Channels: On slopes and in channels prone to erosion, geocells help prevent soil from washing away during rainstorms or high-flow events. The cellular structure holds soil in place, creating long-term stability and reducing maintenance needs.
Sustainable and Eco-Friendly: By allowing the use of locally sourced infill, geocells reduce the need for imported materials and minimize the environmental footprint of a project. Their permeable design also promotes natural water infiltration, helping manage stormwater and reduce runoff.
Cost-Effective with Minimal Maintenance: Geocells are a cost-effective solution for stabilizing weak soils and preventing erosion. Their simple installation process and long-lasting performance mean reduced material costs upfront and less maintenance over time.

Common Applications for Geocells

Load Support: Geocells stabilize unpaved roads, parking areas, and other surfaces by evenly distributing loads, which prevents differential settlement and rutting.
Slope Stabilization: On steep embankments, geocells hold soil in place, reducing erosion while allowing vegetation to take root for natural reinforcement.
Retaining Walls: Geocells offer a flexible alternative to rigid retaining walls, adapting to natural shifts in the landscape and soft sub grade soils while maintaining soil retention.
Channel Protection: Geocells reinforce the bed and banks of stormwater channels, reducing erosion and ensuring long-term stability, even in high-flow conditions.

retaining wall slope channel and load support geocells

Introducing GEOWEB® Geocells: The Original Cellular Confinement System

While geocells are becoming widely used today, GEOWEB Geocells stand out as the original and most advanced system on the market. Presto Geosystems, in collaboration with the U.S. Army Corps of Engineers, pioneered the development of geocells in the late 1970s to address the need for reliable soil stabilization solutions in military and civil applications. This collaboration resulted in the invention of the GEOWEB system, which continues to lead the industry in performance and innovation over the past 40 years.

GEOWEB Geocells are made from high-quality, virgin HDPE, which offers superior strength, flexibility, and long-lasting durability compared to other systems. This ensures that the GEOWEB Geocells can withstand harsh elements and challenging conditions, whether it’s in load-bearing applications or erosion control projects.

The GEOWEB system is a complete geocell system, including ATRA® Accessories such as ATRA Connection Keys, ATRA Anchors, ATRA Tendon Clip, and the ATRA Driver. These components are designed to enhance installation efficiency and long-term performance, providing fast, secure connections that ensure the structural integrity of the entire system.

Comprehensive Construction Services, Engineering Support, and Free Project Evaluations

At Presto Geosystems, our commitment goes beyond providing high-quality products. We offer on-site field assistance, engineering support, and free project evaluations. Our team works with you at every stage, from initial project evaluation assistance to on-site installation support, helping you achieve the best results for your specific project challenges.

Understanding Hoop Stress and Wall Tension in Geocells

Posted September 9, 2024 by Katie Bocskor

Written By: Samantha Justice, P.E., Bryan Wedin, P.E.

Geocells provide one of the most powerful solutions available to engineers and contractors when designing and constructing roadways over soft and weak subgrades. With a successful track record of over 40 years, geocells have proven effective in load support applications over challenging conditions. If you’ve ever wondered how geocells work in load support applications – and the relationship between lateral confinement, hoop stress and wall tension – you’ve come to the right place.

Geocells are used to alter vertical stresses beneath an applied cyclical load. When a vertical, cyclical load is applied over geocells, active earth pressures develop in the loaded cell. These pressures arise due to the friction between the infill material and the cell wall. This friction pushes back against the passive earth pressure in the adjacent cells, helping to support the load. Refer to Figure 1. The balance of active and passive earth pressures activates the hoop stress in the cell walls, which increases the stiffness and bearing capacity of infill material. The infill material is confined within the individual cells with no chance of displacement, or lateral or vertical spreading and the result is increased stiffness. In effect, geocells behave more like three-dimensional structures or a semi-rigid slab by increasing the load distribution angle and spreading the vertical stresses over a larger area which is commonly referred to as the mattress effect.

Figure 1

An enhanced woven geotextile separation layer is typically provided under the geocell system and works in conjunction to provide additional load distribution along with filtration, separation, and controlled drainage. With the enhanced woven geotextile, it is possible to construct over extremely weak subgrades with standard penetration resistance (SPT-N) values less than 2 blows per foot (CBR < 0.5%), where planar geosynthetics, such as geogrids, would otherwise fail.

How Does Hoop Stress and Wall Tension Relate to Lateral Confinement?

Hoop stresses develop within the cell walls as earth pressures increase in response to an applied load at ground surface. In other words, the same earth pressures responsible for developing interface friction between the geocell and the infill material also result in hoop stresses with the cell walls. Although not perfectly cylindrical, geocells can be envisioned to behave similarly to an interconnected network of pressurized cylinders, wherein hoop stresses are a function of the net pressure that develops due to the internal and external pressures acting in and around each cell.
In this manner, radial pressures that develop within each cell are resisted by those that develop in the adjacent cells, and hoop stresses may be estimated using the classic equation for hoop stress for a pressurized thin-wall cylindrical vessel:

σ_H = p_net*(D/2t)

Where,

σ_H = hoop stress

p_net = net pressure = p_i – p_e

p_i = internal pressure

p_e = external pressure

D = geocell diameter

t = wall thickness

The active earth pressure in a loaded cell below a cyclical load can be calculated using the Boussinesq stress equation. The interaction between hoop stresses and passive earth resistance in geocell systems was investigated by Emersleben (2009) and observed that lateral pressures in adjacent cells decrease exponentially with increasing distance from the actively loaded, or “source” cell(s) – in effect, defining a pressure gradient. Based on Emersleben’s findings, it is possible to evaluate the net earth pressure that develops between the interior and the exterior of a cell wall, using the thickness of the cell wall as the distance between two points along the defined pressure gradient line. Refer to Figure 2.

Lateral Pressure vs Distance

Figure 2

The largest net earth pressures, and hoop stresses, occur in cells directly beneath the perimeter of the load footprint—the wheel contact area in the case of vehicle loads. Based on this, it is possible to estimate the maximum hoop stresses expected to develop in geocells in response to standard AASHTO load conditions.

Table 1 summarizes the estimated hoop stress and cell wall tensions developed under standard AASHTO load ratings for a 6-inch geocell-reinforced layer with a 2-inch wear surface. The calculated values assume a nominal 9.5-inch diameter geocell infilled with a granular material having an internal friction angle of 32 degrees and unit weight of 120 lbs/ft³.

Hoop Stress and Cell Wall Tension

AASHTO Load Rating	Wheel Load (lbs)	Tire Pressure (psi)	Hoop Stress (psi)	Cell Wall Tension (lbf)
AASHTO H/HS10	8,000	60	44	16
AASHTO H/HS15	12,000	85	63	23
AASHTO H/HS20	16,000	110	82	30
AASHTO H/HS25	20,000	125	96	34

Table 1

The corresponding tensile forces that develop under working load conditions are relatively modest due to the lateral confinement effect of the adjacent cells. When compared to the typical yield strength for most high-quality HDPE geocells, the above-referenced tensile forces are well within the elastic region for the material and any permanent deformation or “creep” over time is not expected, even when subject to cyclical traffic loads. Due to hoop stresses and earth pressures surrounding the loaded cells, there is no ability for the material to have any appreciable sustained deformation, and therefore, creep is not an issue.

