论文部分内容阅读
用两种加载方式对岩石的破裂进行了实验研究。一种方式是在一定的围压下增加轴压使岩石破裂(A型);另一种方式是在一定围压下增加轴压直到破裂前某一应力状态,然后停止加轴压转而减小围压使岩石破裂(B型)。所用的岩石样品为济南辉长岩和山东掖县白大理岩。着重研究应力途径对岩石脆性—延性变化的影响。辉长岩在1.5千巴以下两种应力途径下的破裂都表现为脆性,但是对于同样的应力状态,B型实验比A型实验显得更脆。随着围压增加到200—250巴之间,大理岩由脆性转变为延性。围压250巴以上,大理岩的A型实验发生延性破裂。样品承受载荷的能力是逐渐丧失的。破裂过程中声发射率极低,听不到破裂声响。最后在样品中形成了剪切断面,但破裂很慢。然而,在大理岩的B型实验中,围压在250巴以上发生了脆性破裂,其表现为轴向应力突然下降,伴随着脆性破裂的声响并有声发射率剧增的前兆。看来,B型应力途径对岩石起了一个脆化的作用。
Two kinds of loading methods were used to study the rock failure. One way is to increase the shaft pressure under a certain confining pressure to rupture the rock (type A); another way is to increase the shaft pressure under a certain confining pressure until a certain stress state before rupture, and then stop the shaft pressure reduction Small confining pressure ruptures the rock (type B). The rock samples used are gabbro of Jinan and white marble of Yexian, Shandong Province. Emphasis is placed on the influence of stress path on brittle-ductile change of rock. Gabions show brittleness under both stresses below 1.5 bar, but Type B experiments are more brittle than Type A experiments for the same stress conditions. As the confining pressure increased to 200-250 bar, marble changed from brittle to ductile. Confining pressure of 250 bar or more, marble type A experiment ductile rupture occurred. The ability of the sample to withstand the load is gradually lost. Acoustic emissivity during rupture is extremely low and no sound of rupture can be heard. Finally, a shear section was formed in the sample, but the rupture was slow. However, in the marble type B experiment, a brittle fracture occurred at a confining pressure above 250 bar, which was characterized by a sudden drop in axial stress accompanied by the sound of brittle fracture and a sharp increase in acoustic emission. It appears that the B-type stress path has an embrittling effect on the rock.