A new history of cave development at Bungonia,N.S.W.     

R. A. L. Osborne 《The Australian geographer》1993,24(1):62-74

Bungonia Caves are the result of three distinct phases of speleogenesis. The first, Late Cretaceous phase is characterised by the development of horizontal passages close to the plateau surface. Caves developed in the lower limestone during this phase probably drained southward to risings in Becks Gully. The second, Palaeocene phase resulted in the development of dolines and large dynamic phreatic conduits. Caves extended to depths approximating the level of the Efflux and drainage from caves in the lower limestone was captured by the caves in the middle limestone, rising above the level of the Efflux. The second phase ended when the caves were filled with laminated clays, blocking underground drainage, and the surface was buried by quartz‐rich fluvial sediments prior to the Eocene. The third, and continuing phase, which began in the Late Tertiary, is characterised by the development of vadose shafts and by the removal of sediment deposited following the second phase.  相似文献   

海底管道悬空防护与治理措施浅谈   总被引：2，自引：2，他引：0  

庄丽华  阎军  李成钢 《海洋科学》2016,40(11):65-73

为了治理一直困扰茂名30万t单点码头的海底管道悬空问题,首先分析了海底管道埋藏状态的识别方法,对国内外海底管线各种悬空治理措施的优缺点和适宜海域进行汇总。在对茂名30万t单点码头海底管道开展了多次路由调查的基础上,针对悬空路段,分别采用人工海草、沉排、碎石回填等不同的防护措施。结果表明,人工海草确实具有明显的降低流速和促进泥沙淤积的功能,但潜水员水下作业工作量较大,不宜在水深大于40 m的海域进行,应避开拖网捕捞海域。水泥沉排在水下较稳定,可有效保护海底管线免受外来损害,但是回淤促淤缓慢。当海床承载力足够时,采用碎石回填办法进行海管维护比较有效,冲刷坑填埋充实,可广泛用于修正悬空。  相似文献   

断层倾角对上/下盘效应的影响   总被引：1，自引：0，他引：1  

王栋  谢礼立 《地震工程与工程振动》2007,27(5):1-6

上／下盘效应是近断层地震动的显著特征之一。上／下盘效应的影响因素很多，由于靠近断层，与震源相关的因素成为主导因素，尤其是断层倾角的影响最为明显。本文采用二维有限元数值模拟的方法模拟了近断层地震动，定量地考查了断层倾角对上／下盘效应的影响。结果表明：无论是走滑型断层还是倾滑型断层，随着断层倾角从0°～90°的增大过程中，上／下盘效应先迅速增大然后缓慢减小。  相似文献   

桩板墙不同类型挂板的技术经济比较          下载免费PDF全文

李菊芳 《中国地质灾害与防治学报》2021,32(2):135-142

桩板墙是边坡和滑坡治理工程中常用的支挡结构形式,不同类型的挂板方式在结构受力、经济效益和环境保护等方面有显著差异。针对西部山区城市土地开发过程中的工程滑坡治理问题,基于技术经济比选阐明了桩板墙挂板类型和适用性。以兰雅星河湾项目为依托,分析了该滑坡的变形特征和治理工程总体设计,重点对桩板墙挂板方式优化比选进行详细阐述。  相似文献   

核心单筒式高层悬挂结构考虑土—结构相互作用的动力分析   总被引：5，自引：0，他引：5  

杨允表  宋启根 《地震工程与工程振动》1999,19(2):64-70

分析了核心单筒式高层悬挂结构考虑土－结构相互作用的动力特性,推导了适合于分析此结构与土动力相互作用的基本方程与核筒的单元刚度矩阵,得出了高层悬挂结构有利于抗振的结论,文中还提出了前三个周期的近似计算公式。  相似文献   