The elastic response of the geocell-reinforced layer will ultimately be governed by the elastic properties of the infill material, and provided that suitable granular infill is used, the development of any significant strain in the cell walls will be heavily constrained by the effects of confinement of the granular material by the cell walls. The actual strain that develops in the cell wall will be significantly less than the amount of strain represented on a typical stress-strain curve generated from laboratory tests such as ISO 10319 or ASTM D4595 where samples are subjected to tensile forces in an unconfined state.

Development of hoop stress is essential for the proper engagement of the lateral confinement mechanism. Moreover, the ability to estimate hoop stresses under specific project circumstances can be useful as it allows engineers to develop a preliminary (and very conservative) understanding that tensile forces in the cell wall will remain within the elastic range for the material. It should be noted that many laboratory test methods such as ISO 10319 ignore the effects of confinement, and therefore, tend to overestimate strain levels that are outside of practical design conditions. Researchers who have completed laboratory and field test on geocells under applied loadings show that the strain in geocell walls is on the order of 0.2%. Evaluating material strength beyond reasonable strains is not relevant for sub grade reinforcement and the focus should be on strains less than 1.0%.

In general, provided the geocell is manufactured with a high-quality HDPE with a flexural storage modulus of at least 116 ksi (800 Mpa) and a 100-year durability rating (ISO 13438), the geocell can be expected to perform as intended throughout the service life of the project.

Using GEOWEB® Geocells in Landfill Capping Applications

Posted July 26, 2024 by Ashley Beyer

Written by: Cory Schneider, Business Development Manager

When contaminated material such as landfill waste or contaminated soil is encountered, there are typically two options available—removal of the material or placing a “cap” over it. In most cases, capping is the easier and more cost-effective of the two options. Caps serve to isolate the contaminated material, preventing people and wildlife from coming into contact with it.

Factors Influencing Landfill Cap Design

Landfill cap design for any particular site depends on many factors, including the type and quantity of contaminants, size of site, amount of rainfall, and future use of the area. It can consist of one or several of the following: asphalt or concrete, vegetative layer, drainage layer, and/or an impervious layer (geomembrane or compacted clay).

Preventing Slope Erosion with Advanced Geosynthetic Technology

close up of geocells infilled When using vegetative covers, especially in sloped areas, one of the best ways to prevent long-term erosion of the cap is to confine the topsoil component using geosynthetics like the GEOWEB Soil Stabilization System (geocells). The GEOWEB Geocells, which are three-dimensional ultrasonically welded strips of high-density polyethylene (HDPE), create small pockets to hold soil in place. By doing so, the system prevents erosion or sloughing when the soil becomes saturated, thereby maintaining the integrity of the cap.

Understanding Superfund Sites

Superfund sites are contaminated areas that require a long-term response to clean up hazardous material contaminations. The federal government designates these sites, and the Environmental Protection Agency (EPA) leads the remediation efforts to ensure public safety and environmental protection.

Case Study: 68^th Street Dump Superfund Site

One notable example of using the GEOWEB Geocells in a Superfund site is the 68^th Street Dump in Baltimore, MD. This project involved capping 51,000 square feet of landfill with slopes up to 60 feet high ranging from 3:1 to 1.5:1. Slopes flatter than 3:1 were deemed to not be at risk of significant erosion, and therefore, no geosynthetics were used on them. The solution effectively stabilized the topsoil, met EPA guidelines requiring a 12-inch cover, and ensured long-term erosion control and environmental safety.

Read the full case study: Superfund Site Landfill Capping | Presto Geosystems

North Carolina Pre-Regulatory Landfill Unit

In 2007, North Carolina established the Pre-Regulatory Landfill Unit within the Inactive Hazardous Sites Branch to address pre-1983 non-industrial landfills and dumps (any land area on which municipal solid waste disposal occurred before January 1, 1983). A tax of $2 per ton on municipal solid waste and construction and demolition debris was imposed to fund the program.

As part of the program, the team published a comprehensive document outlining Unit procedures for completing assessments and implementing remedial action plans. This document includes acceptable procedures and products for dealing with pre-regulatory landfills. Specifically, the document lists GEOWEB Geocells as an approved product for creating soil cover “caps” at these landfills.

Case Study: Franklinton County Landfill

Another example of the GEOWEB Geocells in action is the Franklinton County Landfill in North Carolina. This project involved installing 102,810 square feet of 4-inch GEOWEB GW30V (mid-sized geocell) over 8-ounce nonwoven geotextile fabric, filled with about 2,320 tons of structural fill and 2,500 tons of topsoil. The GEOWEB geocell panels were connected with ATRA® Keys and secured with Woven Polyester Tendons and ATRA® Tendon Clips.

Read the full case study: Franklinton Landfill Remediation Project | Presto Geosystems

Incorporating geosynthetics like the GEOWEB Geocells in landfill capping applications offers an effective solution for isolating contaminants, preventing erosion, and ensuring long-term environmental safety. These case studies demonstrate the practical benefits and successful implementations of these advanced materials in real-world scenarios.

Federal Railroad Administration (FRA) Announces $1.1 Billion Available in the Railroad Crossing Elimination (RCE) Grant Program

Posted July 15, 2024 by Katie Bocskor

The inaugural Railroad Crossing Elimination (RCE) grant program was designed to eliminate or improve roadway and railroad at-grade crossings, with the goal of making roads/rails safer while improving commute times for citizens.

According to the U.S. Department of Transportation website, “this program provides funding for highway-rail or pathway-rail grade crossing improvement projects that focus on improving the safety and mobility of people and goods.”

The grant program helps fund projects that involve:

repairing grade separations,
relocating tracks,
upgrading or improving protective devices, signals, or signs,
maintaining at-grade crossings, and more.

With safety as the top priority for the DOT, repairing and maintaining high-impact areas is critical so the potential for collisions or blockages can be prevented.

Applications for funding are due no later than 11:59 p.m. EST, September 23, 2024. Visit USDOT website for more information and to apply for funding >>

The GEOWEB® System stabilizes high-impact and crossing areas safely and quickly, limiting track downtime.

Areas subjected to heavy stresses at bridge approaches, diamonds, turn-outs, and crossings create the highest maintenance and safety liabilities for operations. The GEOWEB Soil Stabilization System (Geocells) is effective in reducing maintenance in these high impact areas.

The GEOWEB 3D Soil Confinement System has been successfully used by the railroad industry for over 40 years, helping to solve challenging soil stabilization problems for both new construction as well as railroad repair work. It is a proven and versatile ground improvement solution that is beneficial in soft soil environments and high-impact areas subjected to heavy stresses such as bridge approaches and crossings.

