Numerical Study of Soil Arching Mechanism in Drilled Shafts for Slope Stabilization

Abstract

One of the main mechanisms of drilled shafts in enhancing the stability of the soil slope is through soil arching, in which the interslice forces transmitted to the soil slice behind the shafts are reduced. This paper presents a finite element analysis technique for quantitatively studying the soil arching mechanisms associated with the drilled shafts stabilized soil slope. The modeling techniques and the constitutive relationships of the soils are described in detail. By performing a series of numerical studies, the load transfer characteristics due to soil arching are quantified for both cohesive and cohesionless soils. Among the parameters investigated, the ratio of shaft spacing, 5, to the shaft diameter, d, was found to exert the greatest influences on the development and intensity of soil arching. Practical design tables have been developed to relate the arching-induced stress transfer to the s/d ratio, shaft diameter, and soil strength parameters. It was found that the smaller the s/d ratio and the higher friction angle of cohesionless soils, the more soil stresses are being transferred to the drilled shafts due to soil arching. The cohesive soils have greater tendency for soil arching as shown by a small cohesion value needed for fully developing the soil arching. The propensity of cohesive soils to creep may negate the arching to some extent.