【作者】 赵凯；

【导师】 乔春生；

【作者基本信息】 北京交通大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 目前,国内外对不同载荷条件下岩石疲劳力学特性研究相对滞后,尤其缺乏对岩溶石灰岩的疲劳特性和损伤演化规律的系统研究。鉴于岩溶铁路隧道与溶洞(腔)间围岩长期稳定性分析的需要,本文依托国家自然基金项目,以宜昌万州铁路隧道石灰岩为研究对象,采用文献调查、室内试验、理论分析和数值模拟相结合的研究方法,系统的研究了石灰岩在静力学范围内的应变率效应；探索了不同载荷条件下石灰岩疲劳力学特性；建立了考虑多因素影响的石灰岩疲劳寿命预测模型和疲劳损伤演化模型,并将其应用于弹塑性数值计算中。为考虑岩石疲劳损伤的岩溶隧道围岩长期稳定性分析提供了重要的基础资料和可借鉴的研究思路。取得的主要研究成果如下：(1)在静态加载范围内,石灰岩具有很强的率敏感性。试验表明,石灰岩破坏峰值强度随加载速率的增加有明显提高,峰值强度与应变率的对数呈线性关系。而峰值应变随应变率增加却有小幅减小的趋势。分析石灰岩破裂过程,发现提高加载应变率对岩石裂纹不稳定扩展阶段影响不大,对岩石裂纹稳定扩展阶段却有较大影响。加载应变率越高,岩石进入裂纹扩展阶段(塑性阶段)就越晚,塑性段在全应力应变曲线中所占比例相应减小,弹性阶段比例增加,岩石的弹性特性更为明显。(2)研究了测试程序对施密特锤回弹测试结果的影响,给出了一种扰动较小且测量准确的施密特锤测试程序。在对比研究了超声、回弹和超声回弹综合法三种无损方法估算单轴压缩强度方法的预测精度的基础上,建立了一套估算标准试样单轴强度的无损方法。由测试数据建立了双参数指数型石灰岩标准试样单轴压缩强度估算模型。(3)利用宜万铁路石灰岩开展了各种加载条件下的疲劳力学试验。发现：随着上限应力水平的降低,石灰岩疲劳寿命在半对数坐标下呈线性增长的趋势；应力幅值对疲劳寿命起着关键作用,应力幅值越大岩石的疲劳寿命越短;岩石疲劳“门槛值”不仅与岩石类型密切相关,而且随着加载速率的增加而提高；在0.5～3Hz加载范围内,石灰岩疲劳寿命随加载频率的增加而增加,疲劳寿命与加载频率满足双对数坐标下的线性关系。在试验基础上,建立了基于S-N曲线的疲劳寿命估算模型、同时考虑上限应力和应力幅值影响的石灰岩疲劳寿命估算模型以及基于加载频率和上限应力的多因素疲劳寿命估算模型。(4)石灰岩疲劳变形经历初始变形阶段、稳定发展阶段和加速阶段三个不同阶段。对比疲劳极限变形和静力全曲线控制变形,发现两者之间十分接近；在0.5～3Hz范围内,改变加载频率对石灰岩疲劳破坏时轴向极限变形几乎无影响；说明“岩石疲劳破坏时的极限变形规律”不受加载频率的影响。依据石灰岩疲劳变形发展规律,提出了基于平均应变增量的疲劳寿命计算模型。确定该模型计算参数仅需要开展有限次数的循环压缩试验和单轴压缩试验,从而极大的缩减了试验投入。(5)探讨了岩石的非线性变形滞后效应并分析了其形成原因。总结了循环加卸载变形曲线中常见的五种回滞环形态,并就各种形态的成因开展了讨论。(6)利用单轴静态压缩试验、循环动力试验和超声测试三种试验手段,对比研究了石灰岩静态、准动态和动态弹性模量之间的关系。(7)疲劳试验结果表明,石灰岩动态弹性模量随循环加载呈三阶段衰减规律,由此建立了基于剩余刚度的石灰岩疲劳损伤演化模型。结合石灰岩疲劳寿命多因素估算模型,提出了一套适用于岩石工程的能考虑围岩动力疲劳损伤的计算方法。采用FLAC3D进行二次开发,实现了该计算方法的数值程序化,并将其应用于鲁竹坝二号(Ⅱ线)隧道地震灾变作用下的动态模拟计算中。更多还原

