Fracturation d'âge Aptien supérieur sur la bordure orientale de la plate-forme arabique (Haushi-Huqf,Oman)Aptian faulting (Shu'aiba Formation) on the eastern edge of the Arabian Platform (Haushi-Huqf,Oman)     

Christian Montenat  Pascal Barrier 《Comptes Rendus Geoscience》2002,334(10):781-787

In the Haushi-Huqf (Eastern Central Oman) as in other parts of the Arabian platform, a major sedimentary break is recorded between the Early Aptian carbonates (Shu'aiba Formation) and the Albian orbitolinid-rich marls (Nahr Umr Formation). The unconformity corresponds to a succession of events: (1) a brusque interruption of the regressive sequence of the Shu'aiba limestone (algae and small rudistid build-ups); (2) a stratigraphic gap related to the Late Aptian; (3) the development of a thick ferruginous crust (hardground) that covered the top surface of the Shu'aiba; the hardground is related to a forced flooding surface; (4) the Shu'aiba was rapidly drowned and buried under the Nahr Umr marls. Moreover, the Shu'aiba limestone was subject to faulting NW–SE-trending normal faults before lithification and formation of the ferruginous crust. The faulting episode is clearly dated: post-Early Aptian and pre-Albian. The signification of the faulting remains hypothetical. The syndiagenetic NW–SE normal faults may correspond to ‘en echelon’ faults, combined with transcurrent fault movements (for example the Haushi-Nafun Fault). The possible causes of these intra-platform transcurrent movements are discussed. To cite this article: C. Montenat, P. Barrier, C. R. Geoscience 334 (2002) 781–787.  相似文献   

差异性风化岩石作为桩基持力层设计应注意的若干问题          下载免费PDF全文

隆威  李爱民  杨先斌 《探矿工程》2003,30(5):3-5

基岩中存在软弱夹层为岩石的差异性风化的主要特征。在不均匀性地基土上选用该类地层作为钻孔灌注桩持力层时，它的存在将对桩长、单桩承载力、桩体沉降等带来不同程度的影响。以黄石电厂为例，指出在选用差异性风化岩石作为桩基持力层时应注意的若干问题。  相似文献   

桩承载力时效对桩土相互作用及沉降的影响分析   总被引：2，自引：2，他引：2  

郑刚  任彦华 《岩土力学》2003,24(1):65-69

对软土中两根47 m长灌注桩分别在成桩28 d和1 750 d后进行了承载力试验，其极限承载力提高幅度达到30％左右。分析了单桩承载力随时间提高(称为时效)的机理，提出了单桩承载力时效对桩筏基础桩土相互作用影响的分析方法，并结合工程实例进行了分析。  相似文献   

振动沉模大直径现浇薄壁管桩技术及其应用 (Ⅰ):开发研制与设计   总被引：54，自引：25，他引：54  

刘汉龙  费康  马晓辉  高玉峰 《岩土力学》2003,24(2):164-168

振动沉模现浇混凝土薄壁管桩（PCC桩）技术是河海大学自主开发研制的用于地基加固处理的专利技术，是一种适合于软土地区的新型高效优质桩型，可有效地提高地基承载力和减小地基沉降。笔者介绍了振动沉模现浇混凝土薄壁管桩的技术原理、加固机理、施工设备、施工工艺及其设计与质量检测方法。该桩型具有承载力高、质量可靠和工程造价低等优点，具有较大的推广应用价值。  相似文献   

Nonlinear Rate Dependent Model of High Damping Rubber Bearing     

Robert Jankowski 《Bulletin of Earthquake Engineering》2003,1(3):397-403

The accurate analysis of the response of isolated structures requires the application of appropriate models of isolation devices. The purpose of this paper is to analyse a nonlinear strain rate dependent model of a high damping rubber bearing which simulates the horizontal behaviour of the device under specified vertical load using a nonlinear elastic spring-dashpot element. The effectiveness of the model is checked by fitting the experimental data concerning three different rubber bearings. The results of the study show that the model can simulate the bearing behaviour over a wide shear strain range with small simulation errors. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Seismic response predictions of multi‐span steel bridges through pushover analysis     

