Empfehlungen des Arbeitskreises 6.1 “Geotechnik der Deponiebauwerke” der Deutschen Gesellschaft für Geotechnik e. V. (DGGT)

Recommendations of the DGGT Committee “Geotechnics of Landfill Structures”. The Technical Committee “Geotechnics of Landfill Structures” published up to now 76 recommendations. The series is continued by the fundamentally revised recommendation E 2‐7 “Analysis of planar surface failure in lining systems”, at last published in 1998. Experience learned from recent failures as well as the concept of partial safety factors recommended in Eurocode 7 has been considered in this new edition.     

节理岩体边坡模糊稳定性分析方法研究

节理岩体边坡失稳破坏同时受控于节理与岩体抗剪强度。在对具有两组平行节理的岩体边坡失稳破坏机制研究基础上，探讨节理岩体边坡几何物理参数为模糊数情况下边坡稳定性评价的分析方法，给出节理岩体边坡模糊安全系数的计算公式，编制基于潜在滑动面自动搜索边坡模糊稳定性研究程序。算例研究成果表明，采用模糊分析方法可以对节理岩体边坡稳定性有更全面客观的了解，能为潜在不稳定边坡的稳定性评价和锚杆设计等提供重要的参考依据，避免发生由于计算参数不确定性引起的加固节理岩体边坡破坏情况。     

What is the role of tensile cracks in cohesive slopes?

The traditional limit equilibrium method (LEM) is often used to search for the failure surface with a minimum safety factor of slope. In this method, the failure surface is considered as a shear surface, irrespective of its form. However, tensile cracks are frequently found at the outcrops of landslides. In this study, three sets of tests on small-scale landslides with different inclination angles were conducted. The test results demonstrated that tensile cracks could arise in the slope sliding process and the failure surface is composed of both a shear and a tensile fracture surface. Based on the test results, we used the improved LEM, and replaced the traditional shear failure surface by a tensile-shear coupling one, thus new tensile failure modes for slope stability analysis can be established. The safety factors of slope in different failure modes were compared, which show that when considering soil tensile failure and tensile strength less than a certain value (e.g. 15 kPa, 44 kPa and 55 kPa for linear, circular and logarithmic spiral failure surfaces, respectively), the safety factors of slope with three different failure surfaces are less than the one that did not consider the tensile failure. The most critical failure surfaces of the slope may be composed of shear and tensile damages because the tensile strength of the soil cannot be generally greater than its cohesion.     

岩土工程稳定性分析RFPA强度折减法

将强度折减法的基本原理引入到岩石破裂过程分析RFPA方法中，建立RFPA—SRM岩土工程稳定性强度折减分析方法。该方法以有限元方法作为应力分析工具，不仅满足静力平衡、应变相容，且充分考虑材料的细观非均匀特性，并秉承RFPA方法的破坏过程分析优势，能够反映岩土结构随强度劣化而呈现出渐进破坏诱致失稳的演化过程。以岩土工程中的边坡为例，阐述RFPA-SRM方法在边坡稳定性分析中的应用。利用RFPA—SRM方法进行边坡稳定性分析时，不需对滑动面做任何预先假定，对复杂地质地貌的边坡稳定性分析是实用的；同时以基元的破坏次数统计作为边坡的失稳判据，不仅可直观地得到坡体的滑移破坏面，还可求得安全系数，为边坡的稳定性研究提供一种新的便捷、有效方法。特别是RFPA-SRM对边坡破裂过程的模拟对于理解边坡的破坏形成机制具有重要意义，更有利于从边坡失稳的源头入手指导边坡防护设计。最后对RFPA-SRM方法在一连拱分叉隧道安全设计中的应用进行探讨，得到该隧道结构的安全系数及潜在破坏模式，表明RFPA-SRM方法同样适合其他岩土结构稳定分析。     

