动荷载作用下地下洞室楔形体稳定性分析

通过楔形体破坏的3个基本假定建立了地下洞室楔形体物理模型,提出了楔形体稳定性分析的极限平衡方法。该方法得出了楔形体稳定系数计算表达式,并结合几何分析判断楔形体的稳定状态,进一步探讨了楔形体在爆破施工荷载作用下的楔形体稳定性响应。案例分析表明,楔形体在自重作用下处于稳定状态,施加初始爆破荷载时增加了楔形体的稳定性;工程爆炸作用力远远大于楔形体自重荷载,爆破荷载对楔形体稳定性起主导作用;当爆炸荷载反射时楔形体稳定性显著降低,且沿楔形体①面发生单面滑动破坏。     

三维过渡等参单元在岩土工程有限元分析中的应用

土石坝等复杂土工结构物有限元三维建模中多采用精度较高的六面体单元辅以部分过渡用的退化单元,而退化单元由于形态不好,会导致有限元计算精度较差。解决该问题的途径之一是采用过渡性的等参元。总结了几种常遇到的过渡等参单元（楔形体、四面体、金字塔）的插值函数和高斯积分局部坐标和权重,并编入了有限元程序。通过比较六面体单元和金字塔单元剖分理想土石坝的有限元计算结果,说明所引入的金字塔单元是满足精度要求的。将各种过渡单元应用于实际土石坝工程的有限元计算,结果表明,使用过渡等参单元是可以在一定程度上提高计算精度的。最后讨论了二次单元在弹塑性有限元动力计算中的应用。二次单元的使用,可以改善动力计算中的超静孔压分布,提高计算精度。     

楔形桩与圆柱形桩复合地基承载性状对比研究

基于剪切位移法,引入Mylonakis & Gazetas桩-土相互作用及Winkler地基模型,导出了复合地基中桩-桩、桩-土及土-土相互作用柔度系数;在此基础上,提出了一种综合考虑桩-土-垫层共同作用的复合地基分析方法,并利用Matlab软件编制了相应的计算程序。为了验证该方法的可行性,对楔形桩和圆柱形桩复合地基进行了模型对比试验,并利用该方法对两个模型试验进行了计算分析,试验及理论结果均表明,桩顶平面处的桩间土反力保持着类似天然地基的马鞍形分布,圆柱形桩复合地基的承载力明显低于楔形桩复合地基的承载力,同时,圆柱形桩复合地基的桩土平均应力比明显高于楔形桩复合地基的桩土平均应力比,楔形桩对缓解复合地基中桩顶应力集中,充分利用天然地基的承载能力具有良好的调节作用。     

岩质边坡楔形体破坏概率的方向模拟

针对边坡小概率破坏的高效模拟问题,提出采用方向模拟方法进行计算,介绍了方向模拟的基本理论和楔形体破坏功能函数的算法,编制了岩质边坡楔形体破坏概率的方向模拟的Matlab程序,分别将方向模拟结果与重要抽样模拟、子集模拟的计算结果进行了对比分析。结果表明,方向模拟与子集模拟一样适合于小概率破坏的计算,方向模拟方法在抽样次数较少的情况下就能获得较高的计算精度,与其他两种方法相比效率更高。     

开挖边坡松动区的近似解析

介绍了楔形体与开挖坡体模型之间的关系,提出了确定边坡开挖松动区范围的弹性理论分析方法。阐明在用楔形体理论分析出开挖坡体的应力场的基础上,根据一定的坡体材料强度条件（经过安全储备后的摩尔-库仑强度准则和单轴抗拉强度准则）,且考虑三向应力状态,计算搜索坡体在该稳定系数下的开挖松动区,由此计算出在坡体自上而下分步开挖过程中每一步开挖施工完成之后相应的松动区来。提出了分析计算坡体开挖松动区的主要步骤,说明在分步开挖过程中,计算搜索每一步开挖后的坡体松动区主要需通过讨论上一步开挖后的坡体应力场、本步开挖卸荷量及本步开挖后产生的松动区范围等问题来实现。最后,用算例较为详细地说明了用弹性楔形体理论解析坡体开挖松动区的具体操作过程。     

