基于地震时程分析的尾矿坝稳定性评价

采用永久变形分析和地震时程分析相结合的综合研究方法,开展某大型现场尾矿坝的稳定性评价。依据尾矿坝场地地震安全性评价结果,确定50年超越概率10%、5%的荷载时程输入曲线;采用修正UBCSAND模型进行隐式非线性分析;采用粘性输入边界,解决动力荷载时程较长时引起计算不收敛的问题;进行尾矿坝的三阶振型特征周期计算;进行基本烈度下永久变形分析,剖析不同坝体标高的变形特征;绘制位移云图并剖析位移变化特征;采用时程+SRM法,计算绘制50年超越概率10%和5%的安全系数时程曲线。根据永久变形和稳定性系数计算结果,综合判定尾矿坝稳定状态,据此对现场尾矿坝提出加固建议。建立的研究方法和成果可为大型尾矿坝稳定性评价工程提供参考。     

岳城水库土坝抗震加固有效应力动力分析

岳城水库土坝采用了上游压坡铺盖加固的方法,以防止坝体动力和静力坍滑。本文对该坝的有压坡铺盖断面和无压坡铺盖断面进行了大量的非线性静力计算和动力计算。静力计算采用应力和渗流一并考虑的计算方法,并考虑水位骤降的影响。动力计算采用非线性的二维有效应力方法。计算中都用等参数单元。文中分析比较了两个断面的静应力、流网、静力稳定安全系数、加速度反应曲线、剪应力反应曲线,最大动剪应力和动剪应变,振动孔隙水压力的分布、振动残余变形、残余位移、动力稳定系数等等。 分析指出,压坡铺盖加周措施对该坝是有效果的。     

红沿河核电取水隧洞进水口高边坡抗震稳定分析

以红沿河核电取水隧洞进水口高边坡为背景,介绍了核电工程中边坡抗震稳定分析的原理和分析方法。依次采用滑动面法、静力有限元法和动力有限元法计算该边坡的抗震稳定性,得到其在地震作用下的安全系数及滑动面位置;根据安全系数时程曲线进一步得到边坡最小安全系数和最小平均安全系数。结果表明天然边坡安全系数不满足《核电厂抗震设计规范》的要求,必须进行削坡加固。本文的计算方法和分析成果对于类似核电工程中的高边坡抗震稳定分析具有一定的指导意义和参考价值。     

边坡地震稳定性分析探讨

传统的拟静力法和安全系数时程分析法在评价边坡地震稳定性时存在一定的局限性。在提出准确的评价边坡地震稳定性必需因素的基础上,建议对边坡地震稳定性分析方法重新进行分类。根据动力分析得到的边坡在地震作用下的破坏机制和破裂面的性质和位置,提出基于拉-剪破坏的动力时程分析法和强度折减动力分析法。第一种方法将FLAC计算得到破坏时刻的动应力施加到静力情况下边坡上,采用动力分析得到的拉-剪破裂面,结合极限平衡法求解边坡地震安全系数,是一种改进的动力有限元时程分析法;第二种方法考虑了拉-剪破坏的FLAC强度折减动力分析法,是完全动力的方法。最后通过算例分析验证了新方法的可行性,为边坡地震安全系数计算提供了一种新的思路。     

基于全动力分析法的地震边坡与隧道稳定性分析

目前地震边坡和隧道稳定性分析方法尚有一些不尽如人意的地方,如地震边坡的破裂面假定为剪切破裂面,这与汶川地震边坡破坏现象不符;地震边坡稳定性分析采用时程分析法,假定在某一时刻加速度作用下,将其作为静力问题来计算边坡稳定安全系数,没有充分考虑加载的动力效应;同样,未考虑地震作用下隧洞围岩的拉破坏,对隧洞围岩破坏缺少动力稳定性标准,也不能充分考虑隧洞围岩与衬砌的动力效应。为此,基于有限元强度折减法,提出了一种完全的动力分析方法——强度折减动力分析法,计算中同时考虑剪切强度和抗拉强度参数的折减,并采用计算不收敛和位移突变综合判断边坡和隧道是否动力失稳破坏,以极限状态时的强度折减系数作为地震边坡和隧道的动力稳定系数,由此获得拉、剪组合破裂面与全动力稳定安全系数,充分考虑了动力效应。     

