Study On The Influence Of Surface Infiltration On The Strengh Of Expansive Soil In Hefei Area

Expansive soil is a kind of clay with high plasticity, which features are swelling by absorbing water and shrinking by losing water. After the surface of the expansive soil was infiltrated by water, its water content will increase. And then it will result in the volume increase and attenuation in the shear strength index of the expansive soil.Expansive soil distribute widely in Hefei, and with the development of the city, the underground space is currently developing efficiently because of the limited space. A lot of constructions of underground structure are constructed in expansive soil layer. During the construction, the surface of the expansive soil must be infiltrated. In order to provide the research basis for the scientific design, the reasonable and safe construction of the underground structure engineering and test the shear strength index indoor after the attenuation, it was necessary to research the principle of the variations of moisture content after the expansive soil was infiltrated by water and the attenuating range of the strength index. Therefore, it has the practical significance for the study about the change of the strength after the surface of the expansive soil was infiltrated by water in Hefei.In this essay, soil samples are all undisturbed soil samples, taken from the same level of soil at the same deep foundation pit. In order to research the principle of the variations of moisture content after the expansive soil was infiltrated by water, soil samples needed to be infiltrated at different times, their water content after infiltrating needed to be measured and the relation curve between the water content and the infiltrating time needed to be drew. The results showed that the increase of their water content could be divided into three stages:rapid growth, slow growth and basic stabilization. But the increase of their water content was relatively gentle after the surface of the expansive soil was infiltrated by cement slurry. In order to simulate the engineering condition, the soil samples needed to be infiltrated by water and cement slurry. At the same time, the surface of the soil sample should be brushed the cement slurry and then infiltrated them to test the water-blocking effect.Through the infiltration case, the relationship between water content and infiltrating time were gotten. Considering the different time the underground structure construction infiltrated by water, the soil samples with three different results of their water content change after infiltrating needed to be used to do the shear test to get the expansive soil strength index and provide soil strength parameters for a reasonable infiltration time.