岩石内部通常有着不规则、跨尺度的裂纹或孔隙,其中的渗流通道可能存在尺度效应。通过测试不同高度花岗岩和砂岩试样的气体渗透率,分析评价了尺度效应对岩石渗透特性的影响。结果表明:(1)对于花岗岩和砂岩,试样高度的降低对干密度测试结果无显著影响,但会引起孔隙率测量结果的下降;(2)完整花岗岩的渗透特性沿试样高度方向表现出均质性,但是,花岗岩中可能分布着一定量的竖向连通长度不等的渗流通道,使得不同高度试样的渗透率结果出现差异;(3)在室内试验尺度上,砂岩内部的渗流路径仍不能假定为完全均匀分布,试样高度的变化将使得渗透率测试结果出现变化;(4)机械开挖法形成的开挖损伤区使得花岗岩气体渗透率略有增大,并出现非均质特征。上述结论表明,岩石试样高度的在室内试验尺度上的变化依然会引起渗透率测试结果的变化。
There usually exist irregular and multi-scale cracks or pores in rock, and the seepage channels generated by the cracks or pores probably have scale effects. In this paper, the scale effect on gas permeability is studied by carrying out gas permeability tests of granite and sandstone specimens with different heights. The test results indicate that: (1) The decrease in specimen height has no significant effect on the dry density of both granite and sandstone; However, the decrease in specimen height leads to a decrease in porosity. (2) The permeability of intact granite is found to be homogeneous along the direction of specimen height, while the intact granite may have a certain amount of vertically connected seepage channels with different lengths, which lead to the variation of permeability when the specimen height is reduced. (3) The distribution of seepage paths within the sandstone is found to be inhomogeneous even at the indoor-test scale, and thereby the permeability of sandstone is influenced by the specimen height. (4) The permeability of the excavation-damaged zone in granite formed by tunnel boring machine (TBM) excavation is slightly increased and is also found to be inhomogeneous. The above conclusions demonstrate that the change of specimen height at the indoor-test scale will change the permeability of rocks.
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