高温静水应力状态花岗岩中钻孔围岩的 流变实验研究

 采用自主研制的“20 MN伺服控制高温高压岩体三轴试验机”对f 200 mm×400 mm的内含f 40 mm钻孔的花岗岩体高温三维静水应力状态的流变特性进行了深入的研究。研究结果表明：(1) 花岗岩是由多种晶体胶结而成的脆性坚硬岩石，5 000 m静水应力以内及600 ℃以内的恒温恒压状态下，花岗岩中钻孔围岩主要表现为稳态蠕变；当应力达到5 000 m静水应力，温度为600 ℃时的蠕变为非稳态蠕变。(2) 高温静水应力状态下花岗岩中钻孔围岩蠕变过程存在应力阈值和温度阈值。(3) 热力耦合作用下钻孔围岩内部晶间胶结物及晶粒内部产生的位错及微破裂过程，是高温高压下钻孔围岩蠕变存在温度阈值和应力阈值的主要原因。(4) 高温静水应力状态下，含有钻孔的花岗岩体流变破坏的应力为5 000～6 000 m的静水应力(125～150 MPa)，温度为500 ℃～600 ℃，破坏形式为压裂破坏、压剪破坏或两者相结合。同时，获得了600 ℃以内及埋深6 000 m以内静水应力条件下，不同温度不同埋深静水应力状态下花岗岩中钻孔围岩的蠕变率参数，为高温岩体地热开发钻井井壁稳定性研究提供了重要的力学参数依据。

RHEOLOGICAL EXPERIMENTAL INVESTIGATION ON SURROUNDING ROCK MASS OF GRANITE UNDER HIGH TEMPERATURE AND HYDROSTATIC STRESS

The research on rheological property，rheological mechanism of surrounding rock of granite under high temperature and high pressure is of great importance to extracting heat from hot dry rock(HDR) and stability of drilling borehole wall. Utilizing the 20 MN servo-controlled triaxial rock testing machine with high temperature and high pressure developed by the authors，the intensive research on the rheological property of large size granite with borehole samples of f 200 mm×400 mm under high temperature and triaxial hydrostatic stress in depth is carried out. The research results can be found as follows. (1) The granite is a kind of brittle and hard rock，it is constituted with multi-crystal. Surrounding rock in granite shows of steady creep state，main with hydrostatic stress below than 5 000 m in depth and temperature below 600 ℃. However，it appears as unstable creep state when hydrostatic stress is over 5 000 m in depth and temperature above 600 ℃. (2) The creep of surrounding rock of granite has a creep threshold of stress and creep temperature threshold. (3) The main reason of surrounding rock possessing threshold of stress and temperature is the dislocation and cracking of grain and cement of grain under thermo-mechanical coupling. (4) At different temperatures and hydrostatic stresses in depths，the critical hydrostatic stress of rheodestruction of surrounding rock is 5 000–6 000 m；and the critical temperature of rheodestruction is 500 ℃–600 ℃. The failure modes commonly are compression fracture，transpression or both of them. At the same time，the parameters of steady creep state rates of surrounding rock within 600 ℃ and hydrostatic of stress of 6 000 m are obtained；thus it can provide significant mechanical parameter for the stability of HDR borehole wall.