龙首二级面板堆石坝地震永久变形分析

针对龙首二级(西流水)面板堆石坝工程，根据面板坝土石料的大型动三轴试验结果，确定了坝料的残余应变模式，特别是残余体应变模式。在所建立的面板坝三维非线性动力反应有限元法基础上，建立了一套同时计人残余体应变和残余剪应变的面板堆石坝地震永久变形计算方法，对龙首二级面板坝工程进行了地震永久变形的计算，分析了坝体地震永久变形的量值和分布情况，为大坝的抗震设计提供了有力的技术依据。     

地震波对边坡稳定性的影响及其分析方法

介绍了目前地震作用下边坡稳定分析常用的拟静力法、时程法和边坡动力安全度法,通过对这3种方法计算结果的对比分析,表明边坡动力安全度法能更准确地判断边坡的动力稳定性;应用边坡动力安全度法分析了地震作用频率和振幅对边坡稳定性的影响,结果表明频率和振幅对边坡的稳定性有较大影响,动安全系数随着频率的增大而增大,其增幅逐渐减小;随着振幅的增大而降低,其降幅也逐渐减小.     

基于严格条分法的拟动力地震边坡稳定性分析方法研究

将拟动力法基本原理与极限平衡法中的严格条分法(Sarma法)相结合,推导边坡地震力和安全系数的计算公式;在此基础上,基于Python语言开发相应的计算程序,实现一种考虑波动效应的、适用于任意滑面形状和任意滑块条分的拟动力地震边坡稳定性分析新方法;同时,探讨地震动特性和结构面强度对边坡地震稳定性的影响。研究表明：随着地震波初始相位的变化,边坡的安全系数呈现周期性的波动变化,且存在最小安全系数;边坡安全系数随着地震动幅值和地震波波长/坡高比的增大而减小;当滑块结构面抗剪强度参数下降时,边坡安全系数随之减小。此外,通过波动理论揭示拟静力法与拟动力法的区别与联系：当地震波波长与坡高比大于10时,两种方法的结果基本一致;当地震波波长与坡高比小于10时,拟静力法所得结果比拟动力法保守,拟动力法更合理。     

先期震动对土石坝地震永久变形的影响研究

针对经历了5.12汶川大地震的紫坪铺面板堆石坝工程,进行了坝料的大型动三轴试验,研究了先期振动对坝料残余应变的影响。在此基础上,采用基于3维非线性动力反应的地震永久变形计算方法,进行了紫坪铺面板坝地震永久变形的计算,重点分析了先期震动对坝体地震永久变形的影响。结果表明,如果考虑先期已遭受强震作用影响,大坝的地震残余变形明显减小。     

土坝地震孔隙水压力产生、扩散和消散的三维动力分析

本文将地震孔隙水压力与土坝(尾矿坝)的变形和固结紧结合起来,引用著名的皮奥(Biot)方程,用空间等参数有限单元法求解位移和残余孔隙水压力;提出了一种用于土坝动力分析的非线性三维有效应力分析力法。该法不仅可计算地震动应力、动应变、加速度,而且可以计算地震期间和地震后孔隙水压力的增长、扩散、消散、液化的发生和发展过程、土的残余变形及其随着时间的变化。文中用加权剩余值法详细推导了有限单元法的计算公式。文末举有算例。     

温控参数折减有限元法在拟静力土石坝坝坡稳定分析中的应用

土石坝的拟静力计算与温控参数折减有限元法相结合,对土石坝边坡稳定性进行有限元计算与分析。按《水工建筑物抗震设计规范》(SL203-97)的规定,依据坝高动态分布系数施加水平等效地震惯性力,然后用温控参数折减有限元法确定土石坝边坡的临界失稳状态及其所对应的安全系数。结果表明:采用此法进行拟静力土石坝边坡稳定分析与传统的Bishop法相比,计算结果相一致,且可以反映土石坝的应力、应变和整个边坡破坏发展过程。     

