武都碾压混凝土重力坝深层抗滑稳定破坏试验研究

通过建立武都碾压混凝土重力坝典型坝段坝基的地质概化模型,采用三维地质力学模型试验方法对其天然地基条件下的深层抗滑稳定问题进行系统研究.试验对典型坝段的地形、地质条件,包括岩体、断层、节理等主要地质缺陷的特征进行模拟,根据岩体力学参数及软弱结构面力学参数,研制出适合武都工程地质条件的模型材料,采用超载法进行破坏试验研究.根据试验结果,分析坝体、坝基以及主要断层的变形特征,探讨坝与地基整体失稳的破坏过程、破坏形态和破坏机制,揭示影响坝基稳定的控制性因素,获得典型坝段的滑动破坏机制与稳定安全系数.在此基础上,对坝基加固处理措施进行讨论,为典型坝段的深层抗滑稳定安全评价与基础加固处理设计提供科学依据.     

大岗山双曲拱坝整体稳定三维地质力学模型试验研究

针对大岗山双曲拱坝的工程地质问题,采用三维地质力学模型试验技术,研究坝体和坝肩从加荷到破坏的整个过程和机制.试验过程模拟大坝基础的不连续岩体条件、岩体力学特性和整体双曲拱坝.试验考虑拱坝上游超载情况,同时还模拟两坝肩岩体中软弱结构面强度弱化的影响,为此研制适合该工程的变温相似材料及试验模拟新技术,并在一个模型上进行强度储备与超载相结合的综合法试验.试验结果给出拱坝在正常蓄水位和降强之后超载作用下的位移场,获得坝体和坝肩的变形及分布特征、内部断层典型测点的相对位移,揭示拱坝坝体和坝基失稳前后裂缝发展的全过程及其破坏机制.得到强度储备系数为1.25,超载系数为4.0～4.5,确定拱坝坝肩坝基整体稳定安全度为5.0～5.6.对试验数据的综合分析,可以评价边坡的稳定性,并针对坝肩的薄弱环节提出加固处理措施建议.     

小湾高拱坝整体稳定三维地质力学模型试验研究

 结合小湾高拱坝坝肩坝基的地形、地质特征、软弱结构面分布状况、浅层松弛卸荷现象以及加固处理方案,建立三维地质力学模型,研制主要断层的变温相似材料,运用超载与降强相结合的综合法对整体模型进行破坏试验。通过试验获得小湾拱坝坝肩坝基的变形特征、失稳的破坏过程、破坏形态及破坏机制,得到强度储备系数为1.2,超载系数为3.3～3.5,确定拱坝坝肩坝基整体稳定综合法试验安全系数为3.96～4.20。对试验数据的综合分析得出,两坝肩中上部高程部位由于对断层和蚀变带采用了混凝土洞塞置换,其变位相对较小,破坏形态和破坏范围相对较轻,说明混凝土加固洞塞置换起到较好的加固效果。根据试验显示的破坏形态和破坏区域,建议对右坝肩下游1 245 m高程以上的断层F11和F10做一定范围的处理,对左坝肩推力墩以上部分岩体进行适当的加固处理。     

具有软弱夹层的岩基重力坝超载模型试验研究

我国已建与待建的大中型混凝土与浆砌石坝工程,遇到基岩有软弱夹层的情况很多。根据1975年初步统计,有92处出现此种情况。软弱夹层是岩体中最簿弱的部位,故在工程的勘测阶段就必须对坝基软弱夹层的埋藏及分布给予特殊注意。由于坝基存在软弱夹层,对大坝的应力分布及抗滑稳定都会带来不利影响,故必需针对不同情况采取加固处理措施,以保证大坝的安全运用。目前国内外对于具有软弱夹层岩基混凝土坝的应力及稳定分析,常利用电子计算机进行有限单元法计算,而对地质情况身杂或三维的问题,则常采用结构模型试验的方法进行研究分析。华北水利水电学院自1972年以来,曾先后结合河北朱庄水库、湖南双牌水库及河北大黑汀水库等工程,进行超载模型试验,用以分析具有软弱夹层的岩基重力坝抗滑稳定性及加固处理措施的效果,取得了成功的经验。当坝基处于弹性状态时,超载试验的成果可以满足定量的要求,为工程提供重要的安全指标。本文对该项试验研究作一综合介绍,并提出分析意见,供参考。     

浅谈软弱土地基的处理

如何防止建筑物开裂破坏和整体滑动等质量问题的发生,是工程所关注的,因此必须重视地基的变形和稳定问题。对软弱地基处理,消除软弱地基对上部建筑物的不利影响,处理的优劣,将关系到整个工程的质量。处理的目的是要提高软弱地基的强度,保证地基的稳定,降低软弱土的压缩性减少基础的沉降和不均匀沉降。     

浅谈软弱土地基的处理

如何防止建筑物开裂破坏和整体滑动等质量问题的发生,是工程所关注的,因此必须重视地基的变形和稳定问题。对软弱地基处理,消除软弱地基对上部建筑物的不利影响,处理的优劣,将关系到整个工程的质量。处理的目的是要提高软弱地基的强度,保证地基的稳定,降低软弱土的压缩性减少基础的沉降和不均匀沉降。     

