PULLOUT RESPONSE OF HIGH-STRENGTH GEOTEXTILE IN REGIONAL SOILS

Abstract

Recent developments in the petro-chemical industry have led to the production of geosynthetic materials for soil reinforcement purposes. The ability to construct such structures allows for great savings in land, especially in countries where land is rather scarce. In addition, the use of geosynthetics for reinforcement purposes provides an environmental-friendly and aesthetically pleasing structure when compared to traditional methods of constructing soil retaining structures using reinforced concrete. This project seeks to study the feasibility of using poorly draining residual soil as backfill material. The contribution of the drainage capability of the PEC high-strength geotextile in this application will be evaluated.

Two series of pullout tests, one in sand and one in residual soil, were conducted in this project. Of the pullout tests conducted in sand, one was conducted under dry sand conditions while the other was conducted under wet sand conditions. This series of tests serves to determine the effectiveness of the PEC geotextile when it was used as a reinforcement with free draining material. The aim of this series of tests was to investigate the change in the pullout characteristics of the PEC geotextile due to water infiltration into the sand mass to simulate the effect of heavy rainfall, a common occurrence in this region. Results from the pullout tests showed that the infiltration of water into the sand fill had resulted in a 16% increase in the pullout resistance of the PEC geotextile compared to dry sand condition. Analysis of the results showed that this was clue to the increase in the unit weight of sand from water infiltration. It was, however, the drainage capability of the PEC which resulted in maintaining a high level of effective stresses at the sand-geotextile interface which was under water saturated conditions. In addition, the displacements due to sliding were found to be about 4-5 times the displacements due to material stretching.

Three pullout tests were conducted with locally available non free draining residual soil as backfill material. Its effectiveness as a backfill material depends much on the ability of the soil to sustain high pullout strength under long term conditions. The test results showed that the residual soil was a feasible material to be used as backfill material. In fact, the peak pullout resistance of the geotextilc in residual soil at optimum moisture content condition was higher than when the same material was embedded in dry sand. The infiltration of water, however, resulted in a 17% reduction in the pullout resistance. When the pores of the PEC geotextile were clogged, a further I 0% drop in the peak pull out resistance was observed. From the series of pullout test results using residual soil as the backfill material, it was concluded that residual soil would be effective as backfill material provided that the soil must be properly compacted with the appropriate compaction effort and at the appropriate moisture content. Furthermore, a geosynthetic material with adequate drainage capability would be required for maintaining the long term stability of reinforced soil systems if poorly draining soil is used as backfill material.