Mechanism of toppling and deformation in hard rock slope: a case of bank slope of Hydropower Station, Qinghai Province, China

Recently, various toppling slopes have emerged with the development of hydropower projects in the western mountainous regions of China. The slope on the right bank of the Laxiwa Hydropower Station, located on the mainstream of the Yellow River in the Qinghai Province of Northwest China, is a typical hard rock slope. Further, its deformation characteristics are different from those of common natural hard rock toppling. Because this slope is located close to the dam of the hydropower station, its deformation mechanism has a practical significance. Based on detailed geological engineering surveys, four stages of deformation have been identified using discrete element numerical software and geological engineering analysis methods, including toppling creep, initial toppling deformation, intensified toppling deformation, and current slope formation. The spatial and time-related deformation of this site also exhibited four stages, including initial toppling, toppling development, intensification of toppling, and disintegration and collapse. Subsequently, the mechanism of toppling and deformation of the bank slope were studied. The results of this study exhibit important reference value for developing the prevention–control design of toppling and for ensuring operational safety in the hydropower reservoir area.

High Slope Stability of Diversion Power System Intake of Jinchuan Hydropower Station

The excavated height of the left bank slope of the diversion power system intake in Jinchuan hydropower station is about 16o m. The stability and safety of the slope during construction and its operation/utilization become one of the most important geological engineering problems. At the same time, it is also crucial to select a safe and economic excavation gradient for the construction. We studied the problem of how to select a safe and economic slope ratio by analyzing the geological condition of the high slope, including the lithology, slope structure, structural surface and their combinations, rock weathering and unloading, hydrology, and the natural gradient. The study results showed that the use of an excavation gradient larger than the gradient observed during site investigation and the gradient recommended in standards and field practice manuals is feasible. Then, we used the finite element method and rigid limit equilibrium method to evaluate the stability of the excavation slope under natural, rainstorm and earthquake conditions. The calculated results showed that the excavated slope only has limited failure, but its stability is greatly satisfactory. The research findings can be useful in excavation and slope stabilization projects.

Safety monitoring and stability analysis of left abutment slope of Jinping Ⅰ hydropower station

Safety monitoring and stability analysis of high slopes are important for high dam construction in high mountainous regions or precipitous gorges. In this paper, deformation characteristics of toppling block at upper abutment, deforming tensile rip wedge in the middle part and deep fractures are comprehensively analyzed based on the geological conditions, construction methods and monitoring results of left abutment slope in Jinping Ⅰ hydropower station. Safety analyses of surface and shallow-buried rock masses and the corresponding anchorage system are presented. The monitoring results indicate that the global stability of the large wedge block in the left abutment is effectively under control, and the abutment slope is stable in a global sense. After the completion of excavation, the deformations of toppling block at the top of the slope and deep fracture zone continue at a very low rate, which can be explained as 'rock mass creep'. Further monitoring and analysis are needed.

楞古水电站V线右岸边坡深部裂隙成因及边坡稳定性分析

针对楞古水电站V线右岸边坡深部裂隙发育特征,以边坡工程地质条件及坡体结构为基础,结合嘎夏帕滑坡破坏模式对其深部裂隙成因进行了分析,认为其深部裂隙是由于边坡滑移-剪切变形所造成,且边坡缓倾角结构面发育程度决定了边坡深部裂隙分布范围及张开度。分析边坡深部裂隙变形程度,结合边坡整体稳定性FLAC3D模拟,得出蓄水后边坡上游侧稳定性较边坡下游侧更低,以后对边坡采取合理的支护措施提供了可靠的依据,并为同类水电站蓄水边坡稳定性研究提供了参考。

Evaluating the success of engineering disturbed slope eco-restoration in the alpine region, southeast Qinghai-Tibet Plateau, China