强震区高面板堆石坝抗震安全性评价

针对西部强震区高面板堆石坝,在三维非线性动力有限元分析基础上分析评价了面板堆石坝的加速度和应力反应、面板的应力及接缝变形、坝体地震残余变形、坝体单元抗震安全性、坝坡的抗震稳定性,对大坝的抗震安全性进行了综合评价。所提出的抗震安全性评价方法以及有关规律和结论可供工程建设参考。     

Static and dynamic stability analysis using 3D-DDA with incision body scheme

Discontinuous deformation analysis （DDA） provides a powerful numerical tool for the analysis of discontinuous media. This method has been widely applied to the 2D analysis of discontinuous deformation. However, it is hindered from analyzing 3D rock engineering problems mainly due to the lack of reliable 3D contact detection algorithms for polyhedra. Contact detection is a key in 3-D DDA analysis. The limitations and advantages of existing contact detection schemes are discussed in this paper, and a new approach, called the incision body （IB）, is proposed, taking into account the advantages of the existing methods. A computer code 3DIB, which uses the IB scheme as a 3D contact detection algorithm, was programmed with Visual C^＋＋. Static and dynamic stability analysis for three realistic engineering problems has been carried out. Furthermore, the focus is on studying the stability of a gravity dam on jointed rock foundation and dynamic stability of a fractured gravity dam subject to earthquake shaking. The simulation results show that the program 3DIB and incision body scheme are capable of detecting 3D block contacts correctly and hence simulating the open-close and slide process of jointed block masses. In addition, the code 3DIB could provide an effective tool for evaluating the safety of 3D dam structures, which is quite important for engineering problems.     

Decoupled seismic analysis of an earth dam

The seismic stability of an earth dam is evaluated via the decoupled displacement analysis using the accelerograms obtained by ground response analysis to compute the earthquake-induced displacements. The response analysis of the dam is carried out under both 1D and 2D conditions, incorporating the non-linear soil behaviour through the equivalent linear method. Ten artificial and five real accelerograms were used as input motions and four different depths were assumed for the bedrock.1D and 2D response analyses were in a fair agreement with the exception of the top third of the dam where only a 2D modelling of the problem could ensure that the acceleration field is properly described. The acceleration amplification ratio obtained in the 2D analyses was equal to about 2 in all the cases considered, consistently with data from real case histories.The maximum permanent displacements computed by the sliding block analysis were small, being less than 10% of the service freeboard; a satisfactory performance of the dam can then be envisaged for any of the seismic scenarios considered in the analyses.     

水库输水隧洞施工爆破振动对大坝安全影响监测及分析

阐述柏峰水库除险加固工程主坝输水隧洞施工爆破振动对大坝安全影响。选择有代表性的几个部位,采用原位质点振动速度测试的方法对整个施工期间爆破振动对大坝安全影响进行全过程监测与分析。对实测结果分析表明,爆破振动对大坝安全未产生明显的危害。监测成果可为工程爆破振动安全评价提供科学依据。     

考虑堆石料空间变异性的土石坝坝坡地震稳定性随机有限元分析

本文探讨了筑坝堆石料的空间变异性对土石坝坝坡动力稳定性的影响。以新疆某在建高面板堆石坝为例,在蒙特卡洛法的框架下,采用基于局部平均细分法的随机有限元法模拟考虑筑坝堆石料空间变异性时土石坝的地震响应及坝坡滑移情况,通过对比随机有限元法和常规确定性有限元法的计算结果,提出:在地震动作用下,考虑筑坝材料空间变异性时,坝坡滑动体的数量、规模以及滑移量和滑动历时都有不同程度的增大,因而坝坡整体危险程度显著高于不考虑材料空间变异性的情况。坝坡各项动力安全性指标对筑坝材料空间变异性非常敏感;因而,考虑筑坝材料空间变异性时,各项安全性指标的离散性较大。     

Seismic rehabilitation and analysis of Chaohe earth dam

Stability of earth dams during earthquakes has been a major concern for geotechnical engineers in seismic active regions. Liquefaction induced slope failure occurred at the upstream slope of a major earth dam in the suburb of Beijing, China, during the 1976 Tangshan Earthquake. The gravelly soil with loose initial condition liquefied under relatively small ground vibration. In recent years, a major seismic rehabilitation project was carried out on a similar earth dam nearby using dumped quarry stone. Seismic stability analysis was carried out using model test, finite element simulation, and pseudo-static slope stability program after taking into account the influence of excess pore pressure.     