Yi Zheng  Tsutomu Usami  Hanbin Ge 《地震工程与结构动力学》2003,32(8):1259-1274

In the new trend of seismic design methodology, the static pushover analysis is recommended for simple or regular structures whilst the time‐history analysis is recommended for complex structures. To this end, the applicable range of the pushover analysis has to be clarified. This study aims at investigating the applicability of pushover analysis to multi‐span continuous bridge systems with thin‐walled steel piers. The focus is concentrated on the response demand predictions in longitudinal or transverse directions. The pushover analysis procedure for such structures is firstly summarized and then parametric studies are carried out on bridges with different types of superstructure‐pier bearing connections. The considered parameters, such as piers' stiffness distribution and pier–0.5ptdeck stiffness ratio, are varied to cover both regular and irregular structures. Finally, the relation of the applicability of pushover analysis to different structural formats is demonstrated and a criterion based on the higher modal contribution is proposed to quantitatively specify the applicable range. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Efficiency of base isolation systems in structural seismic protection and energetic assessment     

Giuseppe Carlo Marano  Rita Greco 《地震工程与结构动力学》2003,32(10):1505-1531

This paper concerns the seismic response of structures isolated at the base by means of High Damping Rubber Bearings (HDRB). The analysis is performed by using a stochastic approach, and a Gaussian zero mean filtered non‐stationary stochastic process is used in order to model the seismic acceleration acting at the base of the structure. More precisely, the generalized Kanai–Tajimi model is adopted to describe the non‐stationary amplitude and frequency characteristics of the seismic motion. The hysteretic differential Bouc–Wen model (BWM) is adopted in order to take into account the non‐linear constitutive behaviour both of the base isolation device and of the structure. Moreover, the stochastic linearization method in the time domain is adopted to estimate the statistical moments of the non‐linear system response in the state space. The non‐linear differential equation of the response covariance matrix is then solved by using an iterative procedure which updates the coefficients of the equivalent linear system at each step and searches for the solution of the response covariance matrix equation. After the system response variance is estimated, a sensitivity analysis is carried out. The final aim of the research is to assess the real capacity of base isolation devices in order to protect the structures from seismic actions, by avoiding a non‐linear response, with associated large plastic displacements and, therefore, by limiting related damage phenomena in structural and non‐structural elements. In order to attain this objective the stochastic response of a non‐linear n‐dof shear‐type base‐isolated building is analysed; the constitutive law both of the structure and of the base devices is described, as previously reported, by adopting the BWM and by using appropriate parameters for this model, able to suitably characterize an ordinary building and the base isolators considered in the study. The protection level offered to the structure by the base isolators is then assessed by evaluating the reduction both of the displacement response and the hysteretic dissipated energy. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

武汉市高层建筑岩土工程问题分析     

谭松林  江权 《水文地质工程地质》2003,(Z1)

武汉市是华中地区最大的城市,改革开放以来,兴建了许多高层建筑。高层建筑尤其是超高层建筑的主要特点是高度大、重心高、基底压力大及基础埋深大等。而武汉地区的地质条件又比较复杂,就第四纪地层而言,从最新沉积的各类软土如人工填土、淤泥类土、软塑状粘性土等,到全新世(Q4)沉积的各类砂土与卵砾石,直至晚更新世(Q3)及其以前沉积的老粘土均有分布。各类土层的厚度、深度及性质均变化较大。因此武汉地区高层建筑的岩土工程问题就显得复杂与多样,在众多复杂的岩土工程问题中,本文主要分析了比较突出的基础持力层与基础类型的确定,深基坑开挖中的边坡滑移、基坑涌水、流砂、突涌以及基坑防护等。通过对这些问题的分析,从中可以得出一些规律,对今后高层建筑的兴建具有一定的指导作用。  相似文献   

岩体变形模量的尺寸效应   总被引：2，自引：0，他引：2  

喻勇  肖国强  王法刚 《岩土力学》2003,(Z1)

岩土工程中,现场岩体的承压板试验和变形试验可看作是不同尺寸岩体的变形试验。在某工程的现场岩石力学试验中,对同一组试点的岩体先后进行了承压板变形试验和承载力试验,研究了岩体变形模量的尺寸效应,结果表明,岩体变形模量主要受岩体中的裂隙发育状况控制,当岩体质量较好时,可以由承载力试验曲线来确定岩体的变形特性,这一做法具有一举两得的效果。  相似文献   

气象台业务平台和预报制作系统发展的研究--气象台天气分析预报技术走向研究之三     

徐羹慧 《沙漠与绿洲气象(新疆气象)》2003,26(5):1-3,8

目前，业务平台、预报制作系统技术已成为气象台天气预报的关键技术，也是我国与发达国家技术发展的主要差距之一。本文从科学技术论的角度，研究气象台预报制作系统发展的历史及其发展的阶段性，归纳了技术发展的基本特征，提出了预报制作系统技术跨越式发展的应对措施。  相似文献