【作者】 江洎洧；

【导师】 项伟； Joachim Rohn；

【作者基本信息】 中国地质大学 ， 地质工程， 2012， 博士

【摘要】 三峡库区2003年开始蓄水,目前已成功蓄水至设计水位175m,库首段(本研究指三峡坝址至湖北省巴东县)水位较蓄水前提升100m左右。巨大的附加水压力荷载将施加于库盆岩体,且按库区正常水位调度计划,库水位每年将在145m～175m之间呈周期性涨落,这将对本区原始水文地质工程地质条件构成影响,同时也极大提高了库首段诱发地震的可能。据专业文献和媒体报道：自2003年蓄水开始,库首段地震活动呈明显加剧趋势。据不完全统计：2003年共发生地震541次,地震频次较1996至2002年提高近3～13倍；2004年共发震1062次,地震频次比2003年增加近一倍,且地震强度也有所增加；而2008年至目前,地震频次也一直维持在较高水平。诱发地震具有震源浅、衰减快、能量释放相对集中等特征。因此其震中附近地表地震烈度明显大于相同震级的构造型地震,3级以上诱发地震其震中烈度甚至可达到Ⅴ-Ⅵ度。虽然频发微震远小于三峡大坝及重要水工构筑物的设计抗震标准,对其长期安全运营不会构成威胁,但三峡库区作为我国滑坡、崩塌等地质灾害高发地带,频发的微震作用,加上与诱发地震具有密切关联的库水位周期性涨落,如此动力～渗流等复杂耦合作用是否会对本区滑坡,尤其是结构相对松散的滑坡造成影响呢?据近年许多学者对蓄水后库区滑坡活动规律的研究发现,蓄水后库区已有滑坡出现变形复活迹象,其是否与库水位的周期性涨落以及陡然增多的微震作用有关是值得深入研究的,目前尚无与之相关的系统性研究。本研究选取“频发微震作用下三峡库首段典型滑坡变形机制及动力响应”为研究主题,将库首段广泛分布的松散型滑坡归纳为构造松散型和堆积松散型两类,并分别选取仍有变形趋势的巴东黄土坡临江滑坡体和峡口集镇桥头滑坡作为代表。将巴东黄土坡临江滑坡作为研究重点,整个研究过程以基于实际诱发地震数据的统计分析为切入点(第2章),按照微观(第3章：水岩(土)耦合作用对滑坡不良地质单元的影响)——细观(第4～6章：典型滑坡岩土体静、动力学专题研究及测试)——宏观(第7章：多场耦合条件下滑坡体3D仿真计算)为线索,最终达到研究以黄土坡临江滑坡体为代表的构造型松散滑坡体变形机制和动力响应特性的目的；峡口桥头滑坡所代表的堆积松散型滑坡,地质构成相对简单,为研究次重点,通过对地质构造背景的分析、野外调查和实际诱发地震数据的统计分析(第2章),采用多场耦合滑坡3D仿真计算方法(第7章)研究了地质结构相对简单的堆积型松散滑坡的变形机制和动力响应特性。并对这两类松散型滑坡动力响应及变形机制之间的差异进行了详细对比,提出了具有针对性的防治方案。整个研究得到以下结论和创新性成果：1、系统搜集了近年库首段水位实际波动数据和本区已发M2.0以上地震详细数据及地震描述,并分析总结得到本区诱发地震主要发生于以下三种情况：1、库水位蓄至高位后不久,因库盆岩体附加荷载急剧增大,而诱发形成地震(急剧加载型)；2、库水位快速下降以及下降至低位初期阶段,库盆岩体附加荷载突然卸荷,而诱发形成地震(卸载型)；3、汛期水位大起大落阶段(快速加载卸载型)。且诱发地震表现出滞后于应力变化的特征,目前已发地震最大烈度为Ⅳ-Ⅴ度。2、依托“教育部长江三峡库区地质灾害研究中心”国内首条在滑坡体上开挖的巴东黄土坡滑坡大型试验隧洞,笔者对试验隧洞进行了现场跟进地质编录和周边野外调查取样,全面采集了不良地质单元样本(包括滑带土、软弱夹层、软弱泥化带)及滑坡地层典型岩体标本等共计10类。动态分析对比不同样本间矿物化学成分、微结构、粒径分布的变化规律,以水岩(土)耦合作用和滑坡多期次重力改造作用等为理论基础,分析了不良地质单元在黄土坡滑坡中形成、发展及演化或迁移的同源性规律。分析认为：不良地质单元的形成包括相对软岩原岩在水化学作用下结构的破坏、原岩结构逐步丧失、形成软弱夹层及滑坡动力改造形成泥化夹层或主滑带等4步。并根据同源性线索,详细掌握了滑坡体内不良地质单元的空间分布规律。3、主滑带,包括软弱泥化夹层,其在构造松散型滑坡体内分布较为广泛,对滑坡的变形可能起到控制作用。但该类地质单元呈带状分布,通常具有较高的粗颗粒含量,且具有分布不均匀且不连续的特点。这导致实际情况下,难以获取大量而完整的原状样本进行粗粒料大尺寸力学实验；而若按现有小尺寸土工试验,受测试粒径限制,则要剔除样本中含量较多的粗颗粒,使得最终测试获取的力学参数与实际情况可能存在较大偏差。本文探索性提出CT扫描原状滑带土——细组构物理力学实验——数值仿真试验多种手段相结合的新方法,成功获取了原状粗粒滑带土的真实力学指标。研究表明：粗颗粒含量在30%左右,即能显著提高样本总体剪切强度,特别是黏聚力c提高较为明显,内摩擦角Φ略有提升。并结合数值试验、样本微观结构特征和主滑带中碎石表面的力学痕迹,从土-石耦合受力机理角度,分析了粗颗粒对力学指标提升所起作用。该技术手段的优势在于：最大程度考虑原状样本的结构特性并结合力学试验成果,利用数值仿真试验可重复性强、平行对比性好、可视化效果好、计算可靠度高等特点,可进行大量数值试验,为获取原状粗粒土材料力学参数提出一条新思路。4、受褶皱挤压和拉伸作用,构造型松散滑坡中软硬岩层差异部位,多发育有层间剪切带,其强度接近结构面残余强度,是典型的滑坡不良地质单元。该类岩体结构面表面起伏形态复杂,且各向异性明显。受结构面剪切测试的不可重复性,以及不同样本间差异较大导致的平行对比困难等因素限制,目前直接通过结构面剪切强度测试获取其力学指标是较为困难的,这也是通常情况下,结构面剪切测试中遇到的因数据离散性过大而难以直接使用的问题。经典的结构面形态指标——节理粗糙度系数(joint roughtness coefficient,JRC)一方面仅能反映结构面测线2D的形貌特征；另一方面,在进行定量化时,需要与典型测线进行对比,带有较强的经验性。本文探索性的提出结构面剪切强度测试——结构面表面形态3D空间分析——数值仿真试验相结合方法获取结构面的剪切强度参数。该方法中,3D表面形态分析可从机理上将结构面摩擦角部分的内摩擦角和爬坡角完全进行分离,并通过ARCGIS软件对数据空间分析,叠加坡度、坡向、剪切方向等因素,建立具有3D属性的结构面模型,并进行数值试验。通过力学试验成果与数值试验的对比,验证了该方法的可靠性,为精确获取岩石结构面参数提出一条新思路。5、采用GDS土动三轴仪,对滑带土和软弱(泥化)夹层等不良地质单元进行动模量、阻尼比测试。测试采用中等尺寸样本(φ100mm×h200mm)进行,以尽量克服小尺寸试验尺寸效应明显及超限大颗粒剔除过多而造成的测试结果与实际指标偏差较大的问题。试验条件围压及固结比完全按照地质体实际赋存部位应力条件进行确定,并根据循环应力比Rf对样本强度进行估算,以确定动三轴测试中荷载级之间的步长,所有样本均达到了预先设计的进行10级左右动荷载加载的目标。在土的动力学本构模型中,最大动剪切模量Gmax是一个重要参量,然而,目前尚无针对各类土样的普适性统一定量计算方法,现有方法均需要较多的参量和工程经验方能对其进行半定量的计算,实际操作不易。但事实上,一种工况下Gmax的真值是唯一的,为此笔者结合对土体动力学特性具有广泛适用性的修正Davidenkov模型,提出对Davidenkov模型中的三个参量多元回归和对不同荷载步下Gmax自适应逼近迭代的反分析算法,在同时满足Davidenkov模型曲线三参数对测试数据拟合以及反算Gmax残差最小的双重计算约束条件下,对动三轴测试数据进行了拟合,取得了良好的使用效果。在规避了直接获取Gmax存在困难的情况下,顺利得到了适用于三类测试样本的动力学本构模型。6、黄土坡临江滑坡体下覆的巴东组第三段岩层软硬岩层交替频繁。地震荷载作用下,这些典型岩体的动力响应特征直接影响到地震波在滑坡中的传递规律。运用MTS815岩石力学综合测试系统,对采自大型试验隧洞主滑带附近的5类巴东组第三段典型岩样(软岩为(溶蚀)泥灰岩、硬岩为泥质灰岩)进行频繁加卸载循环作用测试。