【作者】 丛宇；

【导师】 郑颖人； 王在泉；

【作者基本信息】 青岛理工大学 ， 结构工程， 2014， 博士

【摘要】 本论文包含两个部分：一是针对地下工程开挖的复杂加、卸荷过程，尤其是卸荷过程，弄清卸荷路径下的岩石破坏机理，重点研究不同卸荷路径下岩石宏细观破坏机理，包括：不同卸荷条件破坏过程中能量演化规律；岩石卸荷破坏过程中声发射特征演化规律与量化分析；基于颗粒流方法岩石卸荷破坏过程数值模拟等。二是针对岩石地铁工程设计计算的实际问题，应用数值极限分析方法，开展对岩石地铁工程的围岩分级与设计计算方法的研究，包括：改进岩石地铁工程围岩分级的基本质量指标；考虑跨度对围岩分级的影响；初衬混凝土的抗剪强度；岩石地铁工程设计计算方法等。论文的研究成果如下：（1）采用能量原理自编程序，研究不同卸荷条件下大理岩卸荷破坏过程中的能量演化规律，取得以下主要研究成果：岩样卸荷破坏过程的轴向吸收能量曲线非线性变化，经历了缓慢增长-快速增长-缓慢增长-释放的演化过程。总能量曲线经历了缓慢增长-快速增长-缓慢减小-释放等阶段。不同卸荷应力路径对破坏过程中能量演化规律的影响主要表现在屈服弱化阶段。围压高的岩样消耗更多的能量，轴向能量曲线增长速率增加；卸荷速率越低，轴向能量增长速率升高，卸荷点处轴向能量曲线转折更明显；卸荷水平接近岩样承载能力峰值时，轴向能量增长速率增大，总能量曲线负向增长速率高，岩样破坏越剧烈。（2）研究不同卸荷条件下岩样破坏过程中的声发射特征演化规律，采用分形的方法自编程序进一步量化声发射特征，取得以下主要研究成果：不同卸荷路径试验过程中，声发射事件计数率最大值都出现在岩样破坏处，达到最大值前，岩样均会出现一段声发射相对平静期。围压越高，岩样的声发射活动水平越高，声发射相对平静期会缩短，声发射事件最大值也增加；卸荷速率越高，相对平静期的振铃计数率越高，持续时间越短；越接近岩样承载力峰值卸荷，岩样破坏前的声发射事件相对平静期持续时间越短。岩样破坏前存在声发射分维值较低区域，破坏处附近的分维值，加轴压、卸围压路径＞恒轴压、卸围压路径＞常规三轴路径。（3）基于颗粒流方法，利用FISH语言实现大理岩加、卸荷破坏过程数值模拟，从细观角度有利地补充宏观的室内试验分析，其创新点为：通过FISH语言设计不同的卸荷应力路径方案，有效实现岩样复杂卸荷试验的数值模拟，研究卸荷破坏过程中摩擦能、动能、黏结能与应变能等细观能量与应力路径之间的联系，破坏过程中细观裂纹数与岩石破坏前兆的关系，以及岩石微观裂纹产生、发展与贯通的过程。通过不同卸荷应力路径试验模拟分析，给出细观参数与岩样宏观强度参数之间的非线性关系；围压主要影响颗粒间摩擦滑动引起的摩擦能，进而改变试样的破坏形式。卸荷速率越高，试样内部裂纹发展越不充分，黏结能越少；试样破坏时颗粒运动引起的动能越大。卸荷破坏过程是由压破坏形成贯通剪切面，与拉剪破坏共同作用引起试样破坏。压破坏剪切面都是由破坏面两端向中间发展，逐渐贯通，试样内部主要破坏形式都表征为压力引起的损伤破坏，拉剪破坏伴随压破坏，在压破坏裂纹尖端有集中的趋势。（4）从细观角度分析卸荷破坏过程，并通过实例验证围岩卸荷分析的可行性，其主要结论：经典强度准则中Mogi-Coulomb准则相对适合加轴压、卸围压路径下的试验分析；将裂纹考虑成椭圆形，从细观力学和单连通域的解析函数出发分析卸荷路径下的强度准则；从单元体裂纹生成的复合应力状态出发，建立卸荷过程中的应力-应变关系。（5）在国标《工程岩体分级标准》和《地下工程围岩稳定分析与设计理论》一书对国标改进意见的基础上，提出岩石地铁工程围岩分级设想，其主要结论：一是对围岩分级表中围岩定性特征进行了改进和调整，改进了各级围岩基本质量BQ值，使定性分级和定量分级协调一致，发展与完善了围岩岩体基本质量标准。二是在围岩分级中反映了地下工程跨度对围岩稳定性的影响，提出按岩体质量和工程跨度为基准的围岩分级思想，结合地铁工程特点，给出区间隧道与车站隧道的亚级分级，量化了亚级的基本质量指标。采用了由安全系数反映围岩自稳性的量化指标和通过反算得到各级围岩物理力学参数。对重庆轨道1#、6#线的岩体物理力学参数和围岩分级进行了调研，采用本文提出的分级方法与国标相比：区间隧道砂岩由III、IV级围岩提升为II、III级围岩；区间隧道砂质泥岩有1/3的Ⅳ级围岩提升为Ⅲ级围岩；车站隧道砂岩约有80%的IV级围岩提升为III级围岩。（6）采用数值极限分析新方法发展与完善了地铁隧道的设计计算方法，提出了合理的设计计算参数和初衬二衬的计算方法。其主要结论是：一是依据现有试验设备条件，提出了将直剪试验与单轴抗压试验相结合的混凝土剪切试验方法，从而确定不同强度等级混凝土剪切强度指标c、φ值；二是依据摩尔库伦公式和数值方法，提出混凝土剪切强度和抗压强度之间的关系，验证了混凝土剪切强度试验结果的可靠性，并将混凝土强度的标准值与设计值换算成剪切强度的标准值与设计值。结合实例，讨论了荷载释放量的确定、不同深浅埋分界标准的适用范围、应力释放后的围岩安全系数、初衬围岩与二衬结构的安全系数计算过程。最后对重庆地铁、青岛地铁车站进行的计算分析表明，Ⅲ级围岩以上可比现行衬砌厚度约减少30%，而Ⅳ、Ⅴ级围岩初衬厚度或强度尚需适当增加，以确保施工安全。更多还原

【Abstract】 In my essay, the developing of my thinking is just based on two subjects. First,failure mechanism of rock under unloading stress paths, especially rock macroscopicand mesoscopic failure mechanism have been studied for complex loading andunloading processes caused by engineering excavation, especially unloading process,including the evolution law of energy during different unloading processes, theevolution law and quantitative characteristics of AE during rock unloading failureprocesses, numerical simulation of rock unloading failure process based on particle flowcode. Then, using numerical limit method, rock classification and designing andcalculating methods of rock underground engineering have been discussed for practicalproblems in designing and calculating methods of rock underground engineering,including improving basic quality index in rock classification, the influence of span onsurrounding rock classification, the shear strength of concreter lining, designing andcalculating methods in rock underground engineering.The following achievements have been obtained:(1) Based on strain energy principle, energy evolution rules