摘要
用7种岩石各制备了几类不同预裂纹的系列试件,并在不同围压下进行水压致裂强度实验。结合典型的水库诱发地震的实际资料和现今构造应力场的实验结果,以及应用岩石强度理论和岩石断裂力学的一些原理、方法,进行岩石孔隙水压诱发地震的探讨。初步结果为:(1)若岩体内构造应力很小,一定大小的孔隙水压力σP可直接使岩体内的薄弱面致裂并发生小地震。(2)若构造应力较大,存在两类诱发地震的可能:①对岩体浅部一些走向与构造应力的主压应力σ1方向相近的薄弱面,σP可促使其发生张性破裂并诱发小地震。②当构造应力接近于断裂的抗剪强度时,因σP降低了断裂面上的正应力σn,使原处于稳定状态的断裂失稳,发生滑移破裂并诱发出地震。σP导致断裂的破裂深度增大,使诱发地震的震级大于原潜在的地震震级。(3)各种岩体均存在着一个极限深度,此深度后不再有诱发地震。
The strength experiment of hydraulic fracturing was conducted in circumstance of different confining pressure,in which seven types of rock specimens respectively with several kinds of preprocessing crack on them were used.Moreover,combining with practical materials of representative reservoir induced earthquake and experimental results nowadays in tectonic stress field,as well as rock strength theory and some principles and methods in rock fracture mechanics were applied,initial results from probing into pore water-pressure of rock which induced earthquakes were obtained as follows:(1)If the tectonic stress inside rock mass is quite small,certain pore water-pressure,that is σ_p,may directly have the weak side inside the rock mass fracturing therefore generate small earthquake;(2)If the tectonic stress is relatively large,there exists two types of possibility of induced earthquake.One situation is σ_p enable the shallow bearing of trend and the weak side nearing σ_1,the principal compressive stress on the orientation of the tectonic stress in rock mass to make tension fracture also induce minor earthquake.Another is that the positive stress σ_n on the fracture surface of rock mass reduced by σ_p when tectonic stress approximate to strength of shearing in rock fracture,so that the fissure which formerly remained stable state now becomes destabilization and cause gliding fracture,thus induces earthquake.This σ_p will lead to the increases of the rupture depth of the fissure and makes the magnitude of the induced earthquake scale larger than that of the original potential earthquake as well. (3)For all various rock have theirs bounding depth,induced earthquake doesn't exist any more after this depth.
出处
《中国地震》
CSCD
北大核心
2005年第2期193-206,共14页
Earthquake Research in China
基金
广东省科学技术厅资助项目(2002C32605)。
关键词
孔隙水压
水压致裂
诱发地震
Pore water-pressure Hydraulic fracturing Induced earthquake
