Abstract A series of gas injection tests on compacted bentonite were carried out at the British Geological Survey. Tests measurements included pressure and rate of gas inflow, gas outflow volume as well as stresses and pore pressure observed at various points of the sample. Tests were performed with two different gas injection systems: injecting the gas from one end of the sample (axial flow) or from one point at the centre of the sample (spherical flow). A coupled hydro-gas-mechanical 3D numerical model has been developed to simulate the tests. Initial permeability is assumed heterogeneous throughout the specimen and embedded fractures are incorporated in the formulation. Gas pressure-induced deformations during the test lead to variations of permeability due to changes in matrix porosity and, especially, fracture aperture. The model is able to reproduce satisfactorily the observed behaviour of the tests including the existence of preferential gas flow paths. A programme of sensitivity analyses involving the variation of different aspects and parameters of the model contributes to a better understanding of the phenomenon and highlights its complexity. The application of the same formulation and parameters calibrated in the axial flow test results in a successful simulation of the spherical flow test.

中文翻译：

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模拟粘土材料中的气体流动，结合材料的非均质性和嵌入的裂缝

摘要 英国地质调查局对压实膨润土进行了一系列注气试验。测试测量包括气体流入的压力和速率、气体流出体积以及在样品不同点观察到的应力和孔隙压力。使用两种不同的气体注入系统进行测试：从样品的一端（轴流）或从样品中心的一点（球流）注入气体。已经开发了耦合的水-气-机械 3D 数值模型来模拟测试。假设初始渗透率在整个样本中是不均匀的，并且嵌入的裂缝被纳入公式。由于基质孔隙度的变化，特别是裂缝孔径的变化，测试过程中气体压力引起的变形会导致渗透率的变化。该模型能够令人满意地再现测试的观察行为，包括优先气流路径的存在。涉及模型不同方面和参数变化的敏感性分析程序有助于更好地理解该现象并突出其复杂性。在轴流测试中校准的相同公式和参数的应用导致了球形流测试的成功模拟。