滑坡作用下X80腐蚀管道的极限宽度分析

针对X80腐蚀管道横穿滑坡时所涉及的安全预警问题,提出将极限宽度作为管道安全状态的判别因子,根据具体滑坡工况建立有限元模型,分析管道不同腐蚀尺寸和空间位置对腐蚀管道的力学行为与极限宽度的影响。结果表明：极限宽度可用于管道安全状态的评判;腐蚀的宽度和深度与管道极限宽度呈负相关,且对于腐蚀深度表现出高敏感性;内腐蚀对于管道安全状态的影响大于外腐蚀;坡度为30°的土质滑坡下,外径10.16 cm的无腐蚀X80管道的临界横穿滑坡宽度为21.2 m,含腐蚀管道横穿滑坡时的临界腐蚀深度为0.25倍的壁厚;腐蚀管道距滑坡区中部的距离大于6 m时对管道的极限宽度影响可忽略;管道应力与极限宽度呈负相关,腐蚀深度为0.2倍壁厚时管道最大应力始终在腐蚀处,其余位置的应力与无腐蚀管道一致。     

Are real-world shallow landslides reproducible by physically-based models? Four test cases in the Laternser valley,Vorarlberg (Austria)

In contrast to the complex nature of slope failures, physically-based slope stability models rely on simplified representations of landslide geometry. Depending on the modelling approach, landslide geometry is reduced to a slope-parallel layer of infinite length and width (e.g., the infinite slope stability model), a concatenation of rigid bodies (e.g., Janbu’s model), or a 3D representation of the slope failure (e.g., Hovland’s model). In this paper, the applicability of four slope stability models is tested at four shallow landslide sites where information on soil material and landslide geometry is available. Soil samples were collected in the field for conducting respective laboratory tests. Landslide geometry was extracted from pre- and post-event digital terrain models derived from airborne laser scanning. Results for fully saturated conditions suggest that a more complex representation of landslide geometry leads to increasingly stable conditions as predicted by the respective models. Using the maximum landslide depth and the median slope angle of the sliding surfaces, the infinite slope stability model correctly predicts slope failures for all test sites. Applying a 2D model for the slope failures, only two test sites are predicted to fail while the two other remain stable. Based on 3D models, none of the slope failures are predicted correctly. The differing results may be explained by the stabilizing effects of cohesion in shallower parts of the landslides. These parts are better represented in models which include a more detailed landslide geometry. Hence, comparing the results of the applied models, the infinite slope stability model generally yields a lower factor of safety due to the overestimation of landslide depth and volume. This simple approach is considered feasible for computing a regional overview of slope stability. For the local scale, more detailed studies including comprehensive material sampling and testing as well as regolith depth measurements are necessary.     

考虑滑坡渐进破坏的改进简布条分法

为考虑位移因素对于滑坡渐进性发育的影响,基于简布条分法基本原理,提出一个新的能够考虑滑带土抗剪能力与剪切位移关系的滑坡稳定性简化评价方法。该方法从以下两个方面对简布条分法进行了改进：（1）将滑动面剪应力-剪切位移本构模型与沿滑动面的剪切位移模型相结合,以考虑滑坡随着变形发展渐进破坏的过程;（2）提出局部安全系数的概念并对整体安全系数进行重新定义,物理意义更加明确。推导了该方法的计算公式,给出了其迭代计算思路,并编制Matlab计算程序。通过计算实例表明,应变软化边坡的安全系数不仅取决于土的抗剪强度指标,还与其剪应力-剪切位移关系密切相关,基于峰值强度的极限平衡条分法应用于实际工程是偏于危险的。同时该方法还可以有效地模拟边坡从开始破坏到最终滑动面贯通的发育过程,实现了坡体位移与安全系数之间一一对应的定量关系,进而实现边坡的稳定性的预测预报。     

基于整体刚体平衡法的膨胀土边坡稳定分析

膨胀土边坡危险滑面受裂隙面影响,常位于强弱风化层界面,且近似为直线,滑坡后缘一般为垂直张拉裂缝,下部主滑床呈近水平状。基于上述特性,提出滑坡体的三折线刚体简化模型,滑体内土体强度采用多次干湿循环后稳定值,并根据整体刚体的静力平衡推导建立边坡安全系数求解公式。以秦淮东河膨胀土边坡为实例,开展膨胀土干湿循环室内试验,并利用推导公式求解边坡长期稳定系数,计算结果与FLAC强度折减法求解结果接近。设计程序分析了强风化层厚度和膨胀土层厚度对边坡安全系数求解值的影响,发现后者随前两者的变化先急剧减小后趋于平缓,在一定范围内影响较大。考虑浅层土体强度和强风化层深度在干湿循环不同阶段的变化,求解了各阶段强弱风化层交界面上滑面的安全系数,发现其呈现指数衰减的趋势,边坡主要在6次干湿循环后发生失稳,滑面深度在1.83 m左右。     