地质力学模型试验在某拱坝稳定分析中的应用

采用三维地质力学模型试验技术,研究某双曲拱坝坝基内的软弱夹层和裂隙对坝体整体稳定性的影响,以及在超载情况下的坝体的破坏形式和破坏发展过程,从而对大坝的安全性作出了科学评价。     

木里河立洲拱坝整体稳定地质力学模型试验研究

采用三维地质力学模型超载法试验,对立洲拱坝的整体稳定性进行研究,在模型中充分反映断层、层间剪切带、裂隙密集带及长大裂隙等复杂地质构造对拱坝与地基整体稳定性的影响。通过超载法破坏试验获得坝体、坝肩、坝基岩体及结构面的变形特征、破坏失稳过程、破坏形态和破坏机制,揭示影响稳定的控制性因素和工程薄弱部位,确定拱坝与地基在各阶段的超载安全系数为：起裂超载安全系数K1 = 1.4～2.2,非线性变形超载安全系数K2 = 3.4～4.3,极限超载安全系数K3 = 6.3～6.6。通过对比分析类似拱坝工程的超载法试验结果可知,立洲拱坝的超载安全系数在统计分布范围之内,但两坝肩中上部的岩体和结构面局部破坏较严重,需对这些薄弱部位进行重点加固处理,以进一步提高坝与地基的整体稳定安全性。     

胶凝砂砾石坝深层抗滑稳定模型试验研究

胶凝砂砾石坝(CSG坝)是一种新坝型,目前学术界主要针对坝体的结构形式、应力分布及结构强度等方面展开了研究,而关于地基对CSG坝的影响相关研究较少.通过设计地质力学模型试验,模拟了CSG坝在复杂地基上的正常运行及破坏状态.具体为,以守口堡大坝的典型坝段及武都水库#18坝段址区的坝基为研究对象,采用超载法,对模型进行了破...     

某工程重力坝地基深层抗滑稳定分析

结合某水坝工程6号与7号坝段坝体参数,采用两种计算方案分析了地基深层抗滑稳定性,重点计算了6号坝段第二层软弱夹层的情况,结果表明:最危险剪切破裂面的起始点在坝趾正下方,软弱夹层越深,抗滑稳定安全系数就越大,两坝段沿软弱夹层面的抗滑稳定最小安全系数均满足混凝土重力坝设计规范要求。     

Experimental study on a geo-mechanical model of a high arch dam

This paper presents the complete experimental study on the Geo-Mechanical Model of Jinping high arch dam to observe the deformation and study the stability of the dam abutment and foundations of the Jinping first stage hydropower project. The model considers various factors influencing the stability of dam abutment and foundation during the test, which includes overloading and strength-decreasing of weak structural planes in the rock mass of the dam foundation. A temperature-analogue material is employed to simulate the decreasing strength of the weak structural planes. The temperature-analogue material and model testing technique are developed for the first time. Secondly, the comprehensive method that considers both overloading and strength-decreasing is applied to the model successfully. Deformation characteristics, failure patterns and mechanisms of the dam abutment and foundation are achieved. The safety evaluation based on the experimental model indicates that the whole stability safety factor of the dam abutment and foundation is 4.7–5.0.     

A comprehensive testing method for global stability analysis of high arch dams

Hydropower projects are rapidly developing in China at present,and a number of high dams and large reservoirs are currently under construction or will soon be built.These large projects are mainly located on the great rivers in West China with complicated topographical and geological conditions.Evaluation of stability and safety of these high dam projects is an important topic.Geomechanical model test is one of the main methods to study the global stability of high dam and foundation.In this paper,a comprehensive testing method that combines overloading and strength reduction in a model is proposed.In this method,both the influence of excessive flooding and the effects of strength reduction of rock masses and weak structural planes on dam stability are considered.Thus,the comprehensive testing method can accurately incorporate multiple factors that affect the global stability of high dam and its foundation.Based on the failure testing principle and model similarity theory,a similarity relation formula for safety evaluation through comprehensive test is established.A new model material,temperature-dependent analogous material,is also developed.By rising the temperature and reducing the strength of the model material,the mechanical behaviors resulting from gradual strength reduction can be simulated.Thus,the comprehensive testing method is realized in a single model.For case studies,the comprehensive geomechanical model test is conducted for Jinping I and Xiaowan high arch dam projects.     