In at-grade crossing applications, the GEOWEB system is a three-dimensional geosynthetic that allows for the effective transfer of lateral earth pressures developed beneath applied loads to an interconnected network of honeycomb-like cells. As a result, stresses are reduced and distributed over a wider area through a phenomenon known as the mattress effect. The mattress effect reduces stress reaching the sub grade, and therefore, can mitigate the negative effects deflection and settlement.

For crossing applications, some of the key benefits of the GEOWEB System are identified below.

The 3D soil confinement technology creates a high-stiffness foundation under the track that reduces vertical stresses, allowing for a reduction of the subballast section up to 50%.
The GEOWEB System’s confinement reduces ballast compression and displacement leading to a more stable track surface requiring less maintenance.
The GEOWEB System limits upward movement of ballast particles and significantly increases stability of the track.
The system is quick to deploy and install, limiting track downtime.

Moreover, as summarized in Table 1, the GEOWEB Soil Confinement System can be used to improve high-impact areas that may be susceptible to settlement and long-term stability issues.

Table 1: GEOWEB Geocell Advantages for High-Impact Areas

High-Impact Area	Challenge	GEOWEB Geocell Advantage
At-Grade Crossings	Prone to stresses from aggressive rail loads and high-volume traffic	Dissipate stresses to control settlement and reduce maintenance/repair costs
Road Crossings	Excessive braking and acceleration forces transferred through the crossing to the subgrade	Dissipate forces from traffic and rail while delivering a floating platform that absorbs the braking and acceleration forces
Bridge Abutments	High-impact loadings and settlement	Dissipate stresses to control settlement and reduce maintenance/repair costs
Railroad Scales	Scales require a very stable subgrade for accurate measurement	Strengthen scale areas with the GEOWEB 3D system for extra stability and accuracy; especially over soft subgrades

The result is a more durable subgrade that increases railway life by preventing long-term settlement and consolidation. The ability to quickly install the GEOWEB panels and limit the track downtime is a critical factor in maintenance and safety operations for the rail industry.

Presto Geosystems offers a free project evaluation service to evaluate the unique needs of each project. Our recommendations will deliver a structurally sound, cost-effective solution based on four decades of accredited research and testing data. Submit your RCE project evaluation today and take advantage of the Grant Funding Program.

If you have questions about the RCE grant program, our project evaluation services, or need on-site support, please contact:

Bryan Wedin, P.E.
Chief Engineer
Presto Geosystem
[email protected]
(920) 791-0291

Energy Infrastructure and Climate Change: Protecting Erodible Slopes in Fire-Prone Areas

Posted June 28, 2024 by Katie Bocskor

Energy infrastructure is critical to the functioning of modern societies, and its protection against natural disasters and environmental threats is a top priority. Climate change exacerbates these disaster risks, with extreme weather conditions and wildfires being of particular concern, considering potential damage to the energy infrastructure and disruption of energy supply. Wildfires cause rapid, severe destruction, and, aside from damage to infrastructure, can impact our climate, vegetation, and atmosphere.

To measure the size and impact wildfires have, scientists use observations from several low Earth-orbit satellites, including the Copernicus Sentinel-3. These tracking satellites gather shortwave-infrared data combined with other techniques to differentiate between burned areas and other low reflectance covers such as clouds. The European Space Agency (ESA) compiles that long-term dataset to analyze global fire trends. According to the ESA, fire affects an estimated four million square kilometers (1.5 million square miles) of Earth´s land each year [1]. That is 400,000,000 hectares (990,000,000 acres) yearly—about half the size of the United States of America, an area larger than the country of India. The United Nations Environment Programme (UNEP) Rapid Response Assessment on Wildfires compiles findings from over 50 experts from research institutions, government agencies, and international organizations around the globe, and confirms that “wildfires are growing in intensity and spreading in range” with an “annualized economic burden for the United States to be between $71.1 billion and $347.8 billion USD” [2].

As wildfire seasons become longer and more extreme, the level of response must be increased. The United States and Canada have renewed an arrangement of cooperation to provide mutual aid during wildfire emergencies [3]. This, as Canada expects the 2023 wildfires, their worst on record, to continue into the winter season, with nearly 18 million hectares (44.5 million acres) burned to date through September 2023, as registered by the Canadian Wildland Fire Information System (CWFIS) [4].

In California, about 4.5 million hectares (11 million acres) have burned in wildfires over the past seven years, with an average of 485,623 hectares (1.2 million acres) per year [5]. The University of California´s Agriculture and Natural Resources (UCANR) Fire Network has studied post-incendiary erosion trends and offers a series of videos and other resources for wildfire and post-wildfire management. UCANR confirms the “chance for erosion is significantly greater and can result in mass movements of soil and water if vegetation has been burned off…with steep, hilly areas especially vulnerable” [6].

Project Case Study: Protecting Energy Infrastructure

The project owner had recently completed facility renovations and needed to repair and protect the slopes and hillsides surrounding the facility. However, the project owner had attempted other vegetated and non-vegetated erosion control methods in the past, and due to recent wildfires, drought cycles, and heavy erosion, those previous efforts did not achieve the desired level of long-term protection. The project owner and their contractor sought to meet initiatives from the U.S. Department of Agriculture (USDA) Forest Service for land management practices designed to mitigate erosion before and after severe fire events, and in evaluating possible solutions, the GEOWEB® Geocell Slope Protection System was identified for further evaluation and analysis. GEOWEB Geocells are three-dimensional cellular confinement products made from strips of high-density polyethylene (HDPE) welded together to create an expandable honeycomb-shaped structure. The geocells confine the soil or aggregate fill, minimizing movement and migration of the embankment materials by functioning as anchored containers in the upper soil layer. The geocell system resists sheet flow, preventing severe erosion and controlling rill and gully formation, especially in erosive post-incendiary soils.

Accordingly, the GEOWEB slope protection system was determined to have a high probability of achieving project objectives, and the facility owner ultimately selected the GEOWEB System utilizing tendon-based anchorage and ATRA® Tendon Clips (load transfer devices) in lieu of conventional staking techniques. The repair areas comprised two hillside areas of approximately 6,500 m2 (70,000 sf), with varying slope angles from 40-100°, and varying vertical heights from 6 m to 34 m (20 ft to 110 ft). After analysis of the site parameters, calculations for appropriate anchorage, planning for proximity to and around energy structures, it was determined that the 15 cm (6 in) GEOWEB Geocell with load transfer devices, integral connectors, high strength tendons, and earth anchors provided proper anchorage of the system without interference with existing infrastructure, as shown in Figure 1 below.

Fig. 1. Installation of tendoned GEOWEB Geocell System at energy facility.

The actual rock size chosen for the infill was based on slope angle and site hydraulic conditions, with earth anchor pullout strength determined by the Engineer of Record based on the manufacturer´s recommended factor of safety and site soil conditions. Aggregate infill was placed from crest to toe, using a rock slinger to assist workers and limiting the drop of the infill to prevent geocell wall distortion, as seen in Figure 2 below.

