共查询到20条相似文献，搜索用时 15 毫秒
1.
This paper describes the results of an experimental, as well as theoretical, analysis of a landslide in a clay slope at the
margin of a small town of Southern Italy, whose reactivation of 1998 caused severe damages to some structures. To protect
the upslope urban area, an anchored diaphragm wall and a drainage system were constructed in 2001. In the meantime, in order
to understand the processes which caused the reactivation, a Department of the Basilicata Administrative Region provided financial
support to a geotechnical investigation. Laboratory tests on undisturbed and reconstituted specimens, in situ pore pressure
and deep displacement measurements were carried out. Both experimental and theoretical in situ water content (and porosity)
profiles were determined. Theoretical analyses of pore pressure distribution and stability analyses were carried out. The
influence of the drainage system on the slope safety factor was evaluated. Experimental and theoretical data suggest that
a first time process occurred in the lower part of the landslide system. The upper part moved on pre-existing surfaces on
which an average shear strength close to the residual strength was available. Noticeable water content increase was found
around some of these surfaces. Erosion at the toe of the landslide was the probable cause of reactivation. The analysis of
the drain system effectiveness suggests that drainage has not significantly influenced pore pressures on the considered slip
surfaces yet, mainly because of the very low permeability of the clay. 相似文献
2.
为探索滑坡灾害中土在复杂条件下的剪切力学特性,本文利用大型环剪试验机,通过进行各种排水条件下的连续大位移剪切试验,对不同法向应力、剪切速率和孔隙水压力等复杂条件下饱和砂土的力学特性及其变化机理进行了研究。结果表明：1）在连续快速剪切条件下,砂土剪切力学特性在干燥、不排水和排水等条件下呈现不同的变化形式。其中在不排水条件下,饱和砂出现一定的应变软化现象。2）在相同正应力和剪切速率的环剪试验中,饱和砂在不同排水条件下（上排水、下排水、上下排水）的抗剪强度出现显著差异。3）在排水环剪试验条件下,砂土剪切应力与强度的差异性变化不仅与土体内细土颗粒运移和结构变化有关,并且受到剪切过程中不同排水条件下孔隙水压力变化的影响和控制。4）排水环剪条件下,饱和砂孔隙水压力的消散变化不仅与不同排水方式下土体内所形成的排水通道顺畅程度有关,并且受到不同剪切速率和法向应力的影响作用。 相似文献
3.
“Sliding Surface Liquefaction” is a process causing strength loss and consequent rapid motion and long runout of certain landslides.
Using a new ring shear apparatus with a transparent shear-box and digital video camera system, shear-speed-controlled tests
were conducted on mixed grains (mixture of three different sizes of sand and gravel) and mixed beads to study shear behavior
and shear zone development process under the naturally drained condition in which pore pressure is allowed to dissipate through
the opened upper drainage valve during shearing. Higher excess pore water pressure and lower minimum apparent friction were
observed in the tests where grain crushing was more extensive under higher normal stress and higher shear speed. Along with
the diffusion of silty water generated by grain crushing, smaller particles were transported upward and downward from the
shear zone. Concentration of larger grains to the central and upper part of the shear zone was confirmed by means of visual
observation together with grain size analysis of sliced samples from several layers after the test. On the other hand, smaller
particles were accumulated mostly below the layer where larger grains were accumulated. The reason why larger grains were
accumulated into the shear zone may be interpreted as follows: grains under shearing are also subjected to vertical movement,
the penetration resistance of larger grains into a layer of moving particles is smaller than that into the static layer. Therefore,
larger grains tend to move into the layer of moving grains. At the same time, smaller particles can drop into the pores of
underlying larger grains downward due to gravity. 相似文献
4.
Rainfall-induced landslides are a significant hazard in many areas of loess-covered terrain in Northwest China. To investigate the response of a loess landslide to rainfall, a series of artificial rainfall experiments were conducted on a natural loess slope, located in the Bailong River Basin, in southern Gansu Province. The slope was instrumented to measure surface runoff, pore water pressure, soil water content, earth pressure, displacement, and rainfall. The hydrological response was also characterized by time-lapse electrical resistivity tomography. The results show that most of the rainfall infiltrated into the loess landslide, and that the pore water pressure and water content responded rapidly to simulated rainfall events. This indicates that rainfall infiltration on the loess landslide was significantly affected by preferential flow through fissures and macropores. Different patterns of pore water pressure and water content variations were determined by the antecedent soil moisture conditions, and by the balance between water recharge and drainage in the corresponding sections. We observed three stages of changing pore water pressure and displacement within the loess landslide during the artificial rainfall events: Increases in pore water pressure initiated movement on the slope, acceleration in movement resulting in a rapid decrease in pore water pressure, and attainment of a steady state. We infer that a negative pore water pressure feedback process may have occurred in response to shear-induced dilation of material as the slope movement accelerated. The process of shear dilatant strengthening may explain the phenomenon of semi-continuous movement of the loess landslide. Shear dilatant strengthening, caused by intermittent or continuous rainfall over long periods, can occur without triggering rapid slope failure. 相似文献
5.
