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1.
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
2.
This paper discusses the results of an investigation on the influence of rainfall intensity and duration on the suction distribution within a soil mass. A series of numerical analyses were conducted on an infinite slope model to simulate the responses of the slope consisting of typical soil types to various rainfall intensities and durations from selected locations in the Malaysian Peninsular. The study showed that the critical duration was governed by three major factors: the saturated permeability of the soil, the geographical location, and the depth of the slip plane. The critical rainfall duration for highly permeable soil was 1 day, while 30 days of antecedent rainfall were required for the stability analysis of a slope made of soil with low saturated permeability. The critical duration of antecedent rainfall in soils with intermediate saturated permeability was found to vary with the rainfall pattern. A chart is proposed to determine the critical duration, critical intensity and critical suction for each type of soil. 相似文献
3.
强降雨作用下堆积碎石土渗流规律研究 总被引：1，自引：0，他引：1
强降雨致堆(残坡)积碎石土渗透特性改变是触发滑坡、泥石流等降雨诱发型灾害的关键因素。为探究降雨入渗诱发滑坡的动态机制, 通过自制一维渗透仪与二维边坡降雨入渗模型, 对水竹湾隧道旁具有级配代表性的碎石土进行强降雨入渗试验, 并通过Seep/w软件进一步分析堆积碎石土湿润锋迁移入渗规律。研究结果表明:一维入渗深度-时间曲线存在阶梯状趋势, 即湿润锋迁移速度首先随表层土含水率的突增迅速增加至最大值, 然后缓慢减小, 最后湿润锋迁移速度略微增大; 湿润锋平均迁移速率随雨强的增大趋近线性增长; 碎石土沉降变形在入渗过程中经历缓慢增长、急剧增大、逐渐停滞3个阶段; 坡顶、坡腰及坡脚处入渗速率与一维入渗速率分别满足指数关系、对数关系及线性关系; 雨水最终入渗深度由大到小依次为坡脚、坡顶、坡腰。 相似文献
4.
渗透系数是研究实际工程渗水问题的关键参数之一。以往对于非饱和土渗透系数的试验研究中,增湿工况较为单一,极少考虑竖向附加应力的影响。基于此,开发了一套一维垂直土柱试验装置以弥补这一缺陷。该装置主要由试验台架、土柱筒、竖向加载装置、供水装置、水分传感器、张力传感器以及数据采集系统等组成,可模拟竖向附加应力作用下降雨、积水入渗、毛细上升工况,可测定增湿过程中水的入渗量与浸润峰时程线、土柱竖向变形以及不同截面的体积含水率与基质吸力的时程曲线,基于瞬态剖面法可获得不同截面处增湿时土的非饱和渗透系数与吸力关系。最后,以兰州Q3非饱和粉质黄土为例,初步开展了不同竖向附加应力作用下土柱积水入渗试验,分析入渗量、湿润锋、体积含水率、吸力及竖向变形时程线变化规律,获取渗透系数与吸力关系的渗透函数变化规律,通过对比类似试验结果,表明试验结果符合渗水规律,验证了研制土柱仪的有效性,但其可靠性还需进一步研究。本试验装置为不同工况下非饱和土体变形、水分迁移规律及渗透特性研究奠定基础,并获得相应试验参数。 相似文献
5.
Response parameters for characterization of infiltration 总被引：2，自引：2，他引：0
H. Rahardjo T. H. Ong R. B. Rezaur E. C. Leong D. G. Fredlund 《Environmental Earth Sciences》2010,60(7):1369-1380
Rainwater infiltration is of particular interest with respect to slope stability hazard management. The process of rainfall infiltration into unsaturated soil is complex due to the number of soil parameters involved and the random nature of moisture flux boundary conditions. In this paper, the effect of rainfall intensity on infiltration is investigated through the use of finite element seepage modeling for a 5 m high soil column subjected to various rainfall intensities. The numerical modeling study identified three response parameters that can be used to describe one-dimensional infiltration into an unsaturated soil. The response parameters are the depth of wetting front, the matric suction reduction depth, and the sectional infiltration rate. The practical application of the rainfall response parameters in slope stability analysis is illustrated. 相似文献
6.
