导　　师： 刘泉声

学科专业： 081401

授予学位： 博士

作　　者： ;

机构地区： 中国科学院研究生院

摘　　要： 深部岩体是由许多节理面和被其切割的岩块组成的块体系统,其力学作用主要受岩体内节理及块体控制,主要运动形式为块体间沿节理面产生的剪切位移,导致深部岩体锚固工程中锚杆常常被剪断、剪弯、拉断、扭曲,这些现象在低压力、埋藏浅的岩体中很少出现。浅部仅仅强调锚杆轴向作用的围岩锚固控制理论远远不能适应深部节理岩体稳定控制的要求,必须尽快发展深部锚控理论,才能有效的指导深部岩体支护设计。 本文以节理岩体和锚杆为研究对象。对于节理岩体中锚杆的加固作用,本文假定：锚杆只对节理面产生加固作用,对岩体内部的影响忽略不计,基于这种假定,建立了节理岩体锚杆加固模型,通过实验手段进行验证,并对其进行数值化；对于节理岩体,本文视其为可变形的块体,提出了围岩稳定的失稳判据,将岩体的结构性失稳和强度性失稳统一起来,并应用安全系数表示围岩的安全性能。 首先,结合锚杆抗剪作用的相关研究成果,基于锚杆与节理岩体的相互作用,揭示了锚固节理岩体抗剪作用机理,提出了适用于节理岩体的锚杆模型。模型引入表征锚杆两塑性铰距离的变量,将锚杆与岩体相互作用段划分为弹性变形段和挤压破坏段,分别考虑了这两部分中的锚杆切向变形和轴向变形规律,推导了荷载-位移的关系,总结了端部锚固与全长锚固两种锚固方式下节理抗剪强度的变化规律,分析了锚杆施加预应力后的状态,讨论了理论上的最优锚固角度。最后综合分析了锚杆轴力和剪力,并对锚杆在剪切荷载作用下的两种破坏形式进行了讨论。 为了研究锚杆对节理剪切性能的作用机理和作用模式,并对提出的锚杆模型进行验证,开展了锚固节理岩体的实验室剪切试验,模拟了不同强度的岩体在剪切荷载作用下的变形特性和受力特征,对比了锚杆加固前后岩体的剪切变形规律,分析了节理岩体强度、预应力及锚固方式对节理的抗剪能力的影响,试验过程中通过应变片测点监测锚杆轴力的变化规律,研究了节理剪切过程中锚杆的轴向受力机制和变形特性。剪切试验完成后,取出剪切变形后的锚杆,统计了变形段长度与各参数之间的关系。 为了使锚杆模型得以应用,将锚杆模型依据离散元原理进行二次开发,基于三维离散元软件3DEC中的fish语言,编制锚杆模型程序,并嵌入3DEC中,通过直剪试验验证模型,计算结果显示模型对全锚与端锚以及预应力的模拟都可以取得满意的效果,并通过直剪试验模拟结果对剪切参数进行了敏感性分析和作用规律的研究。 其次,本文以深部节理岩体为研究对象,以关键块体的判定为基础,综合考虑基于块体理论与基于强度准则的稳定性分析方法,提出了围岩稳定性的判据：围岩失稳优先发生在节理面,块体沿着节理面滑动；当块体经分析确定稳定后,围岩仍可能在块体内部剪切破坏,需要对块体内部利用强度准则进行校验。 结合地下工程的特点,运用Monte-Carlo方法生成节理网络,采用矢量分析方法,分析块体间的相互作用,考虑地应力的影响,判定关键块体,计算块体稳定安全系数和锚杆设计预应力值以及围岩状态的安全系数。编制了判定开挖后围岩关键块体、计算块体安全系数、锚杆需要预应力值和岩体强度安全系数的程序。 最后,以淮南矿区顾桥煤矿深部巷道工程中的断层破碎带为研究对象,应用了节理岩体锚杆模型,建立了大规模地下工程数值模拟模型,分析锚杆加固巷道工程的稳定性,并在围岩稳定性分析研究的基础上,对围岩的支护加固方案进行了优化调整,数值模拟结果和监测数据分析显示出调整后的支护方案能够取得良好的加固效果。 Rockmass in deep engineering can be regarded as block system composed of many joint surfaces and its cutting rockmass. An unloading process related to underground excavations could give rise to structurally controlled instability due to the falling, or sliding, of rock blocks from the excavation perimeter. In these conditions, the design of the underground excavation should be able to define stabilization measures that prevent both major and local rock block instabilities. The main research objects in this paper were jointed rockmass and rockbolt. For the rockbolt, it was assumed that the reinforcement affected on joint surfaces only and the influence inside the blocks was neglected. Based on this assumption, the rockbolt reinforcement model in jointed rockmass was established, and verified through an experiment, then a numerical model compiled by FISH code in 3DEC was proposed; For the jointed rockmass, it can be regarded as deformable block which was explained by the block theory. The criterion of instability of surrounding rockmass was put forward which synthesised the structural instability and strength instability of rockmass, and the safety factor which could express the safety of surrounding rock was calculated. First of all, in order to predict the contribution of rockbolts to the shear strength of a rock joint, a new calculation model is presented in this paper based on the analysis of the interaction between rock and rockbolts in an underground excavation where potentially sliding rock blocks are present. The main characteristics of this model are the accounts for the interaction of the axial and the shear forces mobilised in the rockbolt, as well as the large plastic displacements of the rockbolt occurring during the loading process. The assumed interaction scheme is activated by a small displacement, while this displacement does not induce a destressing of the rock block. According to the state of