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1.
降雨和蒸发对土质边坡稳定性的影响 总被引：11，自引：4，他引：7
降雨入渗降低边坡的稳定性,蒸发增加边坡的稳定性,降雨和蒸发对边坡稳定性的定量研究是很有意义的。采用蒸发和降雨模型对边坡进行非饱和-非稳定渗流分析,用总凝聚力表示的Bishop极限平衡法计算边坡安全系数。采用数值方法对算例土质边坡进行了研究,得到了孔隙水压力随时间变化的关系、边坡安全系数随时间变化的关系。结果显示：土体中孔隙水压力与天气条件、边坡安全系数与天气条件之间存在滞后关系;降雨和蒸发对边坡的表层滑动稳定性影响非常大,对深层滑动稳定性影响相对较小;降雨过程中边坡的临界滑动面由较深位置向较浅位置转变,蒸发过程则相反。 相似文献
2.
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。 相似文献
3.
Predictive Power Evaluation of a Physically Based Model for Shallow Landslides in the Area of Oltrepò Pavese,Northern Italy 总被引：2，自引：0，他引：2
Roberto Valentino Claudia Meisina Lorella Montrasio Gian Luca Losi Davide Zizioli 《Geotechnical and Geological Engineering》2014,32(4):783-805
The use of real-time landslide early warning systems is attracting the attention of the scientific community, since it allows to assess “where” and “when” a shallow rainfall-induced landslide might occur by coupling rainfall amounts, hydrological models and slope-stability analysis. The paper deals with the main results of a back analysis, which refers to the application of a physically based stability model [Shallow Landslides Instability Prediction (SLIP)] on regional scale. The analysis concerns the occurrence of some recent rainfall-induced shallow landslides in the municipal territory of Broni, in the area of Oltrepò Pavese (Northern Italy). The study area is a hilly region 2.4 km2 wide, where more than 40 % of the territory has slopes steeper than 15° and altitudes are between 90 and 250 m a.s.l. As regards the geologic setting, clayey-silty shallow colluvial deposits, with a maximum thickness of about 3 m, overlap a bedrock made of clayey shales, calcareous flysch and marls. The SLIP model is based on the limit equilibrium method applied to an infinite slope and on the Mohr–Coulomb strength criterion for the soil. By assuming that the main hydro-geotechnical process that leads to failure is the saturation of parts of the soil, the model allows to take into account the condition of partial saturation of the soil. The safety factor (F S ) of a slope is also function of previous rainfalls. After the implementation of the model at territory scale, the input data have been introduced through a geographic information systems platform. In the current paper we mainly intend to evaluate the performance of SLIP at catchment scale, by comparison to (1) observed landslide events and (2) another well-established physically based model (TRIGRS). Further, we want to assess the suitability of the model as early warning tool. The results produced by the model are analyzed both in terms of safety factor maps, corresponding to some particular rainfall events, and in terms of the time-varying percentage of unstable areas over a 2-year span period. The paper shows the comparison between observed landslide localizations and model predictions. A quantitative comparison between the SLIP model and TRIGRS is presented, only for the most important event that occurred during the analyzed period. Overall, the results of the stability analyses based on observed rainfalls show the capability of the SLIP model to predict, in real-time and on a wide area, the occurrence of the analyzed phenomena. 相似文献
4.
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。 相似文献
5.
为研究强降雨条件下地表径流和裂隙水流的拖曳力作用对斜坡稳定性的影响,建立斜坡地表径流和地下水渗流耦合分析模型。采用Navier-Stokes方程描述地表径流和裂隙水流,Brinkman-extended Darcy方程描述土体和岩石中的渗流,并根据不同介质交界面处流速相等及剪应力连续的边界条件,推求各介质中的流速分布。应用Newton内摩擦定律求得水流对斜坡产生的拖曳力,进而将拖曳力嵌入刚体极限平衡理论对斜坡稳定性进行分析。典型斜坡实例计算结果表明,当未考虑拖曳力效应时,斜坡的安全系数为1.164,考虑水流对斜坡土体产生拖曳力效应时,斜坡的安全系数为1.089,斜坡安全系数降低了6.44%。这表明拖曳力作用对斜坡的稳定性存在不利影响,斜坡土体在近乎临界稳定状态下拖曳力将对斜坡失稳起到决定性作用。最后分别讨论了考虑拖曳力和不考虑拖曳力情况下斜坡的安全系数与径流水深、斜坡倾角、土层厚度之间的关系。分析表明,在其他条件相似的条件下,斜坡越陡,斜坡土体的安全系数下降越明显;斜坡安全系数随着斜坡倾角增加而不断降低,随着土层厚度的增加而不断降低。 相似文献
6.