低承台扩底楔形桩群桩效应系数研究

基于模型试验方法,开展砂土中竖向荷载作用下低承台2×1和2×2扩底楔形桩群桩桩-土相互作用模型试验,测得不同荷载等级下桩顶荷载-沉降关系曲线、桩端阻力以及桩身轴力等分布规律,同时开展扩底楔形桩单桩竖向承载特性试验作为对比分析。结合JGJ94规范规定的承台效应系数和群桩效应系数,对扩底楔形桩群桩竖向极限承载力进行了理论计算分析。研究结果表明,文中试验条件下竖向荷载作用下低承台2×1和2×2扩底楔形桩群桩的综合效应系数分别为1.16和1.10;无承台作用下2×1和2×2扩底楔形桩群桩的群桩效应系数分别为0.95和0.88;理论计算中扩底楔形桩承台效应系数和群桩效应系数可以参照等直径桩的相关规范取值。     

考虑渗流的多层土盾构隧道开挖面稳定性分析

将传统模式的均匀土层稳定性分析的楔形体模型扩展到渗流作用下多层土盾构隧道开挖面的稳定性分析中,楔形体是由梯形组成的,每一个梯形对应一层土层,利用太沙基有效松动土压力理论和上限定理,推导了渗流作用下盾构穿越多层土的隧道开挖面极限支护压力的计算公式。极限支护压力等于作用于开挖面有效支护压力和渗透力的总和,其中有效支护压力用极限平衡来计算,渗流力采用水头分布的数值方法计算获得的。计算结果发现,渗透力构成了总支护压力的主要部分,分析结果和工程实测数据是一致的。     

基于楔形效应的隧道锚抗拔承载能力研究

悬索桥隧道锚因楔形体外观特征具备强大的抗拔承载能力。基于匀质围岩假定和Mohr-Coulomb强度准则,研究锚碇围岩系统两种破坏模式即岩锚界面摩擦破坏以及围岩受侧向挤压后产生的破裂,根据岩锚界面受力特点建立界面平衡条件,分析围岩破裂面应力状态的改变,并将其与等截面体的抗拔承载力相比较,分别得到对应两种破坏模式的楔形效应系数,由此推导出两种破坏模式下隧道锚抗拔承载力计算公式。研究结果表明,隧道锚抗拔承载力的楔形效应对于不同类别的围岩表现出明显规律。通过与已建隧道锚承载力的研究结果相比较,验证计算较为吻合,进一步证实了考虑楔形效应的简化公式计算隧道锚承载力的正确性和合理性。     

节理岩体中地下洞室超挖预测

本文着重于岩体中洞室超挖-不稳定楔形体的预测。首先,论述洞室超挖的基本概念、主要原因及评价方法;其次分析和比较目前现有的针对洞室超挖的计算软件及其特征;然后介绍本文作者的计算软件;最后,简单介绍一个计算实例,即从野外地质调查着手,应用数理统计理论评价构成不稳定楔形体的主要地质参数及其模型,推导岩体中洞室超挖预测的一般公式;最后评价构成不稳定楔形体主要地质参数中的主要因素及次要因素,为节理岩体洞室防止超挖及其处理提供依据。     

基于透明土的静压楔形桩沉桩效应模型试验研究

楔形桩是一种可以有效提高桩侧摩阻力的纵向变截面异形桩,然而针对该变截面桩沉桩效应特性方面的研究却相对较少。基于透明土材料和粒子图像测速技术（简称PIV）,开展静压楔形桩沉桩模型试验,测得沉桩过程中桩周土体的位移场变化规律;沉桩过程中桩周土体位移场由激光射入透明土材料,与透明土材料之间的相互作用产生的独特散斑场,通过CCD（charge-coupled device）电荷耦合元件相机成像处理而获得。同时进行了等截面桩的沉桩模型试验,并对等混凝土材料用量情况下楔形桩和等截面桩的沉桩效应进行对比分析。最后,将此试验结果与基于常规试验手段的静压楔形桩沉桩模型试验和圆孔扩张理论计算结果进行对比分析,验证了基于透明土材料的静压楔形桩沉桩模型试验的准确性和可靠性。研究结果表明,基于透明土材料和PIV技术可以有效地开展静压楔形桩沉桩模型试验研究;楔形桩静压施工过程中对桩周土的影响范围约为等混凝土用量等截面桩的1.2倍。     