传统降雨入渗分析是以降雨强度在坡面上的正交分量作为边界条件,不符合实际降雨的非正交入渗规律。为了研究非饱和粉质黏土的非正交入渗规律性,首先通过对正交入渗理论的综述,揭示并分析目前降雨入渗理论在坡面流模型和边界条件方面的缺陷。采用自行研制的室内降雨试验装置对非饱和粉质黏土进行不同降雨强度、坡角和孔隙比的降雨入渗试验,结果表明,非饱和粉质黏土坡面降雨入渗是并非简单正交分解入渗而是非正交入渗;对于坡角和孔隙比为定值的土坡,具有最大坡面入渗的最优雨强;土的孔隙比越小,降雨初期入渗率随时间变化越快,入渗率趋于稳定状态越快;入渗率和累积入渗量并不是随坡角的增大呈单调变化,而存在对应入渗水量最少的最优坡角。 相似文献
7.
Water infiltration characteristics of unsaturated soil slope and its effect on suction and stability 总被引：3，自引：1，他引：3
Bujang B. K. Huat Faisal HJ. Ali T. H. Low 《Geotechnical and Geological Engineering》2006,24(5):1293-1306
Rainfall has been considered the cause of the majority of slope failures and landslides that happened in regions experiencing
high seasonal rainfalls. The mechanism of the failures was mainly due to the lost of matric suction of soils by rainwater.
This paper presents the results of a laboratory model study on the effect of slope angle and surface cover on water infiltration
into soil and soil matric suction. A field infiltration test is carried out for comparison. A parametric study is also done
to examine the effect of permeability ratio, development of perched water table and rainfall intensity on the factor of safety
against instability of a soil slope. Results of the model study show that different surface covers on slopes have an effect
on the water infiltration. Generally the covered surface (grass or geosynthetic net) has a lower infiltration rate compared
with the bare (no cover) surface. On the effect of slope angle, it was observed that water infiltration decrease with increase
in the slope steepness. With regards to the movement of the wetting front, it appears that water infiltration is more at the
toe compared with the top of the model slope. Based on the parametric study, it is found factor of safety of the slope against
instability drops for slope with higher ratio of permeability for the permeable and impermeable stratum. As the perched water
table is formed, the factor of safety decreased. The rainfall intensity also has a marked effect on the slope factor of safety.
The higher the intensity of the rainfall, the higher is the infiltration rate into the soil, hence the lower is the factor
of safety against slope instability. 相似文献
8.
9.
连续降雨作用下非饱和土边坡的稳定性分析 总被引：1，自引：1，他引：1
在边坡稳定性研究中,吸力的影响经常被忽略。基于非饱和土的渗流理论,利用数值分析方法研究了一个由于连续降雨导致的非饱和土边坡失稳的工程实例。研究结果表明:非饱和土的吸力对于维持边坡稳定具有重要影响,而吸力与降雨频率、降雨量、降雨时间、蒸发量等密切相关。对于工程实践而言,吸力的监测对于维持土坡稳定具有重要意义。 相似文献
10.
For the assessment of shallow landslides triggered by rainfall, the physically based model coupling the infinite slope stability
analysis with the hydrological modeling in nearly saturated soil has commonly been used due to its simplicity. However, in
that model the rainfall infiltration in unsaturated soil could not be reliably simulated because a linear diffusion-type Richards’
equation rather than the complete Richards’ equation was used. In addition, the effect of matric suction on the shear strength
of soil was not actually considered. Therefore, except the shallow landslide in saturated soil due to groundwater table rise,
the shallow landslide induced by the loss in unsaturated shear strength due to the dissipation of matric suction could not
be reliably assessed. In this study, a physically based model capable of assessing shallow landslides in variably saturated
soils is developed by adopting the complete Richards’ equation with the effect of slope angle in the rainfall infiltration
modeling and using the extended Mohr–Coulomb failure criterion to describe the unsaturated shear strength in the soil failure
modeling. The influence of rainfall intensity and duration on shallow landslide is investigated using the developed model.
The result shows that the rainfall intensity and duration seem to have similar influence on shallow landslides respectively
triggered by the increase of positive pore water pressure in saturated soil and induced by the dissipation of matric suction
in unsaturated soil. The rainfall duration threshold decreases with the increase in rainfall intensity, but remains constant
for large rainfall intensity. 相似文献
11.
