【作者】 张文居；

【导师】 赵其华；

【作者基本信息】 成都理工大学 ， 岩土工程， 2009， 博士

【摘要】 西南部地处我国第一个地形梯度带,区内水能资源十分丰富,一系列已建和拟建大型水电工程座落于这一地区。由于该区域大地构造上位于青藏断块的东部边缘地带,受青藏高原近百万年来持续隆升的影响,地质环境条件特殊复杂。因此,在这些地区进行大型、超大型工程建设,有一系列制约工程设计,施工和运营的重大工程地质问题亟需加以研究和解决,其中之一便是岸坡深部裂缝问题。本文以青藏高原东侧的西南地区为主要研究对象,通过选取雅砻江锦屏一级,大渡河瀑布沟、深溪沟、双江口等大型水电工程勘察中所揭示的深部裂缝为研究素材,采用归纳与演绎的哲学思维方式,强调地质原型现场调研与地质过程分析,重视自然边坡的形成演化过程和深部裂缝所赋存的地质力学环境,运用现代数值模拟技术和岩石力学的理论与方法,对深部裂缝的发育分布及变形破坏特征从地质原型调研、数值模拟反演、岩石力学试验、损伤理论分析四大方面进行了综合集成研究,初步建立了一套深部裂缝研究的基本框架和技术方法体系,取得以下主要成果:(1)通过对典型岸坡深部裂缝的系统研究,归纳总结了裂缝发育的一般性特点,即:①裂缝多发育于距谷底70～120m以上的岸坡岩体中;②裂缝大多呈带状产出,破裂带之间为相对完整的岩体;③裂缝中很干净,几乎未见次生夹泥;④裂缝发育程度总体有随高程增加而增强、随水平埋深增大而减弱;⑤裂缝形成时间总体有随高程增加而变老、随水平埋深增加而变新;⑥裂缝主要沿与坡向大体平行的陡倾角构造结构面发育;等。(2)通过对典型岸坡深部裂缝生成的地质环境的综合分析,归纳提出了裂缝生成所须满足的地质环境条件,即:①在构造改造过程中能存储较高应变能的质坚性脆的岩性条件;②有利于应变能存储和释放的地质构造(如褶皱体)和结构条件(岩性结构和构造裂隙);③作为广义“荷载”能导致岸坡岩体产生压缩变形和强烈卸荷回弹的高地应力条件;④能导致岩体应变能强烈释放的地壳快速抬升(即河谷快速下切)条件;等。(3)认为深部裂缝是在河谷(或叠加横向沟谷)地貌形成演化过程中,伴随区域性剥蚀和河谷下切过程,岸坡应力场不断变化调整,引起岸坡岩体内部先期储存的应变能(与构造改造程度和方式有关)强烈释放,向临空方向产生差异回弹卸荷形成的,属浅生时效结构。(4)依据岸坡地质体的形成演化过程,厘定了岸坡岩体的改造模式,提出岸坡岩体由坡表向内可划分为表生改造、浅生改造、构造改造三个带,表生改造带又可细分为外侧的卸荷拉裂带和内侧的紧密挤压带,浅生改造带则由深部裂缝带及带间板梁组成。并对各带岩体的应力、声波、点荷载、裂隙密度、裂隙开度等进行了统计分析。(5)由典型岸坡实测地应力的详细分析表明:深部裂缝发育地区均存在较大的地质构造作用,属高(中)地应力区,岩体应力主要以水平构造应力为主。(6)依据典型岸坡实测应力值随水平埋深的变化特点,对岸坡应力场进行了分带,即将岸坡岩体应力由坡表向内划分为应力降低、应力增高、应力波动、应力趋稳四个带。其中应力降低和应力波动带,可分别与岸坡卸荷带的范围和深部裂缝发育的范围对照。分析认为,应力波动带的底界即为河谷应力场的影响深度,由此统计显示,我西南河谷地区这一深度大致为150～387m。(7)岸坡应力场的分布特征,与岸坡岩体的浅表生改造过程密切相关,依据成因,将岸坡应力场由坡表向内划分为斜坡应力场区、过渡区和构造应力场区三个区,可分别与表生改造、浅生改造和构造改造三个带相对应,分析了各区应力分布的特点,提出斜坡应力场区主要以自重应力为主、过渡区是构造应力场向自重应力场转化的一个过渡区域、构造应力场区主要以构造应力为主的观点,并根据实测最大主应力倾角随埋深的变化特征验证了这一认识。(8)采用现代数值模拟技术,对岸坡应力场的分带特征进行了验证分析,并探讨了构造应力对分带范围的影响;同时还分析了岸坡应力场演化的基本特点以及深部裂缝的形成过程,并根据地质过程中裂缝单元应力Mohr圆的变化特点,探讨了深部裂缝的生成时间,得出近坡表和高高程裂缝分别比深部和低高程裂缝形成时期要早,验证了地质分析的成果。(9)以深部裂缝形成过程中实际的应力变化状态为试验设计的依据,开展了不同围压、不同卸荷速率下的卸荷岩石力学对比试验,由试验揭示,在卸荷条件下:①随破坏围压的增加,试样破坏形式均从张性破坏向剪切破坏过渡,且在相同围压下,随卸荷速率的增大,试样张性破裂的比例也越重;②试样表现出累进性破坏特征,通常在试样表面附近有卸荷剥落的张性薄片,一般剪切破裂面在部分地段追踪张性破裂面发育,破坏具张剪性质;③卸荷对试样横向应变ε3和体积应变εV影响较大,进入卸荷阶段后,ε3变化梯度明显增大,εV则从压缩变形转为扩容;④多数试样应力-应变曲线在峰后存在较大跌落,表明试样卸荷破坏时的塑性变形较小,破坏更具突发性和脆性等特点;⑤应力-应变曲线峰后与峰前差别较大,峰前曲线较平滑,峰后曲线则凹凸不平,显示峰后试样内部应力、应变分布较峰前要复杂;⑥多数试样应力-应变曲线峰后呈“Ⅱ型”,显示出脆性特征;⑦围压对试样强度的影响要比加荷条件大,并在相同初始围压下,试样的强度和变形模量随卸荷速率的增大呈降低趋势;⑧随卸荷速率的增大,试样的抗剪强度参数c值增大而φ值减小,与加荷条件相比,岩石的抗剪强度参数c值降低而φ值增高;等。依据这些试验成果,对深部裂缝的发育分布及变形破坏特征进行了合理解释。(10)通过假定岩石微元强度及其分布,构建了以名义应力应变表述的损伤演化方程及本构模型,并用其对不同试验条件下岩石的损伤演化特征进行了对比分析,认为试样在受荷过程中的损伤发展演化可分为三个阶段:第一阶段与试验曲线的屈服极限前段对应,该段应力-应变曲线近似成直线,岩石微元主要以弹性变形为主,仅有极少数岩石微元发生破坏,损伤演化从0呈缓慢增加态势,演化曲线斜率缓慢增大;第二阶段与试验曲线屈服极限→残余强度段对应,该段应力-应变曲线成非线性,岩石微元主要以塑性变形为主,大量岩石微元开始屈服破坏,损伤演化呈快速增加态势,演化曲线斜率迅速增大,最后稳定在某一水平保持不变;第三阶段与试验曲线残余强度段对应,该段岩石试样已发生宏观破裂,但仍有一定的承载力,少数岩石微元继续屈服破坏,损伤演化幅度逐渐变缓,演化曲线斜率逐渐减小并趋于1。初步揭示:①在相同围压下,卸荷条件下试样损伤发展的速率要比加荷条件下快得多;②相同围压下,试样损伤发展的速率随卸荷速率的增大而增大;③试样的强度只与损伤演化速率有关,而与各试样破坏时已破坏岩石微元总数的多少无关;等。并依据诸类分析成果,合理解释了深部裂缝的发育分布及变形破坏特征。更多还原

【Abstract】 The southwest is located in the first Terrain gradient band where is rich in hydropower resources. A series of built and ready to build large-scale hydropower project located in the area. Because the region is located in the eastern fringe of Qinghai-Tibet fault block, Qinghai-Tibet Plateau in recent millions years continued to uplift , the Geo-environmental conditions is special complex in the region. Therefore, in these areas for large-scale, very large projects, a series of constraints engineering design, construction and operation of major engineering geological problems need to be studied and resolved, one of which is the deep fracture in the banks. In