【作者】 王志俭；

【导师】 殷坤龙； 罗先启；

【作者基本信息】 中国地质大学 ， 岩土工程， 2008， 博士

【摘要】 川江河段（即现今三峡库区）一直是中国地质灾害多发区和重灾区之一,随着近期三峡移民建设工程的大规模展开,库区地质灾害防治工程所进行的滑坡工程地质勘探揭示:三峡库区一些复杂地质环境中（例如巫山、万州、奉节等）古滑坡的成因及规模等要比早期的工程地质勘察和研究结论反映的问题复杂。万州地区岩层倾角一般在3°-5°,有的滑动面甚至出现反倾现象,最陡也不超过10°。在这样平缓岩层分布区却发育了一系列大型顺层岩质滑坡。这在三峡工程库岸其它平缓岩层地区并不多见。滑坡机理研究是滑坡学的核心内容之一,对于万州地区的近水平地层滑坡的成因机理,是滑坡领域的一个疑难问题。由于滑坡滑床接近水平,而滑带土的内摩擦角远远大于滑床的倾角,这类滑坡的失稳必然有特殊的有利条件,对其成因存在截然不同的认识。万州近水平地层滑坡的成因对该地区防治工程成败尤为重要。这是一个十分严峻而又不可回避的非常现实的问题,亟待研究和解决。因此,本文近水平岩质滑坡的成因机制研究具有重要的现实意义。本论文研究内容共分八章。第一章“绪论”,本章介绍了本论题的背景以及研究现状,根据目前的研究进展和具有争议问题,提出了研究的方法和内容。近水平地层滑坡的成因机理的主要观点是降雨造成滑坡后缘裂隙水头异常抬升,并推动滑坡沿层面平移,故此类滑坡也常被称为“平推式”滑坡,但该观点主要从诱发因素考虑,而且对后缘裂隙的产生原因没有进行解释。本文认为,滑坡孕育过程经历了漫长的地质年代,必须考虑岩土体的流变特性。因而提出在认识红层岩土流变特性的基础上,从流变力学的角度对近水平岩质滑坡的成因机理进行研究的思路。第二章“万州地区区域地质条件地层岩性和降雨特征”,本章从万州区的区域构造,地层岩性以及气象水文等方面论述了万州地区易发生滑坡灾害的原因。无论在自然条件下,还是人类工程活动,滑坡的产生和分布取决于岩性、构造、地貌和地下水这四个地质条件的变化,降雨和人类活动可能改变这些地质条件而诱发滑坡的发生。本章通过对万州区地区的区域地质条件,地层岩性和降雨特征的研究,了解万州区的地质背景和近水平地层滑坡所处的环境。万州地处川东褶皱束万县复向斜北东段近轴部,在逆冲推覆作用下,下盘断坪以上的地层全部卷入了层间的滑移运动,形成了大量的层间剪切带,为滑坡发育创造了有利条件。万州地区出露地层为侏罗系中统上沙溪庙组第二、第三段(J_2s²、J_2s³)和上统遂宁组(J_3s),属红层地层,红层岩土固结时间短,在内外地质作用影响下,容易逆变而泥化,大量钻孔资料表明,沿泥岩顶面普遍泥化,成为斜坡体变形破坏的主要控制面。万州地区处于三峡库区的暴雨中心,多年平均降水量1250mm以上,一日最大降水量在200毫米以上,充沛的降雨是滑坡的重要诱因。第三章“万州区典型岩土物理力学特性试验研究”,本章对万州地层的长石石英砂岩、泥质粉砂岩和安乐寺滑带土进行了矿物成分分析和物理力学性质研究。对安乐寺滑带土进行了固结排水剪切试验,滑带土的内摩擦角为15°～16°远大于安乐寺滑坡滑床倾角,应力应变曲线接近双曲线,采用了邓肯-张模型对其应力应变进行了描述。对长石石英砂岩进行了单轴抗压以及三轴抗压试验,获得了全应力应变曲线,试验表明长石石英砂岩的峰值强度及残余强度都服从莫尔库伦强度理论,根据试验结果确定了长石石英砂岩的强度指标。对泥质粉砂岩进行了单轴试验、变角板试验和点荷载试验,根据试验结果确定了泥质粉砂岩的强度指标,矿物分析结果表明,泥岩含粘土矿物达40%,该泥岩具有极强的亲水性,遇水后易崩解。采用点荷载试验确定了其平行层理面和垂直层理面单轴抗压强度和抗拉强度,试验结果表明,该泥岩各向异性特征不是很明显。第四章“红层长石石英砂岩流变特性试验研究”,本章对长石石英砂岩进行了流变试验,试验获得了该砂岩完整的流变曲线。蠕变曲线具有明显的蠕变第一阶段“衰减蠕变阶段”,蠕变第二阶段“匀速蠕变阶段”和蠕变第三阶段“加速蠕变阶段”。试验表明,砂岩的长期强度只有瞬时强度的0.4倍,试样蠕变破坏的过程与近水平地层滑坡的破坏过程具有相似之处,可见近水平地层滑坡的破坏存在岩石蠕变破坏。在试验数据处理中采用了Boltzmann叠加原理,并对Boltzmann叠加原理在实际应用中的技术问题进行了讨论,并对目前常用的“坐标平移法”作了改进,使每级荷载作用下的瞬时变形量和蠕变变形量可以区分开,每级的蠕变变形都随时间变化而变化,叠加时瞬时变形在初始时刻就进入下级荷载的变形中,而蠕变变形随时间增长逐渐叠加到下级荷载作用的变形中。处理后的数据表明该砂岩的应力应变关系接近线性,并采用Burgers模型对试验曲线进行了识别,确定了模型参数,通过对试验数据的对比表明,Burgers模型可以较好的模拟蠕变的第一阶段和第二阶段。由于Burgers模型不能描述岩石加速阶段的蠕变,本章对岩石加速阶段的蠕变进行了讨论,并提出了可描述岩石非线性蠕变的NBurgers模型。经模型曲线和试验数据比较,该模型可以非常准确的描述蠕变加速阶段,该模型在衰减蠕变阶段和匀速蠕变阶段可退化到Burgers模型,相比Burgers模型只增加了一个参数,参数易于确定和使用,物理意义明确,具有一定的推广价值。基于NBurgers模型,进一步讨论了更一般的非线性模型,称为广义NBurgers模型,理论上这个模型对加速阶段流变具有很强的适用性。第五章“安乐寺滑坡滑带土蠕变试验研究”,本章对安乐寺滑坡的Y1和Y2滑带土进行了蠕变试验研究,试验在排水条件下进行。蠕变试验曲线具有明显的蠕变第一阶段“衰减蠕变阶段”和第二阶段“匀速蠕变阶段”,但未见蠕变第三阶段“加速蠕变阶段”。分别采用了Burgers模型、Singh-Mitchell模型和Mesri模型对滑带土流变性质进行描述,取得了模型的参数。通过对模型参数的分析,认识到各种模型都是一种对岩土流变的一种近似。将各种模型进行了比较并与实测试验数据进行了对比。结果表明,Burgers模型可以描述应力作用下的瞬时应变响应,而经验模型忽略了瞬时应变响应。Singh-Mitchell模型在偏差应力水平20%-80%范围内可以较好描述土的应力应变关系,但超出这个范围的应力条件误差较大,而Mesri模型没有这个限制。第六章“安乐寺滑坡滑带土的松弛试验研究”,本章对安乐寺滑坡的Y1滑带土进行了松弛试验研究。松弛和蠕变是岩土流变特性的两种不同的宏观表现,在滑坡中松弛和蠕变是同时存在的,由于松弛试验难度较大,目前对松弛特性的研究较少。根据本章试验结果,提出了基于松弛试验的流变本构模型。该流变模型可以较好的描述土的松弛过程,与试验数据相比在规律上基本吻合,数值上的误差也在工程许可范围内。根据推导的松弛型流变本构模型,安乐寺滑坡滑带土为完全松弛型土,偏差应力可以持续松弛到零,这对滑坡的机理研究和防治具有重要意义。