降雨条件下顺倾向煤系地层边坡稳定性的影响研究

煤系地层具有岩层软硬不均,层间胶结较差,风化速度快,遇水易软化,结构易破坏导致强度丧失等特点,特别是夹层中炭质泥岩或页岩具有强度低、易活化、易变性和渗透系数相对较小的特点,这决定了其对整体边坡的稳定性具有控制作用。文章分析了煤系地层边坡饱和、非饱和渗流降雨条件（降雨强度）、土性参数（夹层饱和渗透系数）以及边坡形状尺寸（坡脚、夹层倾角、夹层埋深）等因素对边坡渗流特点及稳定性的影响,发现软弱夹层与上下岩体渗透性差异性对边坡稳定性影响明显;软弱夹层埋置越浅,边坡越易失稳;降雨强度越大,边坡越易沿软弱夹层发生滑坡;并非坡脚越大降雨之后边坡的安全系数降低幅度就大,而是随着夹层倾角的增大,边坡的安全系数逐渐降低,边坡越易沿软弱夹层发生滑坡,这些认识对煤系地层边坡的设计和治理有重要的参考意义。      

Semi-two-dimensional numerical model for river morphological change prediction: theory and concepts

This paper presents a new numerical model for river morphological predictions. This tool predicts vertical and lateral cross-section variations for alluvial rivers, which is an important task in predicting the associated hazard zone after a flood event. The Model for the HYdraulics of SEdiments in Rivers, version 1.0 (MHYSER 1.0) is a semi-two-dimensional model using the stream tubes concept to achieve lateral variations of velocity, flow stresses, and sediment transport rates. Each stream tube has the same conveyance as the other ones. In MHYSER 1.0, the uncoupled approach is used to solve the set of conservation equations. After the backwater calculation, the river is divided into a finite number of stream tubes of equal conveyances. The sediment routing and bed adjustments calculations are accomplished separately along each stream tube taking into account lateral mass exchanges. The determination of depth and width adjustments is based on the minimum stream power theory. Moreover, MHYSER 1.0 offers two options to treat riverbank stability. The first one is based on the angle of repose. The bank slope should not be allowed to increase beyond a certain critical value supplied to MHYSER 1.0. The second one is based on the modified Bishop’s method to determine a safety factor evaluating the potential risk of a landslide along the river bank.     

考虑天然气水合物上覆层不排水抗剪强度深度变化的海底斜坡稳定性影响分析

天然气水合物分解可以诱发海底斜坡失稳对海底工程设施产生造成破坏影响。因此,海底斜坡稳定性状态评价对海底工程设施选址、安全运行具有重要意义。文章根据南海北部神狐海域水合物富集区工程地质特征,采用有限元强度折减法分析了斜坡几何参数、土层强度变化,以及水合物储层特征等因素对水合物分解前后海底斜坡稳定性的影响规律。结果表明,未考虑水合物分解时,海底斜坡稳定性主要受控于斜坡坡度和土体强度,且主要表现为浅层滑坡。考虑水合物的分解时,水合物层强度降低会对斜坡的整体稳定性产生影响,但同等上覆层条件下最危险滑动面位置受水合物层埋深影响较大,且存在受地形几何特征与上覆土层强度控制的临界埋深。埋深大于临界埋深时,水合物分解对斜坡稳定性的影响较小,最危险滑动面位置位于上部浅层,表现为浅表层破坏。小于临界埋深时,最危险滑动面位置则经过水合物层,表现为深层滑坡。根据目前模型中的水合物层埋深条件,水合物分解后的深层滑动面安全系数仍高于浅部地层,意味该海域水合物开采仍需要关注浅层海底滑坡灾害的影响。     

沪蓉国道主干线边坡稳定性研究

以沪-蓉国道主干线恩施高坪-吉心段付家坡滑坡地段典型断面为研究对象, 运用强度折减系数法,研究了在天然状态和饱水状态下滑坡体稳定安全系数。 指出了在这两种状态下边坡的不稳定性。并与其他几种方法进行了对比分析,结果表明有限元强度折减系数法应用到该断面是可行的,同时也显示该方法相对于其它方法的优越性。     