this paper, the east side of the south-west of the Qinghai-Tibet Plateau is the main research subjects, by choosing the deep fracture revealed in the Yalong Jinping I Hydropower Station, Dadu Pubugou, Shen Xigou, Shuang Jiangkou large-scale hydropower projects as research material, using inductive and deductive philosophy thinking way, stress the geological scene prototype research and geological processes analysis, attach importance to the process of formation and evolution of natural slope and the environmental geomechanics of deep fracture, apply modern numerical simulation technology and rock mechanics theory and method, integrated research the deep fracture’development characteristics and formation mechanism from the four aspects: geological prototype research, numerical simulation of inversion, rock mechanics experiments, Theoretical Analysis of Damage. A set of deep fracture in the basic framework of research and technical methods of system was initially established. Achieved the following main results:(1) By systemic studying the deep fracture in the typical banks, summarized the general development characteristics of deep fracture. That is :①More cracks developed in the distance 70 ~ 120m above the bottom of the slope rock mass;②Most cracks were banded output, there is relatively complete rock between the rupture zones of the rock;③It is very clean in the Cracks, almost no secondary Mud ;④The development degree of cracks increases with the elevation increasing and decreases with the horizontal depth increasing;⑤The formed time of cracks gets old with the elevation increasing and gets fresh with the horizontal depth increasing;⑥These cracks formed along the steep inclination of tectonic structure which generally parallel with the slope.etc.(2) By comprehensive analyzing deep fracture’geological environment in the typical banks , put forword to the geological environment conditions which are deep fracture can be generated that must be met by:①The hard and brittle lithology which can store a higher strain energy in the process of structural transformation;②The geological structure (such as body folds) and structural conditions (lithology and tectonic fractures) which conducive to the release and storage of strain energy ;③As a generalized "load" could lead to slope compressive deformation and rock mass have a strong rebound of the Heights stress conditions;④Rapid crustal uplift (rapid incised valley) can lead to strongly release the rock mass strain energy.etc.(3) Put forward the formation mechanism of deep fracture. In the valley (or superimposed horizontal valley) process of formation and evolution of landforms, going with regional erosion and the process of valley cutting, the banks to adjust to changing stress field, caused rock slope by pre-stored internal strain energy release strongly and produced the difference unloading rebound to the direction of the overhead,then formed the deep fracture,which belong to epigenetic time_dependent structures.(4) According to the process of the formation and evolution of rock slope, determined the transformation mode of rock slope, rock slope inward from the slope table is divided into there zone : surface reformation zone, epigenetic reformation zone , structural reformation zone . Surface reformation zone can be broken down unloading cracking zone and tightly compressing zone ; eqigenetic reformation zone is made up of deep fracture zone and inter-plate girder zone .Had done a Statistical analysis to the rock stress , sound wave, point load, fracture density, fracture aperture and so on .