The Strength Of Weak Cemented Sand Affected By Matric Suction And The Slope Instability Of Sand Inrush

In this paper, under the conditions of the sand inrush in mining, the strength of weak cemented sand and the instability of sand inrush are analyzed by the method of indoor experiments, model tests and theoretical derivation. Results are listed as following.(1) According to the basic physical properties and disintegration test of undisturbed soil samples, and strength test of reconstituted soil, the strength of weak cemented sand under the dry and water-rich conditions has great varieties. Meanwhile, with the increase of water content, the strength of weak cemented sand decreased sharply, and the strength of weak cemented sand was significantly increased with the increase of clay content.(2) Matrix suction, net normal stress and grain composition were selected as control variables. With the direct shear apparatus for unsaturated soils, the shear strength of weak cemented sand was tested. It is found that the three variables were positively correlated with shear stre ngth of weak cemented sand from the test. The results show that the weight of the matrix suction on shear strength is 0~40%, and the greater the matrix suction is, the greater the weight of the matrix suction on shear strength is.(3) The dry density, clay content and water content were selected as control variables. With the filter paper method, matrix suction was test. And the characteristic curve of the matrix suction of weak cemented sand under different conditions was obtained. It can be concluded that saturation is negatively correlated with the matrix suction; dry density is positively correlated with the matrix suction, but the overall effect is not significant; while the clay content has a great influence on the matrix suction, and it has a positive correlation.(4) By the simulation test of weak cemented sand during sand inrush, it is can be found that in the process of sand inrush, the upper part of sand inrush fissures will form a funnel, and the sand above water level will form a vertical cliff, both of which will form a near vertical angle. An expression for the relationship between the strength of weak cemented sand with matrix suction and the angle was established by the mechanical analysis of soil strip element.