【作者】 冷先伦；

【导师】 盛谦；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2009， 博士

【摘要】 为研究TBM掘进下,隧洞围岩开挖扰动与损伤及其破坏机理,本文以南水北调西线工程为工程背景,对隧洞围岩TBM掘进后扰动和损伤区及其变形特征、应力演化规律和工程岩体的力学特性进行了系统研究与分析,主要研究工作与特点表现在以下几个方面:(1)在充分调研南水北调西线工程复杂的附存环境的基础上,研究了其地层岩性、地质构造、地应力场分布规律和复杂的隧洞施工方案。提出TBM掘进下影响围岩稳定的关键因素:隧洞埋深大、TBM掘进长度大、地应力分布规律复杂、节理裂隙发育。(2)开展了板岩室内单轴压缩实验、三轴压缩实验以及不同围岩在不同卸荷速率下的三轴加卸载实验,并通过Hoek-Brown经验强度准则拟合板岩的岩体力学参数。研究了板岩在三轴压缩实验下和三轴加卸载实验下的力学特性和破坏特征,指出板岩在破坏时表现为脆性破坏,并具有峰后残余强度等特征;其破坏强度亦与卸围压的速率有关,即卸荷速率越快,板岩的强度越高,破坏时的围压越小。(3)总结了圆形洞室开挖后围岩变形、应力及塑性区等理论解的求解过程,并编制了相应的计算机求解程序。对传统开挖方法(钻爆法)进行了数值模拟分析,研究了洞室开挖后围岩的变形量、主应力和主应力方向的变化规律及塑性区大小。针对TBM掘进开挖的特点,即TBM刀盘的顶推作用使刀头嵌入岩体中,刀盘的旋转使刀头切割岩体,提出相应的数值模拟方法,即在刀头作用的区域内施加三个方向的速度来模拟掘进过程,轴向速度模拟刀盘的顶推作用,切向速度和径向速度的合成来模拟刀头的切割作用,并假定岩体在达到塑性剪切状态时认为岩体被开挖掉。在相同条件下,对理论解,钻爆法和TBM法的数值模拟结果进行了对比分析,发现TBM法的位移值仅为理论解和钻爆法的65%左右,塑性区仅为理论解的58%,为钻爆法的70%,而变形的整体趋势,三种结果较为接近。(4)在不同卸荷速率下三轴加卸载室内实验成果的基础上,以Hoek-Brown经验强度准则为依据,拟合出在不同卸荷速率下岩体的力学参数(粘聚力和摩擦角)。在FLAC3D程序中植入加卸载准则,研究了在不同掘进速率下隧洞围岩的开挖扰动区特征和围岩稳定特征。结果显示:掘进速率越快,围岩开挖扰动区越小,围岩越稳定;隧洞围岩在开挖后变形较为均匀;在隧洞的径向,位移和应力变化较为明显的呈现为三个区域,即强变化区、弱变化区和平稳区;最大主应力随着洞径方向逐渐由单向应力状态向二向应力状态和三向应力状态转变,第二偏应力不变量在隧洞轴向方向形成了一闭合的应力集中区域,称为“应力墙”,该区域在TBM掘进过程中对刀头切割岩体达到破岩的效果极为有利;隧洞围岩开挖扰动区随TBM掘进速率变化较大,当掘进速率增加一倍后,其扰动区由1.1m降低到0.4m,减小了64%。(5)根据板岩在室内实验中表现出来的脆性和屈服后强度特性,提出了以CWFS脆性模型为基础,考虑岩体屈服后损伤的本构模型,通过VC++编译dll动态链接库,并将其植入FLAC3D程序中。应用神经网络和遗传方法等优化算法对本构模型中的参数进行了反演分析,并以室内三轴压缩实验为依据,对该本构模型进行了验证,结果表明本文提出的考虑损伤的CWFS模型可以较好的反映板岩的弹性特征、屈服后的强化特征、脆性破坏特征和破坏后残余强度特征。以该模型为基础,模拟了南水北调西线隧洞在TBM掘进条件下隧洞围岩的损伤特征,并与基于Mohr-Coulomb本构关系的计算结果进行了对比分析。本文提出的考虑损伤的CWFS模型能更好的反映隧洞掘进后围岩损伤特征,即损伤沿着弱势区域发展的规律。(6)以UDEC2D程序为手段,研究了在不同埋深、不同节理倾角和不同节理间距情况下,TBM掘进过程中,刀头对岩体的破裂过程。指出岩体内部裂隙的形成分为三个阶段,即裂隙的产生、裂隙的发展和裂隙的贯通;岩体内部损伤时产生两条主要的裂隙,一条平行于节理方向发展,一条与节理相交形成闭合裂隙;综合评价了刀头贯入量与刀头数量之间的关系。基于南水北调西线工程岩石节理的统计规律,假设其分布满足一定的正态分布规律,编制二维随机节理生成器,生成了随机节理分布的隧洞开挖模型,模拟分析了在随机节理结构下,隧洞围岩的开挖损伤特征。结果表明洞室围岩在局部发生块体脱落现象,在洞室底部有整体突起现象;隧洞围岩在洞室附近表现为拉破坏,而沿着洞室径向方向转换为剪切破坏。更多还原

