用强度折减法和FLAC^3D计算边坡的安全系数

对采用强度折减法和FLAC^3D计算边坡的安全系数问题进行了研究。对边坡破坏的判断标准、边坡滑面位置的确定及计算参数对安全系数计算结果的影响进行了分析。结果表明，用FLAC计算时，边坡的破坏可以通过节点最大不平衡力突变、节点最大速度突变、特定点位移的不收敛等特征进行判断，同时边坡破坏的滑面也可以由速度等值线图等方法表示出来。另外，通过分析发现，弹性常数、剪胀角等参数对安全系数计算结果的影响不大。     

基于Monte-Carlo方法的边坡稳定性评价

以兰州九洲开发区某边坡为例,采用Slide软件中的Sensitivity Analysis模块,对边坡进行敏感性分析,得出素填土a的重度和粘聚力是影响稳定性的主要因素,而其他岩土体的物理力学性质对计算结果影响不大;利用Probabilistic Analysis模块,进行了基于Monte-Carlo方法的安全系数与可靠度计算,评价了该边坡的稳定性,并与确定性计算结果进行了对比。结果表明:尽管安全系数基本一致,但从破坏概率来说,该边坡在自重状态下,坡体处于稳定状态,破坏概率最大为0.4%;在暴雨工况下,坡体均处于不稳定状态,破坏概率最小为70.3%;而在地震作用下,东段和南段的部分仍可稳定,破坏概率极小,仅为2.7%,评价结论更加可靠和直观,有利于边坡治理方案的优化设计。     

黄土高原小流域重力侵蚀稳定可靠度分析

在应用有限差分FLAC3D软件对黄土高原小流域概化模型塑性屈服区分布规律进行数值模拟的基础上,采用基于FLAC3D的有限元强度折减法和简化一次二阶矩法相结合的方法研究了小流域概化模型重力侵蚀稳定可靠度和破坏概率。结果表明：小流域剪切塑性区域主要分布于坡面和沟坡大部分区域,张拉塑性区域主要分布于梁峁顶和梁峁坡上部;小流域边坡整体破坏概率达到28.6%,高于1%,表明流域重力侵蚀处于高破坏概率范畴之内,处于不可接受的风险水平,需采取适当的工程措施以提高其稳定性;采用安全系数法和可靠度相结合的二元指标评价体系分析和评价边坡稳定性,能获得更为合理、可靠的分析结果。相关数值模拟和稳定可靠度分析结果可应用于流域重力侵蚀研究中,为推动流域侵蚀产沙时空规律研究的深入发展和小流域水土流失综合治理提供科学依据。     

边坡稳定性分析的可靠度方法

通过边坡破坏概率与安全系数的比较分析,提出基于概率方法的可靠性分析的必要性;同时从边坡可靠度指标β的几何定义出发,建立马氏距离表达式,并对其结果的可行性进行了验证。     

爆破地震效应对坡体稳定性的影响

天然边坡在开挖过程中,由于爆破动力作用破坏了原岩的完整性,造成边坡岩体发生局部或整体层裂而形成边坡岩体松动带,使岩体的自稳能力降低(边坡抗滑力减小),甚至可能导致路堑滑坡或坍塌.而目前在边坡设计中没有考虑由于开挖爆破地震效应对边坡稳定性的影响,从而造成个别边坡在开挖过程中或施工完成后产生滑动.通过现场爆破地震效应试验,根据应力波在岩体中的传播规律和运动规律,得出岩体内质点振动加速度和不同部位岩体平均加速度对边坡稳定性的影响效果,给出了水平和垂直方向振动加速度作用下边坡安全系数的计算公式,并通过了实例验证,从而为边坡稳定性设计提供了有力依据.     

阶梯型均质边坡的开挖效应

关于开挖对阶梯型边坡稳定性及其潜在滑动面位置的影响,目前还缺乏系统研究。以二阶阶梯型均质挖方边坡为研究对象,利用基于有限元应力状态的边坡稳定性分析方法,分别对不考虑开挖效应和考虑开挖效应两种条件下阶梯型边坡的稳定性及其潜在滑动面特征进行了对比,同时对开挖强扰动区的分布特征进行分析。研究结果表明:1.与不考虑开挖效应时计算的边坡安全系数相比,考虑开挖效应后计算得到的边坡安全系数偏小;2.开挖对阶梯型边坡的整体安全系数及其潜在滑动面位置的影响较小;3.在阶梯型均质挖方边坡的设计中,其平台宽度宜大于其上下级坡高平均值的0.5倍,上下级边坡的坡高比宜控制在1~2范围,且下级边坡的坡率小于上级边坡坡率时更有利于边坡的整体稳定。     