确定性模型在黄土沟壑区斜坡稳定性预测中的应用 总被引：2，自引：0，他引：2
SHALSTAB耦合了稳态水文假定模型和无限斜坡稳定性模型,主要用于评价浅层滑坡稳定性的时空分布和发展趋势。选择黄土高原甘肃陇东地区华池县作为研究区,评价SHALSTAB模型在黄土沟壑区浅层滑动稳定性分析中的适用性和可靠性,利用1:5 000地形图获得了数字高程模型和地形坡度,以及室内和现场试验的物理力学参数,结合现场钻探和探槽得到的土层厚度分布和地表稳定性指数等级分布图。现场测量绘制的滑坡分布图与模拟结果对比和统计分析表明,SHALSTAB模拟的总体正确率为70.23%,滑坡预测正确率为72.33%,稳定状态预测正确率为67.51%,模拟效果良好。 相似文献
7.
Cheng-Yu Ku Chih-Yu Liu Yan Su Jing-En Xiao Chi-Chao Huang 《Environmental Earth Sciences》2017,76(16):570
This study investigates the transient modeling of regional rainfall-triggered shallow landslides in unsaturated soil using the Richards equation. To model shallow landslides within a distributed regional-scale framework, infinite slope stability analysis coupled with the hydrological model with consideration of the fluctuation of time-dependent pore water pressure and the soil–water characteristic curve proposed by van Genuchten was developed. The validity of the proposed model is established through several test problems by comparing the numerical results with the analytical solutions. A new procedure to set up wide-range shallow landslide analysis and to integrate regional distribution variations for input data such as geology, groundwater level, hydrogeological characteristics, and rainfall intensity and duration was presented. The results obtained demonstrate that the computed distribution of the safety factor is consistent with the distribution of actual landslides. In addition, the fluctuation of pore water pressure in unsaturated soil dominates the stability of landslides during typhoons accompanied by heavy rainfall. The findings observed in this study are a fundamental contribution to environmental effects for landslides in areas with higher occurrence and vulnerability to extreme precipitation. 相似文献
8.
降雨诱发浅层滑坡稳定性的计算模型研究 总被引：6，自引：0，他引：6
我国是一个滑坡灾害频发的国家,众多事实表明：降雨是影响边坡稳定性,导致边坡失稳的最主要和最普遍的环境因素,是浅层滑坡的触发因素。为了更好地对降雨诱发浅层滑坡进行研究,采用非饱和土VG模型与改进的Green-Ampt入渗模型对Mein-Larson降雨入渗模型进行改进,并结合无限边坡提出了一个降雨诱发浅层滑坡的简化计算模型。与以往提出的简化计算模型相比,该模型既考虑了坡面倾斜的影响,又考虑了非饱和土的特性,并可用于两种降雨形式下的边坡浅层稳定性估算,具有更广的应用范围。通过与有限元得到的结果进行比较可得：在不同降雨条件下,该计算模型得到的各项结果与数值解是接近的,安全系数计算结果是偏于安全的,因此,可将该计算模型用于降雨诱发浅层滑坡的近似估算;该计算模型公式简单,便于计算,计算效率较高。 相似文献
9.