Slope eco-restoration has always received extensive attention as a positive way to reverse ecosystem deterioration derived from human interventions.A simplified frameworkis proposed to undertake a quantitative evaluation of the engineering disturbed slope eco-restoration success in the alpine region,southeast Qinghai-Tibet Plateau.The Daguhydropower project that disturbsthe local ecosystem to some certainwas selected as the study area.Since August 2018,six types of slope(soil,rock,soil-rock,spoil,construction site,hardened)were served as the demonstration test for the slope eco-restoration with two years monitoring in the study area.Meanwhile,the topography,erosion,soil quality,and vegetation were selected as assessment indicators of the methodology.Finally,combined with the weighting method and the expert panel,the slope eco-restoration quality index(SERQI)was established and applied in the six slopes.The results suggested that the frost-resistant ecological substrate performed well in alpine region,and the SERQI value is in accordance with the actual monitoring level with spoil slope>soil slope>construction site slope>soil-rock slope>rock slope>hardened slope.The proposed framework could support slope eco-restoration practitioners for making a more objective and quantitative evaluation easily for the post-implementation restoration.

Evaluation of the possible slip surface of a highly heterogeneous rock slope using dynamic reduction method

A new method, the dynamic reduction method(DRM) combined with the strain-softening method, was applied to evaluate the possible slip surface of a highly heterogeneous rock slope of the Dagangshan hydropower station in Southwest China.In DRM, only the strength of the failure elements is reduced and the softening reduction factor K is adopted to calculate the strength parameters. The simulation results calculated by DRM show that the further slip surface on the right slope of the Dagangshan hydropower station is limited in the middle part of the slope, while both SRM(strength reduction method) and LEM(limit equilibrium method) predict a failure surface which extends upper and longer. The observations and analysis from the three recorded sliding events indicate that the failure mode predicted by DRM is more likely the scenario.The results in this study illustrate that for highly heterogeneous slopes with geological discontinuities in different length scales, the proposed DRM can provide a reliable prediction of the location of the slip surface.

Slide和Geo-Slope在土质边坡中的应用

为验证Slide和Geo-Slope两个边坡稳定分析软件可靠性和准确性,选取论解验证、均质土坡、非均质土坡和均质土坡+水4个考题算例,通过与考题裁判解对比,证明这两款软件计算结果可靠可信。以老挝南湃水电站左坝肩边坡稳定计算分析为例,进一步证明这两款软件计算结果的可靠性。结果表明:Slide上手简单、操作简便,但是Geo-Slope功能更为强大;边坡稳定安全系数对于土体容重取饱和容重或天然容重的影响不敏感;在边坡稳定计算中,将地下水位线以下土体的有效抗剪强度参数进行人为的折减是值得商榷的。

Research on monitoring system for slope deformation

The monitoring system for slope deformation which bases on Leica （TCA series） was researched and developed. This system consists of electronic total stations, high precision thermometer, digital barometer, photoelectric frequency adjustor and other related instruments and data collection and processing software. The system can monitor a series of targets automatically to obtain accurate data of distance at predetermined time, besides, it can timely display targets＇ coordinates and deformation value, velocity, etc. in graph as well. To compare of the results of different monitoring time, we can find the problems of mine slope deformation rapidly and accurately.

西南山区高陡岩质边坡破坏模式及路径分析——以博瓦水电站左岸边坡为例

西南地区由于其丰富的水能资源储备,已成为我国水电站建设最为集中的区域。为了解决高山峡谷区修建水电站时开挖引起的高陡岩质边坡问题,以博瓦水电站左岸边坡3号危岩体为研究对象,结合无人机三维建模手段,采用赤平投影法和极限平衡法分别从定性和定量角度论述了该危岩体的变形破坏模式及路径,并借助数值模拟手段完成结果分析和验证。结果表明:3号危岩体的破坏主要受两侧优势结构面控制,属多级、多次的楔形体破坏模式,其在天然工况下较为稳定,但在暴雨、地震等极端工况下可能发生破坏;数值分析结果则表现出“先滑移后倾倒”的破坏形式,为理论分析提供支撑。研究成果对类似的高陡水电岩质边坡破坏及防治问题提供了一定的科学参考和工程经验。