during the unloadingdamage process of marble under different unloading stress paths have been studied withprogramming method, as follows: axial energy curve during damage process changesnon-linearly, transforms from slow growth to rapid growth, then to slow growth andfinally to release. The total energy curve transforms from slow growth to rapid growth,then to slow decrease and finally to release. The main influence of different unloadingstress paths on energy evolution law during failure process focuses on yield andweakening stage. More energy are consumed by rock as confining pressure increasingas well as increasing rate of axial energy curve significant increases. The lowerunloading rate is, the higher increasing rate of axial energy is, more obvious transitionof axial energy curve at unloading point is; The increasing rate of axial energy increaseswhile unloading stress level is closed to bearing capacity peak, negative growing rate oftotal energy curve is higher.(2) The evolution law of acoustic emission characteristics has been analyzedduring failure processes under different unloading conditions, further quantized withprogramming method based on fractal theory, as follows: AE count rate maximizes at failure point during different failure processes and there is a relatively tranquil period ofAE before AE count rate reaching to maximum. The higher confining pressure is, theshorter relatively tranquil period endures, the higher maximum of acoustic count ratebecomes. The higher unloading rate is, the higher count rate of relatively tranquil periodis, the shorter time of duration is. When unloading point is in plastic stage, there will bea shorter relatively tranquil period before failure. Fractal dimension of AE is lowerbefore failure, stress path with maximum of fractal dimension is loading axialcompression and unloading confining pressure, path with smallest is conventionaltriaxial loading path.(3) Numerical simulations of rock loading and unloading failure process are carriedout by modifying FISH based on particle flow code, powerfully compensatemacroscopical lab tests from the microscopic view, as follows: numerical simulations ofcomplex unloading tests can be done effectively by designing different unloading stresspath. Relationship between stress path and mesoscopic energy such as friction energy,kinetic energy, bond energy and strain energy, relationship between mesoscopic cracksand failure precursors, and process of generating, propagating and penetratingmesoscopic cracks are studied, as follows: There is quite complicated nonlinearrelationship between meso-structure parameters and macroscopic strength parametersby simulating different unloading tests. Confining pressure has great influence onfriction energy caused by sliding friction between particles, further changes failuremode. The higher unloading rate is, the more cracks in rock interior developinadequately, the less bond energy is. Failure process is caused by combination effect ofboth compression failure and tensile-shear failure. Tensile-shear failure develops withdevelopment of compression failure, there is a concentrating trend of tensile-shearfailure along main shear surface.