【Abstract】 It is known that the research on fatigue mechanical characteristics of rock under different loading condition is relatively lagging behind in institute foreign and domestic; a systematic research about the fatigue properties and damage evolution laws of karst limestone is absence in particular. For analyzing the long-term stability of surrounding rock between railway tunnel and karst cave, relying on the project of National Natural Science Foundation, a systematic research which take Yichang Wanzhou railway tunnel limestone as research subject was conducted by using combining methods of literature survey, laboratory testing, theoretical analysis and numerical simulation in this paper. The strain rate effect of limestone within static category was studied systematically; fatigue mechanical properties of limestone in different load conditions was explored; multi-factors fatigue life prediction models and fatigue damage evolution model were established and were applied in elastoplastic numerical calculations in this article. For the analysis of surrounding rock long-time stability when taking rock fatigue damage into account in karst tunnel, important basic information and research ideas for future reference were provided by those research results. The main research conclusions are as follows:(1) In the range of static loading rate, limestone has strong rate sensitivity. Tests show that the peak strength of limestone increases obviously with the rise of loading rate, and the relationship between peak strength and logarithm of strain rate is linear. However peak strain shows decreasing trend with the increase of strain rate. By analyzing the rupture process of limestone, it is concluded that there is little effect on unstable crack expansion phase while greater impacts on the stable crack expansion when increasing strain rate. The higher the strain rate, the later rock sample reaches the crack propagation stage (plastic phase) which means the proportion of plastic stage in the whole stress-strain curve decrease and that of elastic stage increase correspondingly.(2) The effect of tests procedure on the tests results of Schmidt hammer was studied, and a tests procedure of Schmidt hammer with smaller tests disturbance and more accurate was proposed. The accuracy for predicting limestone uniaxial compression strength (UCS) by using ultrasonic, Schmidt rebound and ultrasonic-rebound combined methods, three non-destructive estimation tests, was comparatively studied. Basted on the results, a non-destructive method for estimating the strength of standard samples was established. And, according to tests data, a two-parameter exponential model for predicting UCS of limestone was proposed(3) Fatigue mechanical tests under various loading conditions were carried out by using Yiwan railway limestone. The conclusion is that the fatigue life of limestone was trading to prolong linearly in the semi-logarithmic coordinate with the decrease of upper limit stress; the greater stress amplitude the shorter fatigue life of rock which means stress amplitude play a key role on fatigue life; rock fatigue "threshold value" is not only closely associated with rock types, and increased with the raise of loading rate; in the range of0.5-3Hz, fatigue life of limestone advanced with the growth of loading frequency, and they met a linear relationship in double logarithmic coordinates. According to the tests, the S-N curve based, taking into account the impact of supper limit stress and stress amplitude life estimation models as well as a multi-factors fatigue life estimation model based on loading frequency and supper limit stress were estimated.(4) The limestone fatigue deformation underwent initial deformation stage and stable development stage as well as acceleration phase three different stages. Contrasting fatigue terminal deformation and control deformation of static whole stress-strain curve, it is found that they were very close. It is hardly affected by changing loading frequency to the fatigue axial terminal deformation of limestone which means’the limit deformation law when approaching to fatigue failure’untouched by the load frequency. An average strain increment based fatigue life calculation model was proposed according to the development rules of limestone fatigue deformation. Only a limited number of cyclic compression tests and uniaxial compression tests were required to determine the model parameters, which greatly reduced the fatigue tests inputs.(5) Nonlinear deformation lagged effects of rock was explored and its cause was analyzed. Five common hysteresis loop shapes of cyclic loading and unloading deformation curves were summarized and the causes of those various forms were discussed also.(6) Uniaxial static compression experiment, cyclic dynamic tests and ultrasonic tests were adopted to research the relationship among static, quasi-dynamic and dynamic elastic moduli of limestone.(7) Fatigue tests results showed that the decay of limestone dynamic elastic modulus went through three different stages with the conduction of cyclic loading. Thus, a fatigue damage development model of limestone was established based on the residual stiffness. And, a set of calculation method which can consider dynamic fatigue damage of surrounding rock and suit for application in rock engineering was proposed by combining with multivariate estimation model of limestone fatigue life. The numerical programming producer of this method was achieved by utilizing a secondary development of FLAC3D software. And, it was applied to a dynamic simulation calculation of Luzhuba2nd tunnel under the action of earthquake disaster.更多还原