Triaxial Wetting Test on Rockfill Materials under Stress Combination Conditions of Spherical Stress p and Deviatoric Stress q

Yan-Yi Zhang,Xiao-Hui Wang,Yan-Feng Wen,Shu Yu,Ze-Ping Xu,Gang Deng

doi:10.1155/2018/9853148

Abstract

A GCTS medium-sized triaxial apparatus is used to conduct a single-line method wetting test on three kinds of rockfill materials of different mother rocks such as mixture of sandstone and slate, and dolomite and granite, and the test stress conditions is the combination of spherical stress p and deviatoric stress q. The test results show that (1) for wetting shear strain, the effects of spherical stress p and deviatoric stress q are equivalent, and wetting shear strain and deviatoric stress q show the power function relationship preferably. (2) For wetting volumetric strain, the effect of deviatoric stress q can be neglected because it is extremely insignificant, and spherical stress p is the main influencing factor and shows the power function relationship preferably. (3) The wetting strains decrease significantly with the increase in initial water content and sample density generally, but the excessively high dry density will increase the wetting deformation. Also, the wetting strains will decrease with the increase in the saturated uniaxial compressive strength and average softening coefficient of the mother rock. Based on the test results, a wetting strain model is proposed for rockfill materials. The verification results indicate that the model satisfactorily reflects the development law of wetting deformation.

Highlights

During the impounding process of core-wall rockfill dam, the rockfill materials of upstream dam shell usually experience the transition from “dry” to “wet.” erefore, materials will be softened to a certain extent. e contact parts of the particles may be fragmented, the internal structure of rockfill body may be adjusted
Based on the test results, a wetting strain model is proposed for rockfill materials. e verification results indicate that the model satisfactorily reflects the development law of wetting deformation
In accordance with the combination of spherical stress p and deviatoric stress q designed in the test, the stress conditions included ve spherical stress p conditions, each corresponding to 3–5 deviatoric stress q conditions. e stress conditions of the test and corresponding wetting deformation results are shown in Table 2. e dry density of the test sample is 2.18 g/cm[3], the test materials are air-dried, and the water content of test rock ll materials whose maximum size is equal to 5 mm is 0.4%

Summary

Introduction

During the impounding process of core-wall rockfill dam, the rockfill materials of upstream dam shell usually experience the transition from “dry” to “wet.” erefore, materials will be softened to a certain extent. e contact parts of the particles may be fragmented, the internal structure of rockfill body may be adjusted. E contact parts of the particles may be fragmented, the internal structure of rockfill body may be adjusted. It will eventually produce significant wetting deformation which may cause local collapsibility and threatens the dam safety. In single-line wetting tests, the stress conditions are usually adopted: the combination of confining pressure σ3 and stress level Sl, and the wetting model usually expressed as a function of confining pressure σ3 and stress level Sl. the impoundment process of the dam is usually accompanied by the simultaneous changes with confining pressure σ3 and stress level Sl. As Shen analysed [17] (Figure 1), during the rise of water level, the spherical stress of upstream dam shell rockfill materials clearly decreases, the deviatoric stress slightly changes, and the stress level increases. Volumetric strain εv and shear strain εs Advances in Materials Science and Engineering τ (kPa) Percentage passing (%)

Methods

Results

Conclusion