某边坡变形破坏机理的数值分析 总被引：3，自引：0，他引：3
某花岗岩矿岩土体主要有填土、粉质粘土、淤泥及淤泥质土、含泥中粗砂、粘土、残积砂质粘土,其下为花岗岩基岩。边坡最大高度75m,其中残积土层以上的土质边坡高度约50m。本文运用有限元强度折减法对该边坡的稳定性进行了研究,得出了潜在的破坏模式及各个滑动部分的安全系数。分析结果表明,本边坡存在3个潜在滑动面,其中两个为浅层滑动面,另一个为深层滑动面。两个浅层滑动面的稳定系数在1.13～1.17,处于临界状态。深层滑动面稳定性系数在1.29,目前尚处在相对稳定状态。根据分析结果,提出了如下加固措施:（1）对滑坡体进行削坡处理;（2）在其滑动面下方设置抗滑台阶;（3）采用预应力锚索框架梁结合肋柱进行加固处理。 相似文献
10.
11.
对于大面积浅层风化土边坡,当下部含有浅水位或不透水基岩层时大降雨将导致下部气体被封闭。随着湿润峰的下移,气压不断增大。封闭气压力不仅降低了雨水在边坡土体的入渗率,而且对边坡的稳定有显著影响。通过分析封闭气压力的形成和相关理论,提出取 大小的气压力头来研究边坡的稳定性（Hc为一水头值,与土体孔隙尺寸分布有关; hd为土体进气值水头）。结合非饱和土的Mohr-Coulomb破坏准则和极限平衡法,将封闭气压力引入到边坡的稳定分析中,建立了考虑气压力影响下的稳定分析模型。与传统的不考虑气压力的稳定分析方法作对比,提出了气压力影响率概念。研究表明,封闭气压力显著降低了边坡的安全系数,传统的无限边坡稳定计算方法偏于危险。研究结果对无限边坡的强降雨安全预报具有较好的指导作用。 相似文献
12.
An analytical solution for rainfall infiltration into an unsaturated infinite slope and its application to slope stability analysis 总被引：1，自引：0，他引：1
Surficial slope failures in residual soils are common in tropical and subtropical regions as a result of rainfall infiltration. This study develops an analytical solution for simulating rainfall infiltration into an infinite unsaturated soil slope. The analytical solution is based on the general partial differential equation for water flow through unsaturated soils. It can accept soil–water characteristic curve and unsaturated permeability function of the exponential form into account. Numerical simulations are conducted to verify the assumptions of the analytical solution and demonstrate that the proposed analytical solution is acceptable for the coarse soils with low air entry values. The pore‐water pressure (pwp) distributions obtained from the analytical solution can be incorporated into a limit equilibrium method to do infinite slope stability analysis for a rain‐induced shallow slip. The analysis method takes into account the influence of the water content change on unit weight and hence on factor of safety. A series of analytical parametric analyses have been performed using the developed model. The analyses indicate that when the residual soil slope, consisting of a completely decomposed granite layer underlain by a less permeable layer, is subjected to a continuous heavy rainfall, the loss of negative pwp and the reduction in factor of safety were found to be most significant for the shallow soil layer and during the first 12 h. The antecedent and subsequent rainfall intensity, depth of a less permeable layer and slope angle all have a significant influence on the pwp response and hence the slope stability. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
当采用合理的强度参数时,根据常规极限平衡或极限分析方法的计算结果,很难解释一些膨胀土边坡会在极缓的坡度下发生失稳破坏的原因。事实上,由于膨胀土遇水后会发生显著的变形,在饱和区与非饱和区交界面附近会出现很大的剪应力。因此,在膨胀土边坡的稳定分析中,需要考虑这种因素的影响。根据塑性力学的上限定理,严格地导出了考虑膨胀应力作功的功能平衡方程。根据强度储备定义的安全系数即隐含在这一方程中,它可以通过迭代方法求解。边坡稳定的上限分析在数值上是利用了单元集成法来完成的。这不仅能方便地利用应力分析的成果,而且能进行滑裂面的优化,从而找到最小的安全系数。对一个坡度为1:4的膨胀土边坡的稳定计算结果表明,膨胀变形会使边坡的安全系数显著减小。当考虑膨胀时,优化得到的破坏模式是在浅层出现一个局部的滑动,它会牵动其上部的土体也相继出现局部滑动,这正好符合膨胀土滑坡时所常见的牵引性的特征。 相似文献
14.
