柔性支护结构主动土压力的变分计算方法研究

从基坑柔性支护结构后的滑动土楔体的整体静力平衡方程出发,推导了考虑作用点位置的主动土压力泛函极值等周模型。在此基础上引入拉格朗日乘子,将主动土压力问题转化为确定含有两个函数自变量的泛函极值问题。对于一般黏性土,依据泛函取极值时必须满足的欧拉方程,得到了对数螺旋线的滑裂面函数和沿滑裂面分布的法向应力函数。结合边界条件和横截条件,主动土压力泛函极值问题进一步转化为以两个拉格朗日常数为未知量的函数优化问题。同时,讨论了滑裂面为平面和圆弧面两种特殊情况。通过算例表明,对于一般土体,在作用点位置系数下限处,主动土压力最小,滑裂面为平面;随着作用点位置的上移,主动土压力呈非线性增长,相应滑裂面为对数螺旋面。对于砂性土,位置系数上限值随内摩擦角的增大而增大,其相应的土压力值也随之增加。对于软黏土,滑裂面为圆弧面,随着作用点位置的上移,主动土压力呈非线性下降,滑裂面背离基坑方向移动。     

峨眉山大火成岩省烂纸厂铁矿床地质特征、成因及其找矿勘查启示

烂纸厂铁矿床是峨眉山大火成岩省玄武岩建造中查明的首例中型规模铁矿床。矿床的形成与玄武岩建造具有密切的时空及成因联系,矿体主要赋存于峨眉山玄武岩下段致密块状玄武岩与玄武质角砾岩接触带附近,产出特征受矿山梁子破火山口构造控制,多层位产出,矿石发育草莓状结构、韵律结构和纹层状构造、条带状构造、致密块状构造、绳状构造、角砾状构造等矿石组构,发育铁质结核和铁碧玉,同生沉积层控成矿特征明显。岩(矿)石主、微量元素分析结果表明,研究区岩浆演化遵循Fenner分异趋势,成矿作用与热水沉积作用有关。地质和地球化学特征表明,矿床成因类型为火山喷发(溢)沉积型陆相火山岩型铁矿床。烂纸厂铁矿床是我国在铁矿找矿勘探类型上的新突破和在峨眉山大火成岩省找矿实践取得的新进展,它的发现打破了在玄武岩建造中不具备寻找成型矿床的固有勘查模式的思想束缚,为相似地质环境寻找铁矿给予了诸多启迪和经验借鉴。     

空气反循环钻头井底流场分析及结构优化

为改善空气潜孔锤反循环钻进技术在大口径嵌岩桩施工中的应用效果,运用Fluent软件对嵌岩桩施工用反循环钻头底喷孔水平倾角θ_d和扩压槽水平倾角θ_k做了进一步的分析和研究,得到θ_d和θ_k对反循环钻头抽吸系数ω的影响规律。在分析中发现原有反循环钻头中心贯通孔结构设计中的不足之处,并进行了优化,优化后的反循环钻头抽吸效果明显增强。采用优化后的结构加工了一个直径为660 mm的反循环钻头,并进行现场钻进试验,试验效果良好,平均钻进效率为6.00 m/h,成功嵌入微风化岩层表面,能够满足嵌岩桩施工对嵌入微风化岩层和孔壁稳定、无塌孔的要求。     

基于北斗卫星的大型海洋浮标通信机制研究

针对北斗通信效率低、通信并非百分百可靠等问题,提出了一套新的大型海洋浮标北斗通信机制,包含一套通信协议、一种适用于通信数据的"位拼接-LZW"两重数据压缩机制以及一套适用于通信系统的"主-从"两重状态机通信控制机制。该机制有效地提高了通信传输效率,节约了通信成本,保证了北斗通信的可靠性,并且已成功应用于大型海洋浮标中。     

Comprehensive numerical analysis of fault‐structure systems – Computation of the large‐scale seismic structural response to a given earthquake scenario –

The seismic structural response is affected by temporal and spatial variations in strong ground motion. It can be evaluated through the fault‐structure system: the fault mechanism, wave propagation through the crust, amplification near the surface, and soil‐structure interaction. To analyze this system at high resolution and accuracy, we previously proposed a new multiscale analysis method and numerically verified its validity. However, the problem of the extremely large computation cost of constructing a three‐dimensional numerical model and solving the discretized governing equations still remains. Here, we introduce a new method to resolve these difficulties. By combining this new method with our multiscale analysis, we developed a tool for fault‐structure system analysis. The accuracy of this tool is verified by comparing it to a Green's function solution. Finally, we demonstrate the potential utility of the method by estimating the seismic response of a large and complex underground highway junction in a given earthquake scenario. Copyright © 2011 John Wiley & Sons, Ltd.     

