Study On Tensile Strength Properties Of Unsaturated Silty Sand

Soil tensile failure is a problem that can not be ignored in the field of geotechnical engineering. However, compared with soil’s shear strength, its value of tensile strength is relatively small, so it is generally believed that the soil can not withstand tensile tensile stress. In addition, due to the relative difficulty of the tensile strength test measurements, its research is less at home and broad, and relevant research literature is also relatively scarce. In recent years, with vigorous development of China’s economy, construction of roads, airports, dams and subways are rising increasingly, there will be a higher requirements for tensile capacity and crack resistance of builidings or structures, more and more engineering problems concerning the tensile strength of soil are presented, such as gound fracturing, core wall cracking, hydraulic fracture. Therefore, the research on tensile behaviors of soil not only helps to complete the theory of soil strength, but also to solve the complicated actual geotechnical problems.This paper takes the unsaturated silty sand as research object, using the self-developed soil tensile strength testing apparatus, applying the method of constant speed to carry out systematic research work for unsaturated silty sand, developing experimental research of tensile strength of unsaturated soils under different conditions of initial dry density and water cotent, proposing the tensile strength model of unturated soils based on this research, and using finite element program to carry out numerical simulation and analysis for indoor tensile strength experiments.The main results of this paper are as follows:1. Developing independently the tensile strength experimental device of unturated soils to carry out tensile strength test of unsaturated soils on different initial condtions. Applying this test apparatus to carry out tessile strength testing of unsaturated silty sand on different conditions of initial dry density and initial water content, obtaining tension force-time curve、displscement-time curve、tension force-displacement curve and tensile stress-strain of unsaturated silty sands under tension force under specific condition, finally obtaining tensile strength-moisture curve under conditions of different dry density based on above test results.2. Based on the test findings, revealing the evolution law of tensile strength of unsaturated silty sands with dry density and water content, and furtherly basing on the evolution of the internal microstructure of the soil, analyzing and obtaining the microscopic mechanism of the evolution of tensile strength. On this basis proposing a prediction model of unsaturated soils which can be considered the effect of dry density and water content, and using test results to verify the validity and applicability of this model.3. Based on the finite element analysis software ABAQUS, carrying out finite element simulation and analysis for tensile strength test of untaturated soil, through modeling above indoor tensile strength test, calculating and analyzing the stress distribution and stretching deformation after pulling force, and compare calculated results and experimental results, thus furtherly verifying the evolution law and mechanism of tensile strength of unsaturated soils.