【作者】 柳群义；

【导师】 朱自强； 隆威；

【作者基本信息】 中南大学 ， 地质资源与地质工程， 2010， 博士

【摘要】 近年来,中、西部省区高等级公路建设得到了快速发展,不同程度的穿越红层分布地区。由于红层强度低、抗风化能力差、红层边坡的自稳能力差,从而造成施工期间和施工后路堑边坡不断出现滑坡等地质灾害,红层路堑边坡的稳定性及防治已成为工程界研究的一个热点。研究合理有效地分析红层边坡岩体性质、评价边坡的稳定性及提出合适的治理方案具有重要的理论意义与应用价值。在国家“863计划”项目“山区公路路基边坡地质灾害监测与预警系统研究”的资助下,本文从现场调查、室内试验、理论分析、数值模拟和现场监测五个方面展开工作。主要取得了如下研究成果：(1)通过室内试验,研究不同含水量条件下泥化夹层强度特征,表明：含水量对红砂岩泥化夹层抗剪强度的影响很大,当大于临界含水量后,内摩擦角和粘结力随含水量的增大而减小。水岩相互作用导致泥化夹层强度降低。(2)利用FLAC3D数值分析软件建立三维结构面试样模型,研究不同表面形态、不同边界条件下的结构面强度和变形特征,建立了结构面起伏角与抗剪强度参数之间的关系。结果表明：结构面起伏角较小时,剪切强度与正应力之间符合线性关系,起伏角对内摩擦角的影响程度大于对粘结力的影响程度；随着起伏角的增大,两者之间逐渐呈现非线性抛物线关系特征,结构面的破坏模式从滑移破坏转变为沿结构面滑移和锯齿剪碎的复合破坏。(3)结构面与桩单元之间的耦合作用研究表明：结构面加入桩单元后,剪切强度得到提高,并且等效粘结力的提高幅度较大；无桩和有桩状态对应的剪应力和剪位移关系曲线在峰值前,均表现为显著的弹性特征；而曲线达到峰值后,无桩状态表现为应变软化特征,有桩状态表现为应变强化特征。(4)利用数值模拟方法,分析红层岩体在单轴、常规三轴、以及真三轴压缩情况下的强度和变形特征,研究了红层岩体的单轴压缩条件下的变形特征、应力-位移关系以及倾角对强度的影响规律；研究了红层岩体的常规三轴压缩条件下围压对强度的影响、围压对应力变形特征的影响、围压对抗剪强度参数的影响以及不同结构面倾角下的岩体破坏等规律；研究了真三轴压缩条件下,不同最小主应力方向时,压缩强度与中问主应力之间的关系。(5)利用曲线拟合技术对岩体强度特征进行了拟合,研究结果表明：岩体的压缩强度可以用特定的模型来描述。随着加载速率的增大,岩体的压缩强度逐渐增大,二者之间的关系基本符合线性关系；在试验模拟过程中,须根据实际情况,来选择相应加载速率。(6)采用遍布节理模型(Ubiquitous-Joint特征,建立了基于Ubiquitous-Joint准则的边坡稳定系强度折减分析方法,采用所建立的方法计算安全系数,确立了红层边坡结构面倾角、倾向与边坡稳定性之间的关系；对于顺层边坡,根据岩层倾向与坡面倾向的夹角α的大小将顺层边坡划归为两类：当α≤45°时,为严格顺层边坡；当45°<α<90°时,划归斜向层状边坡。以某公路边坡为工程背景,针对不同边坡体渗透性和水位升降速率,研究水位变化条件下边坡体内孔隙水压力的动态响应,得到：水位升降时,在相同的入渗条件下,饱和渗透系数对初始地下水位有明显的影响；增大饱和渗透系数能降低地下水位,使地下水位线变得平缓,边坡体的动、静水压力减小,有利于稳定；增加水位升降速率,地下水位响应滞后变得显著,地下水位线形态整体变陡,边坡体的动水压力增大,不利于边坡稳定性。(7)利用FLAC3D数值分析软件,研究抗滑桩在红层岩体边坡中的加固效果,分析了抗滑桩设置位置和桩长对于边坡变形、应力的影响,结果表明：抗滑桩设置的位置对于边坡的水平位移影响较大,当抗滑桩设置于边坡坡面的中下部时(但需保证抗滑桩穿过了最危险滑动面),对于岩土体变形的效果最佳；抗滑桩加固后,边坡的剪应变增量得到限制；随着桩长的增大,边坡水平位移突变情况逐渐减少；最大位移值也逐渐减小。但存在一临界桩长Lcr,当桩长超过Lcr后,继续增大桩长对位移的控制效果明显减低。利用FLAC3D建立层状边坡的计算模型,分析注浆加固前后岩土体应力、变形响应,结果表明：当坡体结构面注浆后,边坡中的位移和应力云图变得较为均匀,在边坡中无明显的位移或者应力的突变现象,有利于边坡的稳定性,但是,出于注浆加固区域的有限性,导致了边坡的整体位移仍较大。通过注浆加固后,边坡的拉剪塑性区明显减少,可见注浆能够较好改善岩土体自身性能,提高其承担拉伸和剪切应力的能力。(8)通过对某公路红层坡的现场调查,表明：滑坡体已经历多次滑动破坏,即已发生超过峰值强度的剪切破坏,目前复活变形是在克服残余强度过程中产生的滑动变形。通过滑坡及潜在不稳定边坡的稳定性评价,设计采用抗滑桩支护红层边坡。通过现场监测分析表明：抗滑桩加固后,各个测量点都是稳定的,地表没有发生大的位移,边坡处于稳定状态。同时,将文中所研究得到的规律与前人已有的室内试验结果相对照,验证了数值分析结果的可靠性与正确性；数值模拟技术可部分取代室内试验,可快速指导边坡稳定性评价及防治实际；将抗滑桩加固边坡的研究成果用于常吉高速公路红层滑坡治理的实际中,对原方案进行了大规模的优化设计,减少了工作量、缩短了工期,节约了建设成本,取得了良好的经济和社会效益。更多还原

【Abstract】 In recent years, the rapid development have made in the high standard road in central and west province of China, whose roads more or less pass the red bedded rock mass area. Due to the special geological mechanical characteristic, with low strength, weak wind weather resistance capacity, easy soften and collapsed water. The slope with red bedded rock mass has bad self-stable capacity, which makes the high cutting slope in red bedded area easy to slip, collapse, weathering et al during and after construction, whose slope stability has already become a hot subject in engineering field. So it is important to study the characteristic of red bedded rock mass, stability characteristic of red bedded slope and its reinforcement technique.The project named "The geological monitoring and its predicting system for the road foundation slope in mountain area" from National "863 Plan" is taken as the engineering background, the studies are done by five methods:insitu-investigation, laboratory test, analytical analysis, numerical simulation and insitu-monitoring. The main contents and result are as following,(1) According to the laboratory test, the strength characteristic of mudded intercalation with different water content is studied, showing that the water content has great effect to the shear strength of mudded intercalation of red bedded rock mass. If the water content is larger than the critical water content, the internal friction angle decreases with the increase of water content. The interaction of water and rock mass leads to the strength decrease of mudded intercalation.