Seismic behaviour of cracked concrete gravity dams     

O. A. Pekau  Xueye Zhu 《地震工程与结构动力学》2006,35(4):477-495

A finite element model of incremental displacement constraint equations (IDCE), based on an existing node‐to‐surface concept, is implemented to deal with dynamic contact surfaces in the seismic behaviour analysis of cracked concrete gravity dams. After verification for sliding, rocking and impact, the IDCE model is applied to study the seismic responses of concrete gravity dams with different profiles and crack locations for a variety of parameters, such as coefficient of friction, water level and type of earthquake, as well as impact damping based on the concept of coefficient of restitution. It is revealed that cracked concrete gravity dams can experience not only sliding and rocking modes, but also the drifting mode in some cases of crack either at the base or at a height. Downstream sliding is normally accompanied by rocking, especially for the cases of crack at a height. Due to rocking and drifting, a cracked dam may still acquire a certain amount of residual sliding even if the effective coefficient of friction is relatively high. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

山西峨嵋台地的挤压型地裂     

高树义  苏宗正  赵晋泉  薄建杰  刘义智  杜峰 《山西地震》2006,(1):6-10

考察了山西峨嵋台地万荣城区一带的挤压型地裂,发现其呈北西-南东的条带状,1985年发生,至今仍在发展。地裂带上墙砖、水泥地砖拱曲翘起,水泥地面条带状拱曲,土体发育呈波浪条带状垅岗;墙体开裂,墙体裂缝中间宽上下两头细,地裂带上X型破裂发育。分析了万荣城区一带地裂的特征,讨论了万荣挤压型地裂的力学成因机制。  相似文献   

1995年云南孟连西7.3级地震前震序列特征及其与主震的关系     

刘祖荫  钱晓东  张俊伟 《湖南地质》1998,(4)

在分析１９９５年云南孟连西７３级地震的前震序列时,发现跟踪最大前震６２级的余震序列中,有一组较大震级的地震呈现出随时间的增长不断线性递增的特点,这种特点在云南其他震例中也曾多次出现过。利用修正的大森公式ｎ（ｔ）＝ｋ／（ｔ＋ｃ）ｐ拟合该序列,在获得的参数重新构造的频度－线性化时间坐标中,这一组地震显示出与海城前震序列随时间变化震级出现非线性增强的共同特征。采用表征物质加速应变而失稳的方程ｄ（∑Ｍ０１／２）／ｄｔ＝ｃ／（ｔｍ－ｔ）ｎ,对孟连西前震序列多方面进行跟踪定量分析,预测主震的发生时间平均比实发时间仅推迟２６ｍｉｎ,震级相差０１７级。  相似文献   

Channel erosion along the Carmel river,Monterey county,California   总被引：1，自引：0，他引：1  

G. Mathias Kondolf  Robert R. Curry 《地球表面变化过程与地形》1986,11(3):307-319

Historic maps, photographs, and channel cross-sections show that the channel of the Carmel River underwent massive bank erosion, channel migration, and aggradation in a major flood in 1911, then narrowed and incised by 1939. The channel was stable until 1978 and 1980, when bank erosion affected some reaches but not others. The narrowing and incision were in response to a lack of major floods after 1914 and construction in 1921 of a dam that cut off sediment supply from the most actively eroding half of the basin. Localized erosion in 1978 and 1980 occurred during low magnitude events along reaches whose bank strength had been reduced by devegetation. These events illustrate that the stability of a fluvial system can be disrupted either by application of a large erosive force in a high magnitude event (the 1911 flood) or in a low magnitude event, by reducing the resistance to erosion (bank devegetation). The Carmel River is a potentially unstable system. Its discharge and slope characteristics place it near the threshold between meandering and braided. On the Lower Carmel, the presence of bank vegetation can make the difference between a narrow, stable meandering channel and a wide shifting channel with braided reaches.  相似文献   

尾矿坝治理技术   总被引：2，自引：0，他引：2  

董翠兰  季学培 《世界地质》2003,22(2):172-175,180

尾矿坝在矿山环境的保护和治理中起到很大的作用，它主要应用于堆放和处理矿山生产所带来的废渣、废水等污染物质，而坝体浸润线过高会影响尾矿坝的稳定性。尾矿坝治理技术众多，重点介绍了管井法降水、垂直水平自流排渗法、水平自流排渗法、辐射井排渗法等。在结合实例讨论的基础上，综合分析了不同方法的优、缺点，并提出了其应用范围以及其在应用中应注意的技术问题。  相似文献   