Modeling uncertainty in stability analysis for design of embankment dams on difficult foundations 总被引：2，自引：0，他引：2
A probabilistic 3-D slope stability analysis model (PTDSSAM) is developed to evaluate the stability of embankment dams and their foundations under conditions of staged construction taking into consideration uncertainty, spatial variabilities and correlations of shear strength parameters, as well as the uncertainties in pore water pressure. The model has the following capabilities: (1) conducting undrained shear strength analysis (USA) and effective stress analysis (ESA) slope stability analysis of staged construction, (2) incorporation of field monitored data of pore water pressure, and (3) incorporation of increase of undrained shear strength with depth, effective stress, and pore water pressure dissipation. The PTDSSAM model is incorporated in a computer program that can analyze slopes located in multilayered deposits, considering the total slope width.
The main outputs of the program are the geometric parameters of the most critical sliding surface (i.e., center of rotation/radius of rotation and critical width of failure), mean 2-D safety factor, mean 3-D safety factor, squared coefficient of variation of resisting moment, and the probability of slope failure. The program is applied to a case study, Karameh dam in Jordan. Monitored data of induced pore water pressure in the dam embankment and soft foundation were gathered during dam construction.
The stability of Karameh dam embankment and foundation was evaluated during staged construction using deterministic and probabilistic analysis. Foundation stability was evaluated based on the monitored data of pore water pressure.
The study showed that the mean values of the corrective factors which account for the discrepancies between the in situ and laboratory-measured values of soil properties and for the modeling errors have significant influence on the 2-D safety factor, 3-D safety factor, slope probability of failure, and on the expected failure width.
The degree of spatial correlation associated with shear strength parameters within a soil deposit also influences the probability of slope failure and the expected failure width. This correlation is quantified by scale of fluctuation. It is found that a larger scale of fluctuation gives an increase in the probability of slope failure and a reduction in the critical failure width. 相似文献
6.
Both the occurrence and behaviour of the Vaiont landslide have not been satisfactorily explained previously because of difficulties arising from the assumption that the failure surface was ‘chair’ shaped. It is now known that there was no ‘chair’, which means that the 1963 landslide could not have been a reactivated ancient landslide because the residual strength of the clay interbeds would have been insufficient for stability prior to 1963. Furthermore, the moderately translational geometry reduces the influence of reservoir-induced groundwater and hence of submergence. Standard stability analyses now show that prior to 1960, the average shear strength must have significantly exceeded the peak shear strength of the clay interbeds known to have formed the majority of the failure surface. Three-dimensional stability analyses confirm these results and show that at the time of the first significant movements in 1960, the rising reservoir level had a negligible effect on the Factor of Safety. According to these results, the Vaiont landslide was most likely initiated by pore water pressures associated with transient rainfall-induced ‘perched’ groundwater above the clay layers, in combination with a smaller than hitherto assumed effect of reservoir impounding, then developed by brittle crack propagation within the clay beds, thus displaying progressive failure. Further, very heavy rainfall accelerated the process, possibly due to reservoir-induced groundwater impeding drainage of the rainwater, until the limestone beds at the northeast margin failed. With the shear strength suddenly reduced to residual throughout, the entire mass was released and was able to accelerate as observed. 相似文献
7.
软土地基路堤施工控制的离心模拟试验研究 总被引：1，自引：0，他引：1
软土路基上快速填筑路堤时的稳定控制是非常重要的。为此在现行规范中,采用了一些位移或位移速率的控制标准。但实践表明,采用现行的标准仍然出现一些地基失稳的事例,说明这些标准需要进一步求证和改进。除了继续收集、分析失效事例之外,通过离心模型试验也可以进一步理解堤基失稳的机制。离心模型试验结果表明：路堤快速填筑使得地基破坏时,地基变形略呈马鞍形,坡肩处沉降比道中处沉降略大,坡脚水平位移增加较快;破坏时的位移速率与现有规范建议的控制标准基本符合,但地基内的孔隙水压力是在地基进入破坏状态并发生较大变形之后才有突然增加的趋势;此外,坡脚水平位移和道中沉降的速率比,可能是一个较好的稳定性控制的指标。 相似文献
8.