第七章“近水平顺层岩质滑坡成因机制研究”,本章首先采用FLAC^3D商用软件,对典型的近水平顺层岩质滑坡—安乐寺滑坡进行了数值模拟,对安乐寺的应力变形以及塑性区的分布和变化规律进行了分析,并从岩土流变学角度和滑坡学角度对该类滑坡的成因机制进行了探讨。根据安乐寺滑坡的数值计算结果和大量的滑坡变形特征,本章对该类滑坡的成因提出了新的观点,认为该类滑坡失稳不是由于滑带土强度不足引起的,而是滑带土强度不能充分发挥引起的。此类滑坡属于牵引式滑坡。这一观点可比较合理解释滑坡体后缘张拉破坏陷落带的产生以及滑坡体上的张拉裂隙来源,也合理解释了为何在滑带土强度远远大于滑动带倾角的条件滑坡仍可滑动的原因,而且按此机理产生的滑坡破坏与现场及勘察资料反映的滑坡破坏变形的特征也基本一致。在对滑坡机理认识的基础上提出了近水平顺层岩质滑坡孕育的三个条件,（1）滑坡体具有上硬下软的砂泥岩互层结构;（2）具备宽阔舒展的河谷地形;（3）具备多个临空面地形条件。根据该类型滑坡的破坏机理,该类型滑坡初次快速滑动后,将处于稳定或蠕变状态,只有在极端特殊条件下,如地震条件下,才可能出现失稳或快速滑动。第八章“结论与展望”,本章总结了本论文的研究结论,并对进一步认识红层岩土流变特性和近水平地层滑坡机理的研究内容提出了建议。本论文以试验为基础,对万州地区红层岩土的流变性质进行了研究,并采用数值模拟方法结合滑坡现场的变形特征从岩土流变力学的角度,对近水平岩质滑坡的成因机理做了探讨,提出了近水平地层滑坡的流变力学成因机理。更多还原

【Abstract】 ChuanJiang river (part of Yangtse Rive from Yibin to Yichang) has always been one of China’s geological disaster-prone areas. Following with the civil engineering for transmigrates of the Three Gorges Project; many engineering geological explorations revealed that the mechanics of some ancient landslides in complex geological environment are not as simple as formerly proposed.The sliding of solid rocks on a continuous claystone dipping towards valley at 3-5°, the steepest is not more than 10°. Such gentle-dipped landslides are not common in other areas that have nearly horizontal strata. However, the formation mechanism of these landslides has been debatable. The landslides formation mechanisms are important in prevention and treatment sliding. So it is significant to learn the mechanisms of this kind of landslides. There are eight chapters in this dissertation.Chapter 1 "introduction", Makes an introduction about the situation and tendency in domestic and foreign research, and then schemes the research content. On of the famous views about the formation of landslide occurred in nearly horizontal strata was that the head of water raised by rainfall in steep fissure pushed the landslide to translate, so this kind of landslide also was named "pushed translation landslide". But this view cannot explain why there are many steep fissures in the rear of slope. In this dissertation, the rheology characters of rocks and soils were considered for the formation of landslide is a long geologic age. So in this chapter the idea of research the landslide mechanics based on the f rocks and soils rheology theory was proposed.Chapter 2 "Regional geological, lithology, and rainfall character in Wanzhou area" In this chapter describes the geographic, lithology, and climate in Wanzhou. The occurrence of landslide lies on the lithology, tectonic, geomorpholo and the groundwater. Human activities and rainfall will change these conditions and triggered the landslide failure. Wanzhou lies Chuangdong arcuate strutural zone which formed by the sedimentary covers thrust into each other along the sliding planes between the cover and basement. During the movement, many incompetent beds may become shear zone between strata. It is an advantage to form landslide. The rockmass in red beds can