通过改变循环次数的方法,对各类岩石动弹性模量、动泊松比、阻尼比、单轴抗压强度及强度变化趋势进行了详细分析和总结,并基于破坏面微结构特征判断动荷载对较软的泥灰岩和强溶蚀泥质灰岩可能造成的影响。该研究定量得到了各类岩体在频繁加卸载作用下所表现出的不同动力响应特性,也为后续的3D滑坡多场耦合数值模拟提供了可靠得参数。7、根据对黄土坡临江滑坡和峡口桥头滑坡地质结构的详细实地调查和获取的典型地质剖面,分别建立其精确的3D地质模型。基于各专题研究获取的参数以及对典型地震波基线的解析校准,按照总结获取的诱震规律,选取符合实际条件的Ⅳ度和Ⅴ度两种地震烈度和145m～175m(30d)、175m-145m(60d)、145m-165m-145m(30d)三种易震工况进行数值模拟。得到了两种烈度频发微震作用下,黄土坡临江滑坡和峡口桥头滑坡所表现出的动力响应和变形机制特征,总结如下：(1)、渗流环境对滑坡体产生的不利影响不容忽略,其形成的不平衡渗流矢量对动荷载作用下滑坡的变形不利,渗流作用对堆积松散型的峡口桥头滑坡具有较大的直接影响；(2)、滑坡对动荷载的响应特征存在很大差异,构造松散型的黄土坡临江滑坡中,滑带土、软弱(泥化)夹层阻尼比大、动力滞后特征明显,对地震波具有放大效应,进而加剧滑坡变形趋势；(3)、滑坡变形机制的受控因素方面,黄土坡临江滑坡变形受控于振动荷载的特征明显,而峡口桥头滑坡变形量受易震工况下的渗流环境影响更大；(4)、两类滑坡的变形在频发Ⅳ度地震条件下均呈现稳定收敛的趋势,但频发地震烈度若达到V度,黄土坡临江滑坡的累积变形表现出不收敛的趋势,对滑坡稳定性不利。经过与滑坡监测数据特征对比,验证了数值模拟过程和结论的正确性和可靠性。最后根据两类松散型滑坡在频发微震作用下动力响应和变形机制所表现出的不同特性,分别提出了治理建议。论文研究以贴近实际工程本身为基础,旨在通过采用综合技术手段,系统性研究频发微震作用下库首段两类典型松散型滑坡体的动力响应和变形机制,其研究思路可推广到对其他相似滑坡变形机制和动力响应的研究当中,具有较强的工程借鉴价值。同时,研究中对变形机制和动力响应特征规律的总结,对库区制定合理的地质灾害防治方案、减轻地质灾害可能对库区人民生命财产安全造成的损伤和保障三峡库区的长期安全运营具有重要的工程参考价值。更多还原

【Abstract】 The impoundment of Three Gorges Reservoir begins from2003, and now the water level has achieved to175m successfully. Compared with the original situation, the water level raised about100m in the head area of the reservoir (from the Three Gorges Dam site to Badong Town in Hubei Province), huge additional water pressure load is applied to the rock mass under the reservoir. Meanwhile, the water level will fluctuate cyclically from145m to175m each year, and changes the original hydrogeoiogy and engineering geology conditions greatly. The possibility of induced earthquakes also increased greatly.Professional researches and media reports showed that:the seismic activity trend increased significantly after the impoundment of reservoir, especially in the head area of the reservoir. Based on incomplete statistics:in total,541times of seismic occurred in2003, and compared with1996-2002, the frequency of seismic increased by3-13times; in2004, the frequency of seismic is1062, nearly one time more than that of in2003, the seismic intensity also increased; from2008to the present, frequency of seismic still maintains at a high level.As reservoir induced earthquake was of shallow seismic focus, decay rapidly and relative concentration of energy release, so, compared with the tectonic earthquake which has similar scale, it can cause a higher seismic intensity on the ground surface. Even for a M3induced earthquake, the seismic intensity can reach Ⅴ-Ⅵ. Although the intensity of induced earthquake much lower than the designed seismic performance of the Three Gorges Dam and the other important hydraulic structures, as the areas of high geological disasters (eg. landslide, collapse) in China, the frequency of seismic, combine with the cyclical fluctuation of water level, which also promotes the induced earthquake, whether this kind of dynamic-seepage multi-field coupling activities will cause an adverse effect on the landslides, especially for the landslides with loose structure? According to the research result in last several years, after impounding, signs of revival appeared on many landslides. Whether this phenomenon is closely related to cyclical fluctuation of water level and sudden increase of seismic, and how it works in this process? Until now, there’s nearly no systematic research in this area.In this paper,"the deformation mechanism