Influence Of Matrix Suction Of Soil On Safety Of Loess Slope And Loess Foundation Pit

Based on existing achievement in research on the shear strength of unsaturated loess, the paper discussed the influence of matrix suction for the stability of unsaturated loess slope, and theoretically deduced the influence of matrix suction; and then use the BISHOP method to calculate the stability of loess slope under different matrix suction. The conclusion reflected that matrix suction has obvious influence on the stability of unsaturated loess slope; with the increase of matrix suction the stability of loess slope increases obviously; and in the extend of low matrix suction the change is more notable.The paper mainly studied the influence of matrix suction toward the calculation for the excavation-supporting system. Firstly deduced the Rankine soil pressure theory for the unsaturated loess area on the basis of the statistical rule of the shear strength of unsaturated loess; and took the calculation method for pile supporting system which the country specification recommended, then use the calculation program for pit supporting system of LIZHENG institute to calculate the maximal moment, the maximal shear , the total active soil pressure of the supporting structure and the moving of the excavation under different matrix suction. The outcome reveals that: matrix suction has great effect on the maximal moment, the maximal shear , the total active soil pressure of the supporting structure and the moving of the excavation of unsaturated loess. When the matrix suction increases, matrix suction has great effect on the maximal moments the maximal shear , the total active soil pressure of the supporting structure and the movingof the excavation have decreased obviously; when matrix suction is under the relatively low class(0~200kPa), the above values change more obviously; matrix suction affects the moment of the supporting system most obviously. The paper compare with the maximal moment, the maximal shear , the total active soil pressure of the supporting structure and the moving of the excavation under two common distribution form of matrix suction(which is constant-distribution and inverse-delta distribution), and the outcome reveals that: if the same matrix suction of the surface soil layer is identical, the maximal moment , the maximal shear , the total active soil pressure of the supporting structure and the moving of the excavation under matrix suction of constant-distribution are obviously less than the value of which under inverse-delta distribution.The above study outcome can help the geotechnical engineer to realize the notable influence of matrix suction toward the stability of loess slope, the stress of the supporting structure and the moving of the excavation.