Fig. 2. A rock slinger helps workers place infill on steep slopes.

The tendon-anchored system with aggregate infill satisfied the needs of the project owner´s installation for long-term performance, burn protection, erosion control, and low maintenance while offering flexibility of fit without interference with the newly installed energy infrastructure.

GEOWEB Cellular Confinement System Options and Benefits

The GEOWEB Cellular Confinement Systems (CCS) offers a broad range of surface protection treatments for slopes that are subject to erosive forces. The inherent flexibility of the system, combined with a variety of adaptable anchoring techniques, permits the application of soft or hard armoring techniques to steep slopes. By ensuring the long-term stability and effectiveness of slope cover materials, underlying soils are protected, and customizable aesthetic objectives can be achieved. When slope reclamation and revegetation is desired, the geocell system provides the ability to fully vegetate slope surfaces that could not otherwise support plant life, with appropriate anchorage (based on specific site conditions) to hold the system to slope [7].

The GEOWEB walls, which contain the topsoil infill in a vegetated system, form a series of check-dams extending throughout the protected slope. Normal rill development, produced when concentrated flow cuts into the soil, is prevented since flow is continuously redirected to the surface. This mechanism also disrupts flow velocity and hence the erosive force of runoff. A predetermined depth of topsoil and the developing vegetative root mass is contained and protected within the individual cells. Roots become intertwined with the perforated cell walls, thereby creating an integrated, blanket reinforcement throughout the slope surface. In arid regions, it has been observed that the GEOWEB Geocells can enhance the development of indigenous vegetation by retaining a higher proportion of available moisture in the near-surface soil zone.

When vegetation is not appropriate or desired, aggregates or concrete infill may also be used for GEOWEB slope protection, stabilizing and protecting the surface. Aggregate infill reduces environmental impacts by allowing water infiltration on the slope face, reducing sheet flow runoff, and by precluding the need for irrigation systems, particularly in drought-prone areas, as might otherwise be required to maintain a vegetated slope cover. In this particular energy project installation, it was also chosen as a burn-protection zone around the newly installed energy infrastructure.

Protection of Energy Infrastructure Against Extreme Weather Events & Wildfires

The protection of energy infrastructure against extreme weather events and wildfires becomes increasingly more challenging as climate change exacerbates those threats. The National Park Service and the California Department of Forestry and Fire Protection (CAL FIRE) have started to collaborate with Indigenous communities to return traditional burning to the land as a wildfire prevention method [8]. Local tribes have helped to set prescribed burns in Yosemite National Park, among other wooded areas, as preventative protection against damaging wildfires like the Oak fire that burned over 8,000 hectares (20,000 acres) west of Yosemite National Park as shown in Figure 3 below.

Fig. 3. Oak Fire near Mariposa, California, photo courtesy NPR and David McNew/AFP via Getty Images.

In addition to prescribed burns, erosion control solution sets must perform uniformly with a balance of properties for robust and resilient performance, as highlighted in the Overview of Resilience Concept by Bruneau et. al [9]. Resilience in infrastructure includes qualities that help reduce vulnerability, minimize the consequences of threats, accelerate response and recovery, and facilitate adaptation to disruptive events. All of these are likely to be expressed as essential for the solution sought in pre- and post-incendiary erosion control, especially for energy sector infrastructure.

Within the resilience framework, the concept of robustness presents unique opportunities for innovative solutions such as the high-quality GEOWEB Geocells to be integrated into infrastructure designs and contribute toward achieving infrastructure resilience goals. Redundancy to maintain functional requirements in disruption occurs with the use of aggregate infill, serving as both fire protection and a permeable hard-armoring stabilization of the slope. The resourcefulness of the GEOWEB Geocells with tendons and ATRA Tendon Clips with specific engineering values allows resources to be mobilized in an effective manner, without interference to existing energy structure. The rapidity in response of The GEOWEB Geocell System allows infill to be placed and the slope to be stabilized quickly, achieving project goals in a timely manner with reasonable labor and equipment inputs from contractors.

GEOWEB Geocells should be considered an industry best practice option for slope stabilization and a solution for pre- and post-incendiary erosion control on hilly, dry terrain prone to wildfire, drought, and erosion. The type of system as shown below in Figure 4 is an appropriate option for permanent and resilient erosion control at similar energy infrastructure sites around the world.

Fig. 4. Aggregate infill of geocell system at energy facility.

References

ESA, The European Space Agency, Counting wildfires across the globe, https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-3/Counting_wildfires_across_the_globe, accessed 02 Oct 2023, (2023)
UNEP, United Nations Environment Programme, Spreading like Wildfire – The Rising Threat of Extraordinary Landscape Fires. A UNEP Rapid Response Assessment. Nairobi. (2022). Full report available for download, https://www.unep.org/resources/report/spreading-wildfire-rising-threat-extraordinary-landscape-fires?gclid=Cj0KCQjw1OmoBhDXARIsAAAYGSEzkAlWAeRVeIplu-Z9UovZiWkWwq1NIa6RBs-RtScyBW5gOBOokbEaAumEEALw_wcB, accessed 02 Oct 2023.
S. Department of the Interior, Office of Wildland Fire, https://www.doi.gov/wildlandfire/canada-and-united-states-commit-enhanced-wildland-fire-cooperation, accessed 02 Oct 2023. (2023)
Canadian Wildland Fire Information System, CWFIS, National Wildland Fire Situation Report, https://cwfis.cfs.nrcan.gc.ca/report, accessed 02 Oct 2023, (2023)
CAL FIRE, Statistics on CA wildfires and fire activity, https://www.fire.ca.gov/our-impact/statistics, accessed 02 Oct 2023, (2023)
University of California, Agriculture and Natural Resources (UCANR), Fire in California – Erosion Control, https://ucanr.edu/sites/fire/Recovery/Revegetation/Erosion/, and Post-fire management, https://ucanr.edu/sites/fire/Recovery/Helpful_Presentations/, accessed 02 Oct 2023, (2023)
Presto Geosystems, GEOWEB Slope Protection System, Technical Overview, https://prestogeo.wpenginepowered.com/wp-content/uploads/2016/10/GWSL-Geoweb-slope-technical-overview.pdf, accessed 02 Oct 2023, (2018)
National Public Radio, A Northern California tribe works to protect traditions in a warming world, https://www.npr.org/2023/09/19/1199820474/california-fires-yosemite-indigenous-tribes-climate-change, accessed 02 Oct 2023, (2023)
Michel Bruneau and Andrei Reinhorn, Overview of the Resilience Concept, https://www.eng.buffalo.edu/~bruneau/8NCEE-Bruneau%20Reinhorn%20Resilience.pdf, accessed 02 Oct 2023, Proceedings of the 8^thS. National Conference on Earthquake Engineering, Paper 2040, (2006)

Transforming Transportation Infrastructure: Protecting Road and Bridge Embankments with Geocells

Posted June 11, 2024 by Ashley Beyer

workers installing geocells on highway slope

In a rapidly changing world, maintaining and improving our transportation infrastructure’s resilience and sustainability has become a critical concern for civil engineers. Climate change and increasing frequency of natural disasters present an ongoing challenge to the durability of our infrastructure. In the context of road and bridge embankments, protecting these structures can be of paramount significance to the safety and welfare of the public. These structures are often subjected to fluctuating environmental conditions, heavy traffic loads, and must be able to withstand major storm events to protect embankment materials from soil washouts and the long term damaging effects of erosion. So how can civil engineers meet these growing demands without compromising sustainability or longevity? Increasingly, engineers are turning to geosynthetic solutions, such as the GEOWEB® Soil Stabilization System—a low-maintenance and eco-friendly solution for long-term protection of road and bridge embankments.