An Experimental and Theoretical Approach on the Modeling of Sliding Response of Rock Wedges under Dynamic Loading

The stability of rock slopes under dynamic loading in mining and civil engineering depends upon the slope geometry, mechanical properties of rock mass and discontinuities, and the characteristics of dynamic loads with time. The wedge failure is one of the common forms of slope failures. The authors presented some stability conditions for rock wedges under dynamic loading and they confirmed their validity through the laboratory experimental studies in a previous paper in 2000, which is often quoted by others to validate their softwares, including some commercial software. In this study, the authors investigate the sliding responses of rock wedges under dynamic loads rather than the initiation of wedge sliding. First, some laboratory model tests are described. On the basis of these model tests on rock wedges, the theoretical model proposed previously is extended to compute the sliding responses of rock wedges in time domain. The proposed theoretical model is applied to simulate the sliding responses of rock wedge model tests and its validity is discussed. In the final part, the method proposed is applied to actual wedge failures observed in 1995 Dinar earthquake and 2005 Pakistan–Kashmir earthquake, and the results are discussed.     

Computer aided analysis of rock slope stability

Summary A computer program is written in basic language on a micro-computer to carrying out kinematic analysis of rock slope stability. The program is capable of handling plane sliding, wedge sliding and toppling of rock slopes. Applications of the program are demonstrated by examples on opencast mine excavations and highway cuts. The computer output are presented in the form of tables and illustrations for ease of interpretation. As micro-computers are readily available in design offices nowadays, the present work provides an efficient means for engineers to analyse and design rock slope excavations.     

水力作用下岩质斜坡破坏机制和稳定性分析研究现状

基于国内外研究现状和岩质滑坡案例,总结出岩质滑坡的水力致灾机制,归纳考虑水力作用下的岩质斜坡主要失稳破坏模式,评述了岩质斜坡稳定性分析方法。岩质滑坡的水力致灾机制主要由于水对滑体产生的静水压力（岩体侧面的推力、滑面的扬压力和岩体的浮力）和动水压力（向坡外的渗透力）作用。从渗流—应力耦合的角度可较全面评价水渗流对坡体稳定性的影响。斜坡的岩体结构决定了水力作用方式和坡体的失稳破坏形式,考虑水力作用下的岩质斜坡失稳破坏形式主要有:顺层滑动、平推式滑动、楔形体滑移和危岩的崩塌。对于水力作用下岩质斜坡的稳定性分析方法主要有极限平衡法、有限元强度折减法、基于断裂力学的危岩稳定性分析法和渗流—应力耦合模型分析法,其中前两种方法应用较为广泛。      

Stability analysis of rock wedges with multiple sliding surfaces

Summary Although wedge and plane sliding stability analyses are well established in the geotechnical literature, certain geologic environments produce blocks which cannot be adequately modelled as either wedges or plane slides. An example is blocks forming in cylindrically folded sedimentary rocks, where the surface of sliding is neither a single plane nor a double plane but is curved. This type of block may be idealized as a prismatic block with multiple sliding planes, all with parallel lines of intersection. If the sliding planes number three or more, the distribution of normal forces, and hence the factor of safety, is indeterminate. A new analytical model for sliding stability analysis is described in which the distribution of normal forces on the contact planes is chosen to minimize the potential energy of the system. The classic wedge and plane solutions are shown to be special cases of this more general model, which allows determination of the safety factor for any shape of prismatic contact surface. An example from Tennessee concerning a block with a curved sliding surface is described and the factor of safety compared with the standard wedge analysis. It is shown that with three or more contact planes, the safety factor may be significantly lower than that calculated from the wedge model, which provides an upper limit on stability.     

