A thesis submitted in partial fulfilment of the requirement for the degree of Master of Engineering, School of Civil Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1994

This study is concerned with the laboratory properties of compacted Bangkok clay reinforced by nonwoven geotextiles. Two type of geotextiles, namely, Polyfelt TS420 and TS700 have been invei;tigR1.ed. Three series of 1.riaxial teR1.s on 4 inches diameter samples with and without reinforcement have been conducted. One series of CH J tests on wet specimen compacted at 29% moisture content. The other two series were UU tests on partly saturated samples compacted at wet and dry side of optimum with the moisture content of 29% and 2 1 %, respectively. All specimens were prepared at 95% of standard Proctor compaction. It was observed from this study that most of the failure envelopes in both types of tests, UU and CTU, of the reinforced Ramp lei; almost paralleled hut higher to that of the corresponding unreinforced one with the enhancement of the apparent cohesion intercept. This implied that the geotextiles were stretching during shear. For stiffer geotextile, TS700, at 2 and 1 layers of reinforcements, both friction angle and apparent. cohesion increased although only slightly for friction angle. The strength ratio, R, increased with increasing of stiffeners and number of layers of the fabric in all types of tests. The strength ratio of t.5 and 2 were obtained from UU tests. on wet samples reinforced by 3 layers of TS420 and TS700, respectively. The moisture content at compaction also affected significantly on the strength ratio in UU tests. The wet samples yielded the much higher values of R in comparison t o that of the dry one. For wet specimens compacted at the same moisture content, the CHJ tests gave lower value of R in comparison with UU tests. This is because of the fact that the non-woven geotextile increased the shear strength of the reinforced soil not only by the induced shear resistance caused by the internal reinforcement inclusions hut also hytl1e local drainage in to the geotextile from the surrounding soil.