峰后砂岩非Darcy流渗透特性的试验研究

TESTING STUDY ON PERMEABILITY OF NON-DARCY FLOW IN POST-PEAK SANDSTONE

研究高应力状态下,尤其是峰后低围压下岩石的渗透性具有十分重要的现实意义。利用获得专利权的岩石渗透试验装置与MTS815.02岩石力学伺服试验系统相配套,用来测试单轴峰后给定应变状态下岩样的非Darcy流渗透特性。在阐述岩石Darcy流渗透性的测试原理及误差的基础上,介绍了峰后岩石非Darcy流渗透特性的测试原理、试验系统与测试方案,并给出峰后中砂岩非Darcy渗透特性的试验结果。试验数据表明,单轴峰后应力状态下中砂岩的渗透率k与峰前比较有量级增加,峰后k值随轴向应变e 增长呈二次抛物线关系。

It is of practical importance to investigate the permeability of rock under high stress,especially under post-peak stress with low confining pressure. A patented device,combined with MTS815.02 Rock Mechanics System,makes the measurement of non-Darcy permeability possible. The configuration of test system of permeability measurement of non-Darcy flow in post-failure rock,test principle and plan,and the processing method for test data are presented. The permeability of non-Darcy flow in post-peak rock is carefully measured by using steady seepage method. Sandstone specimens are divided into five groups. Every group consists of ten specimens,which undergo same axial strain before permeability measurement. The permeability of each specimen is obtained by fitting the seepage velocity-pressure gradient curve. The statistical indexes of every group of specimens are calculated. The relation between the indexes and axial strain are established by linear regression. It is shown that the permeability of post-peak rock is remarkably larger than that of pre-peak rock. The permeability of post-peak rock varies parabolically with axial strain. This study provides the method and technique for measuring permeability of non-Darcy flow in post-peak rock,which can be employed in mining,civil and other engineerings.