Written By: Bill Handlos, PE, Director of Presto Geosystems Geocells (cellular confinement) offer a more effective and practical 3D design solution to load support challenges than multilayered 2D geogrid efforts. Geocells transfer applied loads instantaneously, delivering practical soil stabilization in a product that is fast and easy to install. How do geogrids work? Geogrids rely on rutting, displacement and lateral movement of the road material to activate the load support reaction of the product. As shown below, failure of the driving surface must occur before the geogrid reacts. As a result, rutting and soil displacement is a prerequisite reality to the system. Since the geogrid is two-dimensional, material not located directly within the plane occupied by the geogrid is free to move, shift and displace. It is essential that geogrids are placed in a flat or a pre-tensioned manner—but that is not practical in a construction environment. It is common to see geogrids unrolled over a prepared grade with an undulating surface. As aggregate is placed over the top of the geogrid, the material kinks and waves, further warping the 2D plane. The geogrid is rarely pulled tight during installation which does not allow full tension under… Read more »
Posts Categorized: Geocell Confinement System
With this summer’s extremely wet weather conditions across the country, building access roads is a major challenge. Muddy, soft ground is causing construction delays when it comes to moving heavy vehicles and equipment over the soft soils. Presto’s GEOWEB® Soil Stabilization System offers a way to build roads even with these site challenges using low-cost, local fill—and has been doing so for over 30 years. In fact, the GEOWEB system is the go-to solution for many oil companies in remote areas like the Canadian oil sands and the Amazon basin. Recently, EnergyNow Media featured an article on GEOWEB roads addressing the latest access challenges in the energy sector. The EnergyNow article is republished below. Reprint of recent article written by “EnergyNow Media” (North American Energy Magazine) Presto Geosystems: Bringing Stability to an Unstable World Oil and gas is a tricky business. Everything from resource extraction to site management to processing is fraught with difficulties, challenges, and trials. However, one often-overlooked aspect within this industry is that of simply being able to access the resource site in the first place. Once access is established, it’s crucial that there is a clean, stable platform to work on and transport resources back out…. Read more »
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 »
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 »
Written by William G. Handlos, P.E.
Written by William G. Handlos, P.E. Specifying Engineers and Architects work tirelessly to build plans and specifications that capture the essence of their vision as they work to write the guiding documents for their project. They make decisions about product types, grades, and take great pains to build into their documents citations of certifications and standards to assure only quality materials are allowed on the site. Yet, when challenged to accept “or equal” substitutions, it seems that all the standards of care can sometimes be lost and substandard materials seem to too easily find their way onto the site. The reason for this lapse is often a result of the timing of the hand-off between the design team and the project management team occurring just as the contractor award occurs. Contractors are concerned about leaving too much money on the table (the difference in value between the winning and the second bid). Just moments after the bid opening or notice of award, bid shopping commences. Bid shopping on publicly-funded projects is disallowed by legislation in some localities, but even when formally disallowed, informally it occurs widely. With the economic power of the project award and with the pressure of the potential… Read more »