Experimental Study on Cracking Behaviour and Strength Properties of an Expansive Soil under Cyclic Wetting and Drying

Tao Li,Guokun Liu,Yanqing He,Binru Li,Rui Hou,Erkan Oterkus

doi:10.1155/2021/1170770

Abstract

Expansive soil is characterized by its unique structural morphology and drastic volume change. With infrastructure increasingly constructed in expansive soil areas, engineering problems caused by the properties of expansive soils have attracted more attention. Cyclic wetting-drying and shear testing were accordingly conducted on an expansive soil from Chengdu area in China. Crack development and shear strength change were analyzed using the Mohr–Coulomb equation for shear strength by fitting the experimental data. The results show the following: (1) With the increase in wetting-drying cycles, the crack ratio increases, the shear strength decreases, and the shear strength parameters gradually decrease at the same rate of change. The applied vertical load reduces the weakening effect of the wetting-drying cycles on the soil structure and strength by restraining the expansion and contraction deformation. (2) By analyzing the number of wetting-drying cycles and the crack images, the crack development (length, direction, etc.) of the expansive soil can be predicted and described. (3) There is a specific linear correlation between the crack ratio and strength that approached a limit value with ongoing wetting-drying cycles. The strength of the expansive soil can therefore be obtained based on crack development, improving the ability of designers to account for the behaviour of expansive soils.

Highlights

(2) By analyzing the number of wetting-drying cycles and the crack images, the crack development of the expansive soil can be predicted and described. (3) ere is a specific linear correlation between the crack ratio and strength that approached a limit value with ongoing wetting-drying cycles. e strength of the expansive soil can be obtained based on crack development, improving the ability of designers to account for the behaviour of expansive soils
Microscopic deformation is reversible under certain circumstances, while the degree of reversibility of macroscopic deformation is related to the amount of deformation of the expansive soil when subjected to wettingdrying cycles [10]
According to the theory of unsaturated soil strength established by Gili and Alonso [11] and the Mohr–Coulomb theory, two important parameters, the internal friction angle and cohesion of the expansive soil, were obtained from the direct shear test to provide a basis for analysis

Summary

Introduction

Expansive soils have unstable engineering properties, which result in easy expansion when absorbing water and easy contraction when losing water. is volume sensitivity is typically manifested under circumstances of natural rainfall and evaporation. e volume of expansive soil gradually increases when subjected to these cycles over a long period of time. is deformation can cause damage to constructed facilities such as cutting landslides, roadbed rise, embankment collapse and sinkage, uneven building settlement, and cracking, resulting in immeasurable economic loss [1, 2]. erefore, research on the effects of alternating wetting-drying cycles on the expansive soil is especially necessary for improving engineering design.e main reason for cracking inside expansive soils is the application of natural wetting-drying cycles, and the existence and development of such cracks inside expansive soils have an important influence on soil strength and side slope stability [3]. Expansive soils have unstable engineering properties, which result in easy expansion when absorbing water and easy contraction when losing water. Erefore, research on the effects of alternating wetting-drying cycles on the expansive soil is especially necessary for improving engineering design. Some research has shown that the strength properties of expansive soil are influenced by the clay mineral type and content, plasticity index, free swell index, matric suction, water content, cracks, degree of compaction, dry density, and load [4,5,6,7,8,9]. Microscopic deformation is reversible under certain circumstances, while the degree of reversibility of macroscopic deformation is related to the amount of deformation of the expansive soil when subjected to wettingdrying cycles [10]. Gili and Alonso [11] constructed a basic microscopic model of unsaturated expansive soil, leading to further investigations of expansive soil with an emphasis on

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Conclusion