滑坡加固系统中沉埋桩的有限元极限分析研究

采用有限元强度折减法，针对一边坡工程实例进行沉埋桩单桩加固边坡的有限元极限分析，研究了桩长、桩位与潜在滑面、边坡的安全系数及桩身内力之间的关系，研究了边坡滑体与滑带强度之间不同的比例关系与桩长、边坡安全系数的关系。研究结果表明，沉埋桩设在合适的位置上采用较短的桩就可使边坡达到设计要求的安全系数，桩身内力也较全长桩降低，表明沉埋抗滑桩具有良好的应用前景，但是也受到边坡次生滑动面的位置、滑体与滑带强度比例以及桩位置等因素的制约。沉埋桩加固边坡设计中若不考虑这些制约因素，有可能导致工程失败。     

GIS-based three-dimensional slope stability analysis considering rainfall infiltration

Rainfall-induced landslides are a major cause of slope failure in mountainous areas. As rainfall begins to infiltrate a slope the wetting front advances into the soil and reduces its shear strength. Slope failures occur when the reduced shear strength becomes less than the resisting shear strength needed for equilibrium. These areas of instability are usually located near the ground surface where pore-water pressure changes rapidly during infiltration. The wetting front depth in a slope plays an important role in slope stability. In this study a well-known infiltration model, the Green and Ampt model, is integrated into three GIS-based three-dimensional limit equilibrium methods to assess the impact of rainfall on slope stability. This infiltration model can predict the depth of the wetting front during steady and unsteady rainfall. The applied three-dimensional methods are modified according to different positions of the wetting front to reflect the influence of rainfall on slope stability. This approach is capable of calculating safety factors corresponding to individual rainfall events and is also capable of predicting the corresponding failure time. The accuracy of the presented study has been verified by simulating the failure process of a real landslide triggered by a rainstorm.     

Sicherheitskonzept von unterspannten Konstruktionen

Safety Concept for Cable Supported Structures Codes treat permanent actions and prestress as independent actions with different (partial) safety factors. However, for structures whose geometry is controlled during prestressing, there are proposals to consider dead load and prestress as one load case “permanent actions” with the same safety factor. Both approaches are compared systematically with regard to the structural safety. It is shown that combining dead load and prestress in one load case does not yield a sufficient safety level. The results of the investigations lead to a proposal which considers the influence of controlling the geometry during prestressing by modifying the partial safety factor for the action prestress. This results in a sufficient safety level while also permitting more efficient dimensioning.     

Ein ungewöhnliches Stabilitä verursacht Schadensfall

An uncommon stability problem causes failure. When bolted two‐plane connections of box shaped compression members in trusses are designed, it is obvious that the boltability must be observed. If however, in doing so, the classic design principle of constructing truss nodes as compact as possible is falling into oblivion this may have serious consequences, as a recently occurred failure of a truss girder shows. The uncommon stability phenomenon that caused this failure is here presented to the structural engineering community in order to help avoiding similar failures in the future. The eigenmodes and eigenvalues obtained from a linear FEM stability analysis are discussed. Supplementary nonlinear FEM analyses (so called GMNIA analyses) show when compared to the acting loading that the failure was inevitable. Some lessons and recommendations how to avoid the uncommon stability failure are presented. As a concluding remark, the paper is seen within the greater context of “forensic engineering” as an instrument to improve the safety of our structures.     

浅谈抗震设计中短柱问题的处理措施

在工程设计时，应尽可能避免短柱。当无法避免时，应采取有效措施，防止短柱剪切或剪切斜拉破坏。《建筑抗震设计规范》（GB50011-2010）：11对框架柱有明确的延性要求。轴压比和剪跨比是影响柱延性主要的两个因素，本文着重探讨了设计遇到短柱时，宜采取哪些措施。     

坡顶压力下边坡的二维与三维稳定分析(英文)

基于极限分析理论和能量安全系数的定义,提出了一种评估土坡稳定分析的方法,并通过例子阐述了该方法的具体应用。分析表明:对二维的土坡稳定分析,能量安全系数具有明确的物理意义,且容易将其应用和拓展到土坡的三维稳定分析中。结果表明:文中建议的两种土坡三维破坏模式更适用于坡顶局部压力下的三维土坡稳定分析研究。     

