强度折减有限元法分析成层土坡的适用性

通过实例讨论了强度折减有限元法分析成层土坡稳定的可行性,分析表明对于均质土坡,强度折减得到的安全系数在工程允许的范围之内,但折减后的应力场发生了变化,不能用于分析原土坡的稳定性;对于多层土坡,通过简单折减土的强度指标c,tanφ,不能得到正确的应力场,也不能得到土坡的安全系数.     

强度折减有限元法分析成层土坡的适用性

通过实例讨论了强度折减有限元法分析成层土坡稳定的可行性,分析表明:对于均质土坡,强度折减得到的安全系数在工程允许的范围之内,但折减后的应力场发生了变化,不能用于分析原土坡的稳定性;对于多层土坡,通过简单折减土的强度指标c,tanφ,不能得到正确的应力场,也不能得到土坡的安全系数。     

复杂土坡稳定的电算分析

黏性土坡的稳定性分析因为滑裂面不能预先判定和土体受力的复杂性而使计算十分烦琐．为了能够手算,以往的计算模型都尽力简化．现在常用的3种分析方法,即条分法、泰勒法和毕肖普法,都只讨论了简单土坡,过多的简化使计算模型不能反映土坡的实际情况．用电算作土坡稳定分析可以使计算结果臻于精细．     

开关DC-DC变换器斜坡补偿的稳定性控制研究

从混沌稳定性控制的角度研究了采用斜坡补偿的buck、boost和buck-boost开关DC-DC变换器的稳定性控制机理,建立了采用补偿斜坡的开关变换器的离散映射迭代模型,得到了开关变换器电路的稳定性判据和补偿斜坡斜率的表达式。利用分叉图、Lyapunov指数谱和时域波形图,清晰地描绘出补偿斜坡电流(或电压)对开关变换器的电路稳定性能的影响。研究结果表明,采用斜坡补偿技术能有效地改善开关DC-DC变换器的稳定性。     

用复合形法计算土坡稳定性

提出了用优化方法——复合形法寻找土坡最危险圆弧滑裂面位置及相应的稳定系数，并用Ｆｏｒｔｒａｎ７７语言编制了相应的计算程序。经算例验证复合形法是土坡稳定性可靠、高效的计算方法，具有实用意义。     

渗流-应力耦合效应对非饱和土边坡稳定性影响分析

基于VG模型得到土-水特征曲线与渗透系数函数曲线,通过建立有限元数值分析模型,采用有限元软件SIGAM/W与SEEP/W分别进行渗流-应力耦合分析与只考虑渗流的非耦合分析,将得到的渗流场与应力场导入SLOPE/W计算安全系数并对土坡内应力应变进行分析,研究耦合效应对边坡稳定性影响的相关规律。结果表明,渗流-应力耦合效应使得土体中雨水下渗速度更快,土中基质吸力消散更快;降雨对土坡稳定有不利影响,耦合分析土坡安全系数比非耦合分析小,耦合效应对非饱和土边坡稳定性影响不可忽略;降雨入渗条件下,土坡浅层出现应力集中现象,湿润锋深度处出现应力集中带,土坡易发生浅层破坏;坡脚水平位移比坡顶大,土坡失稳多从坡脚开始。     

基于强度折减有限元的非均质土坡失稳判据分析

强度折减有限元法在土坡稳定性分析中已得到广泛应用,但目前大多针对均质土坡,较少涉及非均质土坡.将强度折减有限元法应用于非均质土坡,首先要解决非均质土坡失稳判据的选取问题.基于ABAQUS有限元软件,实现了强度折减的自动运行,探讨了各种失稳判据对非均质土坡安全系数取值的影响,分析了非均质土坡失稳破坏的过程,提出了以特征点位移矢量突变结合塑性区贯通的失稳判据,其更能反映非均质土坡真实的稳定性.     

应用强度折减有限元法分析土坡稳定的适应性

为深入研究土体采用的本构模型以及安全系数的控制标准．讨论了土体采用邓肯E—B模型和理想弹塑性的广义米塞斯模型时,强度折减有限元法分析土坡稳定的适应性．发现邓肯E—B模型的适应性较差,土坡内应变发展不均匀,不能形成明显的剪切带．而弹塑性的广义米塞斯模型则形成剪切带,剪切带两侧土体具有明显的相对滑移趋势．因此,弹塑性模型更适合干强度折减有限元法分析土坡稳定性．     

斜坡稳定性分析的模糊综合评判方法

本文根据对古交市炉峪口煤矿斜坡的工程地质调查研究，确定了影响该斜坡稳定性的四类２０项主要影响因素，并应用两级模糊综合评判的方法对炉峪口煤矿斜坡稳定性进行了综合评价，其结果较好地反映了该斜坡的实际稳定程度。     

水库周边水位变动引起库岸失稳的原因及特征

主要探讨在水库蓄水或放水情况下，造成库周边坡稳定性降低的原因，分析边坡稳定计算方法，探讨土坡各参数取值问题。     

某露天矿陡帮边坡稳定性分析与加固设计

根据某露天矿陡帮边坡的工程实际,采用极限平衡方法等进行了露天矿陡帮边坡的稳定性分析,提出了合理而有效的加固方案,并进行了加固后的边坡稳定性分析和评价.结果表明：该露天矿陡帮边坡长期暴露在自然条件下稳定性会逐渐降低,如遇饱水或渗流,边坡可能会发生失稳.采用预应力锚索框架梁加固后,边坡的稳定系数显著提高,边坡处于稳定状态,从而保证了矿区的安全生产.     

