Application of the Borehole Shear Test to Loess Slope

Abstract

It is a fundamental and important task to accurately determine the shear strength parameters of soil in the engineering design of slopes. In this study, an in-situ test method called Borehole Shear Test (BST) was applied for the first time to obtain the shear strength parameters of loess slope. Based on the improved Iowa borehole shear instrument, this paper aims at proving the applicability of BST to loess slope, and revealing the testing principles and influencing factors of normal stress and consolidation time to BST. The results show that the normal stress is proportional to displacement, which indicates that the soil is elastic deformations stage. To ensure the reliability of the results, the time for consolidation under the first stage of normal stress should be greater than 10 min while in the subsequent steps, the consolidation time should be no less than 5 min. The shear stress-displacement curves have obvious peak values and exhibit a general strain-softening type. The shear strength parameters determined have good correlation overall and the corresponding correlation coefficient is greater than 0.98. In general, the borehole shear test shows a good performance on the determination of the shear strength parameters of loess, which provides valuable guidance for slope design and future study.