高应力岩体的动态加卸荷扰动特征与动力学机理研究

发布时间：2018-01-06 13:22

本文关键词：高应力岩体的动态加卸荷扰动特征与动力学机理研究　出处：《中南大学》2013年博士论文　论文类型：学位论文

【摘要】：摘要：深部岩体由于其自重和地球构造运动的影响,本身是应力和能量的储存体。开挖前,开挖面和周围岩体之间处于准静态平衡(quasi-static)状态。当岩体开挖,原有的平衡状态被打破,引起初始应力和能量的重新分布、转移和释放,这将促使岩体内部损伤演化的累积和发展,进而可能产生宏观的时效断裂。由于开挖导致岩体初始应力的转移、释放以及岩体的松弛变形严重影响地下工程开挖的稳定性。如,深部开挖可能导致开挖面附近岩石的破坏甚至岩爆的发生,这使得深部岩体的破坏形式表现得非常复杂和特别。同时,深部巷道开挖还常常会出现层裂等渐进破坏模式。因此,由于开挖导致原岩应力和能量的释放不但影响开挖过程中的安全性,而且会严重改变巷道围岩的支护要求和支护能力。目前深部岩石力学问题的研究主要是从静力学或准静力学及纯动力学的角度出发,很少考虑高应力岩体由于自身静态初始应力和外界动力扰动混合作用的行为特性。为此,本文围绕初始应力对弹性波传播的影响,冲击载荷作用下引起的层裂破坏,高应力岩体加、卸荷作用下的破坏机理等展开了相关的理论、实验和数值模拟研究,旨在探讨高应力岩体破坏的岩石力学机理。主要内容和结论性成果如下： (1)通过数学物理的方法求得了岩体加、卸荷过程中的定解问题。分析了初始应力和初始应力梯度对应力波传播过程的波动方程、应力波波速等的影响。设计了应力波在有初始应力的花岗岩试件中的传播实验,结果表明纵波和横波波速都随初始应力的增加而增大,验证了理论推导的正确性。 (2)针对冲击载荷作用下层裂破坏的多种表现形式,对一维杆件的层裂破坏特性、地下封闭爆炸的地表层裂特性、地下结构的层裂特性进行了理论分析。首次利用长条形的花岗岩试件实现了一维应力条件下的层裂破坏,并由试验结果推导出岩石层裂试验过程存在明显的损伤破坏效应。同时,把初始应力和初始应力梯度引入到分析地下爆炸引起的地表层裂中,得出了新的层裂分析模型。进一步,考虑到地下岩体存在初始应力的特殊情况,通过将球面应力展开成平面应力的办法实现了有围压情况下的花岗岩试件的层裂破坏,得到了有围压情况下的花岗岩层裂强度。 (3)针对开挖前的岩体本身是储能体和处于准静态平衡状态下的特点,利用通用有限元程序LS-DYNA,运用混合隐式-显式(implicit-explicit)计算的方法成功模拟了高应力岩体的应力初始化-动态卸荷过程。数值模拟的结果表明：在较高的初始应力条件下,当岩体的初始应力快速卸除后,仅仅由于自身应力的释放就导致了岩石的破坏。针对不同的卸荷过程,创造性的提出了“等效应力释放率”和“等效应变能密度率”的概念和计算方法,并通过数值模拟计算证明它们能很好的表征一维和多维高应力岩体的不同卸荷过程。 (4)对深部硬岩巷道周边的加载作用过程进行了数值模拟。通过设置不同的初始应力、不同的加载方式表明高应力岩体的动态加载过程有可能产生破裂区与非破裂区交替出现的现象。进一步研究指出了动态载荷作用在应力梯度逐渐递增的物体上除在作用面产生一个峰值区外,一定还会在离作用面一定距离的地方产生另一应力峰值区,并指出交替破坏现象能发生的主要原因是递增的静态应力和递减的动态加载相互叠加的作用。
[Abstract]:Deep excavation can lead to the accumulation and development of initial stress and energy , which can lead to the accumulation and development of initial stress and energy , which can lead to the accumulation and development of initial stress and energy . At present , the study of deep rock mechanics is mainly from the angle of statics or quasi - static mechanics and pure dynamics . It is seldom considered the behavior characteristic of high - stress rock mass due to its static initial stress and external dynamic disturbance . For this reason , the paper studies the mechanics mechanism of rock mechanics , which is caused by the influence of initial stress on elastic wave propagation , the damage mechanism under the action of impact load , etc . The main contents and concluding results are as follows : ( 1 ) The problem of definite solution in the process of loading and unloading of rock mass is obtained by means of mathematical physics . The influence of initial stress and initial stress gradient on the wave equation , stress wave velocity and so on of stress wave propagation process is analyzed . The propagation experiment of stress wave in granite specimens with initial stress is designed . The results show that both the longitudinal wave and the shear wave velocity increase with the increase of the initial stress , and the correctness of the theoretical derivation is verified . ( 2 ) According to various forms of crack damage under the action of impact load , a theoretical analysis is carried out on the fracture characteristics of one - dimensional bar , the characteristics of ground surface crack in the underground closed explosion , and the layer crack characteristics of the underground structure . ( 3 ) The stress initialization - dynamic unloading process of high - stress rock mass is simulated successfully by using the general finite element program LS - DYNA for the rock mass before excavation itself . The numerical simulation results show that , under the condition of high initial stress , when the initial stress of rock mass is removed rapidly , the concept and calculation method of " equal effect force release rate " and " equal effect variable energy density ratio " are proposed , and the different unloading process of a multidimensional high - stress rock mass can be well characterized by numerical simulation . ( 4 ) Numerical simulation is carried out on the loading process of deep hard rock roadway . By setting different initial stress , different loading methods indicate that the dynamic loading process of high - stress rock mass can result in the alternation of rupture zone and non - rupture zone .

【学位授予单位】：中南大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU452

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