江阴大桥南岸边坡安全性综合评判模型的建立

随着工程开挖、工程荷载的增大以及环境因素的变化，岩土体必然产生相应的变形，甚至失稳破坏。安全监测的目的在于预测、发现失稳征兆。实测的边坡外部变形值，通常可由3部分组成，即边坡岩体的弹塑性变形、沿滑动面的剪切位移以及测量误差，而且目前尚难以将对判别边坡稳定性具有重要意义的沿滑动面的剪切位移分离出来。所以，对于在破坏之前变形量不大的岩质边坡，往往不易根据外部变形来判别稳定性。在阐述岩质边坡和地基外部变形特征的基础上，提出了根据外部变形观测成果对工程边坡安全性进行评判的非单点原则、一致性原则、累进性原则、合理性原则、无因果原则和可视性原则，并采用模糊数学方法，建立考虑多因子边坡安全性的综合评判模型，按地基和边坡的结构类型和边界条件分区，给出了江阴大桥南岸工程边坡的安全性评判实例。     

Reliability-based capacity design for reinforced concrete bridge structures

In the seismic design of reinforced concrete (RC) bridge structures, there should be no brittle failures, such as shear failures, in the components, and a plastic hinge should be formed at the bottom of the bridge pier. These are important concepts in capacity design to guarantee the safety of bridges subjected to severe earthquakes. These concepts can maximise post-event operability and minimise the cost of repairing bridges after a severe earthquake. In this article, a reliability-based methodology to carry out capacity design with partial factors is proposed and applied to the seismic design of RC bridge structures. This ensures that (i) all of the components undergo the desired ductile failure mode, (ii) the damage due to an earthquake is induced only at the bottom of the bridge pier and (iii) the probability of failure is at most equal to a specified value.     

基于降强法数值计算的复杂岩质边坡动力稳定性安全评价分析

分析复杂岩质边坡在地震荷载作用下的动力稳定性的特点,提出基于降低材料强度算法的动力稳定性分析方法。先将软弱结构面抗剪强度指标降低,进行静力计算,在此基础上,再进行动力稳定分析,综合评估边坡的动力稳定性与降强倍数的关系,将边坡处于临界稳定状态下的降强倍数定义为动力稳定安全系数。借助数值计算程序,将上述方法应用于国内某拱坝坝轴线左岸岩质边坡的动力稳定性分析,取得满意的成果。     

Influence of ground anchors corrosion and uncertainty strength parameters: A case study slope failure in northern Taiwan

A significant fatal scale dip slope failure incident occurred at The Freeway No.3, located in Northern Taiwan, on April 25, 2010. From the post-failure investigations, it is found that the deteriorating anchor systems and uncertainties in strength parameters as the most likely the primary reasons for this slope failure. This study main conducted a numerical modeling work using Universal Distinct Element Code (UDEC), a two-dimensional numerical program based on the distinct element method for discontinuum modeling. First, the numerical modeling was generated to check the original design of this dip slope failure. Then a series of parametric studies were introduced to investigate the influences of the triggering design factors that affected this slope-failure event. The ground anchor failure order in this slope is also assessed by bracketing approach and strength-reduction method using a new term called “Adjusted Factor”. Furthermore, this study will focus on an anchors’ failure order from the perspective of the random field to assess whether the anchors’ failure mechanism considering the random field will match or be closely similar to the anchor failure order in the field.     

Probabilistic “φ = 0” stability analysis in strain-softening soil

A key issue in the improvement of geotechnical analysis and design is the assessment of safety and reliability. The value of probabilistic basis for risk assessment is now widely recognised. In this paper, attention is focussed on strain-softening behaviour which may be, and often is, overwhelmingly important for progressive failure. Other factors may also be significant but these are not dealt with here so that the formulation is simple enough to appeal to the geotechnical practitioner. After discussing the importance of strain-softening behaviour under undrained conditions, a method for determining the probability of failure is proposed so that widely available stability charts can be used. Peak and residual shear strengths (undrained) are regarded as the only random variables. The concept of “residual factor” is used to specify the proportion of slip surface which has passed from peak to residual shear strength. The progression of failure is seen in terms of an increasing proportion of the slip surface passing to the residual strength state. The proposed method is applied to an illustrative example using three different probability distributions or models.     

