Mont Terri试验场Mine-by巷道开挖近场响应模拟分析

 瑞士Mont Terri地下实验室于2008年构建Mine-by(MB) Niche巷道，并围绕其中的MB Niche 2进行开挖诱发Opalinus Clay黏土岩围岩变形及流固耦合特征的现场实测分析。以MB Niche 2巷道为背景工程，利用基于双应变胡克模型(TPHM)的数值模拟方法，对MB Niche 2巷道的开挖过程进行模拟分析，计算结果较为准确地反映开挖卸载诱发的近场围岩变形行为、损伤区及孔隙水压力演化特征。模拟结果显示，巷道拱顶径向位移可达甚至超过10 mm，两帮破坏深度可达1.4 m，孔隙压力的扰动区最远可出现在掌子面前方11 m左右，最大孔隙压力可抬升至3.3 MPa，模拟结果与现场实测值表现出较好的一致性。基于双应变胡克模型TPHM的计算结果较基于传统胡克模型SPHM的计算结果更趋于符合实际，这在一定程度上反映出TPHM较好地捕捉到岩石中孔隙、裂隙等的自然应变(真应变)的物理本质，强调合适的本构模型在卸荷开挖工程问题模拟分析中的重要性。

NUMERICAL INVESTIGATION ON NEAR FIELD RESPONSE TO EXCAVATION OF MINE-BY NICHE AT MONT TERRI SITE

In 2008，the Mine-by(MB) Niches were constructed in Mont Terri underground rock laboratory. One of niches，MB Niche2，was selected to investigate the deformation and the coupled hydro-mechanical behavior of the Opalinus clay near excavation. Based on the engineering geological conditions of MB Niche2，a geomechanical simulator incorporating the two-part Hooke?s model(TPHM) was employed to simulate the excavation process of MB Niche2. Numerical results show that near the roof of Niche recorded a maximum of 10 mm of inward movement. Near sidewalls，the damage zone developed up to an average distance of 1.4 m into the rock matrix. Pore pressure increase became visible at about 11 m ahead of the mine-by excavation face. With niche advancing，the zones with local higher pore pressure are mainly found near the edge of the damage zones. The maximum pore water pressure reaches about 3.3 MPa near the advancing face of excavation. Compared with those based on the conventional Hooke?s law(SPHM)，the results based on TPHM are more consistent with the field data sets，which indicates to some extent that TPHM can better capture the physical nature of natural strain(true strain) in porous and fractured rocks and highlights the importance of having appropriate conceptual and numerical models available that accurately capture the complex coupled behavior in response to excavation.