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1.
土坡失稳的有效降雨量研究 总被引：1，自引：0，他引：1
降雨易引起花岗岩残积土边坡失稳。在分析降雨对边坡土体含水率影响的基础上,通过饱和度和含水率的关系推求出土体从非饱和过渡到饱和的有效降雨量。结果表明：对土质边坡,并非所有的降雨都会引起边坡的失稳,降雨入渗使边坡土体从非饱和向饱和状态发展,当边坡土体饱和度达到一定程度的时候易产生边坡失稳;土坡存在饱和区和非饱和区的临界深度,降雨对边坡的影响即为使得该深度以上的土体从非饱和过渡到饱和的过程,须采取不同的抗剪强度来计算处于临界深度上下两部分土体的稳定状态。研究结果对确定土坡失稳的降雨量阀值、进一步认识滑坡失稳机制,对滑坡的预测预报具有理论及实际意义。 相似文献
2.
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
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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
5.
在经验性降雨阈值和边坡稳定性数值分析两大类研究的基础上,考虑了降雨入渗和非饱和土性质,使用岩土有限元软件Plaxis高级模式对滑坡预警降雨阈值进行研究分析。算例表明,将降雨量在降雨时间范围内分成2段后,得到的边坡稳定性变化与实际情况更接近,重新定义前期降雨为在给定初始条件下引起边坡最危险滑裂面到坡面之间土体吸力分布发生变化的降雨。前期降雨时长与潜在滑裂面最大深度成正比,与饱和渗透系数成反比。将前期降雨量引入到降雨强度—持时曲线中作为第三个空间坐标轴,将该曲线拓展为前期降雨量-降雨强度-持时曲面。通过一基岩型边坡算例展示了阈值曲面的建立方法,并通过与模型试验数据的对比验证了其可靠性。 相似文献
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Chollada Kanjanakul Tanan Chub-uppakarn Tanit Chalermyanont 《Arabian Journal of Geosciences》2016,9(11):584
Transient seepage in unsaturated soil slope is one of the significant triggering factors in rainfall-induced landslides. Rainfall infiltration leads to the decrease in stabilizing effect because of increased positive pore-water pressures. SEEP/W and SLOPE/W used in this study have been widely employed to describe frameworks for understanding transient seepage in soil slope, and to perform slope stability analyses, respectively. The study area is in Sichon District in Nakhon Si Thammarat Province, southern Thailand. A landslide there was investigated by modeling the process of rainfall infiltration under positive and negative pore-water pressures and their effects on slope stability. GIS (Geographic Information System) and geotechnical laboratory results were used as input parameters. The van Genuchten’s soil water characteristic curve and unsaturated permeability function were used to estimate surface infiltration rates. An average rainfall was derived from 30-year monthly rainfall data between 1981 and 2011 in this area reported by the Thailand Royal Irrigation Department. For transient condition, finite element analysis in SEEP/W was employed to model fluctuations in pore-water pressure during a rainfall, using the computed water infiltration rates as surface boundary conditions. SLOPE/W employing Bishop simplified method was then carried out to compute their factors of safety, and antecedent precipitation indices (API) calculated. Heterogeneous slope at the site became unstable at an average critical API (APIcr) of 380 mm, agreeing well with the actual value of 388 mm. 相似文献
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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
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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,随着降雨量的增加,边坡稳定性受角度影响逐渐减小。 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.
渗透性与降雨强度对堆积层滑坡稳定性的影响 总被引：2，自引：0，他引：2
本文基于非饱和渗流理论及非饱和土的Fredlund双应力变量强度理论,对一沿岩土接触面滑动的堆积层滑坡模型,分别进行了8种条件下的降雨入渗数值模拟试验,研究了不同土体渗透性及降雨强度对滑坡稳定性的影响。结果表明:(1)堆积层滑坡的稳定性与土体的渗透性有密切关系,在降雨后的短期内,土体渗透性越好,滑面孔隙水压力升高越明显,滑坡的稳定性降低程度越大;(2)降雨期间,埋深较浅的滑面,入渗雨水能够较快到达,对滑坡稳定性的影响较大;(3)在相同的降雨时间内,降雨强度越大,滑坡稳定性降低速率越快;(4)降雨强度影响着滑坡发生的滞后性,在降雨总量一定的条件下,若降雨强度较大,雨停后,滑坡稳定性继续下降的程度较大;(5)降雨总量控制着滑坡的最终稳定性。 相似文献
13.
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
14.
降雨作用下煤系土路堑边坡稳定分析 总被引：4，自引：0，他引：4
基于掌握的降雨气象资料,利用非饱和瞬态渗流有限元程序对开挖后和风化后两种情况下的煤系土路堑边坡进行了降雨入渗坡体渗流场数值计算和分析。依据非饱和土力学强度理论,基于Morgenstern-Price方法,调用不同降雨时间的渗流计算结果,对两种情况下煤系土路堑边坡的瞬态稳定性进行了计算和分析。研究结果表明,水分在风化煤系土路堑边坡体内的渗透迁移对路堑边坡稳定性和最危险滑动面有时空影响;在煤系土路堑边坡降雨入渗和稳定性分析中考虑风化层较为合理。 相似文献
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Horizontal drains have been commonly used in stabilising unsaturated residual soil slopes. This study examines the effectiveness of horizontal drains in stabilising residual soil slopes against rainfall-induced slope failures under a tropical climate. The study includes field instrumentation at two residual soil slopes complemented with a parametric study relating to drain position. Field monitoring results indicate that rainfall infiltration is limited to a certain depth below which infiltration becomes insignificant. This zone tends to be unsuitable for horizontal drains. Horizontal drains were found to be most effective when located at the base of a slope. The parametric study indicated conditions under which horizontal drains are effective or ineffective in improving the stability of a slope. It was also found that horizontal drains have little role in minimising infiltration in an unsaturated residual soil slope. Benefits of using horizontal drains can be obtained through the lowering of the water table. 相似文献
16.
