Closure to 'Analysis and Design Method for Slope Stabilization Using a Row of Drilled Shafts' by Robert Y. Liang, Arash Erfani Joorabchi, and Lin Li

摘要

The writers would like to thank the discussers for their interest in the paper and raising important issues concerning the analysis and design methodology for using a row of drilled shafts in stabilizing a slope. The writers would like to comment or further address a few issues brought up by the discussers in their discussion. 1. For the limit equilibrium procedures, there are currently several existing methods to calculate the factor of safety for a slope. Each procedure has different assumptions, which would necessarily lead to different results. In addition, the resulting factor of safety would be very sensitive to various side force assumptions. The writers agree with the discussers that the assumptions of the proposed procedure are indeed different from those used in any of the existing procedures. In the current version (version 2.1) of the UA Slope program, the force equilibrium procedure has been employed to calculate the factor of safety, instead of using both the force equilibrium procedure and moment equilibrium procedure. Meanwhile, the distributed force between two slices is assumed to be approximately similar to a triangular distribution instead of a uniform distribution. Therefore, the writers assume that the interslice net force is at one-third height above the slice bottom. To perform the validation of the proposed procedure, the results obtained from UA Slope 2.1 have been compared with results from a finite-element analysis, which are shown in Figs. 12 and 13 of the original paper. Additionally, the writers have compared the factor of safety by using both the SLOPE/W program (an early version of the slope program that was created in Geo-Slope International 2007) and UA Slope 2.1. Table 1 shows a comparison of the results. Obviously, the computed factor of safety exhibits sensitivity on the basis of different assumptions employed in each method. For example, the factor of safety using Morgenstern-Price's procedure is 0.845, which is larger than the value obtained from the ordinary method of slices procedure, i.e., 0.794. However, the writers do not necessarily imply that Morgenstern-Price's procedure overestimates the factor of safety more than the ordinary method of slices or produces results on the unsafe side. The factor of safety is indeed sensitive to different assumptions, but currently, there is no ideal or perfect assumption dealing with the limit equilibrium procedure in slope stability analysis. Therefore, the writers suggest using more than one slope stability program during the analysis for a practical slope.