黄土高原边坡特征与破坏规律的分区研究

为了研究黄土高原自然边坡的特征及破坏规律,按山系与水系或水系的分水岭、地貌单元、地层岩性特征等条件,将黄土高原划分为8个区：临洮—永靖区、天水—通渭区、兰州—会宁区、陇东区、靖边—安塞区、隰县—离石区、甘泉—吉县区和汾渭区。根据极限状态边坡的4个野外判别标准,测量了8个区510个自然极限状态黄土边坡断面,分区采用指数模型回归边坡坡高与坡宽的相关关系,计算各区20、50、100m坡高的边坡稳定系数和失效概率。结果表明：黄土高原的边坡特征与破坏形式具有分区特征,且南北差异性明显。临洮—永靖区边坡坡高与坡宽呈线性关系,表明该区边坡坡度不随坡高变化,边坡稳定性受内摩擦角控制;兰州—会宁区和靖边—安塞区高坡陡,低坡缓,高坡不稳定,易发生错落式滑坡;天水—通渭区、甘泉—吉县区和汾渭区高坡缓,低坡陡,稳定性计算结果显示高坡和低坡都较为稳定,但由于地层结构和地貌的特点,高边坡易发生低速蠕变型滑坡或高速远程滑坡;陇东区边坡整体上较为稳定;隰县—离石区受黏粒含量较高的Q1地层控制,高边坡稳定性较差;50m左右坡高的黄土边坡稳定性对强度指标内聚力、内摩擦角的敏感度都高,易于失稳。     

山西乡宁—吉县地区黄土高边坡可靠度研究

在山西乡宁—吉县地区实测了7个具有代表性的自然极限状态黄土高边坡断面,建立边坡地层结构模型; 选取研究区合理的黄土物理力学参数,并分地层年代对10个典型工点的黄土强度参数内聚力和内摩擦角的变异性进行分析; 选取6组典型的强度参数变异系数组合,基于Monte-Carlo法进行可靠度模拟,评价该区边坡稳定性; 采用自然类比法进行边坡设计。结果表明:边坡失效概率随坡高的变化趋势一致,均是中等坡高(49.8 m)的边坡失效概率较大,低坡和高坡的失效概率较低; 当变异系数较小时,边坡失效概率对坡高和坡度的变化敏感,而当变异系数较大时,边坡失效概率对坡高和坡度的变化不敏感; 当坡型一定、强度参数变异系数较小时,边坡的稳定系数基本不变,而当参数变异系数超过某一界限时,稳定系数随变异系数的增大而增大,二者存在非线性相关关系; 研究区黄土边坡处于基本稳定状态,但其失效概率最大达69.3%,平均21.1%,介于20%～30%的比例为33.3%,大于30%的比例为14.3%,可靠度指标介于-0.5～8.5,其中小于2.7的比例为88.1%; 对于坡高约为50 m的黄土高边坡,若取30%作为可接受失效概率,边坡坡度需降至45°以下,如果期望可接受失效概率在10%以内,则坡度不宜超过34°。     

结构性土二元介质模型的有限元模拟

针对土的结构性对边坡稳定性的影响,结构性土二元介质模型将胶结元看成理想弹脆性材料,摩擦元看成硬化型弹塑性材料。基于该模型建立考虑结构性土的强度准则,编制相应有限元程序用于Biot固结的有限元模拟。通过对比初始各向同性和初始应力各向异性结构性土的天然边坡算例计算结果,发现初始应力各向异性天然边坡的安全系数要高于初始均质天然边坡;嵌入初始应力各向异性结构性土的强度准则后可以观察计算过程中边坡破坏区的发展,为采用破坏区贯通作为边坡的破坏标准的天然边坡的稳定性分析提供了一种新的思路且具有良好的工程适用性。     

Comprehensive analysis of slope stability and determination of stable slopes in the Chador-Malu iron ore mine using numerical and limit equilibrium methods

One of the critical aspects in mine design is slope stability analysis and the determination of stable slopes. In the Chador Malu iron ore mine, one of the most important iron ore mines in central Iran, it was considered vital to perform a comprehensive slope stability analysis. At first, we divided the existing rock hosting pit into six zones and a geotechnical map was prepared. Then,the value of MRMR (Mining Rock Mass Rating) was determined for each zone. Owing to the fact that the Chador-Malu iron ore mine is located in a highly tectonic area and the rock mass completely crushed, the Hock-Brown failure criterion was found suitable to estimate geo-mechanical parameters. After that, the value of cohesion (c) and friction angle (e) were calculated for different geotechnical zones and relative graphs and equations were derived as a function of slope height. The stability analyses using numerical and limit equilibrium methods showed that some instability problems might occur by increasing the slope height.Therefore, stable slopes for each geotechnical zone and prepared sections were calculated and presented as a function of slope height.     