9.
孔隙水压力变化规律是饱和粉土体宏观变形细观结构研究的基础。以阳光新城工程为例,采用现场试验方法对长螺旋CFG桩施工时的孔隙水压力(简称孔压)变化进行了监测,并根据监测结果对施工过程的孔隙水压力(简称孔压)变化进行了阶段划分。研究结果,长螺旋CFG桩施工过程中孔压变化规律与常规的剪切液化观点相悖,抽吸与窜孔对孔隙水压力变化影响显著,并解释了产生这种现象的原因。孔压极大值和极小值在一定范围内产生累加效应,表现为非对称性,而变化的幅度值呈近似对称性。根据幅度值大小确定了长螺旋CFG桩施工时的影响范围,其值与小孔扩张理论比较吻合。 相似文献
10.
A pragmatic strain-softening constitutive model, which is based on Modified Cam Clay, was applied to the simulation of the progressive failure of an embankment constructed on a deposit of sensitive (strain-softening) clay in Saga, Japan. A comparison of the predictions for this case indicates that if softening is ignored, only relatively small deflections and consolidation settlements are predicted, especially after construction. In contrast, for the case where softening is included in the analysis, progressive failure within the clay induces large shear deformations and finally failure of the embankment is predicted. This comparison suggests that softening-induced progressive failure should be considered in the design of embankments on such soils, and the residual strength of the deposit may have an important influence on the overall factor of safety of the construction. Detailed analyses of predicted excess pore water pressures, shear strains and shear stress levels in the ground indicate that considering the strain-softening process: (a) is associated with the buildup of excess pore water pressure; (b) promotes strain localization; and (c) results generally in a larger zone of soil involved in the failure. 相似文献
11.
Babadag, in the Denizli province of Turkey, is one of the oldest textile industry settlements. The town has suffered from a very slow slope movement for about 60 years. One-third of the population lives in the unstable area. The slope movement resulted in significant ground deformations and damage to buildings, roads and buried utilities, and negatively affects socioeconomic life in the town. This paper contributes to the understanding of the long-term plane shear slope movement at the town, analyzes the main causes of the movement, and describes the slope instability and its effects. Movement occurs at an annual rate of between 3.8 cm and 15 cm along weak bedding planes in the alternating marl and sandstone beds forming the slope. Engineering geological assessments based on movement, groundwater and rainfall monitoring data, laboratory testing, and stability analyses indicate the following main factors contributing to the movement: (a) the unfavorable orientations and low shear strength of the bedding planes, (b) variations in the groundwater table related to precipitation and waste water seeping from the damaged sewage system, and (c) undercutting at the toe of the slope by a creek. Particularly due to fluctuations in the groundwater table or variations in pore pressures, the slope movement exhibits increasing and decreasing rates of movement without catastrophic failure. 相似文献
12.
Geotechnical assessments of the stability of slopes at the Cakmakkaya and Damar open pit mines (Turkey): a case study 总被引：2，自引：2，他引：0
Fehmi Arikan Fatih Yoleri Sureyya Sezer Dincer Caglan Bengu Biliyul 《Environmental Earth Sciences》2010,61(4):741-755
The on-site observations, monitoring data, and results of back analyses of failures showed that large-scale failures occurred
along both the interconnected sliding surfaces, consisting of (a) discontinuities in the dacites and the contact zone and
(b) the circular surfaces through the weathered soil-like dacites at the Cakmakkaya and Damar open pit mines. Surface water
infiltration through the weathered soil-like material after a short duration of rainfall contributed to the circular-shaped
failures. After a heavy rainy period, an increase in the groundwater table above the contact zone played a major role in the
initiation of bi-planar wedge failures. In addition, the stability of the slopes is likely to have been controlled by the
orientation of this zone. The results of back analyses indicated that the shear strengths of the soil-like materials in the
weathered dacites and the contact zone had reduced to their residual values at the time of initial sliding. The flattening
of the slope angles with an effective surface drainage and long-term monitoring of the groundwater level is proposed as the
most suitable remedial measure. 相似文献
13.
