Seismic response of an urban bridge-support system in soft clay

The numerical simulation of an instrumented urban bridge support and its foundation system was conducted. The bridge works as a deck in a surface subway station and was built 12 yr ago in the so-called Lake Zone in Mexico City, where very soft clays, exhibiting low shear strength and high compressibility prevail. Since the beginning of its construction, pile loads, soil–raft contact pressures and the overall response of the foundation system have been monitored. Within this period, several earthquakes have occurred. Thus, an extensive database of accelerations, pore pressures and load histories have been recorded. In particular, this paper focuses on the bridge response observed during two moderated intensity events, the 2004, 6.3 M_w, Guerrero Coast and the 1999, 7.0 M_w, Tehuacan earthquakes. Finite element models were developed to reproduce the measured responses and to assess the soil–foundation-support performance for long-term conditions, including the effects of potential changes in the dynamic soil properties due to regional subsidence. The computed dynamic responses obtained with the simulation for the free field and structure compares fairly well with the recordings.     

Seismic fragility curves for greek bridges: methodology and case studies

This study focusses on the estimation of seismic fragility curves for all common bridge types found in modern greek motorways. At first a classification scheme is developed in order to classify the existing bridges into a sufficient number of classes. A total of 11 representative bridge classes resulted, based on the type of piers, deck, and pier-to-deck connection. Then an analytical methodology for deriving fragility curves is proposed and applied to the representative bridge models. This procedure is based on pushover analysis of the entire bridge and definition of damage states in terms of parameters of the bridge pushover curves. The procedure differentiates the way of defining damage according to the seismic energy dissipation mechanism in each bridge, i.e. bridges with yielding piers of the column type and bridges with bearings (with or without seismic links) and non-yielding piers of the wall type. The activation of the abutment-backfill system due to closure of the gap between the deck and the abutments is also taken into account. The derived fragility curves are subjected to a first calibration against empirical curves based on damage data from the US and Japan.     

旁压试验在苏通大桥地质勘察工程中的应用

详细介绍了旁压试验的使用方法,以及受潮汐影响的大桥勘察旁压原位测试中的特殊处理措施,分析了旁压试验中各强度参数指标的处理方法和原则,并运用这些方法和原则处理了苏通大桥旁压试验的强度参数指标,为大桥的设计提供了设计强度参数,也可为同类工程提供参考意义。     

某特深基坑支护的非线性三维有限元分析

讨论了润扬长江大桥北锚碇基础施工开挖中50 m特深基坑的三维非线性有限元分析,介绍了工程的有关情况,讨论了其计算模型和参数取值,给出主要计算结果并对有关影响因素进行了分析,在此基础上对该基坑支护的设计作出评价,最后结合施工结果讨论了计算分析的可靠性。     

陕甘宁盆地中部马五段上部成岩层序地层学研究及其意义

陕甘宁盆地具有较有利的成岩层序地层学研究条件。根据多种资料,将盆地中部马五段上部划分出八个准层序。准层序内部的酸不溶物含量、自然伽玛、曲线、稳定碳同位素值及残余含盐量等参数呈现规律性变化,这为相似类型的地层的准层序划分提供了新的方法。在不同的成岩作用中,准层序上站的溶解作用／去膏化作用明显强于准层序下部;准层序上部多为准同生白云岩化形成的泥－粉晶白云岩,下部则多为再次云化形成的细粉晶－粗粉白云岩,     

新亚欧大陆桥新疆段水害时空分维特征研究

基于区域自然灾害发生的复杂性和不确定性,运用分形、混沌理论,对新亚欧大陆桥新疆段近３８年的洪水灾害资料进行了时空分维特研究。结果表明：陆桥新疆段洪水灾害不仅在时间序列上具有自相似性,其容量维Ｄｆ在０．０４９７～０．０６８７间,而且在空间序列上也具有自似性,存在明显分维结构,其信息Ｄ１在０．０５３７～０．０７９７之间。洪水灾严重区段的信息分维值较低,并且信息分维与洪水灾害发生频率呈反相关。这一特征将     

中国西部元古代蓝片岩带——世界上保存最好的前寒武纪蓝片岩

阿克苏附近所发现的元古界阿克苏群为一完整的蓝片岩-绿片岩系列,我们通过野外调查肯定了这一认识,并认为它是高压-温相的变质块体,长40km,宽约2.5km.该变质岩由强烈片理化的绿泥石-黑硬绿泥石石墨片岩、黑硬绿泥石-多硅白云母片岩、绿片岩、蓝片岩及少量石英岩、变铁质岩组成.原岩包活泥质岩、砂岩、基性玻屑凝灰岩、块状熔岩、枕状熔岩及少量深海沉积物.蓝片岩的矿物组合:青铝闪石-绿帘石-绿泥石-钠长石-石英-阳起石.阿克苏群为世界上真正的前震旦纪蓝片岩之一,其变质年龄至少有800Ma.     