In many cases, the GEOWEB Geocells offer a flexible, durable, and environmentally responsible alternative to traditional construction materials that can accommodate a wide range of infill materials, including soil, aggregate, or concrete, to establish hard or soft armor, as necessary, for protection as well as aesthetics. As we explore the capabilities of the GEOWEB Geocells, we will find that this solution not only addresses some of today’s most pressing infrastructure challenges but also paves the way toward a more resilient and sustainable future.

Improving Bridge Resilience with the GEOWEB Geocells at the I-90 Mississippi River Bridge

Bridge stability relies heavily on the long-term integrity of its abutments. Any vulnerability or weakness in these components can lead to structural failure with a potentially disastrous outcome. Therefore, prioritizing the design and construction of resilient abutments is crucial to ensure the stability and longevity of bridges.

In 2013, the I-90 Mississippi River Bridge, or the Dresbach Bridge, underwent a significant reconstruction project led by SRF Consultants. The aim was to replace the old bridge on the Wisconsin/Minnesota border and improve the interchange between Highway 61/14 and I-90 to enhance traffic safety and provide better access for motorists.

The GEOWEB System played a crucial role in two different applications. The GEOWEB sections (4-inch-depth, mid-sized cell) were utilized on slopes directly beneath the bridges and around structural supports, ranging from 2H:1V to 1.5H:1V, with heights up to 45 feet. These sections, filled with aggregate, were custom-produced in a tan color selected to blend in with the local aggregate color, improving visual aesthetics. Standard black GEOWEB sections (6-inch-depth, mid-sized cell) were used around the bridge abutments on slopes varying from 2.5H:1V to 3.5H:1V, reaching heights of up to 48 feet. These sections were filled with topsoil and covered with an erosion control blanket to support vegetation.

To secure the GEOWEB sections to the slopes, 18″ ATRA® Anchors were employed, with the anchor pattern adjusted to suit different slope characteristics, section depth, and infill material. The Presto Geosystems engineering team provided calculations and recommendations for anchor spacing in each of the 11 application areas.

The implementation of the GEOWEB Soil Stabilization System in the Dresbach Bridge project was completed in the fall of 2016. This versatile system continues to provide robust slope protection, offering benefits for both aesthetics and long term project resilience. The Dresbach Bridge project serves as a testament to the versatility and effectiveness of the GEOWEB System in achieving slope stabilization and erosion control objectives around a vital piece of U.S. transportation infrastructure.

Fortifying the Roadway Embankment along River Road in Lewiston, Maine

Roadway embankments are another critical component of transportation infrastructure that face similar challenges. Erosion, washouts, and landslides can all lead to road failure, posing significant safety risks and disruptive repair costs. To protect against these risks, the GEOWEB Soil Stabilization System adds a valuable layer of protection. The three-dimensional honeycomb-like structure confines infill materials and protects slopes from sheet flow runoff, washouts, and shallow translational failures that can occur during and following major storm events.

River Road in Lewiston, Maine, faced a similar challenge due to its steep 1:1 slope and heavy traffic, including constant truck flow. To ensure the long-term safety and integrity of the road, the River Road Reconstruction project was initiated, which included pavement reconstruction, shoulder widening, and construction of a stabilized vegetated slope, among other upgrades.

before and after installing geoweb geocells vegetation

One significant hurdle was constructing a 45-degree vegetated slope, with the risk of erosion heightened during spring seasons due to rainfall and snowmelt. To maintain the slope’s stability and the road’s integrity, the GEOWEB Vegetated Slope Protection System was chosen for soil stabilization and erosion control.

The system’s installation process utilized geogrid lifts for enhanced slope stabilization. The 3D cellular GEOWEB system, combined with a tendon system, held the topsoil in place on the steep slope, enabling sustainable vegetation growth and mitigating severe erosion risk.

The GEOWEB system was filled with rocks at the slope’s toe for a strong foundation, with larger rocks on top for added support. Moving upwards, cells were filled with topsoil and covered with a turf reinforcement mat to promote grass growth, demonstrating the pivotal role of the GEOWEB geocells in providing stability, soil confinement, and vegetation support.

A Step Forward in Sustainable Infrastructure

In the face of modern infrastructure challenges, civil engineers need solutions that are not only resilient but also sustainable. GEOWEB Geocells provide a dynamic response to these demands. They offer significant benefits in terms of durability, adaptability, and environmental consciousness, making them an optimal choice for modern bridge and roadway embankment projects.

Dam Structure Safety Installation and Repair Using Advanced Geosynthetic Technology

Posted June 3, 2024 by Ashley Beyer

Written By: Samantha Justice, P.E.

Dams and Spillways Are a Critical Part of U.S. Infrastructure

With over 91,000 structures nationwide, dams and spillways are essential for controlling flooding, water distribution, and providing hydroelectric power. However, these structures cannot last forever. The average age of dams and spillways in the U.S. is now 61 years, significantly over the typical 50-year lifespan of these structures. Aging infrastructure can lead to serious consequences if safety precautions are not taken or measures are not implemented to address identified problems promptly. Continual inspection and upkeep are crucial for any dam manager.

The 2021 Infrastructure Report Card by the American Society of Civil Engineers rated the condition of U.S. dams with a “D” grade, highlighting the pressing need for repairs and maintenance (Home). State and federal regulations provide a framework for assessing and maintaining dam and spillway structures, requiring at least yearly audit inspections to identify areas needing repair or replacement. Performing these repairs can help extend the lifetime of dams, maintaining essential services without excessive costs or increased failure potential.

Understanding Areas of Concern for Existing Structures

The vast majority of America’s rivers and lakes have existing dams and spillways, and as such, very few new structures are being built. With new construction, safety measures can be incorporated during the design phase to extend the lifetime of the project and help prevent failures. The true threat is with existing structures that have gone past their intended lifetimes or have seen areas of potential failure.