【Abstract】 The South to North Water Transfer Project is taken as the engineering background of this thesis and the excavation disturbed zone and damage zone,deformation characteristics, stress evolution law and rock mechanical behaviors in surrounding rock of tunnel by TBM driving are studied.The Major works of this thesis are summarized as follows:(1) Base on the comprehensive investigation of the complicated existing environment of the South to North Water Transfer Project,the formation lithology,geological structure, distribution of in-situ stress field and complicated construction scheme are studied,and it is indicated that the key influence factors on stability of surrounding rock of tunnel are deeply buried,big length,complicated distribution of in-situ stress field and developing of joint fissures.(2) The uniaxial compression test of slate,the triaxial compression test of slate and the loading and unloading triaxial tests of different surrounding rock in varied unloading rate have been finished,and the Hoek-Brown empirical strength criterion is used to fit the rock mechanics parameters of slate.The mechanical properties and failure characteristics of slate indicate that the slate presents as brittle failure and has post-peak residual.The failure strength of slate is related to the unloading rate,the unloading rate is faster,the strength is higher,and the failure confining pressure is less.(3) The computing program is compiled to reach the theoretical solutions of surrounding rock deformation,stress and plastic zone after circular tunnel excavation.The numerical simulation method is applied to analyze the deformation,principal stress, variation law of principal stress orientation and size of plastic zone of surrounding rock in the traditional excavation.The work theory of TBM driving is that the incremental launching action makes the cutter head embedded in rock,and the rotation of cutter head makes the rock excavated.So in the numerical simulation,three direction velocities are used to simulate the TBM driving process,the axial velocity is to simulate the incremental launching action of the cutter head,the tangential and radial velocity are used to simulate the cutting action of the cutter head,and the plastic zone is assumed to be excavated.In the same conditions,the three results of theoretical solutions,traditional excavation and TBM driving are compared and show that the displacements value in TBM driving are about 65% of theoretical solution and traditional excavation method,and the plastic zone is only 58% of the theoretical solution,70%of the traditional excavation method.However the general deformation tendency is close for the three methods.(4) On the basis of the results of the loading and unloading triaxial tests in varied unloading rate,Hoek-Brown empirical strength criterion is used to fit the slate mechanical parameters including cohesion and friction angle.The FLAC3D program which contains the loading and unloading criterion is adopted to analyze the excavation disturbed zone and stability in surrounding rock of tunnel in varied TBM driving speed.The results show that the driving speed is faster,the excavation disturbed zone in surrounding rock is smaller,and the stability of surrounding rock is better;the deformations of surrounding rock are uniformly distributed after excavation;in the radial direction of tunnel,three zones are obviously shown for the displacement and stress variation:strongly varied zone,weakly varied zone and stable zone;along the tunnel radial direction,the maximum principal stress gradually vary from uniaxial to biaxial and triaxial,and the second deviatoric stress invariant forms a closed stress concentration zone which is called "stress dike" and is great helpful to rock breaking;the excavation disturbed zone of tunnel varies with TBM driving speed,when the speed increases 100%,the excavation disturbed zone decreases 64%,from 1.1 meter to 0.4 meter.(5) Considering the rock post-yield damage,a new constitutive model based on the CWFS brittle model is proposed in this thesis and is implanted to FLAC3D program by debugging dll in VC++.Based on the results of triaxial compression tests,this constitutive model is verified through parameter back analyzing by optimization algorithm such as neural network and genetic algorithm.The results show that the model can reflect the elastic characteristic,post-yield characteristic,brittle failure and post-failure residual strength characteristic of slate.Based on this model,the surrounding rock damage characteristic of TBM driving of the South to North Water Transfer Project are studied and also compared with the results by Mohr-Coulomb constitutive model.And the conclusion is drawn that the constitutive model in this thesis can better reflect the damage rule of the surrounding rock in TBM driving,that damage develops along the weak zone.(6) The process of rock damage by cutting head in TBM driving is studied in condition of varied buried depth,joint inclination and spacing with the UDEC2D code.The conclusions are drawn that the formation of rock fracture goes through three stages, generation,development and transfixion;two main fractures are generated in the damage process,one parallels to the direction of joint,the other intersects to the joint and form a closed fracture.The relationship of cutting head penetration value and the number of cutting head is also evaluated.On the basis of joint statistical law of the South to North Water Transfer Project,it is assumed that joint distribution accords with the normal distribution,and the relative joint generation program is compiled to UDEC.Using random joint distribution model,the excavation damage characteristic in the surrounding rock of tunnel are studied.The results show that part block falling occurs around the tunnel and integral uplift occurs at the bottom of tunnel.The surrounding rock failure of tunnel presents as tension failure around the tunnel and converts to shear failure along the radial direction of tunnel.更多还原