高温高压下花岗岩中钻孔围岩的热物理及力学特性试验研究

 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×400mm的花岗岩体内含f 40 mm的钻孔在600 ℃以内及6 000 m埋深静水压力下钻孔围岩的热弹性变形进行深入的试验研究。根据热弹性变形试验结果反演计算出高温高压下钻孔围岩的热物理及力学特性参数，并对钻孔围岩的热物理及力学参数进行认真细致的分析。研究结果表明：(1) 高温不同埋深应力下钻孔围岩的热变形可分为3个阶段：低温热变形微弱阶段，中高温热变形快速增长阶段，高温热变形平稳阶段，且埋深(即应力大小)对于钻孔围岩的热变形具有明显的影响；(2) 高温高压下含有钻孔的花岗岩体以剪切方式破坏，花岗岩体在经历500 ℃～600 ℃的高温仍呈现出脆性特征，岩体破坏的条件为6 000 m埋深静水压力，600 ℃左右；(3) 高温下钻孔围岩的弹性模量随温度的升高呈负指数规律减小；(4) 高温下钻孔围岩的泊松比随温度的升高总体呈增大的趋势；(5) 高温不同埋深应力下钻孔围岩的热膨胀系数不同，埋深对钻孔围岩的热膨胀系数具有很大影响。研究结果可为高温岩体地热开发深钻施工及钻井围岩稳定性维护提供理论依据与技术储备。

EXPERIMENTAL STUDY OF THERMOPHYSICO-MECHANICAL PROPERTY OF DRILLING SURROUNDING ROCK IN GRANITE UNDER HIGH TEMPERATURE AND HIGH PRESSURE

Utilizing the 20 MN servo-controlled triaxial rock testing machine under high temperature and high pressure developed by the authors，the intensive experimental study of the thermo-elastic deformation of large size granite sample of f200 mm×400 mm with f40 mm borehole under triaxial hydrostatic pressure in depth of 6 000 m and temperatures within 600 ℃ is carried out. Based on the results of thermo-elastic deformation experiments under high temperature and pressure inversion to calculate the thermophysical and mechanical parameters，a careful analysis of the thermophysical and mechanical parameters of drilling surrounding rock in granite is carrial. The results show that：(1) The thermal deformation of the drilling surrounding rock in granite under high temperature and high pressure at different depths can be divided into three stages：low-temperature thermal deformation of a weak phase，the rapid growth stage heat distortion temperature and high-temperature thermal deformation of a smooth phase；and the depth (pressure) is significant impact on the thermal deformation of drilling surrounding rock in granite. (2) The failure mode of drilling surrounding rock in granite under high temperature and high pressure is of cutting damage，granite body in the experience of 500 ℃–600 ℃ high temperature continued to show a brittle emerged in characteristics. And rock mass destruction conditions are triaxial hydrostatic pressure in depth of about 6 000 m and temperature of 600 ℃. (3) The elastic modulus of drilling surrounding rock in granite under high temperature with a negative temperature decreases exponentially. (4) The Poisson's ratio of drilling surrounding rock in granite under high temperature with increasing temperature increases with the overall trend of its variation. (5) The thermal coefficients of expansion about surrounding rock of drilling at different hydrostatic pressures in depth and high temperature are different；the depth has a significant impact on the thermal coefficient of expansion. This experimental study can provide a theoretical basis and technical reserves for hot dry rock of deep drilling and maintenance of stability of drilling surrounding rock.