Slope Stability Analysis of Earthen Levee Strengthened by High Performance Turf Reinforcement Mat under Hurricane Overtopping Flow Conditions

The slope stability of levees during hurricane overtopping conditions involving storm surge and wind generated wave action is an important aspect to assess the safety of earthen levees. A comprehensive slope stability investigation was conducted in this study for an earthen levee subjected to full-scale overtopping scenarios, including storm surge only overflow, wave only overtopping, and combined wave and surge overtopping conditions. The crest and the landside of the levee were strengthened by high performance turf reinforcement mat (HPTRM) to protect against overtopping erosion. A conceptual model for HPTRM strengthened levee as well as a methodology for analysis and incorporation of various overtopping flow conditions in levee slope stability is presented. The findings of this study indicate that HPTRM strengthening of the levee improves the stability of the levee significantly during wave only as well as combined storm surge and wave overtopping conditions. However, during the storm surge conditions, the factor of safety is only improved slightly as a result of strengthening of the levee by HPTRM.     

Erosion Resistance of HPTRM Strengthened Levee from Combined Wave and Surge Overtopping

Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and land-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. This study addresses erosion resistance performance of a levee strengthening technique—high performance turf reinforcement mat under combined wave and surge overtopping conditions using full-scale flume tests as well as erosion function apparatus (EFA) tests. Based on the results of full-scale flume tests, an “upper limit” of soil loss is observed for certain flow conditions. Erosion rate was presented as a function of velocity and freeboard. The effect of duration of overtopping on the erosion depth is also determined. The results of EFA tests indicate that the presence of grass roots substantially improve the critical velocity and soil erodibility.     

Comparative Study on the Stability of Hydropower Station Slope Under Different Earthquake Conditions

Geotechnical and Geological Engineering - In order to explore the stability characteristics of hydropower station slope under different working conditions under seismic action, the...     

地下水对砂类土边坡稳定性的影响

内蒙古地区冬季积雪厚,春季气温回升快,大量雪水浸入边坡及挡土墙墙背的细砂层中,由于上部护坡和下部挡墙的排水孔多数堵塞,地下水无法排出.融化雪水沿土坡表面产生渗流,导致边坡变形失稳.地下水位上升时,挡土墙墙后严重积水,按水土分算原则计算作用在挡墙上的水土压力增大,挡墙极易滑移.     

降雨对土质边坡稳定性影响分析

从降雨对土体抗剪强度的影响、降雨对土体重度的影响、降雨形成的水压力及降雨对土体的化学作用四个方面分析了降雨对边坡稳定性的影响。并通过一个因降雨而失稳的滑坡实例介绍其整治措施。     

Numerical Slope Stability Analysis of Deep Excavations Under Rainfall Infiltration

Geotechnical and Geological Engineering - Rainfall leads to the deterioration of slope stability conditions, while intense rainfall has been commonly associated with landslides on natural or...     

强度指标对滑坡稳定性的影响

讨论了粘性土在不同固结状态下的强度指标变化规律,阐述了土的强度指标对滑坡稳定性的影响,以及雨水对滑坡崩塌滑动的诱发作用.     

平面应变状态下边坡安全系数的近似求解

Mohr—Coulomb屈服准则不考虑中间主应力对材料强度的贡献,是一个保守的强度屈服准则,在近似平面应变状态下,匹配于Mohr-Coulomb屈服准则的Drucker-Prager屈服准则能给出边坡安全系数偏保守一些的估计;相对而言,Matsuoka—Nakai和Lade-Duncan屈服准则均考虑了中间主应力对土体强度的影响,在近似平面应变状态下,匹配于Matsuoka-Nakai和Lade-Duncan屈服准则的Drucker-Prager屈服准则能给出岩土类材料较为合理的破坏强度预测,土体的抗剪强度能被更有效地发挥出来,因而借助这些转化的Drucker-Prager屈服准则能给出平面应变状态下土坡安全系数较为合理和真实的预测。文中的边坡稳定算例证实了这些观点。     

爆破动力作用下边坡稳定性的积分解法与应用

岩质边坡在爆破开挖过程中的稳定问题是一个亟待解决的重要问题。对实际工程进行监测,得到适合该地区的能反应高程效应的爆破地震波传播规律,并采用拟静力法计算爆破地震惯性力,提出边坡在爆破动力作用下稳定安全系数的新计算方法———积分法,同时使用MATLAB程序搜索边坡最危险滑裂面并计算最小安全系数。实例证明,此方法是分析边坡动力稳定性的有效方法之一。     

不同权重条件下降雨对边坡稳定性影响的二级模糊综合评判

边坡稳定性影响因素众多,其中一部分具有明显的不确定性,用经典数学理论及力学模型很难描述。采用二级模糊综合评判法,对影响边坡稳定的离散型和连续型因素采用不同方法确定隶属度,并利用二元对比分析法给出各因素权重值;同时考虑降雨对边坡稳定的重要影响,对降雨后各影响因素的权重进行修正,建立边坡稳定的二级模糊综合评判计算模型,评价降雨前后边坡稳定性的变化。研究结果表明：模型所采用的隶属函数,充分考虑了各个因素的不同特点和分布规律;考虑降雨前后权重的变化,能使评判结果更趋合理。以实际工程为例,模糊综合评判结果显示：降雨前边坡处于基本稳定状态,降雨后处于欠稳定状态,与经典极限平衡法计算结果一致。     