and dynamic response of typical landslides in Three Gorges Reservoir in case of frequent microseisms" was selected as the research issue. Landslides with loose structure which locate in the head area of the Three Gorges reservoir are summarized as two categories:tectonic origin and debris origin.Huangtupo riverside landslide and Qiaotou landslide, both of which still show the deformation trend are selected as the representatives respectively for the two types of loose structure landslide. Huangtupo riverside landslide is the key research subject, the research begin from statistical analysis of the actual seismic data in the head area of the Three Gorges reservoir(Chapter2), then along the clue of microcosmic (Chapter3:the water-rock (soil) interaction mechanism),mesoscopic (Chapter4to Chapter6:static and dynamic testing for unfavorable geologic elements and typical rock mass) and macroscopic (Chapter7:3D numerical simulation for landslide based on multi-field coupling theories), and the deformation mechanism and dynamic response feature of loose structure landslide with tectonic origin are finally got.Qiaotou landslide formed in multi-stage debris flow, it has a relative simpler geological formation and is treated as the sub-key research subject. According to the analysis of geology background, field investigation and statistical analysis of actual seismic data (Chapter2),3D numerical simulation for landslide based on multi-field coupling theories will be done (Chapter7) and get the deformation mechanism and dynamic response feature of loose structure landslide with loose debris origin.In addition, detailed analysis for the differences of deformation mechanism and dynamic response between two categories of loose structure landslides is carried out, and targeted prevention programs are proposed.Throughout the study, the author obtained the following conclusions and innovative achievement:1. The actual water level fluctuating data and the detailed data and description of induced seismic with the magnitude being greater than2.0in the latest3years are collected comprehensively. Using these actual data, the author analyzed and summarized the induced seismic most likely occur under the following conditions:(1) Shortly after the impoundment process has finished and reaching high water level, the additional load increases rapidly and induces the seismic (rapid loading type);(2) shortly after the sluicing process has finished and reaching low water level, the additional load decrease rapidly and induces the seismic(sudden unloading type);(3) the water level fluctuating extraordinarily during the flood season (loading-unloading transformation type). The induced seismic has the hysteresis characteristics, it often occurs shortly after the load transforming process has finished. Since now, the biggest seismic intensity caused by induced seismic between intensity Ⅳ～Ⅴ.2. Relying on the large-scale test tunnel which cross the whole Huangtupo landslide, the author made the follow-up geological record in the field for a long time, comprehensive collected10kinds of typical rock and soil specimens continuously, including slip soil, soft interlayer, typical rock mass and so on. Mineral chemical composition, microstructure and size distribution tests are carried out for each specimen. Then based on the theory of water and rock (soil) interaction and the multi-stage transformation of landslide activity, the homology characteristics of the formation, development and evolution of the unfavorable geologic elements are presented. The research shows the formation process of unfavorable geologic bodies including4stages:the original structure of relative soft rock was damaged under the activity of water chemistry, the gradual loss of the original rock structure, formation of soft interlayer and at last, formed the slip soil or argillization interlayer accompany with the deformation adjustment of landslide. Using these homology regular and clues, spatial distribution of unfavorable geologic bodies are gotten obviously.3. The slip soil, also including the argillization interlayer, is widely distribution in the loose structure landslides with tectonic origin, and they usually control the deformation trend of the whole landslide. These kinds of samples always contain gravels in it and not distribute continuous, so the collecting a large number of these samples is very difficult; and referring the existing laboratory test methods, it has a very strict limit to the particle size of the test samples, the particles of which the size beyond the limited granule should be picked out, this defect makes the test result can’t reflect the actual mechanical properties of coarse soil very good. In this paper, a new method which combines with CT scanning technology, indoor direct shear test and numerical simulation tests was put forward. Only using a small quantity of soil, the particle size distribution, particle distribution characteristics and the arrangement mode of the intact coarse soil keep undisturbed, so as to get the actual and reliable mechanical indices. The result shows:even the proportion of coarse particle is about30%, it can influence the deformation mechanism of the whole soil structure, especially for the increasing of cohesion. Relying on the advantage of CT scanning and numerical test, a large number of tests can be carried out, and makes it possible to summarize the coupling mechanism between granule and course. This research method can provide a new method to obtain reliable shear strength parameters of intact coarse soil.4. With the conditions of squeezing and stretching stress stem from tectonic fold, interbedded shear zones are very developed inner the rock layer, especially the rock layers which have different competency. The shear strength of this special geological element can be treated as the residual strength, so generally speaking, it’s also can be defined as a typical unfavorable geologic element. The shape of rock discontinuities is mostly very complex and anisotropic. In present, it’s not easy to get the shear parameters of rock discontinuities by test directly, because for one rock discontinuity, the shear test is not easy to repeat. But the shear strength results from different rock discontinuity are usually very discrete. JCR index for statistics the feature of rock discontinuities also has some defects as follow:it only can reflect the2D feature of rock discontinuities; during the quantification process, the measurement data should be compared with the typical shape of rock discontinuities, and need a lot of experience. In this paper, a new method which combines with shear tests for rock discontinuities,3D spatial analysis for the