大理岩加卸荷条件下力学特性研究

发布时间：2019-02-13 09:33

【摘要】：在地下工程的建设当中,岩体的开挖则会导致在一个或多个方向的卸荷,在高地应力区域,由于岩体内储存的能量较高,开挖导致岩体内部能量突然释放,多余的能量以动能形式释放,导致岩体爆裂并弹射,对人员生命安全、设备以及工程的安全造成巨大威胁。本文通过单轴循环加卸载试验、三轴卸荷试验以及数值软件RFpA2D,研究了大理岩在不同加卸荷条件下的变形、破坏等特性,分析不同应力环境下岩石内部裂纹发育过程以及声发射分布规律。本文主要取得下列研究成果:(1)通过不同路径的单轴循环加卸载试验,分析了循环荷载作用下岩石的力学特性以及破坏特征。结果表明:循环荷载作用下岩石不同循环阶段的弹模和泊松比随着循环次数的增加而提高,小幅度微扰动荷载对岩石弹性模量的强化作用明显,岩石泊松比则出现降低;循环加卸载作用下岩石最终以纵向劈裂破坏为主,不同应力路径下岩石破坏差别体现在岩石碎屑长厚比上。(2)通过恒轴向位移卸围压试验分析了卸荷过程中初始围压和卸荷速率对岩石力学特征、声发射、破坏形态等的影响。结果表明:(a)在卸荷破坏过程中,初始围压对岩石力学性质强化作用明显。(b)岩石破坏以及发生损伤时对应的应力值以及声发射平均振铃计数值随着卸荷速率的提高,先增大后减小;岩石破裂角随着卸荷速率的提高先减小后增大。(c)随初始围压的增大,卸荷速率的提高,岩石破裂宏观破裂面小裂纹数目减少,微观破裂面逐渐趋于光滑,岩石逐渐由渐进式破坏向突发式破坏转变,岩石更容易发生岩爆。(3)通过RFPA数值软件,对恒轴向位移卸围压试验进行了模拟,结果表明:(a)随着围压的降低,岩石内部失稳单元逐渐从无序向有序发展,最终微裂纹汇集贯通形成大尺度宏观裂纹。(b)卸荷速率一定时,不同初始围压下岩石破坏力学特性模拟结果同室内力学试验结果较为接近。(c)不同卸荷速率下,数值模拟所得结果同室内试验的差异主要体现在岩石破坏时轴压以及岩石残余强度。本文采用单轴循环加卸荷,三轴加卸荷试验和数值模拟方法,对深部岩体开挖加卸荷条件下力学特性进行研究,再现了卸荷诱发岩体破坏的过程,分析了加卸荷诱发岩爆的机理。岩石加卸荷力学特性的研究,不仅可以揭示岩体在开挖卸荷作用下的破坏机理,促进岩爆机理研究,而且对实际工程有很好的参考和应用价值。
[Abstract]:In the construction of underground engineering, the excavation of rock mass will lead to unloading in one or more directions. In the area of high ground stress, because of the high energy stored in the rock body, the excavation results in the sudden release of energy inside the rock mass. The excess energy is released in the form of kinetic energy, resulting in rock burst and ejection, which poses a great threat to the safety of personnel, equipment and engineering. In this paper, uniaxial cyclic loading and unloading tests, triaxial unloading tests and numerical software RFpA2D, are used to study the deformation and failure characteristics of marble under different loading and unloading conditions. The process of crack development and the distribution of acoustic emission in rock under different stress conditions are analyzed. The main achievements of this paper are as follows: (1) the mechanical properties and failure characteristics of rock under cyclic loading are analyzed by uniaxial cyclic loading and unloading tests with different paths. The results show that the modulus of elasticity and Poisson's ratio increase with the increase of cycle times under cyclic loading, and the elastic modulus of rock is strengthened obviously by small amplitude micro-disturbance load, and the Poisson's ratio of rock decreases. Under cyclic loading and unloading, the main failure of rock is longitudinal splitting failure. The difference of rock failure under different stress paths is reflected in the ratio of length to thickness of rock debris. (2) the initial confining pressure and unloading rate during unloading process are analyzed by means of constant axial displacement confining pressure test to analyze the mechanical characteristics and acoustic emission of rock. The effect of damage patterns, etc. The results show that during the unloading failure of: (a), the initial confining pressure strengthens the mechanical properties of rock obviously. The stress values corresponding to the damage of. (b) rock and the average acoustic emission ringer are increased with the increase of unloading rate. First increase and then decrease; With the increase of unloading rate, the fracture angle of rock decreases first and then increases with the increase of initial confining pressure. With the increase of unloading rate, the number of small cracks on the macroscopic fracture surface of rock decreases, and the micro-fracture surface tends to smooth. Rock gradually changes from progressive failure to sudden failure, and rock burst is more likely to occur. (3) through RFPA numerical software, the constant axial displacement confining pressure relief test is simulated. The results show that: (a) decreases with confining pressure. The internal instability unit of rock gradually develops from disorder to order, and finally microcrack aggregates through to form large scale macroscopic crack. (b) unloading rate is fixed. Under different initial confining pressures, the simulation results of rock failure characteristics are similar to those of laboratory mechanical tests under different unloading rates of. (c). The difference between the results of numerical simulation and that of laboratory tests is mainly reflected in the axial compression and residual strength of rock during rock failure. In this paper, uniaxial cyclic loading and unloading, triaxial loading and unloading tests and numerical simulation are used to study the mechanical properties of deep rock mass under the condition of loading and unloading, and the process of rock mass failure induced by unloading is reappeared. The mechanism of rockburst induced by loading and unloading is analyzed. The study on the mechanical properties of rock loading and unloading can not only reveal the failure mechanism of rock mass under excavation and unloading, but also promote the study of rock burst mechanism, and have a good reference and application value for practical engineering.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD313

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