水压影响岩石渐进破裂过程的试验研究

Experimental study of effect of water pressure on progressive failure process of rocks under compression

岩石的压缩过程伴随着裂纹扩展,在低、中围压条件下扩展的裂纹主要受到张拉作用而产生,张拉破坏是首要的作用机制。研究发现,岩石的渐进破裂过程受岩石的结构和构造影响,比如矿物成分、颗粒大小以及胶结情况等,另外,围压以及开挖扰动等外界因素对岩石的渐进破裂过程也有重要影响。基于试验方法探讨水压对岩石渐进破坏过程的影响,首先,阐述岩石渐进破裂过程各个阶段的特征;然后,对岩石渐进破裂指标——岩石的启裂强度ci和损伤强度cd的确定方法进行总结;最后,选取细粒的石英砂岩为研究对象,通过试验研究水压对岩石渐进破坏过程的影响。试验结果表明,相同围压条件下,随着岩样两端水压的增大,岩石的ci有逐渐增大的趋势,而岩石的cd和峰值强度f逐渐变小;随着围压逐渐增大,岩石的启裂强度ci、损伤强度cd及峰值强度f均逐渐增大。

Crack propagation under compression of rocks and cracks in the rock are mainly tensile. Shear band can be formed as the result of interaction of tensile cracks; and shear failure finally occurs with propagation and interaction of cracks in the rock. It has been found that progressive failure process of rocks is affected by mineralogical composition, grain size, texture and foliation, etc. External factors such as the confining pressure and excavation disturbance also have great effect on progressive failure process of rocks. The influence of water pressure on crack propagation of sandstone is studied. Feature of each stage in progressive failure process of sandstone is researched; and stress thresholds--crack initiation stress σci and crack damage stress σcd are summarized. Then the influence of water pressure on progressive failure process of sandstone is studied experimentally. It is indicated that with increase of water pressure at both ends of the rock sample, crack initiation stress σci has a tendency to increase and crack damage stress σcd and peak stress σf decrease gradually. With increase of the confining pressure, stress thresholds during progressive failure process of sandstone decrease gradually.