(5) By analyzing the measured stress of typical slope indicated that there is a big geological tectonism in the development region of deep fracture, belong to the high(middle) stress area, rock stress is mainly composed of the horizontal tectonic stress.(6) Based on the changing characteristics of the measured stress with the level of depth, the rock slope stress field can be divided into four zone: stress decreasing zone, stress increasing zone, stress rebounding zone and stress stability zone. Stress decreasing zone can be compare with the scope of unloading zone.Stress rebounding zone can be compare with the scope of deep fracture formation region. Analysis showed that the bottom boundary of stress rebounding zone represent the impact depth of the valley stress field. Statistics reveal that the depth is about 150 ~ 387m in China’s south-west valley region.(7) The distribution of stress field is closely related to the process of surface- epigenetic reformation in rock slope . Based on the formation mechanism , bank stress field can be divided into there regions from outside to inside : Stress field slopes, Transition zone and Tectonic stress field. They can be compare with the surface reformation zone, epigenetic reformation zone and structural reformation zone. Analyzing the stress distribution characteristics in various zones, put forwoed that the slope stress field based mainly on the self-weight stress field. Transtion zone is that region where the tectonic stress field transit gradually into the self-weight stress field . Tectonic stress filed is made mainly up of tection stress, this viewpoint can be validate according to the Maximum principal stress angle changing with the depth .(8) Using modern numerical simulation techniques, check and analyse the stress field of the slope characteristics of the sub-band, and to explore the impact that the tectonic stress ; At the same time, also analyzing the basic characteristics of evolution of stress field and the deep fracture formation process. In the geological process, according to the changing characteristics of crack unit stress Mohr circle, explore formation times of the deep fracture ,and then, draw a conclusion that come close to the slope table and cracks of high-elevation are earlier ,respectively, than the deep fracture and cracks of low-elevation in the formation period, and verify the results of geological analysis.(9) The basis is the actual state of stress changes in the formation process of deep fractures for experimental design , to carry out comparison of unloading rock mechanics test in a different confining pressure and different unloading rates . Revealed by the test in unloading conditions :①With the destruction of confining pressure increasing, specimen failure damage to the transition from tensile to shear failure, and at the same confining pressure, with the unloading rate increasing, the tensile damage also more serious;②Specimen show the progressive damage of characteristics, usually near the surface of the specimen there are the tension cracks, the general shear failure surface developed from the parts of tensile fracture surface , they are tension-shear nature;③Unloading have a great impact for the specimen horizontal strainε3 and volumetric