Centrifuge Model Tests on a Cohesive Soil Slope Under Excavation Conditions

Problems induced by slope excavations are quite common. An in-flight excavation device was realized to simulate the live excavation of slopes at high g levels during centrifuge model tests. A series of centrifuge model tests was conducted to simulate the excavation of a slope at different inclinations and heights, and the effect of the excavation size was taken into consideration. The displacement histories of points over the slope were measured by an image capture and displacement measurement system. Measurement results showed that the excavation-induced deformation process could be divided into several phases with different displacement distribution features. The excavation was found to only affect a restricted zone of the slope whose boundary could be outlined by an A-surface. A strain analysis was conducted to determine the excavation-induced strain localization area of the slope. The degree of strain localization increased as the excavation time increased, but the width of the strain localization area was nearly invariable. Shear failure first occurred near the excavation surface and then extended upwardly to the slope surface under excavation conditions, while tension failure played a dominant role in the upper part of the slip surface. The strain localization area moved towards the slope surface with an increasing slope inclination. The lower part of the final slip surface was located in the strain localization area.     

大坝堆石体压缩模量计算方法的改进

为提高大坝堆石体压缩模量计算方法的适应性和可靠性,通过分析传统计算方法受拱效应影响较大的局限,提出了采用沉降仪的沉降值和土压力计的压应力值共同计算堆石压缩模量的方法.通过对比2座200 m级堆石坝实测成果,证明引入土压力计的压应力值后,能够取得比较明显的改进效果.     

基于TOPSIS法的堆石坝施工效果综合评价

堆石坝种类较多,堆石体填筑质量的优劣是这类大坝安全运行关注的核心问题之一。在施工过程中,每一个填筑单元质量效果评价因素包括单位面积碾压时间T(i)、碾压超速次数N(i)、振动状态不达标次数L(i)、碾压遍数合格率R(i)和平均压实厚度H(i)。基于此,通过决策矩阵模型计算出各个指标的权重,采用了TOPSIS法计算每个填筑单元各指标的最优隶属度进而排序,形成矩阵模型。从施工进度和质量两方面系统地对堆石坝施工质量效果进行评价。TOPSIS法能够较为客观、全面地反映堆石坝填筑质量的优劣,便于对每一个填筑单元进行及时监控和评价。该方法简单,计算方便,可用于土石坝填筑质量的综合评价。     

垃圾填埋场防渗衬垫特性的离心模型试验与数值分析研究

垃圾填埋场中垃圾体和防渗土工膜的受力变形特性是普遍关心的问题,在现场试验尚无法获得满意的监测结果时,利用离心模型试验和有限元数值分析进行探讨性研究也是可以尝试的途径。通过离心模型试验研究和有限元计算,模拟了垃圾填埋场中填埋垃圾大变形条件下土工防渗膜的变形性状,在模型比率80的条件下,可以找到相应的模型材料来模拟实际工程中的土工膜;选用的防渗膜模拟材料和木屑土能较好地模拟垃圾填埋场中材料;邓肯-张模型和Goodman接触面模型能模拟垃圾土和土工膜以及界面的工作状态;土工膜中最大拉应力靠近坡肩,可达到极限抗拉强度的1/1.5倍;考虑到HDPE膜的抗拉安全,最大设计坡长应加以控制。     

面板堆石坝砂砾石料填筑碾压试验研究

利用天然砂砾石进行大坝填筑,其碾压参数直接影响到大坝施工进度和沉降变形,也直接影响到大坝施工成本和安全稳定,碾压参数的优化一直是大坝填筑施工技术研究重点。为有效地指导现场施工,以某一工程为案例,通过面板堆石坝砂砾石料填筑碾压试验研究,分析数据成果,提出大坝填筑碾压参数。     

Long-term behavior and safety assessment of Sance Rockfill Dam

Safety assessment of the 62 m high Sance Rockfill Dam based on long-term monitoring results and their simulation by numerical models is presented in the paper. Unexpectedly large settlements and horizontal movements of the crest together with the steep downstream slope questioned the safety of the dam. Calibrated 2D and 3D models fitting the monitoring results were applied for the safety assessment of the dam including slope stability analysis and estimation of the clay core cracking and hydraulic fracturing hazard. The modeling results contributed to the rehabilitation concept and project of the dam.     

Analysis of Results of Consolidation Tests of Saturated Clayey Soils

It is shown that the dependence of soil deformation on the distance to the drainage boundary, which is noted by a number of experimenters for the stage of secondary consolidation, is explained by incorrect interpretation of test data. Laboratory results demonstrating an apparent lack of creep in the stage of primary consolidation are explained by characteristic features of the generalized consolidation equations and relationships between their parameters.__________Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 7–10, May–June, 2005.     

Nonlinear Earthquake Response Characteristics of a Central Clay Core Rockfill Dam

The effect of the 2008 Iwate-Miyagi Nairiku earthquake (M_J 7.2), Japan on the Aratozawa dam, which is a 74.4 m high rockfill dam with a central clay core located in the area, was studied with a main focus on the change in the vibration period, shear wave velocity, shear modulus, and pore-water pressure. In a vertical section of the central part of the dam, three sets of 3-component accelerometers and 15 pore water pressure meters were installed. During the main shock, the acceleration exceeded 10 m/s² at the gallery, inducing large shear strains in excess of 10^-3 and a sudden build-up of the excess pore water pressure in the core. Due to the large strains, the shear wave velocity and shear modulus showed a significant decrease from their initial values and the vibration period was elongated. The decreased shear wave velocity gradually recovered toward the end of the main shock, and continued to recover with the passage of time. The full recovery of the wave velocity was found to take at least one year, while the dissipation of the excess pore water pressure proceeded more quickly than the recovery of the wave velocity.     

