堆载下单桩负摩阻力工作性状非线性数值分析   总被引：1，自引：0，他引：1  

林智勇  苏美选 《工程地质学报》2010,18(5):714-719

利用三维非线性数值方法对一算例在堆载作用下桩侧负摩阻力进行了计算分析。计算结果揭示了摩擦型、端承型桩负摩阻力工作性状的异同;分析了堆载速度、桩顶荷载对负摩阻力的影响:堆载越快,负摩阻力越小;在无桩顶荷载作用下,由负摩阻力引起的下拉荷载最大,可视为常规方法设计的上限值;桩顶荷载与堆载施工顺序对负摩阻力的影响也很大,先施加桩顶荷载,后进行堆载所产生的负摩阻力最大,反之最小。  相似文献   

Late Ordovician climbing‐dune cross‐stratification: a signature of outburst floods in proglacial outwash environments?     

JEAN‐FRANÇOIS GHIENNE  FLAVIA GIRARD  JULIEN MOREAU  JEAN‐LOUP RUBINO 《Sedimentology》2010,57(5):1175-1198

Climbing dune‐scale cross‐statification is described from Late Ordovician paraglacial successions of the Murzuq Basin (SW Libya). This depositional facies is comprised of medium‐grained to coarse‐grained sandstones that typically involve 0·3 to 1 m high, 3 to 5 m in wavelength, asymmetrical laminations. Most often stoss‐depositional structures have been generated, with preservation of the topographies of formative bedforms. Climbing‐dune cross‐stratification related to the migration of lower‐flow regime dune trains is thus identified. Related architecture and facies sequences are described from two case studies: (i) erosion‐based sandstone sheets; and (ii) a deeply incised channel. The former characterized the distal outwash plain and the fluvial/subaqueous transition of related deltaic wedges, while the latter formed in an ice‐proximal segment of the outwash plain. In erosion‐based sand sheets, climbing‐dune cross‐stratification results from unconfined mouth‐bar deposition related to expanding, sediment‐laden flows entering a water body. Within incised channels, climbing‐dune cross‐stratification formed over eddy‐related side bars reflecting deposition under recirculating flow conditions generated at channel bends. Associated facies sequences record glacier outburst floods that occurred during early stages of deglaciation and were temporally and spatially linked with subglacial drainage events involving tunnel valleys. The primary control on the formation of climbing‐dune cross‐stratification is a combination between high‐magnitude flows and sediment supply limitations, which lead to the generation of sediment‐charged stream flows characterized by a significant, relatively coarse‐grained, sand‐sized suspension‐load concentration, with a virtual absence of very coarse to gravelly bedload. The high rate of coarse‐grained sand fallout in sediment‐laden flows following flow expansion throughout mouth bars or in eddy‐related side bars resulted in high rates of transfer of sands from suspension to the bed, net deposition on bedform stoss‐sides and generation of widespread climbing‐dune cross‐stratification. The later structure has no equivalent in the glacial record, either in the ancient or in the Quaternary literature, but analogues are recognized in some flood‐dominated depositional systems of foreland basins.  相似文献   

自升式钻井平台悬臂梁负荷试验方法研究     

王凤辉  孙广斌  贺相军 《海洋地质译丛》2014,(2):111-114

悬臂梁负荷试验是自升式钻井平台建造完工交付使用之前的关键试验项目之一.以200 ft自升式钻井平台“海洋石油923”为例,针对悬臂梁负荷试验方法做出了探索研究,试验结果表明,此方法行之有效,具有操作简便,安全可靠的优点,为其它类似工程项目的顺利实施提供了宝贵的经验和借鉴.  相似文献   

基于GPS垂向位移测定云南地区陆地水储量及其对累积降雨的响应机制     

肖家豪  张双喜  韦瑜  蔡剑锋  洪敏 《测绘通报》2022,(1):61-65

本文基于中国大陆构造环境监测网（陆态网）GPS台站垂向形变数据,通过主成分分析计算云南省6大流域陆地水负荷形变,并与降雨数据进行相关性分析和交叉小波分析。结果表明,云南省各流域陆地水储量变化相对于降雨在半年和年周期上分别存在1.5~2.25和3~6个月的滞后,不同周期滞后的叠加使陆地水储量与累积降雨量之间存在显著的负相关性,6大流域的降雨累积天数各不相同,均在47~109 d之间。本文由此提出一种云南地区陆地水储量对累积降雨的响应机制。  相似文献   

