【作者】 张成良；

【导师】 李新平；

【作者基本信息】 武汉理工大学 ， 岩土工程， 2007， 博士

【摘要】 随着国民经济的蓬勃发展，越来越多的工程进入深部开采。深部岩体处于高地应力、高地温和高渗透水压力的特殊环境下，岩体的力学响应明显有别于浅部岩体。由于深部岩体受到各种荷载作用、岩体介质本身的复杂性、认识的不确定性以及深部岩体所表现出来的一系列新的力学特征，致使深部岩体的渗透性、破坏模式、强度特性以及开挖卸荷作用下岩体的变形特性等难于用传统的理论加以合理的解释。针对深部岩体的特点，研究深部岩体在“三高”环境下的力学特性和开挖卸荷作用下的变形规律已经成为一种现实需要，本文研究的主要内容如下：1．研究高温下的岩石结构的变化，用热应力作为桥梁，得出岩石渗透率和温度之间的数学关系式，由岩石渗透率和温度之间的数学关系式可知，温度在开始升高时，渗透率增加缓慢；当升高到一定温度后，渗透率增加的速度迅速增大，这一温度即为门槛值。经过门槛值温度之后岩石的渗透率随温度升高而迅速增加，不同的岩体其温度的门槛值是不同的。2．深部岩体处于中、高应力作用下，应力对岩体的渗透性影响很大，应力的变化将导致有效隙宽的改变，有效隙宽的改变，改变了岩体的渗透性。以有效隙宽的变化为基础，推导了岩体在中、高法向应力和剪切应力作用下岩体的渗透率表达式。结合裂隙渗流规律，建立了三维应力作用下裂隙渗流与应力表达式；通过张量分析，推导了裂隙组和多裂隙组渗透张量与应力的耦合表达式。3．从质量守恒定律、动量平衡原理和能量守恒定理三个原理出发，根据连续性方程、动量平衡方程和能量守恒方程这三个基本方程出发，建立了深部岩体温度场、渗流场和应力场的三场耦合作用控制方程组，包括温度作用下的岩体应力场控制方程、应力场和温度场作用下的岩体渗流控制方程以及渗流场和应力场作用下深部岩体的温度控制方程，定性的分析了三场耦合之间的作用关系和岩体在三场耦合作用下的变化情况。对三场耦合作用下的岩体力学特性情况进行了模拟，并对岩体三场耦合作用进行了定性研究。4．采用常规三轴加载试验和卸荷试验研究在不同围压下岩体的破坏模式和力学参数的变化特性；卸荷试验突破了以加载的方式研究岩体的力学特性。岩体在加、卸荷条件下的变形均随主应力差的增大而增大，但在相同的主应力差下，卸荷产生的扩容量比加荷时的要大，破坏程度也更为强烈。岩体在卸荷破坏失稳时的应力强度较加载破坏失稳时的应力强度更低。加载下岩体易呈现剪切破坏，而卸荷下岩体常呈现张剪复合型破坏。5．在相同的应力状态下，岩石在加载和卸荷作用下，在试样内部岩石微结构的破坏过程和破坏程度是不相同的。地下洞室围岩的失稳主要是由于工程开挖导致岩体卸荷产生损伤，围岩损伤的逐步累积发展造成围岩失稳。由于应力路径的差异，相同条件下岩体在卸荷条件下的力学行为不同于其在连续加载的力学行为。因此，采用基于连续加载条件的岩体破坏准则来分析卸荷条件下的洞室围岩稳定是不合适的。进一步证明，加载试验方法获得的岩体力学参数用于地下工程开挖的计算是不合理的。此外，孔隙水压对岩石内部裂纹的扩展、贯通起到加剧作用，并对围压起到遏制作用，降低了岩体的强度，但水压对岩体强度的降低程度随围压的增大而有所减小。6．岩体开挖本身就是一个应力调整和不断卸荷的过程，采用有限元软件对厂房地下工程进行了开挖卸荷模拟，模拟了不同开挖时步下围岩的位移和应力变化情况以及不同开挖空间岩体的变形规律。结合硗碛水电站地下厂房工程开挖所安装的多点位移计和锚杆应力计所监测到的不同开挖时间和开挖空间所对应的应力和位移资料，通过分析比较，开挖卸荷数值模拟结果和实际监测到的资料具有良好的一致性。通过卸荷开挖模拟和实测数据对比分析可知，采用数值模拟计算得到的不同时步的围岩应力和位移值，来实现对地下厂房工程围岩的稳定性进行评价和控制是可行的。更多还原

