The excavation of a circular tunnel in a bedded argillaceous rock (Opalinus Clay): Short-term rock mass response and FDEM numerical analysis

被引:151
作者
Lisjak, A. [1 ,2 ]
Garitte, B. [3 ]
Grasselli, G. [1 ]
Mueller, H. R. [3 ]
Vietor, T. [3 ]
机构
[1] Univ Toronto, Dept Civil Engn, Toronto, ON M5S 1A4, Canada
[2] Geomechanica Inc, Toronto, ON M5H 3V9, Canada
[3] Natl Cooperat Disposal Radioact Waste NAGRA, CH-5430 Wettingen, Switzerland
基金
加拿大自然科学与工程研究理事会;
关键词
Excavation damaged zone; Numerical modelling; FDEM; Brittle failure; Clay shales; Mechanical anisotropy; Instrumentation; TIME-DEPENDENT BEHAVIOR; DAMAGED ZONE; DISTURBED ZONE; DEEP TUNNELS; SLIP ZONES; SWITZERLAND; DEFORMATION; SIMULATION; FRACTURES; STRESSES;
D O I
10.1016/j.tust.2014.09.014
中图分类号
TU [建筑科学];
学科分类号
0813 ;
摘要
The Opalinus Clay formation is currently being investigated as a potential host rock for the deep geological disposal of radioactive waste in Switzerland. Recently, a test tunnel was excavated at the Mont Terri underground rock laboratory CURL) as part of a long-term research project ("Full-scale Emplacement (FE) experiment") aimed at studying the thermo-hydro-mechanical (THM) effects induced by the presence of an underground repository. The objective of this paper is twofold. Firstly, the results of the rock mass monitoring programme carried out during the construction of the 3 m diameter, 50 m long FE tunnel are presented, with particular focus on the short-term deformation response. The deformation measurements, including geodetic monitoring of tunnel wall displacements, radial extensometers and longitudinal inclinometers, indicate a strong directionality in the excavation response. Secondly, the deformational behaviour observed in the field is analyzed using a hybrid finite-discrete element (FDEM) analysis to obtain further insights into the formation of the excavation damaged zone (EDZ). The FDEM simulation using the Y-Geo code is calibrated based on the average short-term response observed in the field. Deformation and strength anisotropy are captured using a transversely isotropic, linear elastic constitutive law and cohesive elements with orientation-dependent strength parameters. Overall, a good agreement is obtained between convergences measured in the field and numerical results. The simulated EDZ formation process highlights the importance of bedding planes in controlling the failure mechanisms around the underground opening. Specifically, failure initiates due to shearing of bedding planes critically oriented with respect to the compressive circumferential stress induced around the tunnel. Slippage-induced rock mass deconfinement then promotes extensional fracturing in the direction perpendicular to the bedding orientation. The simulated fracture pattern is consistent with previous experimental evidence from the Mont Terri URL. (C) 2014 Elsevier Ltd. All rights reserved.
引用
收藏
页码:227 / 248
页数:22
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