Precipitation infiltration is one of the most significant triggering factors for slope failure occurrence in many places around the world. Knowledge of the mechanisms leading to precipitation-induced slope failures is of great importance to the management of landslide hazard. In this study, a soil water balance model is developed to estimate soil water flux during the process of infiltration from rainfall data, with consideration of storm periods and non-storm periods. Two important assumptions in this study are given: (1) instantaneous uniform distribution of the degree of saturation and (2) a linear relationship between evapotranspiration and the related degree of saturation. For storm periods, the Brooks and Corey model estimates both the soil water retention curve and soil water parameters. The infiltration partition is employed by an infinite-series solution of Philip in conjunction with the time compression approximation. For none-storm periods, evapotranspiration can be derived for the moisture depletion of soil water. This study presents a procedure for calculating the safety factor for an unsaturated slope suffering from precipitation infiltration. The process of infiltration into a slope due to rainfall and its effect on soil slope behavior are examined using modified Mohr–Coulomb failure criterion in conjunction with a soil water balance model. The results indicate that the matric suction, which is closely related to slope stability, is affected by the degree of saturation controlled by rainfall events. 相似文献
17.
降雨入渗条件下非饱和路堤变形与边坡的稳定数值模拟 总被引：1，自引：0，他引：1
对于常常处于非饱和状态的路堤在降雨入渗条件下变形问题的数值模拟研究,由于涉及到非饱和土力学,一直是个热点和难点。现有的强度折减有限元法一般仅对强度指标进行折减,但折减后得到的路堤变形场与实际变形场存在一定差异。论文分析认为,在降雨入渗影响下非饱和路堤不仅强度参数会降低,而且变形参数也会随着应力水平和强度参数的变化而变化。采用基于变模量的弹塑性强度折减法,对不同降雨入渗深度下路堤的变形规律进行数值模拟,并与室内模型试验结果进行比较;同时采用强度折减法和极限平衡法中的Bishop法,分析了不同降雨入渗深度对非饱和路堤稳定性和滑弧变化特征的影响规律。 相似文献
18.
Modeling of layered infinite slope failure triggered by rainfall 总被引：3，自引：2，他引：1
The infinite slope is typically regarded as composed of a single-layered soil with a uniform property in various physical-based models used for modeling rainfall-induced shallow landslides. This study extends the physical-based model to consider the layered infinite slope to examine the importance of soil layer distribution for rainfall-induced shallow landslides. Hypothetical scenarios of infinite slope composed of soil layers with different thicknesses and parameters are employed to conduct this examination. The results show that pressure heads caused by rainfall infiltration are strongly related to soil layer distribution. This shows the significant influence of soil layer distribution in assessing infinite slope stability. Failure of a layered infinite slope does not necessarily occur at the impervious bottom of the hillslope soil, but may also occur at the interface between two soil layers. This result shows that a neglect of soil layer distribution could misestimate failure depth. Hence, soil layer distribution must be considered to reliably analyze infinite slope failure induced by rainfall. 相似文献
19.
降雨作用下,边坡土体的饱和度及含水率升高,基质吸力减小。随着降雨历时的增长,雨水入渗深度对坡体的稳定性产生影响。然而传统多层结构边坡的入渗计算方法并未考虑随入渗深度不断变化的基质吸力与层间积水点的形成,且忽略饱和层内沿坡体层面流动的部分雨水对入渗过程的影响,亦未考虑潜在滑动面位置随降雨历时的变化。将入渗过程分解为若干个子过程,并基于Green-Ampt（G-A）入渗模型对传统多层结构边坡的入渗计算方法进行改进,以对每个子过程进行求解,最后将其合并为整体入渗过程的解。在此基础上对层间积水点的形成时刻进行计算,进而分析雨水入渗深度与时间的关系,并研究降雨强度与雨水入渗深度对边坡不同位置处（湿润锋、饱和层）稳定系数和滑动面位置的影响。研究表明:（1）基于G-A模型的改进计算方法所得结果比传统多层结构边坡入渗计算方法所得结果更接近于数值模拟结果。（2）对于多层结构土质边坡,其安全系数随着雨水入渗深度的增加不断降低,并且在层间积水点形成时产生突变现象。（3）随着降雨历时和降雨强度的增大,边坡中潜在滑动面位置会产生变化,前期潜在滑动面位置出现在湿润锋处,后期则出现在饱和层交界面处。该方法提高了多层结构边坡传统降雨入渗计算方法的精度,更加全面的对多层结构边坡的稳定性进行评价,其工程应用范围亦得到进一步扩大 相似文献
20.
The empirical rainfall threshold concept and the physical-based model are two commonly used approaches for the assessment
of shallow landslides triggered by rainfall. To investigate in detail the rainfall-triggered shallow landslides, many physical-based
models coupling the infinite slope stability analysis with the rainfall infiltration modeling in variably saturated soil were
developed. However, in those physical-based shallow landslide models, the unit weight and the unsaturated shear strength were
assumed constant rather than depending on the degree of saturation. In this study, the effects of the unit weight and the
unsaturated shear strength as function of degree of saturation on rainfall-triggered shallow landslides are examined. Several
designed scenarios and a real case scenario are used to conduct the examinations. The results show that not only the occurrence
of shallow landslides but also the failure depth and the time to failure could be misassessed if the influences of degree
of saturation on the unit weight and the unsaturated shear strength are neglected. 相似文献