strainεV, into the unloading stage, horizontal strains’gradient changes significantly increased , volumetric strain changed from compression to expansion ;④The stress - strain curves of the majority of the samples have a large drop after the curves’peak. Show that the destruction of the specimen have a small plastic deformation at the time of unloading , damage to more sudden and brittle features ;⑤There are larger difference between the behind-peak and the front-peak in stress-strain curves, stress - strain curves are more smoothness before the peak and more uneven after the peak . Show that the stress-strain of samples are more complex after the peak;⑥The majority of the sample stress - strain curve after the peak was "Ⅱ-type", showing that the brittle characteristics;⑦confining pressure impact on the specimen strength more larger than loading , and the same initial confining pressure, the specimen strength and deformation modulus decreased with the unloading rate increasing ;⑧with unloading rate increasing, the sample shear strength parameters c values increased andφvalues of decreased, compared with the loading conditions, the shear strength parameters c values decrease andφvalue increased ; etc . Based on these test results , making a reasonable explanation for the deformation and failure characteristics of the deep fractures.(10) Through assumed that the rock micro-element strength and distribution, constructed the damage evolution equation and constitutive model on nominal stress-strain formulation, and using it to compare and analyse the characteristics of damage evolution of rock in different experimental conditions, the development and evolution of samples can be divided into three stages in the loading and unloading process . The first phase compare with the forepart of the curves’Yield limit , the above stress - strain curve is near a line , rock micro–element is elastic deformation mainly, only a very small number of rock micro-element damaged, damage evolution was slowly increasing from 0 momentum, the curves’slope increased slowly. The second phase compare with the sample curves’Yield limit→residual strength, stress - strain curve into a nonlinear, rock is plastic deformation mainly, a large number of rock micro–element began to yield-damage, damage evolution was rapidly increasing in momentum, the curves’slope increased quickly. Finally, it remains stability in a certain level. The third phase compare with the sample curves’residual strength, the curves’macro-rupture occurred, but there is still a certain degree of capacity, a small number of rock micro-element continue to yield-damage, the rate of damage evolution gradually slow down, the curve slope gradually decreased and tends to 1. Revealed initially :①In the same confining pressure, the rate development of sample damage is more faster in unloading condition than the loading conditions ;②the same confining pressure, the rate development of damage increases with the unloading rate increasing ;③the samples’strength is only related with the rate of damage evolution , but they have nothing to do with the total number of rock micro-element which have damaged when the sample damaged; etc. And based on the results of the various types of analysis, a reasonable explanation have made for the characteristics of development and distribution of deep fractures and the characteristics of deformation and damage of deep fractures.更多还原