morphology of rock discontinuities and numerical simulation tests was put forward. Using this method, the comprehensive frictional angle of rock discontinuities can be separated into internal frictional angle and the frictional angle caused by climbing effect from mechanism. Take the factors of slope, aspect and shear direction into account,3D spatial analysis was done by ARCGIS software, and establish the model of rock discontinuities with3D attributes. Then numerical simulations are carried out for the shear test of rock discontinuities. By comparison with mechanical test results, the numerical experiments are very reliable. This research method can provide a new method to obtain reliable shear strength parameters of rock discontinuities.5. GDS dynamic soil triaxial apparatus is used to test the dynamic modulus, damping ratio for slip soil, argillization interlayer and soft interlayer. Due to high content of coarse particles in the samples, the program of using mid-size samples (Φ100mm×h200mm) is adopted for testing. It can overcome size effect and avoid picking out too many coarse particles, and avoid big different between test results and the actual indicators at utmost. Both confining pressure and consolidation ratio in the test program are obtained by actual stress conditions. Meanwhile, cyclic stress ratio is used to estimate the strength of each sample, and it can be useful to determine the load step. The result shows, the test program is available, nearly10steps of dynamical load are applied to the samples successfully and achieve the test purpose. In the researching for constitutive model of soil dynamics, the maximum dynamic shear modulus (Gmax) is a very important parameter. However, there is no uniform calculation method for each kind of soil so far. The existing methods always require many parameters and engineering experience to calculate Gmax semi-quantitatively, so it’s not easy to be used in actual engineering. But in fact, under a determine condition, Gmax is a unique parameter. Combine with the modified Davidenkov model, which is wide applicability in constitutive model of soil dynamics, the author multiple regression the three parameters in modified Davidenkov model, the adaptive algorithm is also carried out to back analysis, iterative, then to approach each Gmax come from different load steps, which is a variable in the function of the model. The calculation can fitting the curve of Davidenkov three parameters model well, and at the same time approach the true value of Gmax comes from different load step, it can reduce the calculated residual to the lowest level. The method is verified available in this research, and the biggest advantage is avoid reaching the Gmax directly, and obtains the dynamic constitutive model for each sample.6. The terrane under Huangtupo riverside landslide belong to T2b3(Triassic Badong Formation, third member), and it has the characteristic of hard rock interbedded with soft rock. The spread regular of seismic waves and dynamical response characteristics in the terrane are worthy of researching.5kinds of typical rock specimens (including marlite and clay limestone) are collected from the test tunnel, frequent loading-unloading test were carried out on MTS815Flex Test GT rock mechanics test system, the test wave for cyclic loading test was sine wave, and its