黄土动力特性试验及深厚黄土地基上土石坝抗震分析研究

对某深厚黄土地基上土石坝的坝基黄土和筑坝黄土进行动三轴和共振柱等动力试验,求得其动强度、动应力-应变关系,以及用于计算动孔压的动孔压特性曲线及其他动参数。在静力分析的基础上对大坝连同地基进行了三维有效应力动力分析。计算表明,Ⅶ度地震下黄土坝基会出现液化,危及大坝安全。为此,建议了距上下游坝脚一定范围内对坝基进行填土压重的经济便利的大坝抗震措施,并对填土压重的抗液化效果进行了优化分析,最终得到经济合理的填土压重范围和压重厚度。     

Influence of overburden pressure and soil rigidity on uplift behavior of square plate anchor in uniform clay

A numerical study incorporating three-dimensional Eulerian large deformation finite element analyses is performed to investigate the pullout process of horizontal square plate anchors in both hypothetical weightless soil and soil with self-weight. The validity of the numerical model is established through verification against published experimental and numerical results. The failure mechanisms during the pullout process under different conditions are then investigated. Three types of failure mechanism are observed; of which only two have been reported in the literature. The third mechanism identified in this study, which is a partially localized flow mechanism, is operative when the soil overburden ratio is not high enough to mobilize the full flow mechanism. The influence of soil self-weight is directly investigated by incorporating the density of the soil in the finite element model and maintaining the gravitational acceleration field throughout the analysis. The critical overburden ratio corresponding to the full transition to a localized plastic flow mechanism is identified in this study. The effect of the soil rigidity index (E/s_u) on the anchor uplift capability has not been systematically investigated in earlier studies. Contrary to the general failure mechanism and the full flow mechanism described in the literature, the capacity factor corresponding to this new mechanism increases with increasing E/s_u. The capacity factors for square plate anchors corresponding to different anchor embedment ratios, overburden ratios and E/s_u are provided in the form of design charts.     

陕北油田二开井段提下钻遇阻原因分析与对策

陕北油石二开井段遇阻的原因为泥岩的水化膨胀和孔隙性砂岩的泥饼沉积。对策主要有物理方法（如短程起下钻、加大排量等） 、化学方法（加入强抑制剂ＦＡ３６７、加入ＧＰＳ,提高泥饼质量） 等。     

Experimental and analytical studies on earthquake resisting behaviour of confined concrete block masonry structures

To improve the seismic performance of masonry structures, confined masonry that improves the seismic resistance of masonry structures by the confining effect of surrounding bond beams and tie columns is constructed. This study investigated the earthquake resisting behaviour of confined masonry structures that are being studied and constructed in China. The structural system consists of unreinforced block masonry walls with surrounding reinforced concrete bond beams and tie columns. The characteristics of the structure include: (1) damage to blocks is reduced and brittle failure is avoided by the comparatively lower strength of the joint mortar than that of the blocks, (2) the masonry walls and surrounding reinforced concrete bond beams and tie columns are securely jointed by the shear keys of the tie columns. In this study, wall specimens made of concrete blocks were tested under a cyclic lateral load and simulated by a rigid body spring model that models non‐linear behaviour by rigid bodies and boundary springs. The results of studies outline the resisting mechanism, indicating that a rigid body spring model is considered appropriate for analysing this type of structure. Copyright © 2006 John Wiley & Sons, Ltd.     

公路隧道内轮廓形状的数值优化

以云南富广高速公路的老鹰咀隧道为实例,应用有限元数值方法对隧道砌衬的内力进行了模拟与分析。通过调整隧道仰拱和曲面墙的连接方式,来获取较为合理的隧道内轮廓形式。首先,基于围岩类型和初次衬砌的结构型式,建立了该隧道的数值模型,依据隧道规范实施加载,考虑了围岩的弹性抗力;然后,根据数值模拟结果,对原设计断面和添加了过渡圆的隧道断面的内力分布进行了讨论比较。优化结果为单洞大跨隧道的截面设计提供了理论依据。     