公路沿线花岗岩风化区滑坡危险度评价--以日本49号国道合户地区为例

对公路沿线边坡进行稳定性评价及滑坡灾害分析，对于由滑坡、泥石流等引起的公路灾害的防治具有重要指导意义。为了评价处于花岗岩风化区的日本福岛县合户地区49号国道沿线边坡的滑坡危险程度，在调查和分析了该地区的表层破坏模式、并通过简易探测方法摸清了风化土层的厚度分布后，将研究区域划分为边坡单元(Slopeunit)，使用椭球体下半部模拟滑动面的形状，通过随机试算法确定各边坡单元危险滑动面的位置及空间形状；采用一种基于GIS的边坡稳定性三维分析模型计算各边坡单元最小安全系数以及滑坡发生概率，定量评价滑坡灾害危险程度。所有的计算过程及结果显示均在一个基于GIS平台的系统中完成，为如何利用GIS技术更好地为滑坡灾害防治工作服务拓宽了思路。     

An improved approach for evaluating the time-dependent stability of colluvial landslides during intense rainfall

The paper presents an improved analytical approach for evaluating the time-dependent stability of colluvial landslides during intense rainfall infiltration. The approach comprises two steps: first to simulate rainfall infiltration and then to compute the safety factor. In terms of the irregularity of the natural landslide surface in implementation of the method, the landslide is divided into several soil slices with approximately straight sides. Each single slice is regarded as a finite slope so that the infiltration formula and safety factor can be deduced. The infiltration formula is derived with combination of the Green–Ampt model and mass conservation law considering seepage perpendicular and parallel to slope surface simultaneously. In the modified infiltration model, both size effect and angle effect are vividly observed in the process of rainfall infiltration into the finite slope, while the former of which is not presented in the original Green–Ampt model. The safety factor is computed using the limit equilibrium method, with the influence of infiltrating water on the shear strength, gravity and seepage force of soil slices considered. By case study of the Shuping landslide in Three Gorges, decline in the safety factor and the decrease in the tendency are definite. Specifically under the rainfall intensity of 50 mm/h, the failure of Shuping landslide is most likely to occur at the time of 102 h. In addition, the results highlight shallow failure along the wetting front under intense rainfall.     

Field variability of landslide model parameters

 A data set of parameters (slope, soil depth and soil shear strength) relevant to spatially distributed modelling of shallow landslides triggered by rain and snowmelt events was determined from field measurements in 250 grid elements of dimensions 25 m (downslope)×10 m (across slope) in an area of 250 m×250 m on a hillslope in Scotland. These data provide an unusually detailed basis for the evaluation of spatial variability and uncertainty in model parameterisation. The variations in slope and soil strength are represented adequately by normal distributions; a Weibull distribution is suggested for the soil depth data. The factor of safety calculated at each point in the grid was shown partially to identify observed landslides, with a number of false predictions of occurrence. Trend analysis and semivariogram analysis of the data set suggest that the use of kriging could improve upon this approach to landslide prediction by providing areal estimates of parameters at the grid element scale with associated error bounds. Received: 30 October 1996 · Accepted: 25 June 1997     

边坡物理模型倾斜加载方式的研究

模型试验是研究边坡失稳机制的重要技术手段,通过倾斜模型获得滑坡的变形破坏过程也是常用的试验方法。作为一种试验加载方法,倾斜加载方式的可控性、倾斜过程中应力场的相似性都是影响该方法应用的关键性问题。为了研究试验方法的可控性,以块状滑体为例,分析计算了模型倾斜和离心加载两种试验方法对滑块抗滑安全系数的影响过程,结果表明,倾斜加载方法可以随着倾斜角度的增加连续地降低滑块的抗滑安全系数,而离心加载方式仅在1g～10g范围内对滑块的抗滑安全系数产生显著影响。为了比较模型倾斜前后模型内部应力场的相似性,建立了物理模型的数值计算模型,模拟不同倾斜角条件下坡体内的应力场。计算结果表明,模型倾斜过程中,坡体中部应力状态保持稳定,倾斜角较大时,坡体的前缘滑带位置应力状态变化较大,前缘进入塑性变形的可能性增大,局部应力场变化有利于模拟水库型滑坡的破坏机制。为了验证倾斜模型模拟滑坡破坏过程的应用效果,以千将坪滑坡为原型,采用倾斜加载方式进行破坏模型试验,获得了滑坡的破坏过程。与非连续变形分析方法(DDA)模拟的结果相比,模型试验得到的破坏形态更接近实际滑坡。     