天津市堆山造景工程地基稳定监测与防治 总被引：1，自引：0，他引：1
堆山造景工程是一项利用建筑渣土,在坑塘上进行堆载的市政工程。通过对堆山造景工程的工程地质条件分析,结合工程设计、施工工期等条件,提出了清理淤泥、设置反压平台、排水、控制堆填速率等促进地基稳定的防治措施。利用孔隙水压力监测、侧向位移监测及分层沉降监测等原位监测数据,以复合型法进行反演力学计算参数,并将反演结果用于该工程地基稳定性的模拟,以指导后期工程以及类似工程的建设。 相似文献
14.
《Geomechanics and Geoengineering》2013,8(4):295-306
Recent developments in studies of soil response to earthquake loadings have made it possible to incorporate the rates of pore water pressure build-up in soils in to nonlinear response analyses of the grounds. Such pore pressure changes help in computing the changes in stress-strain behaviour of soils in the deposit progressively as the earthquake progresses. The rate and magnitude of pore pressure generation in soils during seismic loading will have important effects on the shear strength, stability, and settlement characteristics of a soil mass, even if the soil does not liquefy. The results in terms of pore pressure response in soils from a series of experimental investigations using strain-controlled cyclic triaxial tests on soils samples collected from liquefied sites are presented in this paper. The effect of relative density, amplitude of cyclic shear strain, number of loading cycles, confining pressure and frequency of cyclic loading on the pore pressure build-up are studied. Analytical expressions are proposed using regression analysis to define mean relationships between normalized pore water pressure and normalized cycles for the prediction of pore water pressure build-up in silty sands. Also, the pore water pressure build-up in soils is independent of frequency of loading. 相似文献
15.
采用大型动三轴试验仪进行重塑高岭土试样的循环三轴试验,试样直径为300 mm,高度为600 mm。圆柱体试样中心放置了一块竖向排水板,在循环加载试验进行时和结束后都可进行径向排水。试验结果验证了径向排水可以有效地消散循环荷载引起的孔隙水压力。通过结合径向固结理论与不排水循环加载土体模型,提出了一个循环荷载作用下径向固结模型,用来描述在允许径向排水的情况下软黏土在循环荷载作用下的孔压累积特性。模型中考虑了应力历史和孔隙水压力消散对孔隙水压力生成的影响,并用大型循环三轴试验结果进行验证。研究发现,当施加较大循环荷载时,径向排水减缓了孔隙水压力累积到临界值的速率,因而土体在破坏前可以经历更多次的循环荷载;当施加中等循环荷载时,径向排水可有效阻止孔隙水压力增长至临界值。除此之外,还研究了加载间歇期对孔压累积特性的影响,结果显示3组循环加载结束后,累积孔隙水压力开始减小,表明之后更多的循环加载并不会引起孔隙水压力的累积增长。 相似文献
16.
An integrated model simulating the initiation and motion of earthquake and rain induced rapid landslides and its application to the 2006 Leyte landslide 总被引：10，自引：7，他引：3
A gigantic rapid landslide claiming over 1,000 fatalities was triggered by rainfalls and a small nearby earthquake in the
Leyte Island, Philippines in 2006. The disaster presented the necessity of a new modeling technology for disaster risk preparedness
which simulates initiation and motion. This paper presents a new computer simulation integrating the initiation process triggered
by rainfalls and/or earthquakes and the development process to a rapid motion due to strength reduction and the entrainment
of deposits in the runout path. This simulation model LS-RAPID was developed from the geotechnical model for the motion of landslides (Sassa 1988) and its improved simulation model (Sassa et al. 2004b) and new knowledge obtained from a new dynamic loading ring shear apparatus (Sassa et al. 2004a). The examination of performance of each process in a simple imaginary slope addressed that the simulation model well simulated
the process of progressive failure, and development to a rapid landslide. The initiation process was compared to conventional
limit equilibrium stability analyses by changing pore pressure ratio. The simulation model started to move in a smaller pore
pressure ratio than the limit equilibrium stability analyses because of progressive failure. However, when a larger shear
deformation is set as the threshold for the start of strength reduction, the onset of landslide motion by the simulation agrees
with the cases where the factor of safety estimated by the limit equilibrium stability analyses equals to a unity. The field
investigation and the undrained dynamic loading ring shear tests on the 2006 Leyte landslide suggested that this landslide
was triggered by the combined effect of pore water pressure due to rains and a very small earthquake. The application of this
simulation model could well reproduce the initiation and the rapid long runout motion of the Leyte landslide. 相似文献
17.
