共查询到16条相似文献，搜索用时 112 毫秒
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选择水平盲沟、土工席垫及水平和竖向PVC渗管3种排水方案,在黄河山东东明某堤段淤背体冲填施工中进行排水效果试验。通过埋设在淤区内的地下水位观测点,得到淤区内地下水位与时间的变化规律。试验结果表明,采取一定的排水措施能加速淤区土体的固结,但排水效果与排水方案有关;土工席垫排水与水平盲沟排水效果相差不大,且排水效果与淤土厚度有关,3 m左右淤土厚度设置一层水平排水盲沟或土工席垫,其排水效果较好;淤土厚度增加,其排水效果变差;但两者均不能有效防止横向围堤坍塌。采用水平和竖向PVC渗管方案,其排水效果好,特别是设置了竖向PVC渗管,能有效防止横向围堤坍塌。试验成果为黄河放淤固堤工程加速淤背体排水固结设计及施工提供参考。 相似文献
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采用淤背方式加固黄河大堤时,河南、山东一期工程堤身多处出现裂缝。目前尚无淤背对堤身影响的定量研究成果,因而放淤固堤的合理施工速率难以确定。淤背体及堤防土体的水分消散过程实际上是非饱和流固耦合问题;淤背分级施工的变水头边界问题,可等效成多级常水头边界问题。采用非饱和渗流分析方法,计算出每级施工后堤防及淤背体的浸润线;将其作为已知边界条件,考虑堤防土体力学特性、排水条件等影响,进行非饱和流固耦合分析,据此提出相应的淤背施工合理速率。研究表明,该模型计算结果与实际情况相符,因而可为黄河标准化堤防工程设计与施工提供理论依据,并可供其它河流治理时参考。 相似文献
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利用真空预压法处理吹填土时,细颗粒常堵塞排水管,导致土体排水不畅。为提高吹填土固结效率,采用自重沉淤排水与加负压排水固结相结合的方式在室内进行吹填土固结试验。试验第一阶段用排水管作为吹填土自重沉淤的竖向排水通道;第二阶段以装入中粗砂的排水管作吹填土排水通道,同时也是压力传递通道。试验监测到吹填土固结过程中不同位置孔隙水压力的变化,通过监测数据着重研究自重沉淤排水阶段吹填土的固结规律。借助渗流平衡方程确定吹填土在自重沉淤阶段孔隙水压力变化主要由排水管中水位、单位土面积控制,解释自重沉淤阶段孔隙水压力变化机理。同时,为了减小由于排水距离远近造成的固结不均,利用自重沉淤与加压固结结合的方法使吹填土达到较为理想的固结效果,将砂井设计理论与孔隙水压力变化曲线相结合确定排水管有效排水范围等效直径,为实际工程提供排水管间距的设计参数。 相似文献
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以延安黄河引水工程管道基础处理施工为例,对抛石挤淤施工技术的施工原理、适用范围和施工方法进行研究可知:抛石挤淤施工技术适用于含水量大、孔隙比大、透水性弱、抗剪强度低的流塑状软土地基,通过实施该技术的实施,可提高地基承载力,减少沉降,加速地基固结,具有施工简便、工艺简单、地基加强效果明显的工程特点,是一种比较常用的软土地基处理技术,值得在类似地基中推广应用。 相似文献
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本刊2001年第四期刊出了“黄河下游窄河段挖河固堤启动工程减淤效果研究”[1]一文引起了国内泥沙和治河工作者的兴趣和关注。目前对黄河中下游挖河减淤的研究,虽然分析方法及所用资料有所不同,但都认为每减淤1m3泥沙,只需挖沙0.74～0.66m3,即挖沙减淤效率为η=135%～150%这一结论是值得商讨的。据笔者理解,挖沙减淤和水库拦沙减淤相似,其效率不可能大于百分之百。就水库拦沙来说,李保如以前统计黄河下游减淤1m3,水库拦沙需15～16m3,即拦沙减淤效率为η=0.65～0.63。 相似文献
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基于向内径向渗流的轴对称固结模型,给出了变荷载下长排水体-短不排水桩组合型复合地基的固结方程,在单面排水条件下推导出组合型复合地基的固结解析解,包括排水体和排水体周边土体中的超静孔隙水压力解答和组合型复合地基整体平均固结度解答。将组合型复合地基固结度解析解与三维有限元数值解进行了比较,证明了解析解的合理性。利用固结度解析解对影响组合型复合地基固结速率的主要因素进行了分析,研究了组合型复合地基的固结特性。结果表明：组合型复合地基的固结速率随着短不排水桩贯入比的增加而逐渐增大,随排水体的井阻和其周边涂抹区厚度的增加而减小。短不排水桩刚度和置换率的变化对组合型复合地基固结速率的影响较小。 相似文献
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塑料排水板在海堤、公路、码头、水闸等软基加固工程中应用较广,塑料排水板处理软地基,是用塑料排水板将地基中的水排除,以增加作用于土颗粒的有效应力来加速地基固结沉降,达到提高强度的目的。在九江市日元贷款城市防洪工程八里湖大堤软基处理中成功应用了塑料排水板施工技术,结合该工程实例。介绍了塑料排水板施工工艺。 相似文献
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采用大型土工离心机对某工程近海软土地基上堤坝施工期及运行期进行了模拟。试验中采用停机加载法模拟分级施工加载过程, 原型中采用塑料排水板固结法处理软土地基, 模型中则根据固结过程相似的原理, 换算成等效圆截面排水体, 在模型制作中采用等效透水滤芯进行模拟。根据激光位移传感器和孔隙水压力传感器数据可以得出相应原型软土地基的沉降特性和孔隙水压力变化情况。根据试验得到的沉降曲线, 采用"经验双曲线法"推算出了地基最终沉降, 然后得出按沉降推算的分层地基平均固结度随时间的变化。对比试验模拟得到的软土地基固结度和理论计算结果, 二者基本接近, 表明塑料排水板模拟方法用于离心模型试验是可行的。 相似文献
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在工程实践中,排水垫层厚度、渗透系数等设计参数高度依赖经验,建筑规范[1]认为粉细砂不宜用于排水垫层。结合上海某围垦工程粉细砂排水垫层的实践与原位观测成果,借助于非线性有限元,对粉细砂排水垫层的特性进行研究,探讨垫层渗透系数、厚度、长度以及堤身相对透水性等主要因素对地基固结排水的影响。在此基础上,提出以导水系数作为垫层设计控制参数,并提出可以考虑以上几个主要因素的垫层设计公式,可为粉细砂取代中粗砂用于垫层设计及施工提供了技术支持。实践证明淤泥地基上利用粉细砂充填土工管袋作为排水垫层是可行的。 相似文献
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An instrumented trial-fill dike was constructed on soft, laminated soils of the Lisan Peninsula foreshore of the Dead Sea.
The earthwork had base dimensions of 180 m by approximately 70 m wide and was raised in two stages to a maximum height of
12.5 m above original ground level. The geotechnical data of the dike were monitored in order to: assess the short- and long-term
strength of the foundation, obtain and analyze the pore-pressure response of the foundation soils for potential use in construction