多剖面合力法分析滑坡稳定性

滑坡稳定性分析最重要的是精度。滑面和坡面是空间三维变化曲面,造成滑体厚度各处变化很大。滑坡稳定性分析通常选择中轴线或其附近的一个所谓“代表性纵断面”进行安全系数计算。由于采用单位宽度纵剖面计算,在多数情况下只能代表该纵剖面两侧不大范围宽度滑体的局部稳定性,而不能代表滑坡整体稳定性,因此提出多纵剖面合力法进行滑坡稳定性分析。为减少多剖面勘探成本的人财物力投入,把滑动面分成了简单滑面和复杂滑面两类。对简单滑面滑坡最少只打两个纵断面共2~4个钻孔,应用几种滑面曲线函数,绘制辅助横剖面,将所需要的多个计算纵剖面剖出。多剖面合力法是基于空间平行力系可移动原理,对各剖面划分条块,把每个剖面条块的剪应力与抗滑力分解成水平与垂直分力,然后计算每个剖面剪应力与抗滑力的垂直与水平分力各自的合力,再对各剖面的剪应力与抗滑力的水平与垂直分力求合力,计算出滑坡的抗滑力与下滑力,得到剪应比——滑坡的稳定系数。用简单滑面和复杂滑面两个滑坡实例进行了分析,验证方法的有效性。     

强降雨作用下堆积层滑坡稳定性分析

强降雨作用易造成堆积层滑坡发生,带来严重的生命财产损失。基于Green-Ampt（GA）模型,同时考虑湿润锋以上饱和带渗流作用,推导了一种新的滑坡降雨入渗函数,弥补了GA模型只适用于无限长坡的不足。为考虑降雨入渗对土体条块强度的影响,采用整体抗剪强度准则评价滑坡稳定性,并在受力分析时考虑了湿润锋以上饱和带渗透力作用,建立了滑坡稳定性系数表达式。研究结果表明：滑坡降雨入渗的尺寸效应非常明显,湿润锋扩展速率随着坡长的增大而增大,当滑坡无限长时新降雨入渗模型与GA模型计算结果相同,说明GA模型是新模型的一个特例。此外,降雨初期,滑坡稳定性下降较快;随着降雨的持续,稳定性下降速率逐渐放缓。与模型试验结果对比表明,提出的降雨入渗模型和评价方法计算结果与试验揭示的现象一致,证明了该方法的可靠性。     

青藏高原多年冻土区斜坡稳定性研究进展

青藏高原多年冻土区斜坡失稳是伴随着青藏公路建设和运营过程中出现的一种灾害性的地质现象，其中以热融滑塌最为显著。本文根据斜坡失稳时所处的环境以融滑塌为例，提出了冻融循环过程中流塑状粉土沿厚层地下冰面滑动的滞水润滑效应的形成机理；通过相似模拟试验，可以看出，垂直于坡面的变形主要表现为融沉变形和部分冻胀变形；建立了温度场、变形场的数值模拟模型，分析了坡体不同深度在冻融循环过程中的位移变化规律，得出冻土斜坡位移主要发生在浅部的结论。最后指出目前研究存在的主要问题及进一步的研究方向。     

Kinematic analysis of pile behavior for improvement of slope stability in fractured and saturated Hoek–Brown rock masses

Because of a multitude of steep slopes being constructed adjacent to roadways, there is greater concern of landslide occurrence, particularly in instances where poor geomaterials are present. Installation of piles along the slope is one commonly adopted method. This paper presents the assessment of the stability of a rock slope with stabilizing piles based on kinematic analysis. The pile effect is introduced with a resultant lateral force and a moment. Upper bound solutions of the pile's lateral force are derived with a log‐spiral rotational failure mechanism. The slope performance based on the bearing capacity of surcharge loading is also discussed with consideration of pore water pressure. In order to substantiate the derived theoretical solutions, numerical analysis with optimization technique is carried out. Results demonstrate that rock materials with high quality are conducive to ensure slope stability. Reduced lateral force on the pile is produced with lower rock weight, slope height, and surcharge loading. Finally, the safety factor and stability coefficient are discussed to complete the evaluation of the slope stability. Copyright © 2016 John Wiley & Sons, Ltd.     

