水压致裂试验过程中诱发的声发射

为了研究水压致裂过程中裂缝的扩展机制,在北京房山花岗岩体中开展了大型水压致裂试验。试验是在一个深 301 m的岩石新鲜完整的FR钻孔中进行的,其周围半径约40 m的范围内布置了4个120 m深的声发射观测孔。在FR孔中深度60 m至140 m的范围内选取了7段没有天然节理的部位进行了水压致裂。在所有的试验中,发现水压致裂形成的裂缝通过天然节理与AE孔连通,只在深度118.5 m进行的试验,观测到由水压致裂产生的AE事件。由声发射的震源机制解得到的P轴和T轴的方向与水压致裂应力测量的方向一致。

AE activity induced during hydraulic fracturing

In order to study the mechanism of crack extension by hyduaulic fracturing, the mass hyduaulic fracturing experiments were carried out in granodiorite rockmass at Fangsan, Beijing, China. A FR borehole of 301 m longth in a fresh and intact rock was used for the experiments. Four AE observation boreholes were deployed surrounding the FR borehole on a circle of 40m in radcus. Hyduaulic fracturing experiments were carried out by selecting 7 spots without natural joints from the section of 60m to 140m in the depth of the HR borehole. In all experiments, the fractures created by hyduaulic fracturing were found to be linked up with the AE borehole through the natural joints. AE event induced by hyduaulic fracturing were observed in the experiment carried out at depth of 118.5m. The direction of P and T axes obtained from the focal mechanism solution of acoustic emissions agrees with those evaluated from the hydraulic fracturing stress measurement.