A recent example of the potential for catastrophic damage due to a dam failure is the 2017 Oroville Dam crisis in Northern California. Extremely heavy rainfall over a number of days raised the level of Lake Oroville, increasing the flow over the main spillway to above-average levels. Almost immediately, damage was observed in the lower half of the spillway, with a large section of the concrete path collapsing. The emergency spillway was utilized to help prevent further damage to the main spillway, however, excessive erosion occurred to the emergency spillway path, and emergency repairs were subsequently required to address damage in both spillway areas. Further damage occurred when more rainfall increased the lake level yet again, including blocking the downstream river and requiring the immediate shutdown of the Oroville hydroelectric power plant. Luckily, total collapse of the dam did not occur, but more than 180,000 residents of the Feather River Basin were required to evacuate for multiple days, and over the next year, more than 1,000 people worked more than 2 million hours to rebuild the spillways to ensure the safety of downstream communities.

With the passage of the 2021 Infrastructure Investment and Jobs Act, states will have access to funds to complete repairs and upgrades of aging dams and spillways before failure can occur. The failure at the Oroville Dam was preceded by rejection of a 2005 upgrade proposal to build a concrete emergency spillway that could have handled the high water flows seen in the 2017 event. Re-evaluating existing structures to ensure that they are still able to withstand 100-year and 500-year flood events is crucial to the longevity of the dam network within the US. Maintaining both upstream and downstream dam faces and spillways is an ongoing process, fighting against wave action and erosion, as well as any potential impact damage caused during storm events. Even simple maintenance of roads and work pads over dams can have a lasting effect on the health of these structures by allowing workers access to inspect and repair the structures quickly and easily.

GEOWEB® Geocells Are a Repair Solution for Dams and Spillway Sites

GEOWEB geocell technology is a versatile geosynthetic system that can be used to create long-term solutions for many of the common dam and spillway problem areas. Geocells function as the support structure for unpaved roadways, capable of supporting maintenance and repair vehicles. They also function as surface erosion control solutions, preventing the formation of rills or the collapse of unstable soils due to water flow, wave action, and storm events.

GEOWEB geocells can be placed on the upstream face of a dam structure to mitigate the effects of wave action on the dam, supporting existing riprap areas, or replacing them entirely with vegetation, gravel or concrete. The flexibility of the GEOWEB system allows for the use of mixed infill materials, such as topsoil above normal water levels for grass growth and small aggregate below the water level for erosion prevention. Comprised of high-density polyethylene (HDPE), GEOWEB geocells are formulated for long term durability to resist weathering, chemical attack, and ultraviolet radiation, and are therefore suitable for use in applications where the material will be subjected to cyclic wetting and drying, permanently submerged, or full sun exposure. The material is not prone to degradation or corrosion due to environmental factors, and can be placed on the downstream face of, or within, a spillway structure. The system is also compatible with concrete infill to accommodate extremely high flow velocities. For comparison, Table 1 summarizes allowable velocities and shear stresses for various channel lining alternatives.

Comparison of allowable velocity and shear stress for channel lining alternatives

In emergency spillway areas, topsoil infill with vegetation can be used to allow for a natural camouflaged look, while still preventing erosion and uncontrolled water flow, and outperforming traditional unreinforced channel lining alternatives.

Staging areas and maintenance roads are also integral parts of a dam site, and when necessary, these features provide vital access and adequate ground support for vehicles and heavy equipment to perform inspections, routine maintenance, and repairs. The GEOWEB system can be used in a variety of load support applications, including unpaved access roads, laydown areas, and parking lots. Reinforcing these roads means significantly reduced maintenance requirements, reduced rutting, and access to areas that might otherwise be unable to support heavy loads due to soft soil conditions. Minimizing stresses on top of dam structures is critically important to preventing the formation of cracks or slumps within the structure that could lead to failure. The GEOWEB road system can be integrated with the slope protection system on the upstream and downstream faces of the dam for a continuously protected berm from water, vehicle, and impact loads.

Design Support & Resources for the GEOWEB System Applications

The engineering team at Presto Geosystems works closely with engineers and project planners, offering free project evaluation services and on-site support. Our recommendations will deliver a technically sound, cost-effective solution based on four decades of accredited research and testing data. Please contact our knowledgeable staff and network of qualified distributors and representatives to discuss your project needs today.

Green Retaining Walls Protect an Advanced Wastewater Treatment Plant from a 500-Year Flood Event

Posted May 2, 2024 by Ashley Beyer

Flood Protection Plan

To meet federal requirements for flood mapping of levee-protected areas, a levee reconstruction project for the Indianapolis Southport Advanced Wastewater Treatment (AWT) plant along Little Buck Creek was part of a more extensive Deep Rock Tunnel Connector project—one of the largest combined sewer overflow projects for the City of Indianapolis.

The project included plans to protect the Southport ATW plant and wastewater-processing pond from a 500-year flood event from an adjacent creek and river. To accomplish this, a wall system designed on the creek side of the levee would have to maintain a narrow profile to increase the water capacity of the creek.

A Natural Erosion Protection Solution

Flood events and high water flow from the adjacent creek caused significant toe erosion of the levee embankment along the north side of the wastewater treatment plant. The AWT required a long-term soil stabilization solution to combat erosive forces from Little Buck Creek’s varying depths and flows. The creek flows as low as a 1-foot depth with velocities of 3 feet per second (fps) to as high as 8 fps with a depth of 12 to 15 feet during a flooding event.

The project engineer preferred a wall system with native vegetation along the levee that would be robust enough to withstand erosive forces from the creek. They chose the GEOWEB® Vegetated Retaining Wall System to reduce the environmental impact, protect the levee from scour and erosion, and satisfy regulatory requirements.

Construction of the Levee Wall

Working within a limited footprint to maintain a narrow profile, the engineer designed the GEOWEB Retaining Wall as a gravity structure. Installers filled the back cells of the GEOWEB System with aggregate to promote drainage and placed a mixture of topsoil and #2 stone in the front outer cells to support vegetation and provide stability and resistance to soil loss during larger storm events.

Wall Dimensions & GEOWEB Green Wall Attributes

Wall length: 1,500 feet; Wall height: 5 to 12 feet
Open fascia cells allow infiltration of stormwater.
Green fascia panels blend with natural environment.
Flexible wall performs well in soft soil environments; conforms well to a waterway’s geometry.
The GEOWEB HDPE material is unaffected by water contact.

Performance Update

Since its installation in 2012, the GEOWEB green wall continues to provide vital protection to the Southport ATW plant and wastewater-processing pond from major storm events. Significantly more economical than the U.S. Army Corps of Engineers’ (USACE) conventional riprap solution, the GEOWEB walls are a practical alternative for levee applications.

With native vegetation, the GEOWEB levee wall proved to be an attractive solution that effectively minimized environmental and permitting impacts.

Living Green Walls + Low Impact Development

An attractive alternative to MSE block walls or riprap, walls built with the GEOWEB geocells offer a green aesthetic and low-environmental impact approach to designing retaining walls. The GEOWEB Retaining Walls conform well to landscape contours, are resistant to environmental degradation, and install 25-30% faster than MSE block walls. The GEOWEB System also offers design flexibility for a variety of wall configurations, including gravity, reinforced, and steeped slopes.