坡度对铁路隧道救援站火灾烟气蔓延特性影响研究

为研究高海拔地区不同坡度条件下隧道紧急救援站火灾烟气蔓延特性,采用Fluent软件建立高海拔坡度铁路隧道紧急救援站列车火灾模型,通过分析救援站内烟气流速、温度等特征参数变化规律,探讨坡度变化对隧道救援站火灾烟气蔓延的影响。研究结果表明:列车停车时刻,随着隧道坡度由0‰变化至±30‰,隧道拱顶烟气流速峰值均逐渐减小。列车停车后,正坡度越大,烟气逆流流速峰值下降,烟气逆流长度越短;负坡度则与之相反。对于正坡度隧道,建议人员向火源的上游方向疏散逃生更安全;对于负坡度隧道而言,建议人员向火源的下游方向疏散逃生更安全。研究结果对高海拔隧道火灾防排烟系统设计以及人员疏散具有重要意义。

基于PSO-LSSVM-BP模型的高边坡力学参数反分析及稳定性评价

基于粒子群优化(PSO)算法和最小二乘支持向量机(LSSVM)算法构建非线性映射关系,结合反向传播(BP)神经网络对非线性映射关系生成的数据库进行机器学习,构建了PSO-LSSVM-BP模型确定最优岩体力学参数。PSO-LSSVM-BP模型以高边坡监测位移数据作为输入信息,通过反分析获得高边坡岩体力学参数,将反分析参数用于FLAC3D位移数值计算,结果表明模拟结果与监测数据吻合较好,验证了该模型的可行性和有效性。基于PSO-LSSVM-BP模型,对不同蓄水位下两河口水电站进水口高边坡稳定性进行了评价,发现水位是影响边坡稳定性的主要因素,随着水位上升,边坡位移逐渐增大,其表面和断层处损伤程度加深,边坡局部点安全系数有所下降,但整体点安全系数均大于1.30,有一定安全裕度。

白鹤滩水电站坝肩边坡开挖爆破振动概率分布研究

为科学准确判定岩石高边坡开挖爆破振动的概率分布形式,为岩石高边坡爆破振动幅值和频率的不确定性预测提供科学理论基础,以白鹤滩水电站右岸坝肩岩石高边坡开挖工程为研究背景,对典型开挖程序和爆破方案下的岩石高边坡爆破振动幅值和主频实测数据进行了概率统计分析,研究了岩石高边坡开挖爆破振动幅值和主频的概率分布及其主要特征。研究结果表明:正态分布和Gamma分布模型对岩石高边坡开挖预裂和主爆破质点峰值振速概率分布的拟合效果均较好,岩石高边坡开挖预裂和主爆破质点峰值振速的概率分布较好地服从正态或Gamma分布;Gamma分布模型相较于正态分布模型对岩石高边坡开挖预裂和主爆破振动视主频的概率分布存在明显拟合优势,岩石高边坡开挖预裂和主爆破振动视主频概率分布较好地服从Gamma分布。岩石高边坡预裂爆破质点峰值振速和视主频的平均值大于对应主爆破质点峰值振速和视主频的平均值,预裂爆破质点峰值振速和视主频下四分位~上四分位量值范围分别为5.4~11.6 cm/s和36.7~97.6 Hz,主爆破质点峰值振速和视主频下四分位~上四分位量值范围分别为3.8~8.9 cm/s和26.7~97.6 Hz。研究结果显示,经常采用的正态分布并不一定是岩石高边坡开挖爆破振动幅值或主频的最佳概率分布形式,其他典型岩石高边坡工程爆破振动幅值和主频的概率分布有待进一步研究。