frequency was1.0Hz. The dynamic modulus of elasticity, dynamical possion ratio and damping ratio were gotten. By changing the frequency of cyclic loading, for each sample, the variation trend of strength is summarized, and it can be reflected by the change of uniaxial compressive strength. Then, based on observing the microstructure of mechanical traces from failure surface, some phenomenon show, the activity of frequent loading-unloading may destroy the structure of marlite and corrosive clay limestone. This research fully quantitative the different dynamical response features for each sample under the condition of frequent loading-unloading, and it also provide many necessary parameters which can be useful in multi-field coupling numerical simulation in the final part.7. Based on detailed field investigation and typical geological profiles, the accuracy3D geological model for Huangtupo riverside landslide and Qiaotou landslide are established separately. Accordance with the foregoing summarized regular of induced seismic, two kinds of seismic intensity (including gradeIV and V) and three kinds of adverse seepage conditions (including145m-175m in30d,175m-145m(60d) and145m-165m-145m(30d)) are determined to make a multi-field coupling numerical simulation for both landslide. The dynamic response feature and deformation mechanism of Huangtupo riverside landslide and Qiaotou landslide in the above conditions are gotten, conclusions are as follows:1, these seepage conditions play adverse effect to the deformation of landslides and the seepage activity can’t be’ ignored, the unbalance seepage vectors will intensify the deformation under the activity of seismic load, especially for Qiaotou landslide (the represent of debris origin landslide);2, the dynamic response characteristics for two kinds of loose structure landslides are quite different. For Huangtupo riverside landslide (with tectonic origin), the damping ratio of slip soil and soft (argillization) interlayer are very big, and the hysteresis damping characteristics is also very obvious. The energy of seismic waves can be amplified in these geological elements, and this effect will aggravate the deformation of landslide;3, By analysis the deformation mechanism for both landslides, the deformation of Huangtupo riverside landslide is mainly controlled by dynamical load, and for Qiaotou landslide, unbalance seepage factor plays a more important role in the deformation process;4, with intensity Ⅳ, the deformation tendency for both landslides is stable and convergence under frequent seismic, but with intensity V, the deformation tendency for Huangtupo riverside landslide shows the tendency of non-convergence under frequent seismic. Then, compared with monitoring data, the process and conclusion of numerical simulation is verified.The research process is close relates to the actual project from beginning to end. Integrated technology methods are carried out to make a systematic study on the dynamic response and deformation mechanism for two kinds of loose structure landslide under frequent microseisms. The conclusions and regulars which are summarized can be very useful in developing the reasonable geological disaster prevention programs, keep the people’s lives and property safety in reservoir area and protect the long-term safe operation of the Three Gorges reservoir.更多还原