Analysis Method for Drilled Shaft–Stabilized Slopes Using Arching Concept

Abstract

The use of drilled shafts to stabilize an unstable slope has gained popularity in highway applications, mainly because it is a structural fix that does not require additional right-of-way. An analysis method for determining the factor of safety of a drilled shaft or slope system and for determining the earth thrust on the drilled shafts for structural design is introduced. The concept of the analysis is cast in the limiting equilibrium approach via the method of slices, while incorporating the drilled shaft–induced arching effects as the soil mass moved downslope and around the drilled shafts. The mathematical equations based on the limiting equilibrium calculation, together with the load transfer factor for accounting for the drilled shaft–induced arching effects, are presented. The three-dimensional finite element model parametric study using ABAQUS program was used to derive the semiempirical equations for quantifying the arching effect. A UASLOPE computer program was written to incorporate these algorithms for applications to real cases. A case study of a fully instrumented and monitored slope stabilization project, ATH-124, in Ohio, is presented. The analysis of the slope at the project site using finite element modeling and the computer code UASLOPE is presented, together with field-monitored data. On the basis of field monitoring data and the comparison between the finite element analysis results with the computer code UASLOPE results, the suggested analysis and design approach appears to be reasonable.

Reliability‐based design for slopes reinforced with a row of drilled shafts

“…In addition to the comparisons between the UASLOPE computational results and the FEM simulation results for 41 cases, a comparison was made with a full-scale field study at the Ohio ATH-124 Project site. Details of comparisons can be referred to Liang et al [8,17], in which computational results of UASLOPE and ABAQUS are compared with field test results at different stages of slope movement. A good result, shown in Table II, for the computed FS and the resultant forces based on the two methods of UASLOPE and ABAQUS FEM analysis was obtained for the ATH-124 Project.…”

“…To quantify the soil arching effects and the load transfer factor in a drilled shaft/slope system, Al‐Bodour constructed a baseline 3‐D FE model using abaqus program (version 6.7‐1) for studying the soil structure interaction behavior of the drilled shafts on a slope under the effect of shear strength reduction method. The strength reduction method in FE simulation was first proposed by Zienkiewicz to study the slope stability problem.…”

“…Details of comparisons can be referred to Liang et al . , in which computational results of UASLOPE and abaqus are compared with field test results at different stages of slope movement. A good result, shown in Table , for the computed FS and the resultant forces based on the two methods of UASLOPE and abaqus FEM analysis was obtained for the ATH‐124 Project.…”

Reliability-Based Optimization Design for Drilled Shafts/ Slope System (DFI Student Paper Competition 2012)

“…where S 0 is the model thickness (distance between center to center of two adjacent drilled shafts), L f is the distance from the top of the shaft down to the failure surface, σ xx is S 11 which denotes the horizontal soil stresses on the up-slope side of the shaft, and σ′ xx is S′ 11 which denotes the horizontal soil stresses on the down-slope side of the shaft. Joorabchi (2011) has proposed a semi-empirical equation, given in Eqn.…”

“…of is 1.01 and 0.15, respectively. As indicated in the following expression, the load transfer factor can be randomly generated through the randomly generated bias: [11] where, is the randomly generated load transfer factor; is the randomly generated bias of load transfer factor; and are the randomly generated soil cohesion and friction angle, respectively; β, D, ξ x and S 0 are considered as deterministic parameters.…”