Research Progress on Key Issues of Shear Strength Theory and New Testing Technology of Roadway Crossing Unsaturated Soil Layer

Abstract

By studying the relationship between the shear strength and water content of unsaturated soil, summarizing and analyzing the previous methods of preparing soil samples with different water content, it is found that the test phenomenon of "critical water content" exists in the specific gravity method. The research shows that the shear strength of unsaturated soil is the result of the common action of compactness and water content. Nine widely used shear strength measurement methods of unsaturated soil are sorted out, and their common shear test methods are divided into three categories, namely direct shear test method, compression shear test method and rotary shear test method. The advantages and disadvantages of each method are analyzed. Many shear strength formulas are divided into four categories: combined water-soil characteristic curve, piecewise function, mathematical fitting and total stress index. The characteristics and shortcomings of shear strength of different kinds of unsaturated soil are compared, and some suggestions on the theoretical research direction of shear strength in the future are put forward. Finally, a variety of new ideas and methods for studying the shear strength theory of unsaturated soil are introduced. This paper improves the theoretical basis of unsaturated soil, which is of great significance to speed up the engineering practice of shear strength theory of unsaturated soil.