Impact of shear induced pore pressures on the ground deformations around underground openings in weak shales

拥有泥质地层的国家一直在研究这些岩石，以评估它们处理核废料的潜力。在加拿大，核废料管理组织（NWMO）已经提交了一份许可证申请，在安大略省布鲁斯场址的富含粘土的沉积岩中，在680米深处建造一个低水平和中等水平的核废料储存库，而泥质地层仍然是处置乏核燃料的可能目标。在瑞士，Nagra已经开始了一项广泛的现场调查计划，以表征蛋白石粘土。在法国，Andra选择了Callovo-Oxfordian地层进行放射性废物处理表征。核废料工业要求对耦合地质力学过程有充分的了解，以便进行工程设计。在这些泥质地层中，地质力学过程是一个复杂速率和耦合现象的函数。为了验证我们对这些耦合过程的理解，将进行现场测量和广泛的实验室测试，以确定适用于储存库设计的相关地质力学过程。在泥质岩石中，必须测量孔隙压力，以解释地下储存库环境中遇到的机械和热载荷期间的基本行为。这种环境创造了独特的边界条件，有可能在长距离的局部区域产生非常大的孔隙压力。这种孔隙压力必须在储存库的设计中加以量化和考虑。本研究有三个具体目标：1)利用常规三轴试验内部安装的光纤尺度压电计，量化和测量剪切过程中平行和垂直于层理的各向异性孔隙压力响应。2)模拟伺服控制直剪装置中的储存库刚度和应力边界条件，利用内部光纤压电计量化剪切平面上的孔压响应。3)利用在瑞士Mont Terri的Opalinus粘土中专门设计的试验隧道的现有和新的孔隙压力数据，重新评估剪切引起的孔隙压力对地下响应的作用。这项研究的长期目标是建立和描述储存库设计所需的粘土页岩的适当原位本构行为。与此同时，还将开发一种方法和框架来实施基于性能的设计。

Countries with argillaceous formations have been investigating these rocks to assess their potential for the disposal of nuclear waste. In Canada, the Nuclear Waste Management Organization (NWMO) has submitted a license application to construct a low and intermediate level nuclear waste repository at a depth of 680 m in clay rich Sedimentary rocks at the Bruce Site in Ontario, and argillaceous formations remains a possible target for used-nuclear fuel disposal. In Switzerland, Nagra has commenced an extensive site investigation program to characterise the Opalinus Clay, and in France, the Callovo-Oxfordian Formation has been selected by Andra for radioactive-waste-disposal characterisation. The nuclear waste industry demands that coupled geomechanical processes are sufficiently well understood to proceed with engineering design. In these argillaceous formations, the geomechanical processes are a function of complex rate and coupled phenomena. To validate our understanding of these coupled processes in situ, field measurements supported with extensive laboratory tests will be carried out to establish the relevant geomechanical processes applicable to repository design. In argillaceous rock, pore pressures must be measured to interpret the fundamental behaviour during the mechanical and thermal loading that will be encountered in a repository underground environment. This environment creates unique boundary conditions that have the potential to generate very large pore pressures on localized zones over large distances. Such pore pressures must be quantified and accounted for in the design of the repository. This research has three specific objectives: 1) Quantify and measure the anisotropic pore pressure response parallel and perpendicular to bedding as shearing progresses using fibre optic scale piezometers installed internally in conventional triaxial tests. 2) Simulate the repository stiffness and stress boundary conditions in a servo controlled direct shear device and quantify the pore pressure response on the shearing plane using internal fibre optic piezometers. 3) Utilize existing and new pore pressure data from a specifically designed test tunnel in the Opalinus Clay at Mont Terri, Switzerland, to re-evaluate the role of shear-induced pore pressures on the underground response. The long-term objective of this research is to establish and describe the appropriate in situ constitutive behaviour of clay shales needed for repository design. In parallel with this work will be the development of a methodology and framework for implementing a performance-based design.