Three-dimensional analysis of slopes reinforced with piles

Based on the upper bound of limit analysis, the plane-strain analysis of the slopes reinforced with a row of piles to the 3D case was extended. A 3D rotational failure mechanism was adopted to yield the upper bound of the factor of safety. Parametric studies were carried out to explore the end effects of the slope failures and the effects of the pile location and diameter on the safety of the reinforced slopes. The results demonstrate that the end effects nearly have no effects on the most suitable location of the installed piles but have significant influence on the safety of the slopes. For a slope constrained to a narrow width, the slope becomes more stable owing to the contribution of the end effects. When the slope is reinforced with a row of piles in small space between piles, the effects of group piles are significant for evaluating the safety of slopes. The presented method is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of plies stabilizing the unstable slopes.     

水平凸型边坡破坏分析

本文根据水平凸型边坡的破坏机理,建立了一套适用于计算水平凸型边坡稳定性的三维极限平衡方法,并用这一方法对水平凸型边坡的稳定性进行了研究。当相对曲率半径R_2/H≥3时,曲率对边坡的稳定性影响很小,曲率影响边坡稳定性的主要原因在于曲率不同时,其边坡体内周向应力的差异。     

临河岩质边坡地震抗倾覆稳定性拟动力分析

基于拟动力法推导出不同工况条件下临河岩质边坡地震抗倾覆稳定安全系数计算公式。通过参数分析,研究不同岩体放大系数下,水平和垂直地震力、张裂缝积水深度、边坡超载、锚固效应、流水淘蚀等对岩质边坡地震抗倾覆稳定性的影响,研究表明,不同工况下,张裂缝积水深度、水平地震力、流水淘蚀不利于岩质边坡地震抗倾覆稳定,但竖向地震力、锚固力、锚固高度、坡顶超载等有利于岩质边坡地震抗倾覆稳定;随着岩体放大系数的增加,水平地震力、竖向地震力对岩质边坡抗倾覆稳定性的影响增大,坡顶超载、张裂缝积水深度、锚固应力、锚固高度、临河水位对岩质边坡抗倾覆稳定性的影响减小,而锚固倾角、坡脚淘蚀高度对边坡抗倾覆稳定性的影响基本不变。     

甘肃天水地区黄土极限状态边坡的统计分析

在实际工程边坡设计中,往往参考临近自然边坡的坡率设计来进行人工开挖边坡。基于这种工程类比法,现场实测甘肃天水地区51个坡高40～150 m的黄土极限状态边坡断面,获得其坡高、坡宽及坡度参数,统计发现坡高与坡宽符合双对数线性关系,建立二者的相关方程;再将坡高按10m间距分段,每个坡高段取3个极限坡高,利用Morgenstern-Price法反演了不同坡高段的强度参数(内聚力和内摩擦角)。由反演结果发现,随着坡高的增大,黄土的综合内聚力增大,内摩擦角减小,此特点与黄土强度参数值随所处深度的变化规律基本一致。基于反演的强度参数和极限状态边坡坡高与坡宽的回归方程,进一步计算获得不同稳定系数下的坡高与坡宽的关系曲线,将该曲线制成图,可用来直接判定一个已知边坡的稳定系数,也可以用来确定拟设计边坡的坡度。     

New risk assessment methodology for coal mine excavated slopes

This paper presents a new risk assessment methodology for coal mine excavated slopes. This new empirical-statistical slope stability assessment methodology(SSAM) is intended for use by geotechnical engineers at both the design review and operational stages of a mine's life to categorise the risk of an excavated coal mine slope. A likelihood of failure is determined using a new slope stability classification system for excavated coal mine slopes developed using a database of 119 intact and failed case studies sourced from open cut coal mines in Australia. Consequence of failure is based on slope height and stand-off distance at the toe of the excavated slope. Results are presented in a new risk matrix, with slope risk being divided into low, medium and high categories. The SSAM is put forward as a new risk assessment methodology to assess the potential for, and consequence of, excavated coal mine slope failure.Unlike existing classification systems, assumptions about the likely failure mode or mechanism are not required. Instead, the SSAM applies an approach which compares the conditions present within the excavated slope face, with the known past performance of slopes with similar geotechnical and geometrical conditions, to estimate the slope's propensity for failure. The SSAM is novel in that it considers the depositional history of strata in an excavated slope and how this sequence affects slope stability. It is further novel in that it does not require explicit measurements of intact rock, rock mass and/or defect strength to rapidly calculate a slope's likelihood of failure and overall risk. Ratings can be determined entirely from visual observations of the excavated slope face. The new SSAM is designed to be used in conjunction with existing slope stability assessment tools.