对锦屏深部高地应力环境下的钻孔岩心饼化现象进行了调查统计分析,在总结已有的研究成果基础上,对岩饼端面宏观破坏特征、饼化数量、厚度及钻孔特征进行了描述,通过数值方法模拟开展了钻孔岩心应力特征及饼化机理研究,并总结钻孔岩心饼化的应力场条件。研究结果表明:①钻孔过程中,岩心径向所形成的拉应力贯通区是岩心饼裂的主导因素,岩饼形貌受岩心中拉应力影响;②足够的应力场是岩心饼化的首要条件,应力场越高,钻孔岩心中拉应力越大,岩心裂纹触发与扩展的应力条件更加充分,所形成的岩饼厚度越小;③钻孔径向应力场增长对钻孔岩心内部拉应力有促进作用,钻孔轴向应力场作用效果相反;④定义了岩心中最大拉应力贯通线均值,与岩石抗拉强度相比较作为岩心饼裂判据,推导了岩心饼裂地应力场关系式,并算得锦屏T2b大理岩饼化的临界地应力场条件为钻孔径向应力场>34.44 MPa。研究成果对高应力条件下地应力场的预测、钻孔取心等工作具有一定的借鉴意义。
Abstract
The rock drilling core discing in Jinping Hydro-power Station under high geostress environment is investigated. On the basis of summarizing the existing research results, the macroscopic failure characteristics, discing quantity, thickness and characteristics of borehole were described. The core discing mechanism and the field stress condition of the core discing were summarized through numerical simulation.Results show that: 1) during the drilling process, the tensile stress zone crossing rock core is the dominant factor of core discing crack, and the morphology of rock disk is affected by the tensile stress in the core; 2) sufficient field stress is the primary condition of core discing, and higher tensile stress is induced in the core with higher field stress,and also the condition of core discing crack initiation and expansion is more adequate, and the rock disk’s thickness gets smaller; 3) the increase of radial field stress of borehole has a positive effect on the tensile stress induced in the drilling core, and the axial field stress is opposite; 4) the average value of the maximum tensile stress cross line in the core is defined by comparing with the tensile strength of rock, and the formula of field stress in the presence of drilling core discing is deduced.According to the calculation,the critical condition of Jinping marble rock(T2b) discing crack is that the radial field stress of borehole should be beyond 34.44 MPa.
关键词
锦屏深部岩体 /
钻孔 /
岩心饼化 /
高地应力 /
岩石强度
Key words
borehole /
rock core discing /
high geostress /
Jinping deep rock mass /
rock strength
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基金
国家自然科学基金项目(51579016);中央级公益性科研院所基本科研业务费项目(CKSF2015047/YT)
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