The Research on Strength and Deformation Behaviors of Buffer/Backfill Material under High-Temperature and High-Pressure Conditions

Hao Chen,Yu-Han Li,Hai-Bo Lv,Zheng-Han Chen

doi:10.1155/2019/5064690

Hao Chen, Yu-Han Li + Show 2 more

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https://doi.org/10.1155/2019/5064690

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Abstract

By using the high-temperature and high-pressure triaxial apparatus, 81 undrained triaxial shearing tests of GMZ bentonite were carried out, and the effects of temperature, confining pressure, water content, and dry density on the deformation and strength characteristics of GMZ bentonite were systematically analyzed. Five results are presented in this paper: (1) confining pressure and dry density have a great influence on the failure forms of GMZ bentonite; under the nonconfined pressure condition, the failure forms of the specimen are brittle failure, and it is the same with high dry density, but the specimens with low dry density and high confining pressure exhibit plastic failure; (2) the strength of GMZ bentonite decreases with increasing water content; the position of the deviator stress-axial strain curve under low dry density rises with the increase of temperature, whereas the location of the curve under high dry density decreases with the rise of temperature; (3) initial Young’s modulus rises with increasing temperature under low dry density, but it is on the contrary under high dry density; with rising water content, initial Young’s modulus generally decreases; (4) Poisson’s ratio rises with rising temperature. The effect of dry density and water content on Poisson’s ratio is insignificant; and (5) the formulae of cohesion and internal friction angle of GMZ bentonite with the changing dry density, water content, and temperature are proposed, respectively. The research results of this paper provide a scientific basis for analyzing the thermo-hydro-mechanical coupling characteristics of buffer materials.

Highlights

With the continuous development of China’s nuclear industry, the stock of spent fuel in the nuclear power station is becoming larger and larger, which has become the main source of high-level radioactive waste in China [1]
Deep geological disposal of radioactive waste in spent fuel is considered worldwide as the best way to protect human beings and the environment. e bentonite is considered as the ideal buffer/backfill material to fill the gap between bedrock and packaging container which contains the radioactive waste
Over the past few decades, a number of research studies have been done on the behaviors of bentonite at room temperature. e swelling behaviors and unconfined compression performance of GMZ bentonite have been studied by Liu et al [2, 3]

Summary

Introduction

With the continuous development of China’s nuclear industry, the stock of spent fuel in the nuclear power station is becoming larger and larger, which has become the main source of high-level radioactive waste in China [1]. Due to the high-level radioactive waste continuing to generate heat and the deep buried depth, the temperature which bentonite suffers will be as high as 100°C [15]; when the bentonite is immersed in groundwater, it will generate an expansion pressure up to 2 MPa [16]. In this complex environment, the behaviors of bentonite are different from those at room temperature.

Experimental Investigation

Experimental Results

Conclusions