用离心模型研究超高填方地基变形特性

在 4 0 0gt大型土工离心机上对 5 7～ 85m厚的高填方地基的差异沉降和最终沉降变形特性进行模拟。土工离心模型预测了该地基 72个月 (包括施工期 38个月 )时间～沉降过程发展曲线。试验结果表明 ,大型离心机模型试验是研究上述工程问题的有效手段 ,所得结论对合理确定地基处理方案、加固处理深度和加固程度以及回填所需方量具有参考价值和指导意义。     

基于三轴试验的南水模型参数的确定方法

土的本构模型是反映土体应力-应变关系的数学表达式。南水模型是弹塑性模型中的一种,其综合了邓肯-张模型和剑桥模型的优点,并采用多重屈服面,克服了邓肯-张模型和剑桥模型不能模拟围压或平均压力不断减小的应力路径的缺点。简单介绍了南水模型的屈服方程及其参数的推导过程,介绍了获得郑州地区主要土层的南水模型参数的方法:首先对郑州地区的粉土进行饱和,然后利用三轴剪切仪对其进行三轴剪切试验,通过对试验数据的整理与分析,确定南水模型的参数。     

钻芯法检测混凝土强度对比试验的数理统计分析

运用配对设计的差值均数与总体均数0作比较的t检验法,对两站钻芯法检测混凝土强度值进行数理统计分析,结果表明芯样的切割、打磨和试压过程容易出现问题,其端面修补厚度和平整度、试压初始速度等对混凝土强度检测值影响较大。     

吹填淤泥质土井点降水模型试验研究

针对吹填淤泥质土渗透性差和含水量较高等突出特点,依据真空井点降水的室内模型试验,采用单井点与群井不同形式的研究方法,对土层真空度、孔隙水压力以及其土工试验指标等进行了测试分析并总结了相应的变化规律,在此基础上考察其加固效果,并得出真空井点降水方法对于淤泥土有一定的加固作用。     

模拟地震振动台模型实用设计方法

本文根据振动台模型试验的经验，介绍了模拟地震振动台试验设计的实用流程和设计思路；提出了不用明确求出π数表达式的似量纲分析法，来求解各相似常数；并阐明考虑模型混凝土强度和钢筋强度之间采用不同的相似系数的原更口以及模型设计中的一些注意事项。     

沉管砂桩与强夯法联合加固吹填土地基试验研究

结合沉管砂桩与强夯法联合加固吹填土地基的现场试验,研究强夯过程中夯坑沉降量的变化过程、地层孔隙水压力的增长和消散规律及其空间分布特征.结果表明,随强夯遍数的增加,夯坑沉降量呈现明显的减小的趋势;强夯荷载作用下,地层中孔隙水压力的上升是十分明显的,且随离开强夯点水平距离的增大,最大孔隙水压力出现的深度有所下移.利用上述方...     

Geotechnical Hybrid Simulation System for One-Dimensional Consolidation Analysis

A system for a hybrid consolidation simulation was developed to predict more realistically the nonlinear behavior of the consolidation settlement of soft clay, including a large strain consolidation problem. The hybrid simulation method can introduce the mechanical behavior of the soils directly by combining numerical analysis and the soil element test in an online state. In this paper, a fundamental study to apply the hybrid simulation method to the consolidation settlement problem, a basic concept, and the corresponding algorithm and components are presented. Furthermore, using preconsolidated Kaolinite clays, verification studies were also conducted in the laboratory to verify the operational performance and data reliability of the system. On the basis of the test results, we concluded that the new consolidation analysis system using the hybrid simulation concept provided an adequate performance in the reproduction of the consolidation behavior of preconsolidated Kaolinite clays in the aspect of the dissipation of excess pore water pressure and corresponding consolidation settlement.     

混凝土面板堆石坝趾板施工技术

趾板是混凝土面板与基础之间的连接构件,其主要作用是防渗.以安徽响水涧抽水蓄能电站为例,介绍混凝土面板堆石坝的结构特点、截面参数、布置形式以及趾板与面板的连接.阐述趾板开挖、混凝土施工、锚杆施工、钢筋制作安装、模板制作安装等施工工艺.同时介绍采用板包法进行止水保护以及混凝土养护措施.     

面板堆石坝三维弹塑性有限元计算分析

通过建立面板堆石坝三维有限元模型,并采用南水模型将整个加载过程分为若干个荷载步,体现了堆石料复杂变形特性和施工分期填筑逐级加载的特点,同时采用中点增量法求解,对两种计算工况下的结果进行了整理分析比较,得出了一些有价值的结论。     

仁宗海堆石坝蓄水初期右岸绕坝渗流监测成果分析

仁宗海水库在开始蓄水后,对仁宗海堆石坝的右岸坝肩绕渗进行了跟踪监测,发现库水位在2910.00m以下时,右岸坝后绕渗水位与坝前库水位保持了很小的水头差,随着库水位的上升而上升,相关性很好,部分绕渗孔水位几乎与坝前水位持平,在库水位超过2910.00m以后,坝后坡面及左右岸灌浆廊道边墙开始出现渗水,多只绕渗孔开始冒水,水...