Pore pressure has a major influence on the effective stress and thus on the mechanical behaviour of rocks. In this study, we focus on the hydro-mechanical behaviour of a low porosity andesitic rock heat-treated to 930 °C to induce thermal cracks and increase the permeability of the samples. First, we show that permeability decreases from 8 × 10⁻¹⁶ m${}^2$ to 1.5 × 10⁻¹⁷ m${}^2$ with a confining pressure (P${}_c$) increase from 2 MPa to 40 MPa (pore pressure being approximately 0.2 MPa). Then, we used fibre optic pressure sensors to monitor pore pressure diffusion at three points along the sample during the propagation of a pore pressure pulse under hydrostatic (P${}_c=40$ MPa) and triaxial stresses (P${}_c=40$ MPa, differential stress of 356 MPa). When the pore pressure pulse was applied, the fibre optic sensors showed a sudden pore pressure increase one after the other as a function of their location along the sample. Pore pressure increase downstream was very smooth under hydrostatic stress and almost zero after the duration of the experiment (50 min) under triaxial stresses. This lack of downstream pore pressure increase under triaxial stresses is due to the fact that a differential stress of 356 MPa decreased permeability from approximately $10^{-17}{\mathrm{m}}^2$ to approximately $10^{-19}{\mathrm{m}}^2$. Finally, the pore pressure diffusion process was modelled considering a uniform spatial distribution of permeability in the andesite sample and the dead volume attached at the downstream side.

孔隙压力对有效应力有很大影响，从而对岩石的力学性能也有很大影响。在这项研究中，我们专注于热处理至930°C的低孔隙率安山岩的流体力学行为，以引起热裂纹并增加样品的渗透性。首先，我们表明渗透率从8×10 ^-16  m减小${}^2$至1.5×10 ^-17  m${}^2$ 围压（P${}_C$）从2 MPa增加到40 MPa（孔压约为0.2 MPa）。然后，我们使用光纤压力传感器来监测在静水压力下孔隙压力脉冲传播过程中沿样品三个点的孔隙压力扩散（P${}_C=40$ MPa）和三轴应力（P${}_C=40$MPa，压差356 MPa）。当施加孔隙压力脉冲时，光纤传感器显示出孔隙压力突然突然增加，这是它们沿样品位置的函数。在静水压力下，下游的孔隙压力增加非常平滑，在三轴应力下的实验持续时间（50分钟）后几乎为零。在三轴应力下缺乏下游孔隙压力的增加是由于以下事实：356 MPa的压差使渗透率从大约$\mathrm{1个}{0}^{-17}{\mathrm{米}}^2$ 大约 $\mathrm{1个}{0}^{-19}{\mathrm{米}}^2$。最后，考虑安山岩样品中渗透率的均匀空间分布和下游侧的死体积，对孔隙压力扩散过程进行建模。