为了分析降雨入渗影响下非饱和土坡渗流特性,利用自制降雨模拟系统和实时监测系统,对降雨诱发非饱和土坡失稳过程进行全方位、多参量的实时监测,研究不同降雨条件下,不同坡度、不同压实度边坡坡体不同位置雨水入渗率和湿润峰的实变规律.结果表明:降雨入渗条件下,陡坡和高压实度土体不利于雨水入渗,而缓坡和低密实度土体入渗率变化快;实际土体吸力和含水量实时变化规律不同步,提出试验湿润峰概念,含水率（吸力）湿润峰点可按含水率（吸力）实时曲线的过渡区和雨后残余含水率（吸力）的线性交叉点确定;考虑单向吸湿或脱湿路径下土体含水率和吸力具有唯一对应关系,含水率湿润峰点与吸力湿润峰点的绝对值时差即为形成湿润峰所需时间;对比湿润峰实测值与Lumb半经验值散点分布规律,基于Lumb湿润峰深度计算公式提出非线性修正表达式. 相似文献
12.
为研究物质组成空间分布特征对降雨下碎石土斜坡变形破坏的影响,以不同成因碎石土斜坡的特点为依照,进行了4种物质组成空间分布的碎石土斜坡模型及1种均质斜坡模型试验。结果表明,物质组成空间分布特征对降雨下碎石土斜坡变形破坏所发挥的作用与降雨入渗方向和应力调整方向有重要关系。当土料变化方向与入渗方向大角度相交且与应力调整方向相同时,斜坡渗透性为土料各自的渗透性,斜坡力学性质偏向于组成土料力学性质的最大值。当土料变化方向与入渗方向相同且与应力调整方向大角度相交时,斜坡渗透性接近组成土料渗透性的最小值,斜坡变形破坏受控于其中的软弱土料。降雨下斜坡各处均发生变形,且变形向周围调整并产生影响。破裂面更易发于软弱土料中。该研究有助于斜坡灾害勘察、预测评价及防治向精细化方向发展。 相似文献
13.
Rainfall-induced landslides can cause loss of life and damage to property, infrastructure, and the environment. Rainfall patterns affect the pore-water pressure of unsaturated soil slopes, and are related to the slopes’ stability. Four rainfall patterns were chosen to represent natural rainfall patterns for an examination of rainfall infiltration into soil slopes using numerical models incorporating coupled water infiltration and deformation in unsaturated soils. Our analysis showed that rainfall patterns play a significant role in the distribution of the pore-water pressure in soil slopes, and influence the slope stability. The pore-water pressure profile of soil slopes and the factor of safety are affected by the ratio of rainfall intensity and the coefficient of permeability. The depth and shape of the shallow sliding plane of the landslide is closely related to the rainfall pattern; moreover, the results showed a correlation between the factor of safety of the slope and the rainfall intensity. This relationship can be described by a dimensionless rainfall intensity. The nonlinear relationship can be used to estimate the slope stability resulting from rainfall infiltration when the hydro-mechanical coupling in unsaturated soil slopes is considered. 相似文献
14.
While the evolution with time of the factor of safety against slope failure is well understood for excavations performed under fully saturated conditions, this evolution has not been extensively studied for excavations carried out in unsaturated soils. The objective of this paper is to investigate the relationship between the factor of safety and time for an excavation performed in an unsaturated silty soil, employing the finite element method. A hypothetical boundary value problem is considered and two types of analyses performed; in the first one, unsaturated soil behaviour is modelled through appropriate constitutive and soil–water retention curve models, whereas in the second one full saturation is assumed. The effect that the saturated soil permeability, its variation with suction, the increase of apparent cohesion due to suction, the depth of the groundwater table and the hydraulic hysteresis have on the results of the unsaturated analysis is examined in a parametric study. The analyses results demonstrate that for unsaturated soils the factor of safety may increase with time, in contrast to what is commonly accepted to be the case in fully saturated soils. Furthermore, it is not possible to know in advance which one of the two types of analysis performed (i.e. the saturated or the unsaturated) will produce conservative results. It is, therefore, advisable to perform unsaturated analysis in geotechnical practice, when dealing with excavations in such soils. 相似文献
15.
