Research On The Influence Of Groundwater To Expansive Soil Embankment By Model Test

As expansive soil is easy to absorb water to swell and then soften, which causes the strength degradation, expansive soil is often modified by mixing ash, otherwise abandoned in the subgrade construction of past expressways. Thus the investment cost of highway construction increases, soil and water loss will appear, and environment will be destructed. The research group of changsha university of science and technology put forward a method of enveloping and wrapping using expansive soil to fill the embankment directly in some trial sections of several expressways. For testifying and improving such a physical treating technique, the influence of groundwater to the expansive soils in the center of embankments is researched. Therefore, the paper carrys out the model experimental research of expansive soil embankments under the action of groundwater.Firstly, the paper represents the concept of building expansive soil embankments through the method of enveloping and wrapping, analyzes treating effects of every enveloping schemes and demonstrates the validity of the physical treating schemes. Secondly, take Baise expansive soil as fills, analyze the soil characters and its road related performances, design and build full-scale model of expansive soil embankments, in which corresponding testing components were buried. By changing the conditions of groundwater under embankments, the variation laws of water moisture, pore water pressure, soil pressure and temperature are acquired. The results manifest that: as the variation curve of water content in different layers of embankments caused by groundwater is distributed as exponential function (y = a e-b x); as there are evident responses for the variation of the pore water pressure and soil pressure to water content, the relation of swelling pressure (lateral pressure) changed with water content can also be described with exponential function; under the unchangeable condition of groundwater, the soil water content of embankments changes with the environment temperature variation.Through the model experimental research, the variation regulations of water content, pore water pressure and soil pressure under different conditions of groundwater are achieved and then the effective range of groundwater at the bottom of the embankments is analyzed. According to the above study, combing with the research result, it has brought out different treating measures for several conditions of ordinary embankment bottom, and brought out the requirement in detail of the enveloping thickness, expansive soil fill height, and paving, grinding and compaction controlling during construction.