关于《建筑边坡工程技术规范GB 50330—2013》的讨论

针对《建筑边坡工程技术计规范》(GB 50330—2013)中的一些问题进行了讨论。指出该规范的一些不足、不当及不对之处。指出关于锚杆的抗拉和从砂浆中的抗拔设计应当使用分项系数法,而不是安全系数法;在安全系数法设计中,抗力应使用极限抗力的标准值,而非设计值。该规范所列的一些主动土压力计算的半经验公式,主要是源于无限斜坡的朗肯土压力理论解,但主动土压力的方向不正确,会造成较大的误差。在饱和黏性土边坡的稳定分析中,使用饱和重度与固结不排水强度指标的水土合算是错误的,有害的。     

单锚及群锚失效对边坡稳定性影响的模型试验研究

针对典型岩土体边坡,通过室内模拟试验,研究锚力变化或锚失效在群锚中引起的荷载转移现象,探讨群锚失效后边坡稳定性的劣化过程、失稳形态以及坡面设置格子梁对锚索张力及边坡稳定性的影响等问题。群锚抑制坡体的变形效应,可使岩体均匀性、整体性加强,增加韧性和承受大变形而不破坏的能力。群锚中某一锚索锚力变化会导致其承担的荷载在群锚内部发生较明显的转移现象,结构面压缩带同时被削弱,结构面的整体安全度降低;某一锚索的失效也会引起相邻锚索接连失效的多米洛效应,导致边坡稳定性急剧降低。坡面施加格子梁结构可调动坡面更大范围岩土体发挥自承能力,分担锚索承担的部分荷载,改善边坡的稳定性。岩坡加固设计中应注意格子梁结构强度与锚索锚固力相匹配。     

Application of rock mass classification systems to rock slope stability assessment: A case study

The stability of rock slopes is considered crucial to public safety in highways passing through rock cuts, as well as to personnel and equipment safety in open pit mines. Slope instability and failures occur due to many factors such as adverse slope geometries, geological discontinuities, weak or weathered slope materials as well as severe weather conditions. External loads like heavy precipitation and seismicity could play a significant role in slope failure. In this paper, several rock mass classification systems developed for rock slope stability assessment are evaluated against known rock slope conditions in a region of Saudi Arabia, where slopes located in rugged terrains with complex geometry serve as highway road cuts. Selected empirical methods have been applied to 22 rock cuts that are selected based on their failure mechanisms and slope materials. The stability conditions are identified, and the results of each rock slope classification system are compared. The paper also highlights the limitations of the empirical classification methods used in the study and proposes future research directions.     

招银高速公路路堑边坡稳定性分析及加固措施

选取漳州招银高速公路工程典型路堑边坡进行稳定性分析及其加固措施研究,考虑天然T况和暴雨T况。通过稳定性分析,自然条件下的安全系数在两种工况下的安全系数均较低;设置锚索加固措施后,两种工况下的安全系数稍有提高;若采用锚索抗滑桩综合加固措施,安全系数提高较大。由于该边坡地质条件的特殊性,建议进行动态设计。     

膨胀土边坡的稳定性分析

根据膨胀土边坡失稳破坏现象，将其破坏类型归结为表层溜塌、浅层破坏和深层破坏，同时对其破坏发生机理进行探讨。然后在考虑膨胀土工程特性和环境因素影响的情况下，对南阳一中等膨胀土边坡进行稳定性分析。进而在此基础上，对上述3种破坏类型的滑面进行研究，提出该实例边坡的合理坡率和浅层破坏滑面位置。