A coupled elastic–plastic finite element analysis based on simplified consolidation theory for unsaturated soils is used to investigate the coupling processes of water infiltration and deformation. By introducing a reduced suction and an elastic–plastic constitutive equation for the soil skeleton, the simplified consolidation theory for unsaturated soils is incorporated into an in-house finite element code. Using the proposed numerical method, the generation of pore water pressure and development of deformation can be simulated under evaporation or rainfall infiltration conditions. Through a parametric study and comparison with the test results, the proposed method is found to describe well the characteristics during water evaporation/infiltration into unsaturated soils. Finally, an unsaturated soil slope with water infiltration is analyzed in detail to investigate the development of the displacement and generation of pore water pressure. 相似文献
16.
降雨入渗下强风化软岩高填方路堤边坡稳定性研究 总被引：12，自引：1，他引：11
降雨入渗是影响边坡稳定性、导致边坡失稳的最主要和最普遍的环境因素。强风化软岩用于高填方路堤填土边坡时,填土的压实度直接影响路堤土的渗透性和强度。利用饱和与非饱和渗流有限元模拟降雨入渗时高填方路堤的暂态渗流场,将计算得到的暂态孔隙水压力分布用于边坡的极限平衡分析,并考虑基质吸力对非饱和土抗剪强度的影响。探讨降雨强度、持时和压实度对边坡稳定性的影响。研究表明,强风化软岩用于高填方路堤压实度不能低于90 %;当暴雨强度为200 mm/d时,边坡就会失稳。其成果将为高填方路堤边坡防护设计提供科学依据。 相似文献
17.
Landslides are mainly triggered by decrease in the matric suction with deepening the wetting band by rainfall infiltrations. This paper reports rainfall-induced landslides in partially saturated soil slopes through a field study. A comprehensive analysis on Umyeonsan (Mt.) landslides in 2011 was highlighted. The incident involves the collapse of unsaturated soil slopes under extreme-rainfall event. Fundamental studies on the mechanism and the cause of landslides were carried out. A number of technical findings are of interest, including the failure mechanism of a depth of soil and effect of groundwater flow, the downward movement of wetting band and the increase of groundwater level. Based on this, an integrated analysis methodology for a rainfall-induced landslide is proposed in this paper that incorporates the field matric suction for obtaining hydraulic parameters of unsaturated soil. The field matric suction is shown to govern the rate of change in the water infiltration for the landslide analysis with respect to an antecedent rainfall. Special attention was given to a one-dimensional infiltration model to determine the wetting band depth in the absence of the field matric suction. The results indicate that landslide activities were primarily dependent on rainfall infiltration, soil properties, slope geometries, vegetation, and groundwater table positions. The proposed methodology has clearly demonstrated both shallow and deep-seated landslides and shows good agreement with the results of landslide investigations. 相似文献
18.
基于非饱和土力学理论,利用有限元法对降雨条件下边坡的饱和-非饱和渗流及稳定性进行了探讨。数值分析表明,雨水入渗使边坡非饱和区土体的基质吸力减小,是导致边坡稳定性降低的主要因素。进而考察了基质吸力的不同取值及裂隙的不同位置对边坡稳定性的影响,结果表明：在降雨初期基质吸力取值越大,得到的边坡安全系数越高,但经过长时间降雨即边坡土体基本达到饱和后,基质吸力的取值不同对边坡安全系数基本上没有影响;裂隙的存在为雨水入渗提供了良好的通道,因而导致边坡稳定性相对于无裂隙状态来说有所降低。降雨初期下游裂隙使边坡稳定性降低较快,但随着降雨历时的增加,即下游土体逐渐变为饱和状态后,边坡的稳定性变化则主要由上游裂隙控制。 相似文献
19.
有效应力参数的合理确定是非饱和土有效应力研究的重要内容。然而,现有的有效应力参数未能较好地考虑孔隙水的微观赋存形态对有效应力的影响。为此,分析了孔隙水的微观赋存形态,明确了孔隙水可分为收缩膜、吸附水和毛细水,建立了非饱和粉土的扩展三相孔隙介质模型,即孔隙气、毛细水和广义土骨架。基于该模型,采用分相平衡分析法,推导了非饱... 相似文献
20.
研山铁矿设计采用露天开采,最终最大边坡高达600m。边坡上部为粉土和粉砂、中砂、卵石、粉质粘土,下部为砂质粘性土和砾质粘性土。由于边坡高,受环境动应力影响因素大,因此分析粉土和粉质粘土层在动应力作用下对变形和强度的影响,对边坡稳定分析具有重要意义。 相似文献