A macro‐element model for non‐linear soil–shallow foundation–structure interaction under seismic loads: theoretical development and experimental validation on large scale tests

In this paper, different formulations of a macro‐element model for non‐linear dynamic soil‐structure interaction analyses of structures lying on shallow foundations are first reviewed, and secondly, a novel formulation is introduced, which combines some of the characteristics of previous approaches with several additional features. This macro‐element allows one to model soil‐footing geometric (uplift) and material (soil plasticity) non‐linearities that are coupled through a stiffness degradation model. Footing uplift is introduced by a simple non‐linear elastic model based on the concept of effective foundation width, whereas soil plasticity is treated by means of a bounding surface approach in which a vertical load mapping rule is implemented. This mapping is particularly suited for the seismic loading case for which the proposed model has been conceived. The new macro‐element is subsequently validated using cyclic and dynamic large‐scale laboratory tests of shallow foundations on dense sand, namely: the TRISEE cyclic tests, the Public Works Research Institute and CAMUS IV shaking table tests. Based on this comprehensive validation process against a set of independent experimental results, a unique set of macro‐element parameters for shallow foundations on dense sand is proposed, which can be used to perform predictive analyses by means of the present model. Copyright © 2011 John Wiley & Sons, Ltd.     

Identifying the sensitive areas in targeted observation for pre-dicting the Kuroshio large meander path in a regional ocean model

With the Regional Ocean Modeling System(ROMS), this paper investigates the sensitive areas in targeted observation for predicting the Kuroshio large meander(LM) path using the conditional nonlinear optimal perturbation approach. To identify the sensitive areas, the optimal initial errors(OIEs) featuring the largest nonlinear evolution in the LM prediction are first calculated; the resulting OIEs are localized mainly in the upper2 500 m over the LM upstream region, and their spatial structure has...     

中国都市区和大城市群的界定——兼论大城市群在区域经济发展中的作用

大城市群正在成为城市化空间组织的主要形态,构成国家经济发展的重心。改革开放以来,中国重新纳入到世界经济体系之中,工业化与城市化加速发展推动了城市群规模壮大与能级提升。本文首先采用"五普"资料对大都市区进行界定,以大都市区为基本组成单元界定中国的大城市群,分析了中国13个大城市群的空间分布特征及在区域经济发展中的引领作用。     

中国地震预报发展规划应突出探索性和实验性

作者提出中国地震预报发展规划在指导思想上应突出探索性和实验性,探索内容应包括：地壳运动状态(方向、速率、范围及机理);地壳应力集中点(应力集中点数量、各点应力积累速度、范围、持续时间及其与震级的相关关系,应力集中点的演化与区内地震活动、前兆异常的相关关系);震源应力演化产生的应力扰动所能影响的范围及其量级;前兆观测仪器和预报判据等。探索的技术路线作者提出：短临预报要抓大放小,主要抓7级左右大震的监测预报,对5～6级地震采取抗震技术措施进行预防;对地壳运动状态及应力集中点的研究采取GPS大地形变、绝对应力测量等方法进行长时间短周期的综合观测。抓住预报实验区、重点危险区及余震区等现场不放,进行以上述内容为主的实验观测。     

土壤—大宗农产品中Cd的分配及其环境意义

基于多目标地球化学调查成果,以土地生态效应为重点,研究成都经济区大宗农产品——水稻、玉米、小麦籽实中Cd元素的含量,同时讨论了农产品籽实与土壤中Cd含量的关系。结果表明大宗农产品籽实中Cd元素的累积状况为小麦>水稻>玉米;土壤酸碱度(pH值)环境对土壤中Cd元素的转移和在农作物籽实中积累影响较大,酸性土壤中Cd元素更容易进入植物体并积累下来,从而形成环境生态危害。