【摘要】 圆柱试样的轴向压缩因压头刚性而存在端部摩擦效应使强度偏高;K.Mogi进行白云岩和花岗岩的不同长度试样在低围压下压缩试验,发现端部效应对强度的影响随着围压增大而消失。基于以往对砂岩、粗面岩、大理岩和白云岩以及众多花岗岩的试验结果,围压较高时试样达到峰值强度时变形较大,经试样断面修正后的强度仍会因端部摩擦效应而偏高。花岗岩由力学性质差异显著的多种晶粒组成,试样尺度较小时端部摩擦可通过晶粒传递而引起高围压下强度的极端离散。讨论了不同围压下端部效应以及尺度效应对花岗岩强度的影响程度,评价指数强度准则的适用性,并预测高围压下花岗岩的破裂强度。更多还原

【Abstract】 A clamping effect,ends effect namely,on cylindrical specimens compressed axially,is induced from the rigidity loading heads to enhance rock strength. Specimens with various lengths of dolomite and granite were compressed under low confining pressures by Mogi K,ends effect on strength may be neglected with increase of confining pressure. However,test results of sandstone,trachyte,marble,dolomite,and various granites from public literatures show that the ends effect will enhance specimen strength at high confining pressure,even after the area correction to the barrel specimen. Mechanical properties are greatly different of crystals in granite,i.e. quartz,feldspar and mica. Extreme scatter of granite strengths from small specimens under high confining pressure results from the ends friction transferring by crystals in the specimen. Both ends effect and size effect are discussed on strengths of granites specimens under various confining pressures. The applicability of the exponential strength criterion is evaluated to predict the genuine fracture strength of granites under high confining pressure.更多还原