【Abstract】 With the development of national economy, the exploration of underground space becomes deeper and deeper. Being in the conditions of high stress, temperature and seepage pressure, the mechanical behaviors of deep rock mass shows a quite difference from that of shallow rock mass. Because of the actions of various loadings, the complexity of rock medium, the uncertainty of perceptibility and a series of new mechanical properties of deep rock mass, the permeability, failure mode, strength and deformation characteristics under excavation and unloading are difficult to be interpreted with traditional theories reasonably. Consequently, it’s essential to study the mechanical properties of deep rock mass under high stress, temperature and hydraulic pressure, together with the deformation regularity under excavation unloading. The content of this paper is summarized as fellows:1. Based on the study on the changes of the rock mass structure under high temperature, the expression of rock permeability and temperature is put forward with thermal stress as a bridge. According to the formula, permeability increased slowly with the rising of temperature, while increased rapidly when temperature reached a certain value. This temperature is threshold temperature and permeability of rock mass still increased rapidly when temperature beyond the threshold. The thresholds of different rock mass are different.2. Owing to the high in-site stress, permeability of deep rock mass is greatly affected by stress, for the variation of stress will lead to the variation of the effective width of fracture which will influence the permeability. Based on the variation of effective width of fracture, the expression of rock mass permeability is brought forward in the case of medium and high normal stress and shear stress. And, the formula of crack seepage and stress under three dimension stresses are obtained by virtue of seepage regularity. Additionally, the coupling equation of the stress and the seepage tensor of the joint sets and cross joint sets is deduced through tensor analysis.3. According to the mass conservation law, linear momentum equilibrium principle and energy conservation law, the governing equations for coupled Thermo-Hydro-Mechanical (THM) behaviors in deep rock mass are derived. The governing equations include those for thermal, hydrological and mechanical fields, and are based on the conservation equations for fluid and solid masses, linear momentum and energy. The interaction of THM field and the response of the deep rock mass to the THM coupling are analyzed qualitatively. Furthermore, mechanical characteristics of deep rock mass in THM coupling are simulated and corresponding qualitative research is performed. 4. Triaxial compression test and unloading test are carried out to study the failure modes and mechanical behaviors of rock mass under different confining pressure. Unloading test is distinguished from the conventional test which is by loading. The strains of rock mass under loading and unloading both increases with the growth of principal stress difference. However, with the same principal stress difference, volumetric dilatancy caused by unloading is greater than that of loading, as well as the damage of rock mass. Strength of rock mass in unloading tests is less than it in loading tests. And shear failure always occurs in rock mass under loading condition while tensional shear failure under unloading.5. The process and extent of microstructures damage inside the samples caused by loading and unloading are different under the same stress state. Failures of surrounding rock mass in the underground cavity mainly result in the unloading during excavation and which will lead to the accumulation and developing of the damage gradually. Due to different stress paths, the mechanical behaviors under unloading are distinguished from those in the tests of loading under the same stress condition. So, it is not appropriate to perform the stability evaluation of unloading rock mass according to the traditional strength criterion and it is also unreasonable to apply the mechanical parameters obtained from the loading test to the calculation of excavation engineering. Strength of rock mass will be weakened as pore water pressure will redound to the developing and coalescence of fractures and keep the confining pressure within limits. The decreasing effect pore water pressure to rock mass strength will be lowered with the increase of confining pressure.6. Excavation is a process of stress adjustment and unloading ceaselessly. Numerical software is used to simulate the excavation unloading. Variations of displacement and stress in different stages as well as the deformation regularity of different parts of rock mass are discussed. By comparison, results of numerical simulation are well in accordance with the monitoring data obtained from the multi-points extensometers and bolt stress meters which are installed in the underground power plant of Qiaoqi hydroelectric power station. And it is feasible to appraise the stability and control the deformation of surrounding rock mass in underground engineering with numerical simulation results.更多还原