Digital world meets urban planet – new prospects for evidence-based urban studies arising from joint exploitation of big earth data,information technology and shared knowledge

ABSTRACT

The digital transformation taking place in all areas of life has led to a massive increase in digital data – in particular, related to the places where and the ways how we live. To facilitate an exploration of the new opportunities arising from this development the Urban Thematic Exploitation Platform (U-TEP) has been set-up. This enabling instrument represents a virtual environment that combines open access to multi-source data repositories with dedicated data processing, analysis and visualisation functionalities. Moreover, it includes mechanisms for the development and sharing of technology and knowledge. After an introduction of the underlying methodical concept, this paper introduces four selected use cases that were carried out on the basis of U-TEP: two technology-driven applications implemented by users from the remote sensing and software engineering community (generation of cloud-free mosaics, processing of drone data) and two examples related to concrete use scenarios defined by planners and decision makers (data analytics related to global urbanization, monitoring of regional land-use dynamics). The experiences from U-TEP’s pre-operations phase show that the system can effectively support the derivation of new data, facts and empirical evidence that helps scientists and decision-makers to implement improved strategies for sustainable urban development.     

ERODIBILITY CRITERION FOR AUXILIARY SPILLWAYS OF DAMS

lINTRoDUCTIONDamshavebeendesignedtraditionallynottobeovertoppedduringprobablemaximumfloodevents.AccordingtoPowledgeet.aI.(l989),manytensofthousandsofdamshave,however,becomepotentiallysubjecttoovertoppingasaresuItofimprovementsinthequalityofflooddataandinthemethodsfordeterminingprobablemaximumfloodsforwhichitisnotpossiblenoreconomicallyfeasibletoconsidermodificationstopreventovertopping.SomedamshavemoreoverbeenobservedtohavewithstoodmoderateoveFtopping.Effortshaveasaresultbeenconcentrated…     

Modified approach to evaluation of undrained shear strength from piezocone tests in soft clays

This paper proposes a modified-theoretical approach to interpreting the undrained shear strength from piezocone tests in clays. Assuming the shear and normal stresses on the cone face to be the friction at the cone–soil interface and the ultimate expansion pressure, respectively, an expression of the tip resistance is first derived at force equilibrium. The undrained shear strength is then determined by combining the derived expression of tip resistance with the formulation for pore pressure at the cone shoulder position. Many factors, such as the penetration rate and the cone roughness, are considered in this model. Different shaped model penetrometers, including cone- and ball-shaped ones, are adopted in centrifuge tests to investigate the validity of the proposed method. The undrained shear strength estimated from the piezocone test is found to agree well with that from ball penetrometer test. Case studies are also presented to show the application of the proposed method. Comparisons between the predicted and measured values of undrained shear strength indicate that the proposed approach is generally applicable for nonfissured clays, especially intact clays.     

由星载GPS相位数据确定地球重力场模型若干问题研究

人造地球卫星在地球引力场中运动,可以探测地球重力场的长波信息。随着GPS技术的发展,星载GPS技术日趋成熟,因此由星载GPS相位数据确定地球重力场模型是当前国际地学研究的热点之一。本文给出了确定地球重力场模型中的星载GPS星地相位双差观测量,阐述了Cowell II数值轨道积分公式,导出了参数估计中星地双差观测量的偏导数,利用分块Bayes最小二乘参数估计地球引力场位系数等有关参数。     

粤北下庄矿田小水铀矿床地球化学特征分析

粤北小水矿床是下庄矿田典型的交点型铀矿床。通过对矿床内发育的花岗岩、辉绿岩及铀矿石采样分析．发现小水矿床矿石具有轻稀土富集的稀土元素特征和富集大离子亲石元素Rb、Th的微量元素特征。与辉绿岩的相应特征十分吻合,与花岗岩的相应特征差异很大,推测其成矿物质来源于深部地幔流体（富含U、F、CO2）,且交点型矿石的形成很有可能伴有幔源成矿流体对与花岗岩有关的早期红化矿石的叠加改造作用。