Create Strong, Long-Lasting Mechanical Connections Using the New ATRA® Wall Key The new ATRA Wall Key is the most effective device for connecting the GEOWEB Retaining Wall sections, ensuring the long-term success of your project. Made of non-reactive, chemically inert high-density polyethylene, the ATRA Wall Key provides a more secure and permanent mechanical connection over staples or zip ties, and they are the only geocell connector specifically designed for use in exposed wall face applications.

The innovative ATRA Wall Key includes an integrated washer at the base of the handle to provide coverage of the I-slots, frictional barbs for an improved interlock with the GEOWEB sections, and an ergonomic handle with S-shaped contouring for ease of installation.

Formulated to withstand weathering and ultraviolet radiation, the ATRA Wall Keys will not corrode or photodegrade, even when exposed to harsh environments. Securing sections with the ATRA Wall Keys is faster than using staples or zip ties, requires no tools, and can be completed by one installer with one easy turn.

Design Support for Retaining Walls

Presto Geosystems offers fast and easy-to-use resources and tools for designing GEOWEB Retaining Walls. Let our Design Engineering Team prepare a complimentary project evaluation for your next project. We also offer free licenses for our GEOWEB® MSE Design software for retaining wall applications.

Creep is not a factor for geocell load support

Posted April 30, 2024 by Katie Bocskor

Written by: Bryan Wedin, Chief Engineer

An accurate understanding of creep resistance is essential to proper material selection when using polymers, and in the case of geocells, this science is being misapplied.

The definition of creep deformation is “the tendency of a solid material to move slowly or deform permanently under the influence of mechanical stress.”

This potential failure mode creates fear and uncertainty among designers wherever the possibility of creep factors exists. Yes, creep can occur in almost all materials including plastics, metals, and concrete. In cases such as bridge and building design, it is important to properly understand creep factors and account for creep in engineering calculations. However, in the case of designing with geocells for load support, creep factors have no relevance.

What causes creep?

In order for creep to occur, two factors must be present:

1) A constant load applied to the area and

2) A sustained deformation of the geocells.

Creep only applies when there is a sustained load on a material for an extended period. In a case of repeated on- and off-loading, this type of deformation would be governed by fatigue, not by creep, because it is not a constant applied load.

The second required factor for creep to occur is an ability to undergo sustained deformation of the material. When a polymer has a load applied, the molecules of the material start to pull apart and stretch. This leads to elongation of the material in one direction and typically results in a thinning of the material’s thickness.

Creep not a factor in load support

Now, consider a geocell load support application. The geocell material is expanded to cover the project area on-site and then an infill material is placed into the cells. At this point, there is not an applied load or deformation occurring in the material.

Next, the infill material is compacted. This compaction applies a load to the cells, but this load is removed as soon as the compaction equipment is no longer positioned over the cells.

As an individual cell is loaded, it exerts an outward force while each of the adjacent cells pushes back on it (passive resistance) and prevents any sustained deformation. Therefore, at the time of compaction, there is neither a constant load nor is there a sustained deformation. Thus far, the material is successfully installed without any creep effects.

After the geocell load support system has been installed, the two types of loads that will affect the system are driving (live) and stationary (parked) loads. When a vehicle drives over a geocell system, the load is applied vertically. As the geocell distributes the load laterally, there is a temporary load applied to the geocell material. The load is not a sustained load, and therefore, would not have a creep effect.

In the case of stationary loads, the load is continually applied to the geocell, so it meets the first criteria for creep. Due to the pressure from all adjacent cells surrounding the loaded cell(s), there is no ability for the cells to move enough to have any appreciable sustained deformation. Therefore, creep cannot affect this scenario.

ASTM D6992 creep test is not applicable

Those who make claims about creep potential in geocell load support applications have cited ASTM standard methodology as the reasoning for concern.

ASTM standards provide an accepted means for standardizing testing to be able to directly compare products. It is important to review the intention and scope of a test to ensure that it is appropriate and will give relevant results. The Stepped Isothermal Method (SIM) is used to accelerate creep testing. ASTM D6992 uses SIM to predict the expected deformation of geosynthetics over time when used for reinforcement applications. This method can be effective; however, it is not suitable for a polyethylene geocell evaluation.

ASTM D6992 5.3 Note 1 states, “Currently, SIM testing has focused mainly on woven and knitted geogrids and woven geotextiles made from polyester, aramid, polyaramid, poly-vinyl alcohol (PVA), and polypropylene yarn and narrow strips.”

Additionally, the note continues with a warning against expanded scope of the test saying, “Additional correlation studies on other materials are needed.” While this test has applicability for geogrids and geotextiles, the test is not intended for evaluating geocells and correlations for polyethylene have not yet been established.

Further, D6992 cannot be considered in isolation.

D6992 states, “Results of this method are to be used to augment results of Test Method D5262 and may not be used as the sole basis for determination of long-term creep and creep-rupture behavior of geosynthetic material.”

This reinforces the importance of reviewing each test standard to ensure that the product is within the scope of the test and that the results are relevant and complete. In the case of geocell evaluation, using ASTM D6992 is inappropriate as it has not been properly correlated to provide accurate evaluation of polyethylene and without ASTM D5262, it provides an incomplete overall evaluation of the product.

HDPE’s long history of success and repeatability

High Density Polyethylene (HDPE) has been used as the industry standard material for geocells since it was invented over 40 years ago. HDPE has been extensively researched by independent scientists across multiple industries, allowing for a comprehensive understanding of its performance capabilities. Using a virgin HDPE material allows for direct verification of resin consistency through laboratory testing to ensure that each manufacturing location and production lot have consistent material performance. This laboratory verification also allows for the comparison of the material to independent scientific results and does not rely solely on manufacturer’s claims.

Challenges with Fabricated Inelastic Blend (FIB)

A few geocell manufacturers are promoting a Fabricated Inelastic Blend (FIB) to cut manufacturing costs and increase material stiffness utilizing recycled and other unpublished polymer materials. These FIB-based materials can vary widely, even for the same product. Due to the vast number of combinations possible with FIB materials, they pose two key problems when included as a material choice: validation and consistency.

Because of the unpublished nature of the blending mixture there is no way to validate this material in comparison with published testing. Any testing of FIB materials must start from the beginning without any experience to rely on for long-term performance.

The second concern with FIB materials is controlling consistency of the blend. Because each FIB blend is so variable, there is no way for a third-party tester to fully determine consistency of the blend between different manufacturing plants or even between different production lots. This inability to determine consistency creates uncertainty because there is no way to determine if there has been improper blending or changes to material blend.

Manufacturers using FIB materials promote the advantages of increased material stiffness. This stiffness is often a function of multiple generations of recycling. It is important to review the differences between elastic and inelastic materials and how they affect geocell performance. An elastic material is able to undergo a deformation (strain) and then spring back to its original state without permanent (plastic) deformation.

