【作者】 张后全；

【导师】 贺永年；

【作者基本信息】 中国矿业大学 ， 岩土工程， 2010， 博士

【摘要】 本文以深部围岩分区断裂为工程背景与研究主题,利用厚壁圆筒岩样加、卸载试验,紧紧围绕厚壁圆筒壁内环状断裂机制(能量峰值不稳态分布及其能量判断准则),厚壁圆筒高压卸载轴向劈裂机制两个着重点进行研究,并对岩石破坏的尺度效应、卸载破坏的冲击倾向性及岩石破坏的结构效应等与厚壁圆筒卸载破坏相关的力学行为进行拓展研究,以期能够有效地揭示分区破裂力学产生机制,为此类破坏巷道实现结构性稳定提供理论支持。研究内容及研究方法如下:(1)首先对岩石微结构面和岩石基本物理力学性质进行描述与测试,同时开展单轴抗压强度尺度效应研究,为准确描述岩石物理力学性质及后续真三轴能量破坏准则建立提供准确参数服务。(2)采用厚壁圆筒试件,根据深部巷道开挖围岩受力特点(加载、卸荷),对厚壁圆筒岩样进行加、卸载,实验研究厚壁圆筒壁内环状现象。(3)利用厚壁圆筒壁内断裂时的三向应力,建立和验证可考虑中间主应力对能量释放影响的真三轴能量破坏准则。(4)考虑卸荷损伤对厚壁圆筒三向应力变化,根据岩石破坏的能量原理,研究厚壁圆筒壁内环状断裂机制。(5)根据加、卸载受力变化特点,依据Griffith理论,研究厚壁圆筒高压卸载轴向劈裂机制。(6)根据岩石强度破坏两种基本模式耗能情况,研究岩石卸荷破坏的冲击倾向性。(7)根据岩石破坏的结构效应特点,探讨厚壁圆筒完整承载结构与出现环形断裂关系;利用RFPA2D进行深部围岩破裂演化结构效应数值模拟,得到围岩深处远场裂纹的发生位置及产生前提条件。研究得到如下创新性成果:(1)在高压卸载条件下,获得了与单、三轴压缩破坏情况截然不同的,具有张拉破坏性质的厚壁圆筒壁内环状断裂现象;从实验角度证明了灰岩厚壁圆筒只有在卸荷条件下才会发生有规律的壁内环状断裂。(2)初步建立和验证了可考虑中间主应力对能量释放影响的真三轴能量破坏准则,获得了灰岩厚壁圆筒中间主应力能量释放影响系数。(3)对厚壁圆筒壁内能量峰值不稳定分布状态以及峰值处能量是否满足能量破坏准则进行了判断,并根据最小耗能原理及Griffith理论,有效揭示了厚壁圆筒高压卸载壁内环状劈裂机制。(4)基于岩石卸荷劈拉破坏特性以及张拉破坏最小耗能特点,从岩石冲击破坏产生的刚度条件和能量条件两个角度,阐明了岩石卸荷破坏的冲击倾向性。(5)根据岩石破坏的结构效应特点,解释了厚壁圆筒内壁完整承载结构对壁内出现环形断裂的影响;利用RFPA2D对深部围岩破裂演化结构效应进行了数值模拟,获得了围岩深处远场裂纹的发生位置及产生前提条件;远场裂纹发生位置符合规律( )为巷道半径),与分区破裂位置规律一致。更多还原

【Abstract】 Zonal disintegration in deep underground surrounding rock mass is the engineering background and research subject of this dissertation. Based on the unloading experiments of thick-walled cylinder rock samples after high compression, this research is focused on ringlike failure mechanism in thick wall (unstable distribution at energy peak-value point and energy judgment criteria) and axial splitting failure mechanism of rock cylinders under unloading condition after high compression. It also studied the related mechanical behavior about the unloading failure of rock cylinder after high compression such as scale effect of rock failure, rock burst tendency of unloading failure and structural effect of rock failure. The research results can supply reasonable explanation of zonal fracturing mechanism and theoretical foundation for the supporting of similar roadways to keep the structural stability.Research contents and methods are as follows:(1) The description of rock structural plane and the measurement of basic physical and mechanical behavior were firstly performed. The scale effect of uniaxial compressive strength was also studied. These results were the basis of description of rock physical and mechanical behavior and supply accurate mechanical parameters for setting up the real triaxial energy criteria in the following.(2) Based on the stress change characteristics of surrounding rock mass in deep underground engineering (loading to unloading), the unloading experiment of rock cylinders after high compression was performed. Ringlike failure in thick wall of rock cylinder was studied by this experimental method.(3) The real triaxial energy criteria taking account of the influence of intermediate principal stress on energy release was set up and validated by the three principal stresses of ringlike failure in rock cylinders.(4) Taking account of the influence of unloading damage on the variation of three principal stresses, ringlike fracturing mechanism was studied based on the energy principles.(5) Based on the stress variation, axial splitting mechanism of rock cylinders under unloading condition after high compression was studied by the Griffith theory.(6) Based on the energy release condition of two basic failure modes of rock strength failure, rock burst tendency of rock unloading failure was studied.(7) Based on the structural effect of rock failure, the relation of intact loading structure of rock cylinders and the occurrence of ringlike failure was discussed. Based on RFPA2D, the fracturing structural effect after deep surrounding rock failure was studied by numerical simulation. Producing location and formation condition of remote cracks in the middle part of rock was studied.The main innovative achievements were obtained as follows:(1) Ringlike failure pattern with highly tensile behavior was obtained under unloading condition; this failure pattern is obviously different from uniaxial, triaxial compressive failure. It was validated by experiments that the ringlike failure occurred only under the unloading condition.(2) The real triaxial energy criteria (in the following) taking account of the influence of intermediate principal stress on energy release was preliminarily set up and validated. The influential coefficient of intermediate principal stress on energy release of limestone cylinders was obtained.(3) The unstable distribution of energy peak-value in thick wall of rock cylinders and whether the energy at peak-value point conforms to the energy failure criteria were judged. Based on the principles of minimum energy dissipation and Griffith strength theory, the ringlike axial failure mechanism was effectively discovered.(4) Based on the splitting fracturing characteristics of rock unloading failure and minimum energy dissipation characteristic of tensile failure, from the two viewpoints of stiffness and energy conditions, rock burst tendency of rock unloading failure was effectively illuminated(5) Based on the structural effect characteristics of rock failure, it was clarified the influence of intact loading structure of rock cylinder on the occurrence of ringlike failure. Based on RFPA2D, Producing location and formation condition of remote cracks in the middle part of rock was studied by numerical simulation. The producing location of remote cracks conforms to thedenotes the radius of circle roadways), which are in relatively consistent with the fracturing location of zonal disintegration.更多还原