change to soil under the inner and outer effects of geological processes. Many engineering geological exploration reveals that the mudstone changed to soil and become the landslide slip surface. Wanzhou area is the center of rainstorm of Three Gorges reservoir area and profuse rainfall is an important factor result in landslide.Chapter 3 "experiment study on representative rock in Wanzhou area" The samples of red plagioclase quartz sandstone, muddy fine sandstone and sliding zone soil in Wanzhou were taken, their physical attribute mineral components and mechanics attribute were studied. The results show that angle of shearing resistance of the sliding zone soil is larger than the angle of slip surface gradient. The strength of sandstone obeies the Mohr-Coulomb failure criterion, the shear strength parameters are abtained by experiments. One axis compact tests point load tests are performed in study muddy fine sandstone and the shear strength parameters are also abtained.Chapter 4 "Rheological Experiments on red sandstone in Wanzhou of Three Gorges Reservoir area" In order to discover the cause of these landslides, rheological experiments were conducted on the sandstone of Erchengyan landslide bedrock in Wanzhou with RLM-2000 triaxial rheology test machine. Before the specimen failures, there was an accelerated creep stage, which lasted about 8 hours, this course is similar to the deformation of some approximately horizontal slip surface landslides failure. Tautochrone of test data indicates this kind of rock is close to liner visco-elastoplastic materials. Burgers rheology model was used to identify the curves, and the Burgers three dimensional rheology model and its parameters were obtained. The results show that the proposed Burgers rheology model exactly presents the rheology characterization of Jurassic red strata in Wanzhou. And it can also describe the mechanism of the approximately horizontal slip surface landslides occurring in Jurassic red strata in Wanzhou. There was a nearly linear correlation between the creep strain rate and time in the beginning of accelerative creep stage and a nonlinear rheological model NBurgers was proposed to describe this accelerative creep stage. The creep strain rate behaved close to exponential growth with time in the last of accelerative creep stage. That accelerative creep stage was highly nonlinear chracterastic, the creep strain rate showed a discontinuous form, which occurred in jumps change. Furthermore, the experimental results reveal the fact the long-term strength of the rock is only 44 percent of the peak strength in triaxial tests. This conclusion is very helpful for the research on the mechanism and prevention on the horizontal slip surface landslides.Chapter 5 "Creep experimental study on sliding zone soil of Anlesi landslide." Creep text have been carried out to study the rtheology property of sliding zone soils. Burgers