近断层速度脉冲地震动的三维有限差分模拟   总被引：1，自引：0，他引：1       下载免费PDF全文

罗全波  陈学良  高孟潭  李宗超  李铁飞 《地震工程学报》2019,41(6):1630-1636,1678

根据台湾西部地质地貌特征和1999年集集M_W7.6地震的研究成果,建立三维速度结构模型和震源模型,并采用三维有限差分法对双冬断层可能产生的近断层脉冲型地震动进行数值模拟。结果表明,方向性效应引起的双向速度脉冲集中在垂直于断层滑动分量的方向上,而滑冲效应引起的单向速度脉冲则集中在平行于断层滑动分量的方向上。受方向性效应和上盘效应的共同调制,近断层脉冲型地震动反映出不对称带状分布的特征,速度脉冲主要分布在距离断层面约10 km的范围内。凹凸体的特性影响着地震动的时空分布,由地震波场显示南投和台中处于强地震动危险区。近场脉冲型地震动的研究对分析速度脉冲形成机理以及地震危险性有一定的参考意义。  相似文献   

Internal structure and sources of selected ice jams on the lower Vistula River          下载免费PDF全文

Bogusław Pawłowski 《水文研究》2016,30(24):4543-4555

The lower stretch of the Vistula is the most ice‐jammed river section on the North European Plain. Since 1982, the structure of hanging dams has been studied by means of a mechanical non‐core sampler. In this article, a selected of field research results of the hanging dams' structure and the degree of filling of the cross section with ice obtained during surface ice‐jam events in the years 1995–2014 are presented, along with an explanation of their causes. Surface ice jams occurred during spring snowmelt surges and ice breakups and also during freeze‐up and ice‐covered periods. Their main cause was changes in the river flow and was also those affected by anthropogenic sources. A characteristic feature of the analysed cross sections was the considerable share of the underhanging ice dam's firm accumulation with ice floes, when the cross section would be filled with ice in excess of 70%. In most cases, due to low river discharge, there was no substantial flooding damage. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

白马雪山发育现代冰斗冰川的条件基础及其发育特征     

刘啸  刘亮  毕伟力  刘蓓蓓 《云南地理环境研究》2012,24(5)

位于横断山脉中部的白马雪山是著名的世界遗产地——三江并流中澜沧江与金沙江的分水岭。依据2011年5月对白马雪山冰川环境的考察,发现白马雪山4200m以上部分区域有终年积雪覆盖,根据Ohmura对70条中高纬现代冰川的相关研究所得出的山岳冰川雪线处降水量与气温的关系（此关系也被Hebenstreit用于计算台湾部分偏低纬度的山地现代雪线计算）并结合当地的气候数据,计算出白马雪山现代理论雪线位置大概为4800m,低于山体顶峰海拔高度。且位于4800m以上的部分地形适合冰川发育,依据这些可形成冰川的理论条件,可见白马雪山部分较高地区至今仍有小规模的现代冰川发育。白马雪山现代冰川变化以及终年积雪分布特征反映了一段时间内当地的气候环境变化。  相似文献   

大型工业厂房室内天面吊挂装置标高测量的实现     

景兆骥  康晋明 《北京测绘》2012,(5):75-77,80

许多大型工业厂房室内天面吊挂装置,在安装施工中,对其标高有一定的精度要求,但因厂房天面吊挂装置的测量仰角过大,测量人员和仪器设备不能到达测量目标,采用有协作目标的传统测量方式很难对该类目标进行标高测量。本文介绍的多种测量仪器联合作业的方案,实现了在地面上对该类空中物体进行标高测量。  相似文献   

Rupture directivity and hanging wall effect in near field strong ground motion simulation   总被引：1，自引：0，他引：1  

陶夏新  王国新 《地震学报(英文版)》2003,16(2):205-212

A random synthesis procedure based on finite fault model is adopted for near field strong ground motion simulation in this paper.The fault plane of the source is divided into a number of sub-sources,the whole moment magnitude is also divided into more sub-events.The Fourier spectrum of ground motion caused by a sub-event in given sub-source,then can be derived by means of taking the point source spectrum,attenuation with distance,energy dissipation,and near surface effect,into account.A time history is synthesized from this amplitude spectrum and a random phase spectrum,and being combined with an envelope function.The ground motion is worked out by superposition of all time histories from each sub-event in each sub-source,with time lags determining by the differences between the triggering times of sub-events and ddistances of the sub-sources.From the example of simulations at 21 near field points in a scenario earthquake with 4 dip angles of the fault plane,it is illustrated that the procedure can describe the rupture directivity and hanging wall effect very well.To validate the procedure,the response spectra and time histories recorded at three near fault stations MCN,LV3 and PCD during the Northridge earthquake in 1994,are compared with the simulated ones.  相似文献