饱和黄土边坡的动力稳定性分析

考虑地震荷载作用下饱和黄土的孔压增长模式及液化规律,建立了饱和黄土无限边坡的动力稳定性分析模型,并将此类边坡的破坏分为液化型破坏和滑动型破坏两种基本类型。分析结果表明,由于孔压的累积,屈服地震系数将随时间而减小,并且明显地受到有效粘聚力、初始孔压比等参数的影响。另外还证实,考虑孔压累积时的永久位移计算值要大于常规的Newmark法分析的结果。     

块状岩体边坡地震滑动位移分析

岩体边坡在强震作用下往往会产生滑动残余位移。这种位移是边坡稳定性评价的重要参量。本文利用块体动力学原理推导出层状和块状岩体边坡地震滑动位移微分方程式, 并编制了相应的计算程序, 给出了实例的计算结果。     

The impact of analogue material properties on the geometry,kinematics, and dynamics of convergent sand wedges

Simulation of geodynamic processes in sandbox experiments requires analogue materials with a deformation behaviour that reproduces the deformation mechanisms of typical crustal rocks. We present data on the frictional strength of different sand types employing static and dynamic shear tests. The sand types analysed are characterised by an elastic/frictional plastic mechanical behaviour with a transient strain-hardening and strain-softening phase prior to transition to stable sliding. This is in conflict with the standard assumption of an ideal cohesionless Coulomb-material with constant frictional properties. The influence of the identified transient material properties on the kinematics, growth mechanisms, and internal deformation patterns of convergent sand wedges results in characteristic wedge segments which vary—depending on material compaction—between wedges with well defined segments (i.e. frontal-deformation zone, frontal-imbrication zone and internal-accumulation zone) with straight slopes and wedges with a continuous convex topographic profile. For most materials, only the frontal part of the wedge is critical during experimental runs. Taper and strength of the wedge segments can be shown to be controlled by the frictional properties of active faults. Wedge segmentation is controlled by a bulk-strength increase toward the rear of the wedge due to fault rotation in mechanically less-favourable orientations and plastic material hardening. The limit between the frontal critical parts of a wedge and internal stable parts is largely controlled by a critical state of stress upon which either renewed failure or fault inactivation occurs. On this basis, we suggest that critical-taper analysis of wedges must be restricted to specific kinematic segments. Comparison of the experimental results with the Nankai accretionary wedge suggests that our interpretation also applies to natural convergent wedges. Moreover, we provide constraints for the selection of adequate granular analogue materials to simulate typical crustal rocks in natural convergent wedges.     

楔形体破坏模式下红层边坡岩体质量SMR法评价

简要介绍了边坡岩体质量分类的SMR法,将之应用于2个典型楔形体破坏模式下红层岩体高边坡稳定性宏观评价。 指出在评价过程中要注意对边坡起控制作用的优势结构面,并将其作为SMR法中结构面项评分的主要依据,这样得出的评分 值与边坡的实际情况才会比较相符。对地应力的影响进行了定性的分析,指出高地应力地区边坡SMR法应该慎用。     

基于可靠度理论的阻滑键加固渣土边坡多目标优化设计方法

随着城市建设的发展,渣土边坡的数量和规模急剧增加,渣土边坡的防控研究受到了广泛关注。针对渣土边坡人工分层堆填建筑余渣土体参数的不确定性,采用预埋阻滑键加固渣土边坡的方式,提出了基于可靠度理论的阻滑键多目标优化设计方法。考虑不同阻滑键潜在组合对渣土边坡预估破坏损失的影响,将渣土边坡的预估破坏损失、稳定安全性和加固设计成本作为设计目标,通过多目标优化理论确定帕累托前沿并计算其关节点,获得预埋阻滑键加固边坡的最佳设计方案。以深圳市某渣土边坡为例,计算结果表明,将破坏概率作为衡量阻滑键加固渣土边坡效果指标时,应在渣土边坡前缘预埋两组尺寸长3 m、间距5 m的阻滑键加固边坡。采用上述阻滑键设计组合加固该渣土边坡时,可实现该边坡预估破坏损失、设计成本和稳定性达到最佳平衡。     

Geotechnical assessments of the stability of slopes at the Cakmakkaya and Damar open pit mines (Turkey): a case study

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.