降雨入渗过程中,土体吸力降低,体积明显改变。天然浅层土体长期受到季节性气候变化的影响,因此,开展水-力耦合及干湿交替对浅层残积土坡稳定性影响的数值分析,分析浅层土坡孔隙水压力、湿润锋及安全系数的时空演变规律,并对水-力耦合及干湿交替条件下的浅层土坡失稳破坏机制进行探讨显得尤为必要。研究结果表明：随着干湿循环次数的增加,水-力耦合分析下孔隙水压力以及湿润锋的迁移速度增加更快,边坡也更易失稳破坏;干湿交替初期,雨水入渗易引起地下水位上升,边坡可因正孔隙水压力的增加而失稳;干湿交替后期,湿润锋的快速推进加剧基质吸力迅速丧失及土体强度下降,边坡安全系数显著降低,发生失稳破坏的时间缩短。因此,可将湿润锋处的安全系数(局部最小值)作为控制边坡长期稳定性的临界值。 相似文献
15.
根据覆盖层边坡特性设计室内降雨试验模型,提出初始含水率分布沿高程呈反比例分布。根据边坡表面未饱和时降雨入渗受总降雨量控制的基本假设,建立了不排水状态下覆盖层边坡降雨入渗的解析计算方法。基于上述降雨入渗理论,考虑非饱和土抗剪强度变化规律,建立适用于非饱和覆盖层边坡的边坡稳定性计算方法。分析了覆盖层厚度、初始含水率分布参数以及覆盖层边坡角度对边坡稳定性的影响规律。具体结论如下：(1)覆盖层边坡内部初始含水率分布可采用反比例分布近似表示,基于总降雨量控制假设,得到可考虑初始含水率分布的覆盖层边坡降雨入渗解析计算方法。(2)基于半无限空间体边坡假设,给出覆盖层边坡在降雨入渗条件下不同位置滑动面的稳定系数计算方法。(3)在相同降雨量条件下,边坡初始稳定性随覆盖层土体厚度的增加而下降。降雨入渗对覆盖层边坡稳定性的影响随着上覆土层厚度的增加而减小。(4)当降雨量相同时边坡稳定性随着覆盖层土体初始含水率分布参数的增加而下降,降雨时间越长,初始含水率分布对边坡稳定的影响越明显。(5)不同角度的覆盖层边坡稳定性均随降雨量增加而逐渐减小。在初始状态下边坡角度增加所引起的最小稳定系数下降幅度最大,随着降雨量的... 相似文献
16.
Apip Kaoru Takara Yosuke Yamashiki Kyoji Sassa Agung Bagiawan Ibrahim Hiroshi Fukuoka 《Landslides》2010,7(3):237-258
This paper describes the potential applicability of a hydrological–geotechnical modeling system using satellite-based rainfall
estimates for a shallow landslide prediction system. The physically based distributed model has been developed by integrating
a grid-based distributed kinematic wave rainfall-runoff model with an infinite slope stability approach. The model was forced
by the satellite-based near real-time half-hourly CMORPH global rainfall product prepared by NOAA-CPC. The method combines
the following two model outputs necessary for identifying where and when shallow landslides may potentially occur in the catchment:
(1) the time-invariant spatial distribution of areas susceptible to slope instability map, for which the river catchment is
divided into stability classes according to the critical relative soil saturation; this output is designed to portray the
effect of quasi-static land surface variables and soil strength properties on slope instability and (2) a produced map linked
with spatiotemporally varying hydrologic properties to provide a time-varying estimate of susceptibility to slope movement
in response to rainfall. The proposed hydrological model predicts the dynamic of soil saturation in each grid element. The
stored water in each grid element is then used for updating the relative soil saturation and analyzing the slope stability.