倾角变化条件下反倾层状斜坡倾倒变形演化研究

倾倒变形是反倾层状岩质边坡的一种典型破坏模式,为了研究不同岩层倾角对反倾层状岩质边坡倾倒变形的影响,以澜沧江上游古水水电站坝前倾倒变形体为原型,从岩层倾角变化的角度出发,利用大型土工离心机试验分析了反倾层状岩质边坡的失稳破坏过程、变形演化特征与最终失稳模式等。结果表明:①反倾层状斜坡的变形演化过程基本概括为岩层压密-坡脚压裂阶段、弯折面形成-部分失稳阶段和弯折面贯通-彻底失稳3个阶段,岩层倾角的改变并不会影响斜坡阶段性演化过程;②岩层倾角越大的斜坡,斜坡形成弯折面所需时间越短,失稳破坏发生后坡体贯通性倾倒破坏深度更大,对应的变形范围越大,折断岩层的破坏程度越剧烈;③岩层倾角变化会导致斜坡的倾倒变形过程与最终失稳模式存在一定差异。倾角较小的55°和70°模型斜坡前部岩层在重力作用下发生明显弯曲倾倒变形,最终以“倾倒-弯曲-滑移”的失稳模式发生破坏;倾角最大的85°斜坡岩层发生的弯曲变形较小,最终以“倾倒-折断-崩塌”的模式发生破坏。研究结果对大型工程项目的顺利开展具有一定指导意义。

抽蓄电站粘土心墙坝浸润线及坝坡稳定变化特性

基于孔隙介质饱和-非饱和渗流理论,将物理模型试验与数值模拟相结合,研究了库水位周期升降时,粘土心墙坝上游坝壳浸润线及坝坡稳定性的变化规律及其影响因素。结果表明,坝体内部的渗流场较库水位变化具有滞后性。上游坝壳渗透系数是影响浸润线位置和坝坡稳定性的主要因素,上游坝壳渗透系数小1个数量级,上游浸润线位置要高2.60~3.00m,约占浸润线变化幅度的30%。水位降落速率、上游坝坡坡度对浸润线位置变化影响较小。此外,上游坝坡的稳定性随着水库水位周期性变化而呈周期性变化。

西藏扎拉水电站倾倒边坡失稳模式及加固措施研究

西藏扎拉水电站枢纽区边坡倾倒变形现象普遍发生,对工程的安全建设和运行带来隐患。对此,采用三维非连续分析方法,对大坝右岸倾倒边坡开挖失稳模式及加固措施开展研究。结果表明:(1)大坝右岸倾倒边坡开挖后,潜在失稳区域主要集中在开挖边坡上部钙质板岩极强倾倒区岩体内,后缘主要发生边坡上部崩坡积层破坏,失稳岩体沿着钙质板岩极强倾倒变形区和弱倾倒变形区分界面滑动,呈现典型的“滑移-拉裂”型变形破坏模式;(2)锚索+锚杆的联合支护措施可有效限制开挖施工期间大坝右岸倾倒边坡上部钙质板岩极强倾倒区岩体的变形。采取支护措施后,大坝右岸倾倒边坡各工况下的安全系数均可满足规范要求。

抽水蓄能电站水库岩质边坡消落带生态修复探讨

抽水蓄能电站是我国水利水电开发的重要组成部分,建成运行后将形成库水周期性涨落的消落带,生境条件极为脆弱,是生态环境修复的重难点区域。对岩质边坡生态修复关键技术和水库消落带生境改善方法开展系统分析,结合河南天池抽水蓄能电站上水库岩质边坡消落带生境特征,提出土工格室+生态袋+挂网复合工程技术可作为水库岩质边坡消落带生态治理的关键措施。基于消落带库水涨落节律和植物自身遗传特性,指出消落带下端优先配置长期耐淹多年生草本植物(如狗牙根),消落带中端配置耐淹能力较强的灌木和草本(如秋华柳、黄荆、紫穗槐、中华蚊母和狗牙根等),消落带上端可综合配置抗旱耐淹能力较好的乔木、灌木和草本(如银合欢、桑树、紫穗槐、黄荆、秋华柳、狗牙根和苘麻等),以及生态适应性较强的乡土植物(如藜和诸葛菜等)。研究成果对抽水蓄能电站水库岩质边坡消落带生态治理具有重要指导意义。