滑坡治理中抗滑桩桩位分析

采用有限元强度折减法对单排桩、桩间距为4 m的抗滑桩在不同设桩位置加固滑坡进行数值模拟,研究发现不同的桩位影响滑坡的稳定安全系数、滑动面的位置和形状。桩位不同决定了是桩后土体还是桩前土体滑落。桩位选择的一个重要原则是加固后滑坡体的稳定安全系数必须大于设计要求的安全系数,否则就会出现桩端越顶破坏或桩前土体滑落。斜坡在同一稳定安全系数下,桩位不同时抗滑桩所受的滑坡推力、桩的内力（剪力、弯矩）和桩的挠度不同。抗滑桩位于斜坡中部时,桩身长度较长,推力和内力大,是不合理的桩位;但桩身挠度大,提供的桩前抗力也大。按常规方法与按有限元法计算桩前无土体的悬臂桩桩上推力是相近的。把桩视作埋入滑坡体中的梁单元,按有限元法算出的推力比较小,因为它已经充分考虑了桩前土体的抗力。     

甘肃黑方台滑坡类型与活动特征研究

由于农业灌溉水的长期入渗软化作用,1984-2019年甘肃黑方台已频繁发生滑坡灾害约150次,沿黄土塬边形成长约10公里的滑坡密集发育带。滑坡类型以中、小型黄土层内滑坡为主,占90%以上;大、中型黄土-泥岩顺层滑坡次之。黄土层内滑坡速度快、滑程远,突发性、频发性、继发性强;黄土-泥岩顺层滑坡速度慢、滑程近、复活性强。高陡的台缘地形和强度低、水敏感性强的岩土体和岩层倾向坡外的地质结构是滑坡发生的基础,台塬区长期大量的农业灌溉是主要引发因素,大量水体入渗软化斜坡岩土体,使抗剪强度降低,并形成了约20多米厚的饱和软弱基座,导致斜坡失稳滑动,侧压力、季节性冻结滞水和溶滤作用等也有一定影响。黄土层内滑坡高速远程滑动的主要原因是：滑坡剪出口位置高,滑动势能大,释放条件好,剪出口下部有陡坡加速段和开阔、平缓的滑动空间,滑体底部饱和软弱黏性土持续产生超孔隙水压力、液化等低摩阻效应,是远程滑动的润滑剂。黄土-泥岩顺层滑坡的主滑面沿外倾15°左右的泥岩层面发育,且剪出口位于斜坡下部坡脚部位,能量释放条件差,决定了黄土-泥岩顺层滑坡的滑动速度较低、滑动距离较短,滑体易再次复活滑动。     

A time-space based approach for mapping rainfall-induced shallow landslide hazard

A rainfall-induced shallow landslide is a major hazard in mountainous terrain, but a time-space based approach is still an unsettled issue for mapping rainfall-induced shallow landslide hazards. Rain induces a rise of the groundwater level and an increase in pore water pressure that results in slope failures. In this study, an integrated infinite slope analysis model has been developed to evaluate the influence of infiltration on surficial stability of slopes by the limit equilibrium method. Based on this new integrated infinite slope analysis model, a time-space based approach has been implemented to map the distributed landslide hazard in a GIS (Geographic Information Systems) and to evaluate the shallow slope failure induced by a particular rainfall event that accounts for the rainfall intensity and duration. The case study results in a comprehensive time-space landslide hazard map that illustrates the change of the safety factor and the depth of the wetting front over time.     

基于组合楔形体原理的采动坡体稳定性研究

地下采煤通常会引起地表严重开裂,甚至发生滑坡、崩塌等地质灾害,采动坡体的稳定性研究一直是工程实际关心的问题。本文以贵州省都匀市煤洞坡采动坡体为例,在斜坡破坏机制分析基础上,采用组合楔形块体原理构建了采动坡体稳定性系数计算方程,并从实验、经验类比、采空率等方面对采动坡体的强度指标进行了综合取值,计算了采动坡体在天然、饱水及裂隙水作用下的安全系数。结果表明:煤洞坡山体是处于稳定状态的,这与坡体上的裂缝位移监测成果是相符的。但在长时间降雨或暴雨情况下,煤洞坡山体稳定性就会逐渐变差,甚至发生滑动; 坡体稳定性安全系数随内摩擦角的降低而降低,随裂隙水充水高度的增加而降低; 一旦后缘块体挤压前缘块体时,就会存在一个安全系数急剧降低的阀值。从裂缝水柱高度与降雨渗入裂缝的雨水量关系出发,建立了裂缝水柱高与降雨量之间关系式。经计算当降雨量(短时间内)超过192mm,斜坡就会失稳。