Thomas V. Edgar

EFFECTS OF GEOTEXTILES ON LATERAL PRESSURE AND DEFORMATION IN HIGHWAY EMBANKMENTS

Abstract A procedure to lower the lateral loading acting on the back of a highway abutment wall utilizing geotextiles is described. A gap is formed between the wall and the geotextile reinforced backfill using either corrugated cardboard (which is wetted after construction) or removable plywood forms. This allows the backfill to deform and go into the active state. The fabric sustains the resulting tensile forces, essentially forming a free-standing fabric wall behind the abutment. Laboratory testing indicates that less than 25 mm lateral movement is required to reduce lateral loads by 90 percent. Four reinforcement schemes were compared on two Interstate bridges. The fills were instrumented with inclinometers, Sondex tubing and pressure cells. The results indicate that an initial gap reduces the lateral load to essentially zero and settlements were no greater with the voided system than that experienced by a nonvoided fill

The finite layer method for groundwater flow models

The finite layer method (FLM) is an extension of the finite strip method familiar in structural engineering. The idea behind the method is to discretize two space dimensions using truncated Fourier series, approximating variations in the third via finite elements. The eigenfunctions used in the Fourier expansions are orthogonal, and, consequently, the Galerkin integrations decouple the weighted residual equations associated with different Fourier modes. The method therefore reduces three-dimensional problems to sets of independent matrix equations that one can solve either sequentially on a microcomputer or concurrently on a parallel processor. The latter capability makes the method suitable for such computationally intensive applications as optimization and inverse problems. Four groundwater flow applications are presented to demonstrate the effectiveness of FLM as a forward solver.

Utilizing geotextiles in highway bridge approach embankments

Abstract Geotextiles have been employed to reduce lateral deformation of bridge approach embankments and to prevent closure of the expansion devices in the bridges. This unique application of geotextile materials has been successfully used by the Wyoming Highway Department for several years. The concept has recently been modified by eliminating the lateral pressure on the abutment wall. This is achieved by creating a free standing geotextile supported wall. This concept will be implemented in an existing bridge undergoing reconstruction. Problems concerning the retrofit design and construction are discussed. A laboratory testing program has been developed to obtain the deformational characteristics of the soil-geotextile composite. The significant findings are: 1. (1) Lateral deformations of 80–150 mm are required for the geotextile to totally support the soil. The range is dependent on the initial tension of the geotextile during forming. Once the free standing face has been developed, subsequent loading produces only minor additional lateral deformations. 2. (2) Preliminary testing indicates for a fixed lift height, the amount of deformation required to reduce the lateral stresses by specified amounts can be predicted. 3. (3) Common plastic foams do not appear to provide sufficient flexibility to reduce the lateral stress developed on abutment walls.