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考虑变形影响的基坑土压力计算方法 总被引:3,自引:0,他引:3
土压力的分布和大小与变形密切相关。分析了目前考虑变形的土压力设计计算方法,并提出了考虑变形的土压力计算模型,对两个工程实例进行了计算分析,计算所得的主动土压力和被动土压力都在合理的范围内,显示出了该方法的合理性。 相似文献
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为了研究桩间存在土拱效应的挡土板土压力,本文根据桩间土拱的静力平衡条件和拱脚处土体强度条件,建立计算模型,得出了桩间土拱形状的空间函数。在分析桩间土拱形状的基础上,确定了桩间土体的滑裂面,从理论上推导出了桩间挡土板土压力计算公式。对影响土压力大小的各种参数进行了分析得出:在不同参数条件下,将其与朗肯土压力进行比较。结果表明在其他因素不变的情况下,挡土板土压力大小受桩间距影响最大,它随着桩间距的增大而增大。土压力明显小于朗肯土压力,说明考虑土拱效应的土压力计算方法使挡土板设计更加经济准确。 相似文献
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目前关于临近地下室外墙影响的挡土墙空间土压力的计算理论的研究还比较少,原有的平面应变条件下的理论不能满足挡土墙的长高比B/H较小时的挡土墙土压力计算要求。通过将土拱效应原理引入顾慰慈[8]建立的空间土压力计算模型,建立了考虑土拱效应的临近地下室外墙影响的空间土压力计算模型,根据挡土墙和地下室外墙的间距与土体破裂面状态的关系将该模型分为3种情况,并将各模型划分为Ⅰ、Ⅱ、Ⅲ、Ⅳ四个区域,通过在各个区域内取水平微分单元体,建立各微分单元体的水平和竖向静力平衡方程,推导出了各区相应的挡土墙空间主动土压力计算公式,该公式可以计算出墙背任意位置的主动土压力;并提出了空间土压力合力及其合力作用点的计算方法。通过算例计算可以直观地看出挡土墙后主动土压力的空间分布,由此可以看出,当空间效应存在时,考虑土拱效应的挡土墙主动土压力沿墙长的分布与平面应变条件时有很大的不同,此时挡土墙两端附近区域的主动土压力远小于平面应变条件下计算出的主动土压力,同时可以看出,考虑空间效应的挡土墙主动土压力合力作用点要比平面应变条件下的位置要高,挡土墙长高比B/H越小,空间效应对主动土压力沿墙长的分布和主动土压力合力作用点位置的影响越大。 相似文献
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以不同土压力状态与静止土压力状态时的压力差值计算分布力,基于Mindlin应变解建立了任意土压力变化下的土体侧向位移计算模型,计算得到土体达到主动极限状态下土体位移和达到被动极限状态下的土体位移。通过编制的程序研究了不同计算参数对土体达到主(被)动极限状态下土体位移的影响规律,包括土的内摩擦角、黏聚力、计算深度、计算宽度等,研究了土体主动极限位移和达到被动极限位移相关性规律。通过模型试验的实测资料验证了土压力位移计算模型的有效性和合理性。利用计算模型可以得到不同位移限值要求下的侧向土压力,从而为不同工程中土压力的合理取值提供了理论依据。 相似文献
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扩展剑桥模型参数的优化选择及其应用 总被引:4,自引:0,他引:4
在有限元计算中合理选取土的本构关系与模型参数,对于计算成果的可靠性是十分重要的。剑桥模型是一个应用广泛的弹塑性模型,其参数一般是通过室内试验来确定的。通过建立扩展剑桥模型在三轴条件下的弹塑性本构关系的表达式,并以此为依据,利用数值模拟常规三轴试验和单向压缩试验过程并利用正反分析技术优化求解剑桥模型参数,在小浪底大坝固结计算的应用中证明了这种方法的合理性与实用性。 相似文献
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An analytical model to simulate the penetration of the piezocone penetrometer in cohesive soils is presented here. The elasto-plastic coupled field equations of the saturated cohesive soils (given by Voyiadjis and Abu-Farsakh) is used in this analysis. The numerical simulation of the piezocone penetration is implemented into a finite element program. The analytical model is used to analyze the miniature piezocone penetration tests (PCPT) conducted at LSU calibration chambers. Simulation of the piezocone penetration is done for two cases. In the first case, the soil–penetrometer interface friction is neglected, while in the second case, the soil–penetrometer interface friction is taken into consideration. The constraint approach is used to model the soil–piezocone interface friction in which the Mohr–Coulomb frictional model is used to define the sliding potential. Analysis is done for three different soil specimens with different stress histories. The results of the numerical simulations are compared with the experimental measurements of the miniature piezocone penetration tests (PCPT) in cohesive soil specimens conducted in LSU calibration chambers. The resulting excess pore pressure distribution and its dissipation using the numerical model are compared with some available prediction methods. © 1998 John Wiley & Sons, Ltd. 相似文献