高拱坝坝肩坝基整体稳定地质力学模型试验研究

锦屏一级水电站是雅砻江干流上的重要梯级电站。工程主要开发任务是发电，同时还兼有拦沙、防洪、蓄能作用。该工程大坝为混凝土双曲拱坝，最大坝高305m，为目前世界上最高拱坝。坝址区地质构造复杂，两岸谷坡为近千米的高陡边坡，两坝肩岩体内存在断层、煌斑岩脉、层间挤压带、深部裂隙等各类软弱结构面，对拱坝坝肩坝基稳定带来不利影响。采用三维整体地质力学模型试验研究方法，研究了锦屏一级高拱坝坝肩坝基的整体稳定性。试验中充分考虑了影响坝肩坝基稳定的各种因素，既考虑拱坝上游超载情况，同时还重点模拟两坝肩岩体中软弱结构面强度弱化的影响，为此研制了适合该工程的变温相似材料及试验模拟新技术，并在一个模型上进行了强度储备与超载相结合的综合法试验。通过试验获得了坝肩坝基的变形及分布特征、失稳的破坏形态和破坏机理，确定了拱坝坝肩坝基整体稳定安全度为4．7～5．0，评价了工程的安全性，并针对坝肩的薄弱环节提出了加固处理措施建议。     

白鹤滩水电站拱坝及坝肩加固效果分析及整体 安全度评价

 白鹤滩水电站拱坝左侧坝肩断层及层间、层内错动带发育,拱推力作用下易发生剪切变形。坝基柱状节理层发育,变形模量等力学指标相对较低,表现出显著的各向异性力学特性。由于以上地质缺陷的影响,设计采取沿拱推力方向设置抗剪洞及扩挖坝基处柱状节理层岩体设置垫座的工程处理措施,以期对坝肩、坝基岩体的抗剪、传力等进行改善。采用三维非线性数值分析方法,根据实际地质信息建立三维数值模型,模拟白鹤滩中坝址主要地质现象及相关工程措施,通过坝肩、坝基岩体及坝体的应力、位移对比,定量分析主要地质缺陷的影响以及工程处理措施的效果。采用超载法、强度折减法及点安全系数法评价下坝线拱坝的安全度,为该水电站坝线比选提供技术依据和科研成果支撑。     

Numerical analysis of geocell-reinforced retaining wall failure modes

Numerical analyses on the failure mode of geocell-reinforced retaining walls by the finite element strength reduction technique are reported. The effectiveness of the numerical model was validated by the centrifuge model test results. Parametric studies were conducted using the calibrated finite element procedure to investigate the effects of the apparent cohesion of geocell-reinforced soil, the friction between the wall base and the footing, the weak interlayer in the wall, and the layout of the two-tiered geocell-reinforced retaining wall on the failure surface and the factor of safety. The study results indicated that when the apparent cohesion was very large, or the friction between the wall and the footing was small, or there existed a weak interlayer in the wall, sliding failure was found to occur in geocell-reinforced retaining walls, similar to the failure mode of rigid retaining walls. Coulomb's wedge theory was suitable for the stability analysis of geocell-reinforced retaining wall in these conditions. However, in other conditions, which are more relevant in engineering applications, the failure mode of geocell-reinforced retaining walls was similar to that of slopes and the strength reduction technique for the stability analysis of slope may be suitable to analyze the stability of geocell-reinforced retaining walls.     

Stability assessment of the Three-Gorges Dam foundation, China, using physical and numerical modeling—Part II: numerical modeling

Sliding in a dam foundation along potential sliding paths is generally caused by two kinds of external factors: one is the overloading of the designed upstream hydrostatic load due to flooding; and the other is the gradual degradation of the shear strength of joints due to seepage, deformation, damage, and geochemical reactions between water and joint surface minerals. Based on the conceptualized geomechanical model of the Three-Gorges Dam, described in the Part I paper, in this Part II paper the limit equilibrium method and finite element method are used to study the effects of gradual degradation of the shear strength of joints on the stability of the dam foundation. The numerical modeling focuses on the stability conditions of the no. 3 powerhouse-dam section which are estimated to be the most critical. The constraint influences from the adjacent no. 2 and no. 4 powerhouse-dam sections are also included. The failure mechanisms, factors of safety and critical displacements of these dam sections are derived numerically as the measures for stability evaluation. The factor of safety is defined as the ratio between the combined shear strength of joints and intact rock bridges, and the mean shear stress along potential sliding path required for limit equilibrium under the designed external loads. All the results obtained from these different numerical models, together with the results of physical model tests as presented in Part I, are compared in this paper. The comparisons show that both the numerical modeling and physical modeling results support each other and demonstrate the stability of the Three-Gorges Dam foundation as designed. Nevertheless, considering the overall engineering and social–economical importance of the Three-Gorges Dam complex, some additional treatment and reinforcement measures are recommended in this paper.     

拱坝-坝肩三维可变形离散元整体稳定分析

三维可变形离散元是模拟不连续介质力学行为的有效数值分析方法。由于该方法采用显式差分方法和自动接触检索技术，故尤其适合于求解弹塑性、大变形和动力问题。首先介绍三维可变形离散元的基本原理及特点。然后对拱坝一坝肩系统整体抗滑稳定进行超载仿真分析和强度折减仿真分析。分析结果表明：超载计算时，拱坝坝肩失稳可能性很小，但是，当水压超载到3．5-4．0倍时，坝体材料会出现较大范围的受压屈服；强度折减计算时，当结构面强度折减3．5倍时，拱坝左坝肩在水压和渗压的作用下开始向下游坍塌，并最终导致拱坝失去支撑而溃决。