【作者】 杜坤；

【导师】 李夕兵；

【作者基本信息】 中南大学 ， 岩土工程， 2013， 博士

【摘要】 矿山深井开采面临着众多难题,如何改善深部岩体所处的复杂力学环境——高地应力、高地温、高岩溶水压力及爆破、机械开挖等引起的动力扰动(“三高一扰动”)就是其中之一。高应力意味着高岩体储能。在工程开挖卸荷过程中,高应力岩体内的高储能被诱发释放,从而导致围岩破裂并诱发岩爆等大规模工程灾害。本文从高地应力受力环境出发,利用自行研制的岩石真三轴电液伺服诱变(扰动)试验系统,深入研究真三轴卸荷状态下高应力岩石的力学特性及动载荷诱发岩爆的可能性,揭示深部岩爆灾害的扰动诱发机理。主要研究内容及研究成果如下：(1)深部工程岩体主要受到卸荷损伤和应力调整集中的作用,利用自行设计的岩石真三轴电液伺服诱变(扰动)试验系统对不同应力状态下花岗岩、红砂岩及水泥砂浆的立方试件进行了真三轴卸载压缩破坏试验。研究结果表明卸载后二维受力下岩石的抗压强度随中间主应力的增大而增大,但增大的幅度逐渐降低。当单轴压缩或中间主应力较小时,岩石破坏模式为剪切破坏；随着中间主应力的增大,岩石的破坏模式逐渐由剪切破坏转变为板裂破坏。从本文的研究结果得出岩石发生板裂破坏不仅与岩性有关,还与其应力状态有关。(2)基于莫尔-库伦强度准则分析了岩石破坏模式的转变。通过莫尔-库伦定律计算的不同应力水平下岩石的计算强度与花岗岩和红砂岩试件的测试强度的比较发现,测试强度值明显低于计算强度值,说明岩石破坏时强度不再符合莫尔-库伦强度准则,破坏模式由剪切破坏转变为板裂破坏。(3)利用声发射测试系统与红外热像仪对岩石板裂破坏时的声发射数及温度变化进行了监测。通过声发射计数分析得出剪切裂纹的产生伴随着整个加载过程,而板裂裂纹不同于剪切裂纹,是在岩石受力达到一定程度时才产生。单轴压缩条件下,岩石发生剪切破坏,压缩椎体表面温度变化显著；当中间主应力较小时,岩石下半部分先发生破坏,然后再发生整体破坏,岩石破坏形式为剪切破坏；当中间主应力较大时,整个试样表面温度均有明显的升高,说明岩石的破坏形式为板裂破坏。(4)根据地下工程开挖下岩体受力路径及板裂破坏发生条件,开展了扰动诱发岩爆试验。对真三轴卸载下试件施加扰动载荷,研究证明无论扰动载荷是垂直最大主应力方向还是沿着最大主应力方向施加,只要载荷幅值达到一定程度均可诱发岩爆破坏。根据扰动诱发岩爆试验,提出了扰动诱发岩爆结构演化模型。(5)运用离散元PFC3D程序对扰动诱发岩爆进行了数值模拟,从微观角度分析得到了与试验结果相一致的结论。当扰动载荷的幅值为300、400、500kN时,试件内部有微裂纹扩展,但趋于稳定,岩石未发生破坏；但扰动载荷幅值为600kN时,微裂纹扩展迅速,岩石发生岩爆破坏。更多还原

【Abstract】 There are many difficulties for deep mining. For example, how to improve the complicated stress environment of deep rock mass which contains high in-situ stress, high ground temperature, high hydraulic pressure and dynamic disturbance caused by blasting and mechanical excavation. High in-situ stress means high strain energy stored in deep rock. The high strain energy stored in deep rock mass can be induced to release by excavation unloading engineering. The phenomena of rock burst and zonal disintegration induced by excavation unloading in high depth buried rock mass prove that the release of elastic strain energy can cause rock failure and induce severe disasters.In view of the aforementioned problems, the main purpose of this study is using self-designed true triaxial electro-hydraulic servo-controlled test system to study the failure characteristics of highly-stressed rock mass and the mechanism of strain rock burst under true triaxial unloading condition. The main contents and conclusions are as follows:(1) The true triaxial electro-hydraulic servo-controlled test system can apply load to high stress level independently in three directions (σ1> σ2>σ3≠0, where σ1is the maximum principal stress;σ2is the intermediate principal stress; σ3is the minimum principal stress). It can also impose dynamic load.The studies on the mechanical characteristics of granite, red sandstone and cement mortar cubic samples under true triaxial unloading condition were carried out. When intermediate principal stress is low, the failure mode was shear failure. While intermediate principal stress increased, the failure mode changed into slabbing. The occurrence of slabbing related with lithology and stress state of rock. (2) When intermediate principal stress is low, the peak strength of rock samples is smaller than the calculated strength based on Mohr-Coulomb criterion. This is the further evidence for slabbing failure.(3) The characteristics of slabbing failure were monitored by AE test system and infrared cameras. With the increase of σ2, the shear crack initialed and propagated during the whole compressive progress. But AE count rate of rock specimen with slabbing failure had a catastrophe point and slabbing crack began forming.Under compressive test the temperature of compressed vertebral surface significantly changed and the rock failure mode is shear failure. When σ2is low, the lower part of specimen firstly damaged and overall destruction occurred subsequently, the failure mode is shear failure. When σ2reached a higher level, the failure surface is planar and failure mode turned into slabbing.(4) According to the stress path after engineering excavation and the occurrence condition of slabbing failure, the experimental studies on strain rock burst induced by dynamic load were carried out. Regardless of dynamic load parallel or perpendicular to the direction of the maximum principal stress, rock burst could be induced as long as the load amplitude reaches a certain level.(5) Rock burst induced by perturbation was simulated by PFC3D particle flow code, the conclusions were consistent with the experimental result. When the disturbance load amplitude researched to300,400,500kN, propagation of micro-crack expanded stably but the rock samples did not damaged; while disturbance load amplitude equal to600kN, micro-racks rapid expanded rapid and rock samples failed.更多还原