山东烟台大季家地区海水入侵界面划分的意义     

宋希利  ;宋鹏  ;时彦芳  ;耿祥峰 《山东地质》2014,(6):58-61

在沿海地区划分海水入侵界线具有重大意义,在海水入侵范围内,地下水由于含盐量高,虽然工业生产、人畜生活不能利（饮）用,但深部海水可为海产品养殖业带来较高的利用价值。利用高密度电法和可控源音频大地电磁2种方法准确划分了浅、深部海水入侵界线,并根据电性特征分析探讨了海水入侵区域的由浅至深的侵入特点,推测了不同深度上岩石破碎及富水规律,为探讨沿海养殖业利用温度相对稳定或较高的深部入侵海水进行了积极、有益的探讨。  相似文献   

重力负载对库车褶皱冲断带盐构造的影响     

程海艳  李江海 《地质通报》2014,33(10):1502-1506

库车褶皱冲断带新生代沉积了库姆格列木群和吉迪克组2套盐岩,发育复杂的盐构造,重力负载对其形成和发育具有重要影响。利用水压头分析方法,分析了重力对库车褶皱冲断带盐构造的影响。重力负载对盐岩流动的影响包括重力扩张和沉积负载2种,重力扩张作用由盐岩受自身重力控制,而沉积负载作用由上覆沉积物重力作用控制。水压头分析表明在盐岩高程大的地方,其沉积负载往往更小。在重力扩张和沉积负载共同作用下,库车褶皱冲断带不会发生由盐岩自身重力而形成的重力扩张,重力负载对库车褶皱冲断带盐岩的影响仅表现为沉积差异负载作用。  相似文献   

On the influence of vertical loads on the lateral response of pile foundation     

《Computers and Geotechnics》2014

The influence of vertical loads on the lateral response of group piles installed in sandy soil and connected together by a concrete cap is studied through finite elements analyses. The analyses focus on the five piles in the middle row of 3 × 5 pile groups. The vertical load is applied by enforcing a vertical displacement equivalent to 2% of the pile diameter through the pile cap prior to the application of the lateral loads. The results have shown that the lateral resistance of the leading pile (pile 1) does not appear to vary considerably with the vertical load. However, the vertical load leads to 23%, 36%, 64%, and 82% increase in the lateral resistance of piles 2–5, respectively. The increase in the lateral pressures in the sand deposit is the major driving factor to contribute the change in the lateral resistance of piles, depending on the position of the pile in the group. The distribution of lateral loads among piles in the group tends to be more uniform when vertical loads were considered leading to a more economical pile foundation design.  相似文献   

Assessment of the dynamic behaviour of saturated soil subjected to cyclic loading from offshore monopile wind turbine foundations     

《Computers and Geotechnics》2014

The fatigue life of offshore wind turbines strongly depends on the dynamic behaviour of the structures including the underlying soil. To diminish dynamic amplification and avoid resonance, the eigenfrequency related to the lowest eigenmode of the wind turbine should not coalesce with excitation frequencies related to strong wind, wave and ice loading. Typically, lateral response of monopile foundations is analysed using a beam on a nonlinear Winkler foundation model with soil–pile interaction recommended by the design regulations. However, as it will be shown in this paper, the guideline approaches consequently underestimate the eigenfrequency compared to full-scale measurements. This discrepancy leads the authors to investigate the influence of pore water pressure by utilising a numerical approach and consider the soil medium as a two-phase system consisting of a solid skeleton and a single pore fluid. In the paper, free vibration tests are analysed to evaluate the eigenfrequencies of offshore monopile wind turbine foundations. Since the stiffness of foundation and subsoil strongly affects the modal parameters, the stiffness of saturated soil due to pore water flow generated by cyclic motion of monopiles is investigated using the concept of a Kelvin model. It is found that the permeability of the subsoil has strong influence on the stiffness of the wind turbine that may to some extent explain deviations between experimental and computational eigenfrequencies.  相似文献   

桩基优化设计经济效益分析          下载免费PDF全文

陈红玲  曹庆霞 《探矿工程》2014,41(7):70-72

分析岩土工程勘察报告中所揭示的地基土层特性,根据所掌握的大量桩基工程检测试验数据、沉降观测实测数据,对桩周（端）地基土的受荷性能以及基桩工作性状进行研究,通过静载荷试验的实际桩基承载能力,分析推导出优化地基土桩基设计参数。据此优化带来了一定的经济效益。  相似文献   

车载修井机井架静强度有限元分析          下载免费PDF全文

刘智 《探矿工程》2014,41(10):72-74

车载修井机井架静强度分析中,通常略去绷绳和风载的影响,这与井架的实际工况不符。以ABAQUS软件为工具,对某车载修井机井架进行了有限元分析。在不同的静钩载及风载作用下,得出了井架所能承受的最大静钩载以及确定了井架薄弱点所处的位置。并通过计算合理地缩短了绷绳的斜拉范围。  相似文献