rock in the borehole interacting with unilateral bolt, such a model introduces a variable which divides the active length, the short length of reinforcement which spans the discontinuity and changes orientation during shear displacement, into the elastic deformation zone and the failure zone. Based on analysing the failure mode of rockbolts, the maximum rockbolt contribution is obtained, meanwhile, the complete curve of the rockbolt contribution as a function of the displacement along the joint can be computed. The shear tests of bolted jointed rockmass were carried on in the laboratory to further study the mechanical behaviors of rockbolt in the jointed rockmass, and to verify the rockbolt model. In the experiment, rockmasses of different strength, different anchor mode and different prestress were simulated, meanwhile, the deformation characteristic of rockbolts was monitored to compare the shear deformation regularity before and after bolting and to analysis the influence of pretension, rock strength, the mode of anchorage on shear capacity of jointed rockmass. In the process of test, the strain of axial force bolt was monitored through the strain gauge in order to study the axial deformation mechanism and characteristic of rockbolt. After shearing test, the failure rockbolt was taken out to statistic the relationship between the deformation length and other parameters. The rockbolt model compiled by the fish language in the three-dimensional discrete element software-3DEC was estalished and was embedded into 3DEC successfully. In order to verify the model, a simple shear test was simulated with 3DEC, whose result shows that the model can achieved satisfactory effect on simulating the prestressed, end-anchored, and full length anchoring rockbolt. At last, the sensitivity analysis and acting law of the shearing parameters was discussed. Secondly, taking jointed rockmass as the research object, the stability methods of block theory and strength criterion were considered comprehensive based on the judging method of keyblocks, and the instability criterion of surrounding rockmass was put forward:Instability of block sliding along the joint surface in surrounding rock occurred prior to all others; when the block was determined to be stable, shear failure in block may happen, and the rockmass should be checked with strength criterion. According to the characteristics of underground engineering, joint network was generated using Monte-Carlo method. Then, taking the influence of in-situ stress into consideration the interaction between blocks was analyzed using vector method to find the keyblocks, and its blocky safety factor, the designed anchor prestress value and the safety factor expressing the state of surrounding rock were calculated thougth the procedures compiled by FISH code for the safety evaluation of the project in deep underground. Finally, taking the fault fracture zone in deep roadway of GuQiao coal mine as the research object, a large-scale underground engineering numerical model was established, then the stability of bolting reinforcement roadway engineering was evaluated, and in this foundation, the rock bolting reinforcing scheme was optimized adjustment, and the numerical simulation results showed that the support could meet requierment.

关 键 词： 预应力锚杆 节理岩体 模型研究 抗剪性能 大变形 试验研究 离散元 二次开发 块体理论 围岩稳定性分析 安全系数 断层破碎带

分 类 号： [TU476]

领　　域： [建筑科学] [建筑科学]