【作者】 吝曼卿；

【导师】 夏元友；

【作者基本信息】 武汉理工大学 ， 岩土工程， 2013， 博士

【摘要】 随着矿业工程、水电工程和隧道工程逐步向深部岩体发展,深部硬脆岩体开挖扰动造成局部应力集中,围岩所受应力梯度增大,伴随而来的岩爆灾害也逐步增加。而对于不同应力环境和应力路径下岩体开挖扰动产生应力梯度对岩爆灾害的研究非常少,且目前岩爆试验还大多处于小尺寸试件的均布加卸载阶段,为研究梯度加载对岩体受力直至发生岩爆的影响,本文通过对在地下工程不同应力环境与应力路径下岩体的受力变化进行分析,总结深部岩体开挖引起围岩应力场分布的主要形式,采用典型的应力梯度加卸载路径,结合自主研发的岩爆加载装置对试件进行室内试验研究,以分析不同应力梯度对试件产生岩爆的影响,并通过数值模拟与室内试验验证的方法,系统研究了不同应力梯度和应力环境下的岩爆机理。论文主要取得以下研究成果：(1)通过对隧道开挖影响区岩体进行应力弹性理论解析解分析,并利用FLAC3D有限差分软件对不同开挖深度、不同侧压力系数下的马蹄形隧道进行开挖模拟,得到不同开挖深度和侧压力系数下,隧道开挖引起岩体应力梯度分布趋势,总结隧道开挖掌子面逐渐接近岩体监测面并随开挖进一步推进的过程中,测试面岩体受开挖影响的应力梯度变化规律,推导出对隧道围岩所受应力梯度值随开挖步骤的拟合公式。(2)选择满足岩爆倾向性的相似模型材料,并通过室内试验得到模型试件的基本物理力学指标。利用自主研发的YB-A型岩爆加载装置对大尺寸试件进行顶部梯度加载的四组不同加卸载路径的岩爆试验,通过改变不同侧压力系数、单面卸载时顶部不同加载力大小,对顶部进行不同速率加载的方式,对试件在四种加载路径下发生岩爆时,其卸载面的岩爆破坏形态进行分析,并得出试件产生岩爆时,其顶部所受应力梯度大小与试件经历加卸载环境和加载路径的关系。(3)为分析试件在四种加卸载路径下发生岩爆与试件顶部所受应力梯度分布的影响,通过采集试件在各加载路径中的应变片变形数据,对比试件在加卸载前后的CT成像分析,并对岩爆试验后的岩爆碎屑进行分形分析,得出试件发生岩爆的过程是试件卸载面附近岩体经历了：试件在受加载时能量吸收-卸载面压密-试件卸载后在其卸载面中部拉裂破坏-破裂成板的岩爆破坏过程。CT成像图直观地反应出试件卸载面附近的加载压密区和卸载后试件内部的损伤区；最后通过对岩爆碎屑的分形维数值计算,建立了岩爆烈度与试件加载路径的关系。进一步分析了试件在四种加卸载路径下的岩爆特性。(4)基于能量耗散原理,利用3DEC离散元软件并嵌入弹性能密度的fish语言,计算并追踪测点的弹性能密度变化的全过程,选择与室内试验相类似的加载应力梯度对模型试件进行加卸载模拟,以对室内试验结果进行验证与补充。模拟结果再现试件在高应力梯度条件下卸载时,随着试件顶部应力梯度的逐渐增加,试件卸载面呈局部剥落,乃至出现块体喷射的岩爆过程,数值模拟试验与相同路径下的室内试验结果较吻合。更多还原

【Abstract】 With the development on mining site, hydropower engineering and tunneling project to deep rock mass gradually, deep brittle rock stress redisturbution by excavating, causing local stress concentration, stress gradient in surrounding rock increases and rock burst accompanied also gradually increases. There are few researches about the impact of stress gradient after excavation under different stress environments and stress paths on rock burst disasters, and rock burst test is also present on small size specimen uniform unloading stage. To study effect of gradient loaded on rock burst, the paper analyzes the force changes under different stress environments and stress paths on rock in the underground construction, summaries the main forms of surrounding rock stress field distribution caused by deep rock excavation, applies typical unloading paths of stress gradient, combined with independent research and development of rock burst loading device for specimens in lab, and analyses the influence of different stess gradients on rock burst. It also uses numerical simulation and experimental models validation to study mechanism of rock burst under different stress gradients and stress environments. The main achievements can be expressed as follows.(1) Through the stress theory analysis of rock mass elasticity solution in tunnel excavation influence area, by using the software of FLAC3D to simulating the tunnel excavation in different excavation depth and lateral pressure coefficient, the rock stress gradient distribution trends caused by tunnel excavation in different excavation depth and lateral pressure coefficient were analyze. Study showed that, when the excavating face of tunnel pass tested rock, tangential stress of tunnel wall rock increased dramatically, radial stress reduced obviously, surrounding rock under great stress gradients. Stress distribution in stable surrounding rock got by numerical simulation experiences the same trend of stress distribution derived by theoretical formulas.(2) The laboratory test chooses the model materials which meet the rock burst proneness options to cast specimens, uses the self-developed YB-A rock burst loading device to conduct gradient loads rock burst tests on the top of large size specimens in four different loading-unloading paths, and analyzes the rock burst morphology of unloading surface under the three conditions of specimens at different lateral pressure coefficients、different top loading when unloading and different loading rates. specimen suffers relatively lower load value at the top when one side unloading, and in the same stress gradient further loading, the specimen’s top stress gradient is relatively lower when rock burst occurs; if specimen suffers higher loading rate at the same loading path, the specimen’s top stress gradient is relatively lower when rock burst damage occurs.(3) Analyzing the influence of rock burst under the four loading-unloading paths on the stress gradient changes at the top, the characteristics of rock burst under the four loading-unloading paths have been studied. CT imaging assay pre and post of loading-unloading and clastic rock burst fractal analysis had been conducted through analyzing the strain gauge deformation of in different loading paths. Finally rock failure process had been obtained near the unloading face during process of rock burst. That was energy absorption, unloading face compaction, tension failure in the middle of unloading face and rupturing into plate. The damage zone and compaction area are clear showing by CT imaging figure. The loading velocity of the specimen in the same surrounding pressure is larger, the range of rock burst when unloading in single face is smaller, the vertical load of rock burst is smaller, the boulder yield of specimen is less, the fractal dimension is larger relatively.(4) Based on the principle of energy dissipation, the changing process of elastic energy density of measuring points had been calculated and tracked by using3DEC embedded the fish language. Simulation test of the specimen model in the loading-unloading process was carried out with stress gradient similar to laboratory test, in order to validate and supplement the laboratory test results. Simulation results showed that the unloading surface had been destroyed in the shape of local spalling under high confining pressure with the gradual increase of stress gradient, even block injection during the process of rock burst. The numerical experiments and the laboratory test resulted with the same path are in good agreement.更多还原