地震作用下顺层岩质边坡稳定性的拟静力分析

通过对顺层岩质边坡的受力分析,应用极限平衡理论和Mohr-Column准则,按照Bishop关于边坡稳定性安全系数的定义,推导出在爆破震动载荷作用下,用于判别顺层岩质边坡稳定性的计算方法。研究结果表明垂直向下、水平指向坡外的爆破荷载以及两者的联合爆破荷载对边坡稳定性影响最大,尤其是后两者;水平指向坡外、垂直向下爆破荷载拟静力系数分别与边坡稳定性安全系数间呈负指数关系和S曲线关系;从动荷载拟静力系数0起,爆破震动水平指向坡外、垂直向下动荷载拟静力系数每增加0.05,有层裂长度的顺层边坡安全系数分别减少7.79%-10.67%、1.28%-1.98%,无层裂的顺层边坡安全系数分别减少7.61%-10.55%、1.47%-2.29%。同时,爆破震动产生的层裂长度、边坡长度以及联合爆破荷载的方向对顺层边坡稳定性也有影响。     

高地震烈度区堆积体边坡动力响应时程特征分析

考虑到在地震过程中,工程边坡的动安全系数最小值出现在某一瞬间,而用这个值评价边坡在地震荷载作用下的抗滑稳定性不合适宜。在简单分析地震荷载作用下边坡稳定性评价的主要方法及差异基础上,介绍了地震动力响应时程分析法的基本原理和计算过程,明确指出了边坡动力稳定分析时应注意的边界条件、材料参数等问题,建立了评价动力稳定性的有限元应力法表达式。基于地震动力时程反应,结合金安桥水电站库岸堆积体边坡工程,用动力有限元计算获得了边坡的动力响应在空间的变化规律(包括动应力和加速度等)和整体稳定性,计算成果合理地评价了其稳定性。     

矿山地质环境边坡修复工程设计中应注意的几个问题——以某铁路客运专线陕县段沿线矿山修复为例

通过分析陕县段沿线矿山地质环境及地貌景观边坡修复工程设计实例,提出了在此类工程设计中应注意边坡稳定性、截排水系统合理性、生态绿化适宜性等方面的问题,认为修复工程设计需从长远和综合考虑,这更能体现环境、社会和经济效益。文章选取工程区的2个典型区块--大平地矿渣堆放场和石堆村东山废弃采石场进行分析,认为大平地矿渣堆放场在边坡工程稳定性的治理过程中,由于上部只采用削坡修整,未留置二级卸荷台阶和相应的截排水沟,易造成水土流失和破坏相连部分植被的可能,隐伏着牵引滑坡的可能性。通过采用概率分析法对边坡稳定性进行计算,以及对边坡极端汇水流量的计算,认为边坡应按2级放坡设置防护,对截排水沟应进行因地制宜的优化设计。石堆村东山废弃采石场上部边坡生态工程则缺少对覆土稳固性的考虑,容易造成水土流失,使生态护坡失去有效作用,按该采石场区的地貌条件,宜设置成梯田式绿化或坡面防护绿化。     

岩土参数的取值与强度理论的关系分析

基于基坑边坡支护设计的现状,本文主要以工程实例为基础,探讨了在基坑边坡支护设计中,地下连续墙及水泥土搅拌桩等支护形式由于岩土参数选取的不同所得到的不同优化,以及选取岩土参数的不同计算限值所对应安全系数,最后建立基坑支护设计中岩土参数选取模型,通过强度理论方面进行论证和实际施工检验,证明本文中所建立的模型的适用性。     

A multi-index coupling system of ice slope stability and its application

Based on the Simplified Bishop Method, the minimum safety factor of ice slope both with and without tension cracks is calculated in combination with triaxial compression tests. It is found that there exists a critical depth for each crack. Then, factors influencing ice slope stability such as slope ratio, slope height, ice cohesion, internal friction angle, unit weight and temperature were analyzed. Meanwhile, a regression equation between the aforementioned factors and safety factor is obtained, with which sensitivity analysis is carried out. The performance function is built in combination with random distribution of physical and mechanical parameters to analyze the reliability index. The Advanced First Order Second Moment Method is employed on the solution to the performance function. The one-way coupling system of ice slope stability is therefore formed based on safety factor and reliability index. Finally, an illustrated example of ice slope is provided, which shows that failure probability is relatively high, up to 6.18%, although safety factor is 2.77. Thus, it is objective and reasonable to apply the coupled system method to the slope stability rating.     

Identifying the effects of parameter uncertainty on the reliability of riverbank stability modelling

Bank retreat is a key process in fluvial dynamics affecting a wide range of physical, ecological and socioeconomic issues in the fluvial environment. To predict the undesirable effects of bank retreat and to inform effective measures to prevent it, a wide range of bank stability models have been presented in the literature. These models typically express bank stability by defining a factor of safety as the ratio of driving and resisting forces acting on the incipient failure block. These forces are affected by a range of controlling factors that include such aspects as the bank profile (bank height and angle), the geotechnical properties of the bank materials, as well as the hydrological status of the riverbanks. In this paper we evaluate the extent to which uncertainties in the parameterization of these controlling factors feed through to influence the reliability of the resulting bank stability estimate. This is achieved by employing a simple model of riverbank stability with respect to planar failure (which is the most common type of bank stability model) in a series of sensitivity tests and Monte Carlo analyses to identify, for each model parameter, the range of values that induce significant changes in the simulated factor of safety. These identified parameter value ranges are compared to empirically derived parameter uncertainties to determine whether they are likely to confound the reliability of the resulting bank stability calculations. Our results show that parameter uncertainties are typically high enough that the likelihood of generating unreliable predictions is typically very high (>  80% for predictions requiring a precision of < ± 15%). Because parameter uncertainties are derived primarily from the natural variability of the parameters, rather than measurement errors, much more careful attention should be paid to field sampling strategies, such that the parameter uncertainties and consequent prediction unreliabilities can be quantified more robustly.     