model, Singh-Mitchell model and Mesri model have been used to describe the creep character of sliding zone soils. Each model is evaluated compared with the test data.Chapter 6 "Experimental study on stress relaxation of Anlesi landslide in Wanzhou". Triaxiality stress relaxation experiment on GDS Unsaturated Triaxial Testing Systems was carried out to investigate the stress relaxation properties of slide zone soils of Anlesi landslide. During relaxation tests the soil volume deformation is almost could to be ignored. Test data shows stress relaxation is direct ratio to initial strain but independent of confining pressure. Based on stress relaxation tests, a new constitutive model for the stress-strain-time behavior of slide zone clays was introduced by assuming a hyperbolic stress-strain relationship and a logarithmic time-tress relationship. The comparison between the rheology model and experimental result shows that the new rheology model presents the relaxation characterization of the slide zone clays nicely. That also provides the model and parameter for the further researches about approximate level landslides exist in Jurassic red strata in Sichuan basin. The new relaxation model indicates the shear stress of this kind of clay will relaxat to zero. That is significance for approximate level landslides research and control.Chapter 7 "mechanism research on approximately horizontal slip surface rockslides" Flac3D was used to simulate typical approximately horizontal slip surface landslide in Jurassic red strata in Wanzhou city. After synthetize the numberic results about the stress and strain distributing and changing, and many phenomena about landslide, a new viewpoint was brought out on the point of rock and soil Rheological mechanics. This new opinion point considers that this kind of rockslide slide not result from the failure of sliding zone, but be caused the sliding zone cannot exert its strength enough. So the gentle- dipped slope instabilities must be connected to following conditions: (1) landslides have plastic substratum and rigid layer over, so the landslide body have viscosity great larger than the sliding zone soils; (2)landslides lies on wide water gap,so the landslide bady have to bear enough tension stress;(3) landslides’s lateral erosion by river, so the landslides has weak lateral restrict.Chapter 8 "conclusion and prospecf’In this chapter the conclusions and innovations of this dissertation have been summed. And some suggestions have been proposed for further research about the mechanics of gentle-dipped landslides of Jurassic red strata in Wanzhou city.In this paper, the rheology charactes of the red rocks and soils in the Wanzhou area were studied based on experiments. Along with the deformation characteristics landslide site, from the perspective of rheological mechanics the mechanism of approximately horizontal landslides were discussed.更多还原