(2) The three dimensional model for rock sample with structure plane is founded by the numerical analysis software FLAC3D. The surface of structure plane, boundary condition and reinforcement with pile are changed during calculation, to study the variation of strength and deformation characteristic of structure plane. The effect of the undulating angle to the internal friction angle and cohesion of structure plane are analyzed, showing that, when the undulating angle of joint plane is small, the effect of the undulating angle to cohesion is in larger magnitude than that of undulating angle to friction angle; with the increase of undulating angle, the failure mode of joint changes from slipping along joint plane to the compound failure model consists of slipping along joint plane and crushing through saw tooth.(3) The compound effect of structure plane and pile element shows that, after being reinforced by pile, the shear strength and cohesion of structure plane are highly increased. The relationship curve of shear stress and shear displacement for structure plane with and without bolt reinforcement shows the obvious characteristic of elastic before it reaches its peak value; but after it reaches its peak value, the curve for the structure plane without bolt reinforcement shows the characteristic of strain softening, while the curve for the structure plane with bolt reinforcement shows the characteristic of strain hardening.(4) Numerical simulations for bedded rock mass under compressive load are done to study the strength and deformation of bedded rock mass with load of axial compression, normal triaxial compression, and real triaxial compression. The deformation characteristic, stress-strain relationship, and effect of inclination of structure plane to the strength of the bedded rock mass under axial compression are obtained. The normal triaxial compression simulations are done to study the effect of surrounding stress to the strength, surrounding stress to the stress-deformation characteristic, surrounding stress to the shear strength parameters, as well as the inclination of structure plane to the failure modes of rock mass. The real triaxial compression simulations are done to study the relationship between compressive strengths and media principle stress for different minor principle stress.(5) The fitting description model is founded for the corresponding strength characteristic, showing that, the compressive strength of the rock mass can be described by the special model. The compressive strength of rock mass increases with increase of loading velocity, whose behavior is in the linear form. In the simulation tests, it is recommended to choose corresponding velocity according to the real situation.