滑坡稳定性判别的非计算方法

用计算来确定滑坡的稳定性，由于参数选取存不确定因素，就必然导致了其计算结果的不确定性。而滑坡稳定性判别的非计算方法，是通过对滑坡发育程度、形成条件的综合分析来确定滑坡的稳定程度的方法。文中通过归纳分析波坡的形成条件，然后从滑坡地貌条件、动力作用、堆积物特征、诱发因素等方面详细阐述了滑坡稳定性判别的方法，最后，例举了川藏公路102滑坡实例对该方法进行了验证。实践证明该方法是滑坡稳定性中非常实用和有效的方法。     

坡顶条形荷载作用边坡潜在滑裂面与稳定性分析

边坡的潜在滑裂面可能不通过坡趾,而是在坡面上某点发生了局部剪切破坏。研究条形荷载作用下边坡的滑裂面位置及其稳定性判识方法,应用M-C线性破坏准则结合极限分析上限定理,建立稳定性系数与多变量的函数,将相关问题转化为含有多变量的数学优化问题并给出最优解。结果表明:边坡的潜在破裂面、稳定性与边坡几何形状、土体物理力学性质、荷载特性等因素有关。     

从岩石力学系统运动稳定性研究滑坡问题

从岩石力学系统运动稳定性的基本理论出发,将边坡力学系统的破坏分成五类,对其中的连续协调变形边坡的稳定性问题进行了描述,并分析了该系统的稳定性及其判据,找出了系统的控制变量是系统的广义刚度系数,同时对影响系统控制变量的因素进行了初探,指出影响边坡系统稳定性的控制变量主要是系统的几何结构因素和系统的力学参数性质,最后提出对系统控制变量进行人为的调控,达到调整系统、加强系统稳定性和防灾的目的．     

不同坡面植被空间布局对坡沟系统产流产沙影响的实验

植被在有效控制水土流失、改善生态环境中具有重要作用。为探讨坡面不同植被覆盖度、不同植被空间布局对坡沟系统侵蚀产沙的影响,以4 m长坡面(坡度为20°)和3 m长沟坡(坡度为50°)组成的坡沟系统为研究对象,采用不同放水流量(3.2 L/min、5.2 L/min)的放水冲刷实验,研究了不同放水流量、不同植被覆盖度、不同植被布设部位对坡-沟系统及沟坡侵蚀产沙的影响。结果表明,在实验条件下,不同植被布设部位在相同放水流量、相同植被覆盖度条件下对坡沟系统侵蚀产沙有明显影响,而对产流量无明显影响;沟坡部分侵蚀产沙量不随坡面植被覆盖度的增大而减小,相反呈增大趋势。说明在实验条件下,对坡沟系统而言,仅在坡面部分布设植被,尽管能在一定程度上减少坡沟系统侵蚀产沙,但并不能有效减小沟坡部分的侵蚀产沙,甚至引起沟坡部分侵蚀产沙的增大。因此,水土流失治理过程中采取有效措施进行坡沟兼治将是减少水土流失的有效手段。     

A study of provincial differences in China’s eco-compensation framework

In this study, we developed a theoretical framework to analyze the provincial differences in eco-compensation and selected appropriate measurement methods to investigate these differences in the operation of the eco-compensation framework. Via the use of the coefficient of variation, Atkinson index, and Gini coefficient, we investigated the overall differences in Chinese provincial eco-compensation time series data from 2004 to 2014 and studied the driving mechanism underlying these differences. The results showed that: (1) The provincial eco-compensation standard has geographical features. For example, the provinces crossed by the “HU Huanyong Line”, or located to its northwestern side, have obtained extensive eco-compensation. (2) There was a trend for differences in eco-compensation to increase over time, but with some fluctuations in 2006, 2009, and 2014 as shown by the coefficient of variation, in 2005, 2007, 2011, 2013, and 2014 as shown by the Gini coefficient, and in 2007, 2008, 2011, and 2012 as shown by the Atkinson index. (3) Time series curves indicated that while the signals from the three metrics (coefficient of variation, Atkinson index, and Gini coefficient) differ in a short-term analysis, they show the same tendency in the longer term. The results indicate that it is necessary to evaluate the differences in eco-compensation at the provincial level over a long period of time. (4) Via the calculation of the virtual Gini coefficient, we found that among the factors that influence provincial differences in eco-compensation, the economic value of eco-resources played the decisive role, explaining more than 73% of the difference. The cost of environmental pollution abatement was the second most important factor, accounting for more than 19% of the difference. The input to environmental pollution abatement had the least influence, accounting for less than 8% of the difference. The results agreed with those obtained from other studies, and could be used as a reference by policy makers.