摘要:
针对深井、超深井钻遇的花岗岩地层,通过对花岗岩进行加温后纵波波速测量和常规三轴压缩试验,并基于所得到的试验结果研究不同温度后花岗岩的纵波波速和三轴压缩状态下的宏观力学特性,分析了花岗岩纵波波速、峰值应力、弹性模量、峰值应变与温度的关系;同时对三轴压缩条件下花岗岩的宏观破坏形式进行总结。研究结果表明,经过加温冷却后,花岗岩的纵波波速随着温度的升高呈降低趋势;同时,围压一定时,温度为20~200℃时,随着温度的升高,试样的峰值应力、弹性模量、峰值应变呈增大趋势,而在200~400℃,这些力学参数呈降低趋势。温度的升高,不仅会使得岩石内部的含水量逐渐减小,而且由于岩石内部矿物成分的热膨胀性不同等因素使得岩石内部产生附加热应力,从而使得岩石内部的初始裂纹发生扩展、贯通或产生新裂纹,进而影响井壁及围岩的稳定性。
Abstract:
According to the granite formations of deep wells and ultra-deep drilling, through the measurement of the longitu-dinal wave velocity after the granite heating and conventional tri-axial compression tests, and based on the experimental re-sults, the study is made on the longitudinal wave velocities of granite by different temperatures heating and macro mechani-cal properties under tri-axial compression stat.The analysis is made on the relationship between the granite longitudinal wave velocity, peak stress, elastic modulus, peak strain and the temperature; at the same time, the granite macroscopic failure form under the condition of tri-axial compression are summarized.The results show that, after heating and cooling, granite longitudinal wave velocity is decreasing with increasing temperature; meanwhile, under a constant confining pres-sure, when the temperature changes from 20℃to 200℃, the peak stress, elastic modulus, peak strain tended to increase with the temperature increasing, but when the temperature changes from 200℃ to 400℃, these mechanical parameters is decreasing.Temperatures can make the water content of rock gradually decreases, and because of different thermal expan-sion of rock internal mineral compositions, the additional thermal stress inside the rocks is generated, thereby the initial crack inside the rock will have propagation and coalescence or new cracks generate to affect the stability of the borehole wall and the surrounding rock.
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