(4) The damage process of unloading rock has been studied from the microscopicview, the results of the examples show that analysis of unloading surrounding rockisfeasible, as follows: Mogi-Coulomb rule in classical failure rules is relatively moresuitable for experimental analysis under loading axial stress and unloading confiningpressure path; microcracks of rock can generally be assumed to be elliptic which candescribe more exactly strength criterion under unloading stress path from the point ofview of micromechanics and analytic function of single connectivity domain; thestress-strain relationship has been established during unloading failure process based on complex stress state of cracks of unit.(5) The assumption of surrounding rock classification about rock undergroundengineering has been put forward based on standard for engineering classification ofrock masses and the stability analysis and design theory of surrounding rock ofunderground engineering, as follows: first, qualitative characteristics of surroundingrock are improved and tweaked in table of surrounding rock classification. Forcorresponding to basic quality BQ values of different levels surrounding rock areadjusted for qualitative classifications corresponding to quantitative classifications.Then, surrounding rock classification ideas are put forward, benchmarked against rockmass quality and engineering span, to reflect the impact of span on stability ofsurrounding rock. Sub-classifications of station tunnel and running tunnel are provided,basic quality indicators of sub-classification are quantified, combined with characters ofunderground engineering. Quantitative indicators of rock self-stability are reflected bysafety factor and physico-mechanical indices of rock are obtained by the way ofinversion. By researching physico-mechanical indices and surrounding rockclassification of Chongqing Metro1#and6#, compared to national standard, theclassification method can get the following main conclusions: sandstone classificationof running tunnel promotes from III and IV to II and III, about a third of sandymudstone classification of running tunnel promotes from IV to III, about80%ofsandstone classification of station tunnel promotes from IV to III.(6) Designing and calculating methods of rock underground engineering have beendeveloped and perfected using numerical limit method, then reasonable designing andcalculating parameters and calculation method about lining have been discussed, asfollows: first, a new method of concrete shear strength is presented combing shear testsand uniaxial compressive tests under the present condition of laboratory, to determineshear strength indexes c、φ of several different strength grades of concrete; then, therelationship between shear strength and compressive strength of concrete has beendiscussed, stability of shear strength test results is validated and standard value anddesign value of concrete strength are taken usually into shear strength based onmohr-coulomb theory and numerical method. Some parameters such as loading burstsize, standard of dividing line, safety factors of rock about stress release and computingmethod of safety factor of surrounding rock and lining structure are determined withexamples.Finally, calculated results of Chongqing Metro and Qingdao Metro show that thickness of lining may be decreased in the III level surrounding rock; thickness orstrength of initial support should properly increase to ensure construction safety.更多还原