control, obtain data on embankment settlement in order to refine end-of-construction and post-construction settlement assessments,
and optimize the height of the dike to be constructed by providing information on the construction sequence for use in calculation
of capital costs and alternative layouts and dike heights. The successful completion of the trial dike has demonstrated that
steep-side dikes up to 12.5 m high can be constructed rapidly on soft soils. The construction of the trial dike has therefore
proved a very substantial benefit to the evaluation of the likely performance of a dike constructed along the Lisan shore.
The key factor which made this fast construction possible was the unexpected, very rapid consolidation of the majority of
the foundation soil which has been shown to occur. The principal observations from the trial dike were: (1) end of construction
settlements may be calculated using drained stiffnesses where E′/su initial has a value of around 65; (2) post-construction settlements can be calculated using a coefficient of secondary compression,
Cα equal to 0.015; (3) a rapid increase in undrained shear strength occurred when loading the soil up to a value of su equal to around 30 kPa. The value of su/σv′ was as high as 0.5 at this stage. With further loading the strength increase was more modest and su/σv fell to around 0.25 for a vertical effective stress of 160 kPa; (4) for the undrained stability analyses of the trial dike,
the mean vane shear-strength profile provided an appropriate assessment of the short-term factor of safety against failure,
5) For the drained stability analyses of the trial dike, lower bound effective strength parameters for the foundation and
embankment fill (c′=0, φ′=30° and c′=2 kN/m2, φ′=33°, respectively), combined with field measurements of end of construction pore water pressures provided an analysis
which was broadly compatible with the undrained analysis; and (6) the trial dike has been stable, pre- and post-construction,
because of the well drained nature of its foundation which prevented the build up of high pore water pressures and led to
rapid consolidation.
Received: 22 June 1998 · Accepted: 30 October 1998 相似文献
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Theoretical and experimental study of consolidation settlement characteristics of hydraulic fill soil in Shanghai 总被引：1，自引：1，他引：0
Yiqun Tang Jie Zhou Xiaojun He Ping Yang Jianxiu Wang 《Environmental Earth Sciences》2012,67(5):1397-1405
To determine the influence of load and drainage on the engineering consolidation characteristics of hydraulic fill soil in Shanghai, a detailed study has been carried out using three controlled model tests under different conditions. The governing equation of one-dimensional large strain consolidation with the load and self-weight was also quoted to discuss the influence. Three consolidation settlement stages and two consolidation periods of growth in strength were observed. The effect of applying load was more obvious than improving drainage condition in the first consolidation time. Prolonging consolidation time had no significant influence on increasing strength. It is shown that the increase in strength is concentrated in the first period of consolidation and the load and drainage play their different roles in different consolidation periods. Conclusively, some relevant recommendations are offered for the construction of hydraulic fill soil. 相似文献