基于InSAR的乌东德水电站库区边坡形变监测及分析

水电站建成投产后,水库水位变化频繁,改变了库岸边坡原有的稳定性,易诱发边坡失稳破坏,从而对水电站的安全运行及周边居民区产生一定安全隐患。为了更好地掌握乌东德水电站蓄水过程中库区边坡的形变情况,通过SBAS-InSAR技术对该区域2020年5月至2022年8月间的升降轨哨兵数据进行解算,获取了研究区的地表形变特征;结合库水位变化情况、SAR数据反演出的边坡土壤含水量后向散射系数,对识别出的5处不稳定区域的形变机理进行分析。结果表明:运用升降轨InSAR可准确识别出库岸边坡的形变情况,研究区最大年平均沉降速率为-92 mm/a;库岸边坡的形变趋势与库水位及土壤含水量后向散射系数变化有着明显的相关性,水库蓄水是致使边坡体加速沉降的主要因素。

新疆阜康抽水蓄能电站含泥夹层变形体稳定性分析

新疆阜康抽水蓄能电站上水库0号变形体底部含泥夹层较为发育,严重威胁工程稳定运行。为了评价含泥夹层变形体稳定性,基于变形体有限元分析以及表面位移、测斜孔位移监测数据,研究变形体失稳破坏特征及位移时空变化规律。结果表明:变形体在天然情况下处于稳定状态,在压坡体的作用下,边坡整体安全系数由1.33提高至1.51,安全系数较天然状态下增加13.5%。压坡处理后变形体稳定性明显提高,但是含泥夹层的强度参数对变形体稳定性影响较大,含泥夹层强度参数降低40%,变形体整体安全系数低于1.0。变形体各表面变形测点累计水平位移最大8.56 mm,累计垂直位移最大10.03 mm;测斜孔上下游与左右岸最大平均位移不超过0.6 mm。变形体的变形主要表现为沿含泥夹层蠕滑变形,应在工程施工、水库蓄水及运行期间对变形体不同部位进行系统的变形监测工作。

西藏扎拉水电站陡倾层状岩质边坡稳定性分析及支护设计

为探究陡倾层状岩质边坡支护设计及稳定计算方法,结合扎拉水电站边坡开挖支护工程,通过分析边坡结构类型,研究边坡整体失稳破坏模式,分别考虑锚杆抗拉和抗剪作用,分析锚固力对边坡稳定性的影响规律,探究该边坡顺层滑移稳定性及支护设计方案。计算结果表明:不同规范推荐的安全系数计算方法得到的边坡稳定分析结论基本一致,考虑锚杆抗剪作用计算得到的边坡抗滑稳定安全系数较大,且数值计算分析结果验证了支护设计方案的合理性。研究成果可为类似边坡治理工程提供参考。

新疆阜康抽水蓄能电站工程上水库渗流三维有限元分析

为分析各水位工况下阜康抽水蓄能电站上水库坝体及坝基渗流场,获得坝体和坝基的位势分布、库区渗透流量等要素,根据工程坝址区地质、地形条件,建立渗流三维有限元模型并进行计算。计算结果表明,由于全库盆混凝土面板防渗方案库盆四周均布置了混凝土面板,库周和库底混凝土面板底下分别设有透水性较强的无砂混凝土垫层和碎石垫层用以排水,库区地下水位低于库盆防渗面板及其底下垫层。因此,无砂混凝土垫层和碎石垫层及其库底回填区和上部岩体均处于非饱和状态,不会直接作用在防渗结构上,因此库周及库底混凝土面板的抗浮安全性可以得到保证,本方案技术上是合理的。