沉桩会对码头边坡稳定产生不利影响,一是引起桩周土体超孔隙水压力的急剧上升,导致土体有效应力降低;二是沉桩的振动加速度会产生对边坡稳定不利的瞬时惯性力。对于灵敏度低的土质岸坡来说,前者是影响其稳定性的主要因素。考虑沉桩时初始超孔隙水压力的分布,根据Biot固结方程超孔隙水压力消散解的一般表达式,建立了沉桩引起的超孔隙水压力随时间消散的解析式,在条分法的基础上考虑沉桩产生的超孔隙水压力的不利影响,建立了沉桩时边坡稳定安全系数的计算公式。根据沉桩顺序对某码头进行边坡稳定分析,结果表明：考虑打桩作用的岸坡稳定安全系数明显降低,沉桩产生的超孔隙水压力逐渐消散,边坡稳定安全系数随沉桩工序历时变化,施工中期由于超孔隙水压力叠加,岸坡最危险,沉桩结束3个月以后,超孔隙水压力基本消散,边坡稳定安全系数接近不考虑沉桩时的值。工程中要根据打桩计划进行边坡稳定计算。 相似文献
18.
利用真空预压法处理吹填土时,细颗粒常堵塞排水管,导致土体排水不畅。为提高吹填土固结效率,采用自重沉淤排水与加负压排水固结相结合的方式在室内进行吹填土固结试验。试验第一阶段用排水管作为吹填土自重沉淤的竖向排水通道;第二阶段以装入中粗砂的排水管作吹填土排水通道,同时也是压力传递通道。试验监测到吹填土固结过程中不同位置孔隙水压力的变化,通过监测数据着重研究自重沉淤排水阶段吹填土的固结规律。借助渗流平衡方程确定吹填土在自重沉淤阶段孔隙水压力变化主要由排水管中水位、单位土面积控制,解释自重沉淤阶段孔隙水压力变化机理。同时,为了减小由于排水距离远近造成的固结不均,利用自重沉淤与加压固结结合的方法使吹填土达到较为理想的固结效果,将砂井设计理论与孔隙水压力变化曲线相结合确定排水管有效排水范围等效直径,为实际工程提供排水管间距的设计参数。 相似文献
19.
排水刚性桩是一种将竖向排水体与刚性桩相结合的新型抗液化处理措施。为研究排水刚性桩群桩的抗液化作用效果,开展了桩顶竖向荷载作用下排水刚性桩处理可液化地基的振动台试验研究,分析了地基土体的超孔压响应、加速度响应及桩顶结构的水平位移响应,并与未设置排水体的普通桩群桩工况进行对比。结果表明：加载开始后,排水桩桩身排水通道有大量超孔隙水排出,普通桩桩身没有排水现象。采用排水桩时超孔压比峰值比普通桩中减小12%,孔压消散稳定后超孔压比减小13%左右,排水桩桩身的排水通道对超孔压的消散作用集中在振动作用的前期。排水桩桩顶的侧向永久位移较普通桩桩顶侧向永久位移减小约27%。试样土体液化前,剪应力-应变滞回圈包络面积较大,土体呈现一定的剪胀特性。液化后,排水桩的剪应力-应变滞回圈的割线模量更大。上述试验结果均表明了排水刚性桩在抗液化方面的有效作用。 相似文献
20.
为探究孔隙水压对岩体结构面剪切蠕变特性的影响,自主研制了结构面一体化制作模具和多功能剪切流变仪,开展了孔隙水压力下锯齿状结构面的剪切蠕变试验,分析了孔隙水压对结构面蠕变变形、蠕变速率和长期强度的影响。试验结果表明：不同孔隙水压力下的结构面先后经历了瞬时变形阶段、减速蠕变阶段和稳定蠕变阶段,并且孔隙水压力的增大促进了结构面非线性特征的发展;随着孔隙水压力的增大,结构面瞬时位移、蠕变位移和稳态蠕变速率逐渐增大,而蠕变时长、破坏应力和长期强度均呈现明显降低的趋势。根据试验结果,考虑孔隙水压力对模型参数的影响,将蠕变模型中的瞬时剪切模量、黏性剪切模量以及黏性系数替换为孔隙水压力的函数,构建了能够反映孔隙水压力影响的结构面蠕变模型,并对模型参数进行辨识,将试验曲线和理论模型曲线进行对比,验证了模型的正确性和适用性。研究成果对富水区岩体长期稳定性分析提供一定的理论指导。 相似文献