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A new one-dimensional model for penetration analysis of a rigid projectile into a soil target is presented. The soil medium is represented by a set of discs of constant thickness, responding in the radial direction under plain strain regime. When penetration through a typical disc occurs, the projectile displaces soil material and a radial plastic shock wave propagates in the disc. The interaction pressure between the projectile and soil material is compatible with the motion of the contact boundary, between them. The instantaneous resistive force is obtained by summation of the contributions of all the discs which are in contact with the nose surface of the projectile. Soil is considered as a ‘floating’ ideally locking material, in which the locking volumetric strain is adjusted to the physical stress–strain properties of the soil material. Friction between projectile and soil is assumed to be negligible. Comparison is made with both twodimensional computer program results and experimental data, and very good agreement is observed. Comparison with other analytical methods reveals that the present model most closely resembles existing experimental results and permits further analysis of the problem as predictions of target response and of stress distribution on the projectile nose. The calculations require very small amounts of computer time. Analysis with the present model yields an efficient and comprehensive means to analyse penetration and perform parameter analysis. 相似文献
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从极限平衡理论角度对刚性桩复合地基中垫层作用机理进行分析,提出桩顶垫层厚度、垫层材料内摩擦角等参数对桩土应力分担的控制公式,推导出在已知表面应力情况下考虑桩土共同作用的桩土沉降计算公式,在此基础上提出一种桩土应力比的迭代计算方法。编制程序实现对算例的计算,总结分析计算结果并与实测值进行对比验证。 相似文献
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在使用TOUGH+HYDRATE程序进行水合物开采数值模拟时常用van Genuchten模型计算毛管力,而毛管力大小直接影响水合物开采过程中的产气和产水,因此在数值模拟过程中正确选用模型参数尤为必要。我国某海域天然气水合物储层为未胶结泥质粉砂储层,常规的毛管力测定方法如压汞法、离心法等对该类岩心并不适用,如何测定该类岩心的毛管力并将其应用于van Genuchten模型参数选取具有重要意义。本文探讨了如何应用土壤水分特征曲线测定实验间接获取该类岩心的毛管力数据,为验证该方法的可行性,本文对参考文献[7]中公开的粉砂土壤水分特征曲线测定实验数据进行换算和拟合后得到T+H程序所需的van Genuchten模型参数,结果可为泥质粉砂储层水合物产能研究工作提供参考。 相似文献
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Compaction grouting is the injection of a viscous grout into a soil under high pressure, which then densifies the surrounding soil by reducing void space. Laboratory and field tests of compaction grouting have been carried out. In this paper, a numerical model is used to simulate the compaction grouting process with the primary purpose of investigating relationships among various control parameters, such as injection pressure, void ratio and excess pore water pressure at various radial distances from the injection point. The compaction process is treated as a cavity expansion process in the numerical simulation. The soil is modelled with an elasto-plastic Mohr–Coulomb model using the commercial finite element program ABAQUS. In addition to numerical simulations, pressure-controlled cavity expansion laboratory tests were carried out on completely decomposed granite (CDG) soil specimens. Data collected from laboratory tests are compared with the finite element simulation to validate the finite element analyses. Factors that control the compaction process, such as the coefficient of earth pressure (K), initial void ratio, number of loading cycles and effective confining pressure, are explored in the numerical simulations. 相似文献