(6) The anisotropic characteristics of stratified rock mass are described by ubiquitous-joint model; the calculation method of safety factor based on ubiquitous-joint model is proposed; then the relationships between stratification dip angle a, inclination and slope stability are analyzed by FLAC3D. According to the value of a, the stratified rock slope can be divided into two types:a≤45°for strict bedding rock slope; 45°<α<90°for oblique stratified slope.One slope in reservoir area is chosen as the background engineering. The dynamic response of pore water pressure in the slope by the fluctuation of water level is studied when considering the infiltration characteristic and fluctuation velocity of water level, the analysis results show that, when the water level fluctuates, the saturated permeability coefficient has great impact on the initial water level under the same infiltration condition; with the increasing of the saturated permeability coefficient, the water level becomes lower with more smooth shape, which has smaller impact on the dynamic and static pore water pressure, and good to the stability of slope; with the increasing of fluctuation velocity of water level, the response of water level lag behind, while the shape of water level becomes steeper, which cause greater dynamic pore water pressure to the slope, and worse to the stability of slope.(7) The reinforcement effect of the pile in red bedded slope is studied by the numerical analysis software FLAC3D. The effects of the pile location, pile length to the deformation and stress of slope are analyzed. The analysis results show that, the location of pile has great influence to the horizontal displacement of slope. If the pile is driven at the mid-bottom place of slope surface, the effect of controlling deformation of rock mass is the best. With increase of the length of pile, the maximum displacement of slope is decreased gradually. There exists a limit pile length Lcr, if pile length is larger than Lcr, the effect of pile length to deformation control will reduce.Numerical calculation model is founded for stratified rock slope by FLAC3D, the stress and deformation response of the rock mass before and after grouting reinforcement have been analyzed. The analysis results show that, after grouting, the displacement and stress contour are more smooth, and there does not exist the stress and displacement mutation, which is good for the slope stability. But due to the limitation area of grouting, the whole displacement of the slope is still very large. After grouting, the tensile and shear plastic zones of the slope are reduced greatly, showing that, grouting can improve the mechanical characteristic of the rock mass, and it capacity to resist the tensile and shear stress.(8) According to the insitu-investigation to the red bedded slope, the failure of the slope has occured many times, showing that the shear strength of the rock mass has surpass its peak strength. The present deformation is the slip deformation due to the shear stress larger than the residual shear strength. The slope stability analysis is done to the unstable slope, the reinforcement of pile to the bedded slope is proposed. The insitu monitoring analysis shows that, each monitoring point is stable after pile reinforcement, there does not happen large displacement on the ground surface, the slope is in stable state.Meanwhile, the disciplines from the present paper are compared with the results of others’test, which validates the correctness of the results from the present paper. The numerical simulation techniques can partly replace laboratory tests, and give guidance for the slope estimation and reinforcement. The results from the slope with pile reinforcement are applied in the Changji highway slope reinforcement, the optimum designs are done to revise the initial design scheme, which reduce the construction cost, construction time, lead to great economical and social effect.更多还原