Experimental Study on Shear Strength Parameters of Soil in Borehole Wall under Slurry Supporting Construction

摘要

Slurry supporting is an effective measure to avoid the borehole collapse in the process of boring construction. Based on the indoor slurry-supported models, this paper has analyzed change law of shear strength of borehole wall with time by using indoor direct shear test. The following conclusions has been obtained through experiment: 1. with the progressive increase of exposure time of side wall soil to the mud, the water content is first increased quickly, then increased slowly; 2. the internal friction angle of side wall soil is first decreased then increased, and tends to be decreased slowly with the passage of time; 3. as the exposure time of soil in the borehole wall to the mud is longer, the cohesion force is smaller, and tends to be first decreased sharply at the earlier stage and then decreased slowly. In the process of slurry supporting construction, the special attention should be paid to the situation that internal friction angle of the soil in the borehole wall is rapidly reduced within a short period of time, and the construction period should be reduced as far as possible so as to avoid the phenomenon of borehole collapse caused by the reduction of cohesive force.