拱坝WES堰流量系数的验证分析     

邵卫云  张土乔  王霆 《水文》2002,22(5):35-37,17

结合拱坝的水工模型试验,对小桥墩的设置、出口堰宽的变化等因素对拱坝WES堰流量系数的影响进行了对比试验和分析,并得出了相应的结论。  相似文献   

塔里木盆地阿克库勒凸起于奇地区哈拉哈塘组油气成藏机制   总被引：2，自引：0，他引：2  

旷理雄  郭建华  黄太柱 《吉林大学学报(地球科学版)》2008,38(2):249-254

于奇地区是塔里木盆地塔河油区外围重要的油气勘探地区。研究结果表明:区内哈拉哈塘组油源主要来自阿克库勒凸起南部寒武系—下奥陶统烃源岩,油源充足,具有一定的勘探潜力;原油总体具有油质较轻、含硫量较低但含蜡量较高的特点;天然气属于典型的伴生气;圈闭类型主要为低幅度的构造圈闭,油气分布主要受低幅度背斜和断层所控制;区内储层至少发生了3次油气注入成藏期,即侏罗纪—白垩纪、古近纪古新世晚期—始新世和古近纪渐新世早期—新近纪中新世;成藏机制可归结为油气多期充注和多期次生成藏,燕山期为圈闭的形成与油气藏初步建立阶段,喜山期为圈闭的定型与油气藏重建阶段,成藏模式为它源-双向排烃-多期次生成藏或古生新储-双向排烃-多期次生成藏。  相似文献   

龙溪隧道初期支护监控量测技术初步研究     

李春林  李天斌  陈强  王希宝 《地质灾害与环境保护》2007,18(4):85-90

针对龙溪隧道在施工过程中常出现软弱围岩变形现象,选取其左线LK22 083～LK22 153段为试验段:采用H20型钢施作初期支护.对锚杆轴力、围岩压力和钢拱架应变开展监控量测工作,验证H20型钢支护是否合理.在试验段范围内选取三个监测断面,对应里程桩号:LK22 084、LK22 100和LK22 125;每个断面在拱顶、两侧拱腰和边墙5个测点埋设监测仪器,每个测点处的锚杆计、土压力计和钢拱架应变计埋设在同一点,便于在数据分析时相互补充说明;通过实测数据分析,结合施工实践,综合表明H20型钢支护是合理的,确保了隧道施工顺利快速通过F8断层.  相似文献   

Lacustrine transgressions in the late Cenozoic Ussuri-Khanka depression (Primor’e)     

A. M. Korotkii  T. A. Grebennikova  L. P. Karaulova  N. I. Belyanina 《Russian Journal of Pacific Geology》2007,1(4):352-365

In the Ussuri-Khanka depression of Primorye, the Quaternary alluvial-lacustrine and lacustrine sedimentogenesis progressed under conditions of transgressive accumulation in response to the depression tectonic subsidence and recurrent climatic fluctuations. The alluvial dams and irregular accumulation are proved to have been the leading factors of lakes’ formation within the depression. As is shown, fluctuations of the water level in limnic reservoirs depended on the climatic changes. New data considered in this work confirm the lacustrine genesis of a greater part of the Middle Pleistocene-Holocene sedimentary succession in the Khanka depression. Two transgressive phases, when the water level in the lakes rose by 1.5–2.0 m above the present one, are established for the Subboreal. The general conclusion is that the mesorhythmic structure of the sedimentary succession in the Ussuri-Khanka depression reflects the influence of climatic fluctuations in the Late Cenozoic.  相似文献   

深基坑挡土桩土拱效应特征分析          下载免费PDF全文

刘建民  程小彬 《探矿工程》2007,34(1):4-7

土拱效应是挡土桩工作原理的基础。采用有限元法首先研究了一个真正土拱的受力特征，以此为基础，分析了深基坑挡土桩后土体的受力状态；指出挡土桩后的土体可以分为3个区域：拱底应力区、土拱区和拱顶均匀应力区。在拱底应力区，最大主应力为拉应力；在土拱应力区，其受力特征与真正的土拱相同。给出了这3个区域的分界线特征，并讨论了荷载及挡土桩净距等因素对土拱区形状的影响。  相似文献