Hydraulic And Mechanical Behaviour Of Huai-an Expansive Soil

With the development of the national economy and transportation in China, thehighway plays a very important role on the way of developing the moderntransportation as a national symbol of modernization. In the huge highway networkof our country, a lot of highways are built on the expansive soil foundations soil,which is a typical "problematic soil". The engineering disasters often occurring inexpensive soils have caused the engineering and researchers’ attention because of itseasily cracking destroy in the process of swelling and shrinkage. On the basis ofconsulting and organizing related literatures at home and abroad, the following teston Huai-an expansive soil was performed, and some conclusions are obtained:1、The basic physical properties of Huai-an expansive soil are obtained by aseries of basic physical tests. According to test results, the soil sample grain size hasa good distribution and the natural soil sample is in soft plastic state. The soil isweak expansive soil and the compression index of Huai-an expansive soil atsaturated state is obtained.2、To study the strength and deformation characteristics，the shear strengthindex is obtained from consolidation-drained triaxial shear test on Huai-an expansivesoil by using the triaxial shear testing apparatus. The results showed that under thecondition of the same void ratio, the confining pressure has significant effect on thestress ratio and strain curves, and the greater the confining pressure, the lower is thestress ratio versus strain curves, the smaller the peak stress ratio. The volume changeduring shearing which is at a larger confining pressure tends to be shear contraction.Under the condition of the same confining pressure, void ratio has little influenceupon the stress ratio versus strain curves, and has an obvious effect on volumechange. The greater the initial void ratio, the bigger is the volume contraction.3、To study the swelling behaviour, the tests for soaking swelling deformation and the swelling pressure test have be conducted by using oedometer. The resultsshow that the swelling rate due to soaking decreases with the increases in theoverburden and the initial water content, and increases with the increase in the initialdry density. A linear relationship between void ratio and the logarithmic ofoverburden load at full saturation is found. Swelling pressure increases with theinitial void ratio and has a good linear relationship with the initial void ratio.4、In order to investigate soil-water characteristic Curve (SWCC) of Huai-anexpensive soil, three different suction control or measurement methods are used. Thepressure plate method is used for low suction, while the filter paper method and thevapor equilibrium technique are used for high suction. The results show that thesoil-water characteristic Curve (SWCC) has obvious hysteresis phenomenon duringdrying and wetting circle in the low suction range. When the suction is greater than100MPa, the hysteresis effect of SWCC disappears, and the drying and wettingcurves are almost the same. Test data of SWCC by the filter paper method arelocated between the main drying and wetting SWCCs. The tendency of SWCC in thehigh suction by the vapor equilibrium method shows that the water content almostequals to zero when the suction closes to1000MPa. According to the result ofexpensive soils by the filter paper when SWCC expressed by water content versussuction relation, the SWCCs are almost same and the dry density has no effect on theSWCC. When SWCC expressed by the degree of saturation versus suction relation,the SWCC with higher dry density is located at the upright side in the relatively lowsuction range and the dry density has little effect on the SWCC in the relatively highsuction range.