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Geofluids
Volume 2017 (2017), Article ID 9010572, 12 pages
https://doi.org/10.1155/2017/9010572
Research Article

A Numerical Investigation on the Effect of Gas Pressure on the Water Saturation of Compacted Bentonite-Sand Samples

1State Key Laboratory for Geomechanics and Deep Underground Engineering and School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China
2State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, Sichuan 610059, China
3CNNC Beijing Research Institute of Uranium Geology (BRIUG), Beijing 100029, China
4Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China, China University of Mining and Technology, Xuzhou 221116, China
5Laboratoire de Mécanique de Lille (CNRS, LML) and École Centrale de Lille, CS 20048, 59651 Villeneuve-d’Ascq Cedex, France

Correspondence should be addressed to Jiang-Feng Liu; moc.liamtoh@uilfaej and Bing-Xiang Huang; moc.kooltuo@tmucxbgnauh

Received 8 June 2017; Revised 19 September 2017; Accepted 8 October 2017; Published 27 December 2017

Academic Editor: Qinghui Jiang

Copyright © 2017 Jiang-Feng Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In deep geological disposal for high-level radioactive waste, the generated gas can potentially affect the sealing ability of bentonite buffers. There is a competition between water and gas: the former provides sealing by swelling bentonite, and the latter attempts to desaturate the bentonite buffer. Thus, this study focused on numerically modelling the coupling effects of water and gas on the water saturation and sealing efficiency of compacted bentonite-sand samples. Different gas pressures were applied to the top surface of an upper sample, whereas the water pressure on the bottom side of the lower sample was maintained at 4 MPa. The results indicated that gas pressure did not significantly affect the saturation of the bentonite-sand sample until 2 MPa. At 2 MPa, the degree of water saturation of the upper sample was close to 1.0. As the gas pressure increased, this influence was more apparent. When the gas pressure was 6 MPa or higher, it was difficult for the upper sample to become fully saturated. Additionally, the lower sample was desaturated due to the high gas pressure. This indicated that gas pressure played an important role in the water saturation process and can affect the sealing efficiency of bentonite-based buffer materials.