秦岭山阳-柞水矿集区150~140Ma斑岩-矽卡岩型CuMoFe(Au)矿床成矿作用研究

秦岭造山带内的山阳-柞水古生代弧前盆地中出露有池沟、小河口、冷水沟、园子街、下官坊及双元沟等CuMo、CuFe(Au)矿床,与这些矿床具有成因联系的岩体为形成于150~140Ma的高钾钙碱性和钾玄岩系列花岗岩,为华北和扬子大陆碰撞后伸展阶段壳、幔混合岩浆的产物。矿化主要发生在岩体与泥盆、石炭纪地层中碳酸盐岩的接触带附近,主要类型为矽卡岩型,少量为斑岩型,部分矿床具有统一的矽卡岩-斑岩型成矿系统,矿化组合主要为CuMo、CuFe(Au)和Cu矿化。外接触带主要发育有矽卡岩和角岩化蚀变,内接触带主要为岩体内部的硅化、钾化、绢云母化、绿泥石化及粘土化,内矽卡岩不发育。矽卡岩矿物主要有石榴石、透辉石、绿帘石、透闪石,阳起石等,其中石榴子石主要为钙铁榴石和钙铝榴石,透辉石是辉石的主体,早期形成的石榴石和透辉石等无水矿物组合常被后期的绿帘石、透闪石和阳起石等含水矿物及石英、方解石等所交代。金属矿物比较简单,最主要的含铜矿物为黄铜矿和斑铜矿,铁矿化主要为磁铁矿和镜铁矿。尽管这些矿床以矽卡岩型矿化为主,但部分矿床中已发现有斑岩型矿化和蚀变特征,这可能暗示了该区可能具有统一的矽卡岩-斑岩型成矿系统,进而表明山阳-柞水矿集区深部具有寻找斑岩型矿床的巨大潜力。     

方解石脉双晶纹方法在工程勘察中的应用

在工程区基岩被第四纪土、江水等覆盖的情况下，如何充分利用好获得的钻孔岩芯来分析断层的发育和活动性情况就显得非常重要。为此，地基勘察中引入一种显微构造分析方法，即方解石脉双晶纹分析方法。方解石脉双晶纹能解决断层的活动期次、每一期次的强度、断层应力场、断层性质、断层活动时的环境条件和最后一次活动的时代等问题。由于方解石脉双晶纹发育的广泛性，使之具有推广价值。     

Tracing the 850-Ma continental flood basalts from a piece of subducted continental crust in the North Qaidam UHPM belt,NW China

A Paleozoic ultrahigh-pressure metamorphic (UHPM) belt extends along the northern margin of the Qaidam Basin, North Tibetan Plateau. Eclogites in the Yuka eclogite terrane, northwest part of this UHPM belt, occur as blocks or layers of varying size intercalated with granitic and pelitic gneisses. These eclogites have protoliths geochemically similar to enriched-type mid-ocean ridge basalts (E-MORB) and oceanic island basalts (OIB). On the basis of Ti/Y ratios, they can be divided into low-Ti and high-Ti groups. The low-Ti group (LTG) eclogites exhibit relatively low TiO₂ (most <2.5 wt%) and Ti/Y (<500) but comparatively high Mg# (48–55), whereas the high-Ti group (HTG) eclogites have high TiO₂ (most >2.5 wt%) and Ti/Y (>500) but lower Mg# (46–52). Zircons from two eclogite samples gave a magmatic crystallization (protolith) age of ∼850 Ma and a UHPM age of ∼433 Ma. The occurrence, geochemical features and age data of the Yuka eclogites suggest that their protoliths are segments of continental flood basalts (CFBs) with a mantle plume origin, similar to most typical CFBs. Our observation, together with the tectonic history and regional geologic context, lend support for the large scale onset of mantle plume within the Rodinia supercontinent at ∼850 Ma. The Qaidam block is probably one of the fragments of the Rodinia supercontinent with a volcanic-rifted passive margin. The latter may have been dragged to mantle depths by its subducting leading edge of the oceanic lithosphere in the Early Paleozoic.