Conversely, an inelastic material does not undergo immediate deformation, but rather ends in catastrophic (complete) failure. Many of engineering’s worst failures have resulted from catastrophic failures of inelastic materials that were subjected to unexpected loads. This absolute nature of inelastic failure puts projects at great risk because it does not give indication prior to collapse. With elastic materials, as material limits are reached, the material will stretch and yield prior to complete material failure. This yield zone allows for changes to loadings prior to catastrophic failure.

The mobilization of soil strain and geocell strain occurs from not only deformation of infill, but deformation of subgrade materials. For reasonable ranges of geocell stiffness, subgrade deformations will cause the strain to occur in the geocell system. For a given strain stemming from subgrade deformation, a stiffer geocell will realize larger tensile stresses, both in its wall and especially at the seam, which will result in seam rupture and system failure.

The material stiffness is not the most critical point in geocell performance. It is a combination of stiffness, tensile strength, seam strength, and passive resistance of adjacent cells. Published data shows that strain in geocell cell walls is on the order of less than 0.5 to 1.0%. At such low strains, the effect of creep should be ignored for all practical purposes. Properties such as seam strength, strip flexibility, environmental stress cracking resistance, and passive resistance from adjacent cells play a much larger role than stiffness of the material. Also, at these strain rates, HDPE (including virgin mixes, most recycled and other polymer alloy geocell) stress-strain behaviors are similar.

In load support applications, loadings are transient and quite small due to the stress-distributing behavior of the pavement material and geocell mattress effect, which further compounds the irrelevance of creep in reinforcement applications. Thus, overall system strength is not related to any performance factors that are tied to creep. Therefore, the focus should be on how much strain is mobilized in geocells.

Some manufacturers have examined theoretical 2% to 5% strain rates, both of which are far above actual field conditions, and therefore, not applicable. Five percent strains in load support applications are not applicable since compacted granular materials fail at much lower strain rates. At 2% strain, granular materials would fail within a geocell, as well as outside of the confined system, due to significant rutting and deformation. The geocell material would not be the failure point, and a stiffer geocell would not affect the failure of granular materials at 2% strain.

Geocells used in load support applications prevent high strains from occurring due to the very nature of the geometry, its confining behavior, and passive resistance of adjacent cells. Evaluating geocell material strength beyond reasonable strain values is not relevant for subgrade reinforcement as it contradicts actual measured data and represents conditions outside of practical design and application. The basis of comparison should focus on stress-strain behavior at very low strains – less than 1.0%. This information is readily available from large-scale laboratory tests, field tests, and numerical modeling.

True HDPE Performance vs FIB Results

FIB materials bring a new uncertainty to the geocell market. These materials are of unverifiable composition so connecting material to performance is nearly impossible. Ultimately, these FIB materials beg your trust in their performance touting their unnecessary creep resistance. They hide the truth that creep resistance comes at a cost – inelastic material that can fail catastrophically at the seam. FIB material prioritizes a single material property of the geocell at the expense of a uniformly designed system with measurable material consistency and applied field testing.

After 40 years, HDPE continues to be the industry standard material for geocells. Presto Geosystems proudly pioneered the use of HDPE material in its GEOWEB® Geocell products due to proven performance and reliability of that material.

Over these four decades, GEOWEB Geocells have been used in load support projects worldwide without a single failure due to creep effects. Although this consistent performance is impressive, it is not surprising given that creep forces are irrelevant in these applications.

Advancing Rail Resilience: How Geosynthetics Help Achieve CRISI Objectives for Robust and Stable Infrastructure

Posted April 8, 2024 by Ashley Beyer

train along track stabilized with geoweb geocells

Discover the Latest CRISI Rail Infrastructure Funding Opportunities: Apply Before the May 2024 Deadline

The U.S. Department of Transportation is bolstering rail infrastructure advancements through the Consolidated Rail Infrastructure and Safety Improvements (CRISI) program. With a recent allocation of $2.47 billion, the CRISI program is set to significantly impact rail safety, efficiency, sustainability, and reliability across the United States.

This funding initiative is designed to support a variety of projects that are pivotal to enhancing the nation’s passenger and freight rail systems. It represents a call to action for rail industry professionals, including engineers, planners, and project managers, to leverage this opportunity to advance their rail infrastructure projects.

The deadline for application submissions is 11:59 p.m. ET, May 28, 2024. Professionals in the rail sector are urged to prepare their proposals that align with CRISI’s mission to improve the rail infrastructure’s overall landscape.

For a comprehensive overview of the application process and to assess project eligibility, stakeholders are encouraged to review the Fiscal Years 2023-2024 Notice of Funding Opportunity (NOFO) available through the CRISI program. This funding presents a pivotal chance for those involved in rail infrastructure to gain the support and resources needed to propel their projects forward.

The GEOWEB® Soil Stabilization System (Geocells): A Proven Solution for Rail Infrastructure

Mainline Ballast Reinforcement

The GEOWEB Rail Ballast Stabilization System stands out as an innovative solution for addressing ballast stabilization challenges, creating a more resilient and stable layer underneath the track. The 3D geocellular system yields unparalleled performance and construction benefits, surpassing the capabilities of 2D methods like planar geogrids or Hot Mix Asphalt (HMA), especially in areas with soft subgrades.

The performance of the GEOWEB system is backed by extensive research and rigorous field testing at renowned institutions such as TTCI and Oregon State University. It has demonstrated its ability to reduce settlement and track displacement under the strain of heavy freight loads on soft subgrades, and has already been adopted for use in railway track beds by international authorities in other advanced nations, such as Network Rail in the United Kingdom, with their recent published guidance on “The Use of Geocells in the UK Railway Track Bed”. Additionally, SmartRock testing by the University of Kansas revealed significant reductions in ballast abrasion, movement, and rotation, as further evidence the life of the ballast can be extended when the right geosynthetic product is incorporated into the project design.

Bridge Approaches, Crossings, Diamonds: Ballast Reinforcement in High-Stress Areas

Areas like bridge approaches, diamonds, turn-outs, and crossings face immense stress and usually require a lot of upkeep. The GEOWEB Soil Confinement System helps lower the need for maintenance in these challenging spots. It strengthens the ballast layer, reduces movement and deflection, and cuts down on maintenance in these crucial transition zones.

GEOWEB Geocells: BABA-Approved

Last year, the White House provided guidance on the Build America, Buy America (BABA) initiative. BABA specifies certain products must be manufactured in the United States to qualify for federal funding under the IIJA.

Selecting the GEOWEB System for enhanced track stabilization allows projects to achieve improved resilience and longevity, ensuring compliance with the standards set by the CRISI program, the Infrastructure Investment and Jobs Act, and Build America, Buy America. Presto Geosystems is ISO 9001 certified, and the GEOWEB Soil Stabilization System is 100% U.S. made. (A copy of our Certificate of Registration can be provided upon request.)

Need Assistance with Your Rail Projects?

Presto Geosystems offers free project planning support for all GEOWEB Geocells applications in rail projects. Our experienced engineers are ready to assist with project evaluations to ensure your project’s success from start to finish. If you’re dealing with challenges related to soil stabilization or looking for innovative track stabilization solutions, please reach out to us.

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