Effects of vertical seismic acceleration on 3D slope stability

The conventional pseudo-static approach often neglects the effect of the vertical seismic acceleration on the stability of a slope, but some analyses under plane-strain (2D) conditions show a significant effect on the slope stability. The purpose of this study is to investigate the effect of the vertical acceleration on the safety of three-dimensional (3D) slopes. In the strict framework of limit analysis, a 3D kinematically admissible rotational failure mechanism is adopted here for 3D homogeneous slopes in frictional/cohesive soils. A set of stability charts is presented in a wide range of parameters for 3D slopes under combined horizontal and vertical seismic loading conditions. Accounting for the effects of the vertical seismic acceleration, the difference in safety factors for 3D slopes can exceed 10%, which will significantly overestimate the safety of the 3D slopes.     

Reliability analysis of three-dimensional dynamic slope stability and earthquake-induced permanent displacement

Different models were developed for evaluating the probabilistic three-dimensional (3D) stability analysis of earth slopes and embankments under earthquake loading using both the safety factor and the displacement criteria of slope failure. In the 3D analysis, the critical and total slope widths become two new and important parameters.The probabilistic models evaluate the probability of failure under seismic loading considering the different sources of uncertainties involved in the problem, i.e. uncertainties stemming from the discrepancies between laboratory-measured and in-situ values of shear strength parameters, randomness of earthquake occurrence, and earthquake-induced acceleration. The models also takes into consideration the spatial variabilities and correlations of soil properties.Five probabilistic models of earthquake-induced displacement were developed based on the non-exceedance of a limited value criterion. Moreover, a probabilistic model for dynamic slope stability analysis was developed based on 3D dynamic safety factor.These models are formulated and incorporated within a computer program (PTDDSSA).A sensitivity analysis was conducted on the different parameters involved in the developed models by applying those models to a well-known landslides (Selset landslide) under different levels of seismic hazard.The parametric study was conducted to evaluate the effect of different input parameters on the resulting critical failure width, 3D dynamic safety factor, earthquake-induced displacement and the probability of failure. Input parameters include: average values and coefficients of variations of water table, cohesion and angle of friction for effective stress analysis, scales of fluctuations in both distance and time, hypocentral distance, earthquake magnitude, earthquake strong shaking period, etc.The hypocentral distance and earthquake magnitude were found to have major influence on the earthquake-induced displacement, probability of failure (i.e. probability of allowable displacement exceedance), and dynamic 2D and 3D safety factors.     

基于多源遥感数据的山西省交口县某尾矿库堆载过程回溯与失稳模式分析

2022年3月17日,山西省交口县某铝矿尾矿库发生溃坝事故,造成较大经济损失。为了探究尾矿库溃坝的原因,基于多时相光学卫星立体像对数据和SBAS-InSAR等遥感技术,回溯分析该尾矿库的堆载过程、库容变化和坝体形变,并采用GeoStudio软件Slope/W模块评价溃坝前边坡的稳定性。结果表明:(1)该尾矿库于2019年9月前已堆积至最大库容,2021年12月前在2^#坝后方子库堆载至96万m³,超出设计库容4.8万m³,从而降低了坝体的稳定性;(2)溃坝物源主要来自2^#坝以上库区,在2^#坝与1^#坝之间以及1^#坝到沟口区域均主要以堆积为主;(3)该尾矿库溃坝属于典型的渗流场诱发尾矿坝失稳,尾矿加载导致其坝体边坡稳定性安全系数由1.125降至0.991,是该尾矿库溃坝的直接诱发因素。