Abstract

Continuous field monitoring during drifts excavation at the Meuse/Haute-Marne Underground Research Laboratory showed anisotropic hydromechanical responses, which are mainly evidenced in: (1) pore pressure field around the drifts with zones of marked overpressure; (2) the development of a dissymmetrical fractured zone induced by the excavation. These observations suggest that in addition to the initial stress state, the inherent anisotropy of the Callovo-Oxfordian claystone plays a key role in the response of rock formation. Numerical modelling show that inherent elastic anisotropy is not adequate to fully explain the pore pressure evolution during excavation. This paper aims to show and explain qualitatively and quantitatively the main trends of the excavation induced pore pressure evolution around drifts. First, a qualitative analysis is performed, based on a closed-form solution of elastic fields around an elliptical opening (in order to simulate fractured zone shape), embedded in a transversely isotropic rock. Then, a coupled poro-elasto-plastic analysis is performed, by taking into account a perfect poro-elasto-plastic behavior for both the intact rock and the induced fractured zones with different plastic parameters. It is shown that upon the determination of extension and shape of fractured zone, overpressures induced by the excavation can be well reproduced.

摘要

Meuse/Haute-Marne 地下研究实验室在巷道开挖过程中进行的连续现场监测显示出各向异性的流体力学响应，主要表现为：（1）巷道周围的孔隙压力场具有明显的超压区域；(2)开挖诱发的不对称破碎带的发育。这些观察表明，除了初始应力状态外，Callovo-Oxfordian 粘土岩的固有各向异性在岩层响应中起着关键作用。数值模拟表明，固有弹性各向异性不足以完全解释开挖过程中的孔隙压力演变。本文旨在定性和定量地展示和解释开挖引起的巷道周围孔隙压力演变的主要趋势。第一的，基于嵌入横向各向同性岩石中的椭圆形开口（以模拟断裂带形状）周围的弹性场的闭合形式解，进行了定性分析。然后，通过考虑完整岩石和具有不同塑性参数的诱导断裂带的完美孔隙弹塑性行为，进行孔隙弹塑性耦合分析。结果表明，通过确定破碎带的延伸范围和形状，可以很好地再现开挖引起的超压。通过考虑完整岩石和具有不同塑性参数的诱导断裂带的完美孔弹塑性行为。结果表明，通过确定破碎带的延伸范围和形状，可以很好地再现开挖引起的超压。通过考虑完整岩石和具有不同塑性参数的诱导断裂带的完美孔弹塑性行为。结果表明，通过确定破碎带的延伸范围和形状，可以很好地再现开挖引起的超压。