A grid of slope is defined to be unstable when the relative soil saturation becomes higher than the critical level and is
the basis for issuing a shallow landslide warning. The method was applied to past landslides in the upper Citarum River catchment
(2,310 km2), Indonesia; the resulting time-invariant landslide susceptibility map shows good agreement with the spatial patterns of
documented historical landslides (1985–2008). Application of the model to two recent shallow landslides shows that the model
can successfully predict the effect of rainfall movement and intensity on the spatiotemporal dynamic of hydrological variables
that trigger shallow landslides. Several hours before the landslides, the model predicted unstable conditions in some grids
over and near the grids at which the actual shallow landslides occurred. Overall, the results demonstrate the potential applicability
of the modeling system for shallow landslide disaster predictions and warnings. 相似文献
17.
强降雨作用下堆积层滑坡稳定性分析 总被引：2，自引：0，他引：2
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。 相似文献
18.
Lucio Di Matteo Cristina Pauselli Daniela Valigi Maurizio Ercoli Mauro Rossi Giacomo Guerra Costanza Cambi Remo Ricco Giuseppe Vinti 《Landslides》2018,15(1):173-180
Shallow landslide failures are distributed worldwide and cause economic losses and fatalities. A proper evaluation of the possible occurrence of shallow landslides requires reliable characterization of water content. Volumetric water content (θ) is commonly estimated using dielectric sensors, which use manufacturers’ calibration curves developed for specific soil types. In this study, we present the experimental results achieved during a laboratory calibration of a capacitance probe (PR2/6 probe), tested on two sandy soils widely outcropping in Central Italy. The proposed equations demonstrate a more reliable estimation of θ with respect to the generalized soil equation provided by the manufacturer, which overestimates θ by up to 10 percentage points. Such overestimation could affect the evaluation of suction stress in partially saturated shallow soils affecting the slope stability analysis. Although the use of θ from correct calibration equations provides less precautionary factor of safety values, a reliable evaluation of the soil moisture condition is fundamental when mapping and predicting the spatial and temporal occurrence of shallow landslides. The use of the PR2/6 probe with the appropriate soil calibration equations in early warning monitoring systems will provide a more reliable forecast, minimizing the number of false alarms. 相似文献
19.
降雨条件下浅层滑坡稳定性探讨 总被引：8，自引：0，他引：8
降雨条件下浅层滑坡是一种常见、多发的地质灾害现象,为了解边坡稳定性随降雨入渗过程的变化情况,以Green-Ampt入渗模型为基础,并考虑了动水压力的作用,建立了降雨入渗条件下浅层滑坡的概念模型,分别推导了降雨前有、无地下水位条件下的边坡安全系数与降雨时间的关系表达式。从分析结果中可以看出,对于这两种情况下边坡稳定性发生突变的主要原因归结于：前者为在湿润锋与地下水位面接触的短时间内,滑带处的孔隙水压力迅速增高;后者为滑带在浸水饱和情况下,岩土体的强度迅速降低。在此基础上,根据降雨过程中边坡是否达到饱和,提出边坡饱和临界时间的概念,考虑了初始降雨强度小于土壤入渗能力的情况。这个时间可以作为一个参数指标用于浅层滑坡的预警。 相似文献
20.
Pressure-grouted soil nails have been increasingly used for stabilizing slopes. The pullout resistance of a soil nail is the main factor for reinforcing the slope stability. In this study, a two-dimensional axisymmetric finite element model is developed to simulate the pullout behavior of a pressure-grouted soil nail. This model is verified with field pullout tests result of a pressure-grouted soil nails by comparing with gravity-grouted soil nails. Based on the analysis, a three-dimensional finite element model is proposed for stability analysis of a slope reinforced with pressure-grouted soil nails using the shear strength reduction method. A series of numerical slope stability analyses for a slope composed of weathered soil are performed to investigate the effects of grouting pressure on the slope stability and the behavior of the soil nails. Special attention is given to the installation effect of a pressure-grouted soil nails. It is found from the result of this study that the pressure-grouted soil nails increase the safety factor by fifty percent in a slope by increasing the stiffness of the nailed slope system. Numerical analysis results confirm the fact that the pullout resistance of a soil nail is the main factor for stabilizing slopes rather than the shear resistance of the soil nail. 相似文献