Posts Tagged: Geocell

Railroad ballast performance improvement using GEOWEB®

Every year, railroads dedicate a great deal of capital and maintenance expense towards the creation and upkeep of high quality ballast layers. Enduring well-designed ballast is quite literally the foundation on which a successful rail line operates. With ballooning rail traffic carrying heavier loads than ever, GEOWEB cellular confinement (Geocell) effectively takes the pressure off critical ballast systems. Oregon State University (OSU) recently performed state-of-the-art, three-dimensional dynamic Finite Element modeling to analyze the reinforcing benefit of GEOWEB geocells in railway applications. This study was completed in cooperation with the University of Kansas (KU) who simultaneously performed a testing program of Geocell reinforced ballast placed over weak subgrade material using HDPE GEOWEB material. The digital modeling results were reinforced by the laboratory tests and showed a significant decrease in settlement of the railway ballast when GEOWEB confinement was used. The use of GEOWEB technology not only decreased settlement, but reduced pressure on point-to-point aggregate load transfer contact which in turn resulted in less damage to ballast aggregate particles leading to less progressive deformation and longer maintenance frequencies of the entire ballast embankment. In short, more cycles means less track down-time for maintenance. The research results were clear. The benefits of applying… Read more »

Choosing the Right Geocell

Written By: Bryan Wedin P.E., Chief Design Engineer, Presto Geosystems Not all geocells are created equal. While most manufacturers can provide similar-looking written specifications, you need assurances that the material delivered for your project is of the high quality that you expect. Important factors in the success of your geocell project include: Quality The geocell material is proven, strong, and will last Require only the highest quality virgin High Density Polyethylene (HDPE) resin Low quality or recycled resin can lead to weak and/or inconsistent seam strength, putting the success of your project at risk. Non-HDPE materials cannot match the nearly 40 years of in-ground experience of HDPE geocells and plastic alloy proprietary blends can mask cheap stiff filler materials. ISO Certification Important, but the manufacturer sets the testing protocol for the certification. Require a Certificate of Analysis (COA) for the material that is shipped to your project. An ISO certification that does not require continuous testing is lacking. Integral Components The complete solution includes proper components Non-corrosive, high-strength panel connection method (ATRA® Keys vs. weak staples or zip ties) Anchors that provide secure connections to the geocell (ATRA® stakes vs. J-hooks) Load Transfer Devices for tendon applications that are non-corrosive and… Read more »

Creep Not a Factor for Geocell Load Support

Written by Matthew Kuester and Bill Handlos, PE 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.  Creep is something that creates fear and uncertainty with all designers where the possibility of creep factors exist. 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.  Yet, in the case of designing with geocells for load support, creep factors have no relevance. What Causes Creep? In order for creep to occur there must be; a constant load applied and a sustained deformation.  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 would be governed by fatigue and not by creep.  The second required factor for creep to occur is an ability to undergo sustained deformation of the… Read more »

Use Product Differentiation for Good, Not for Evil

Written by William G Handlos, P.E. Product differentiation is often thought of as a way to create a competitive advantage. Typically, a company decides to focus and promote upon a certain attribute(s) of a product making this attribute a key feature of their value proposition statement. For example, a major automobile company might focus and promote a rear lift gate automatic opener actuated by the movement of the driver’s foot under the rear bumper. This inexpensive addition to an SUV’s feature set may be the difference in a buying decision between competing automobile brands, particularly in a market with fierce competition and similar option sets.  In this case, the manufacturer has created a product differentiator that truly adds benefit to the customer. Presto Geosystems® developed the original geocell in the late 1970s and GEOWEB® Geocell product enhancements have been developed every few years, always with the intent of offering benefits to their customers with each refinement. For manufacturers who sell to contractors who bid on projects that are based upon engineered plans and specifications, the waters can be murkier. Is product differentiation created for the benefit of the customer or is differentiation simply crafted to create a unique set of… Read more »

Highway Stormwater Control: Porous Vegetated Road Shoulders

Written by William G. Handlos, P.E. Highway Stormwater Control: Porous Vegetated Drivable Road Shoulders Gravel road shoulders are not porous. Rainwater sheet flowing off highway pavement passes right across the aggregate shoulder carrying with it sediment and other pollutants that ultimately end up in freshwater creeks and rivers. Aside from pollutant loading, re-grading shoulders is a continuous activity for State and County crews to repair eroded sections after several rain events. Some counties have taken a smart solution approach to this problem and are using geocell cellular confinement systems to reduce maintenance costs and to improve water quality.  Shown below are the cross sections detailing a GEOWEB® geocellular drivable vegetated shoulder solution. The infill to the geocell is made up of 2/3rd clear stone aggregate (void ratio 30 – 40%) and 1/3rd topsoil. The topsoil remains uncompressed within the interstitial spaces between the stone, and the stone is the structural component that carries the load. The topsoil allows for the vegetation roots to grow and feed upon the nutrients and water in the topsoil.  This system percolates runoff from the highway while offering proper load support for vehicles that pull off the side of the road. The GEOWEB® cells confine the… Read more »