The Effect of Scale and Criticality in Rock Slope Stability

Summary The apparent shear strength of rock discontinuities is considerably smaller than that of small scale samples. At the same time, the sliding behavior is characterized, in situ, by marked instabilities, with the typical features of Critical Phenomena. Contact mechanics permits to calculate normal and tangential forces at any point, and to follow the stick-slip transition for arbitrary loading histories. On the other hand, the above aspects are not captured by the classical theories, including those based on roughness indices. We argue that the multiscale topology of contact domains plays a fundamental role in determining the behavior of rock joints. In particular, experiments and numerical simulations show that these domains are lacunar sets with fractal dimension smaller than 2.0. This provides peculiar scaling of normal and tangential pressures at the interface, and the consequent size-dependence of the apparent friction coefficient. Moreover, we implement Renormalization Group to determine the critical point (e.g. the critical shear force) when rock sliding occurs. We show that the critical force is less than the one predicted by the classical Coulombs theory, and that it depends on the specimen size and on the topology of the interface. The same reasoning can be extended to other phenomena, e.g., to the rupture of brittle materials.     

三维边坡稳定性分析中的边界约束效应

边界约束条件是影响边坡强度折减有限元分析稳定性计算结果的一个重要因素。结合典型边坡算例计算给出了不同边界约束条件下的三维边坡稳定性安全系数及潜在滑动面,并进行了差异性的对比研究,最后结合存在软弱夹层与地下水的三维边坡开展了应用性研究。结果表明：边界约束条件对边坡稳定安全系数具有显著的影响。在全约束条件下安全系数最大,其次为半约束边界条件,自由边界条件下的稳定安全系数最小,全约束边界比自由边界条件下的安全系数提高大约30%。边界约束条件对边坡潜在滑动面有重要的影响。在土性参数完全相同的条件下,与全约束条件相比,半约束边界条件下的滑体体积更大,滑动面更深,滑出点位置从离坡脚不远处向坡脚变化的过程更加明显。自由边界条件下与二维计算结果较接近。     

Failure Effect of Seismic Faults and the Slope Stability Along Highways Under Seismic Hazards Based on Dynamic Finite Element Analysis and Genetic Algorithm

Geotechnical and Geological Engineering - In order to investigate the failure effect of seismic fault and the slope stability under seismic damages along highways, the spatial distributions of...     

超声波振动下不同应力条件对岩石强度影响的试验

振动有助于碎岩,以往关于振动碎岩机理的研究大多在低频率段展开。为填补超高频率段下振动碎岩机理的空白,采用单轴动静组合加载模式,开展了超声波振动下不同应力条件对岩石强度影响的试验研究,其中超声波振动频率为20kHz,预压范围为100～500N。研究结果表明:当预压小于200N时,岩石内部应力状态无法满足强度准则,岩石强度下降不明显;当预压大于等于200N时,岩石强度随振动时间的增加而逐渐降低且存在最优预压力值(400N)使得岩石强度最低。缩短振动频率与岩石固有频率的差值有利于提高超声波振动碎岩效率。     

Assessment of the Stability of Rock Slopes by the Slope Stability Rating Classification System

Given the lack of suitable systems in the characterization of slope stability of heavily jointed rock masses, a new rock mass classification system called Slope Stability Rating (SSR) is proposed. In addition to the so-called modified Geological Strength Index, the proposed system considers five additional parameters whose relative effects on the stability of fractured rock slopes were precisely examined based on data retrieved from eight different rock slope sites in Iran. An overall rating for the rock mass is obtained from the summation of the individual ratings of each parameter. A number of design charts are provided as illustration. The new system was then validated based on 46 slope case histories from Iran and Australia. For this, by means of the design charts previously mentioned, a recommended stable angle for each slope was given and compared with the current slope conditions. As a result, SSR design charts for maximum excavation angle (FS = 1.0) and also for other more conservative excavation angles (FS = 1.2, 1.3, 1.5) were presented.     

Influence of Morphology of Sliding Surface on Its Seepage Characteristics and Slope Stability Under Fluctuations in Reservoir Water Level

Geotechnical and Geological Engineering - The fluctuation in reservoir water level is one of the key external factors affecting the stability of slopes. Finite element models are established for...     

基于Monte-Carlo模拟的狮子包边坡稳定性研究

以三峡库区巴东县沿江路云沱段狮子包边坡为例,综合边坡工程地质、水文地质、岩体结构特征及边坡前期交形破坏迹象,基于Monte-Carlo法得到边坡稳定的破坏概率及安全系数,进而用可靠性理论对边坡稳定性进行了探索。结果表明,通过Monte-Carlo法得到的狮子包边坡安全系数为0．857,而用传统安全系数法得到的安全系数大干1。实际上,该边坡在2003年曾经产生过滑动,因此,基于Monte-Carlo法的可靠性理论对边坡稳定性评价更符合实际。     

静水压力对岩体边坡稳定性的影响分析

静水压力对岩体边坡抗滑移稳定性的影响无处不在,在河道和水库两岸常会发现因河道或水库水位的交替消长而发生岸边岩体的滑移与坍塌,通过长期的观察和总结,发现这种情况的发生与岩体边坡外邻水水位的消长以及岩体节理裂缝内水位的变化密切相关。本文通过对水位在不同变化情况下边坡稳定性的定量分析,结合不同实际场景,讨论了边坡外邻水和节理裂缝内充水这两种情况对岩体边坡稳定性影响大小的对比,得出了以下结论:岩体边坡外邻水水位的上涨会增大岩体边坡的抗滑移稳定性;而岩体节理裂缝内水位的上涨会减小岩体边坡的抗滑移稳定性,并定量对比了二者之间的大小关系。