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Abstract 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.
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Received: 25 December 2009
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