Experimental Study On Behavior Of Reinforced Soil With Small Reinforcement Spacing

Reinforced technique has been widely used in civil engineering technology. But the traditional reinforced structure has its limitations. In recent years, some foreign scholars such as Adams M.T. put forward the GRS (geosynthetics reinforced soil) structure. The GRS is used for reinforced soil with well-compacted granular soil reinforced with closely spaced geosynthetics specially. Now the research in the field of GRS is still in its infancy. In order to better understand the behavior of the GRS structure, a laboratory test of reinforced soil with small spacing on the resilient performance and the unconfined compressive performance was carried on in this paper. The specimens were made by the granular soil which was reinforced by biaxial geogrid and nonwoven geotextile respectively. All the specimens were with the reinforcement layers of 0,1,2,3,4 or 5.In the resilient performance test, a number of samples of the biaxial geogrid-reinforced soil at 88%,92% or 96% of compression degree and a number of samples of the nonwoven geotextile-reinforced soil at 92%,96% or 100% of compression degree were used to measure their resilient modulus. In addition to the resilient performance test, a number of samples of the biaxial geogrid-reinforced soil at 88%,92% or 96% of compression degree and a number of samples of the nonwoven geotextile-reinforced soil at 96% or 100% of compression degree were also used to measure their unconfined compressive strength. The effect of reinforced arrangement, number of layers, and the soil's compaction degree on the reinforced soil with small spacing was analyzed and summarized. And the following conclusions were presented:(1)Improving the degree of compaction and reducing reinforcement spacing can both improve the strength and rigidity of the GRS structure. But the increasing range reduced gradually with the increasing of compaction degree or the reducing reinforcement spacing.(2) The reinforcement layers which are near to the upper surface improve resilient modulus of the structure significantly, for the reinforcement layers that are far from the upper surface, the effect is very little.(3) The deformation characteristics of the geogrid-reinforced soil and geotextile-reinforced soil are slightly different. The former performs enhancement for interlocking at the geogrid-soil interface, it is mainly friction reinforcement mechanism. The latter performs that geotextile adapts to the internal deformation and can handle a lot of limit strain,it is mainly the tension membrane reinforcement mechanism.(4) The biaxial geogrid-reinforced soil is much harder, and the nonwoven geotextile-reinforced soil is more flexible. The well-compacted granular soil reinforced with closely spaced geosynthetics has a high compressive strength and exhibits a ductile and flexible failure mode. This makes GRS a desirable material for the flexible retaining structures.(5) GRS structure has the extremely strain bear ability. It was observed that even if the vertical strain exceeded 60%, the stress was still increasing. Excellently ductility has been showed. So it is an ideal of anti-seismic structure.