单桩极限承载力时间效应估算方法比较     

王伟  卢廷浩  宰金珉 《岩土力学》2005,26(Z1):244-247

沉入饱和软土中的预制制桩的极限承载力随间歇期的增长而增大,这一现象虽已被工程界广泛认可,但至今仍然没有得到很好地解决。有效地确定单桩承载力随时间变化的规律对桩基础设计非常重要。人们提出了多种估算预制桩随时间变化的桩承载力的方法,但由于不同方法有各自的适用性和局限性,算出的结果有时差别很大,在使用时很难准确把握。首先分析了用于估算饱和软土中预制桩承载力随时间变化的几种方法：对数函数法、双曲函数法、人工神经网络法和基于超孔隙水压力消散的理论解析公式法。再以简洁性、理论性、适用性等为准则,结合工程实例,对以上几种方法进行比较,指出各自优缺点,推荐基于超孔隙水压力消散的简化解析方法来估算软土中预制桩承载力随时间变化的规律。  相似文献   

CFG桩复合地基沉降计算探讨   总被引：8，自引：0，他引：8  

潘星 《岩土力学》2005,26(Z1):248-251

CFG桩（水泥粉煤灰碎石桩）复合地基是新近发展起来的一项地基处理技术,具有承载力提高幅度大,地基沉降小,适用范围广,造价低,施工方便等特点。阐述了CFG桩复合地基加固机理及沉降模式,详细讨论了其沉降计算,包括它的计算厚度、影响因素、压缩模量选取及附加压力计算等。提出按变形控制理论进行变形计算有其优点,但仍有很多工作要做。  相似文献   

基桩屈曲的几何非线性有限元分析     

赵明华  汪优  黄靓 《岩土力学》2005,26(Z2):184-188

将桩身视为空间受力的梁单元,利用更新的拉格朗日坐标体系考虑梁单元的几何非线性;并采用弧长控制法求解有限元非线性方程组,进行基桩屈曲的几何非线性有限元分析。利用Matlab语言编制了相应的计算程序,将某现场木桩压屈试验实测屈曲临界荷载与理论分析比较,吻合良好。大量计算分析表明,桩周土地基系数、基桩埋入比、桩身材料和基桩长细比是影响基桩屈曲荷载大小的重要因素,在设计和施工中都应重视和考虑。  相似文献   

Transverse seismic kinematics of single piles by a modified Vlasov model     

Qijian Liu  Fangjun Deng  Yibin He 《国际地质力学数值与分析法杂志》2014,38(18):1953-1968

Within the framework of soil–pile interaction, a novel displacement scheme for the transverse kinematic response of single piles to vertically propagating S waves is proposed on the basis of the modified Vlasov foundation model. The displacement model contains a displacement function along the pile axis and an attenuation function along the radial direction. The governing equations and boundary conditions of the two undetermined functions are obtained in a coupled form by using Hamilton's principle. An iterative algorithm is adopted to decouple and solve the two unknown functions. In light of the governing equation of the pile kinematics, a mechanical model is proposed to evaluate the present method on a physical basis considering material damping. The coefficient of the equivalent Winkler spring is derived explicitly as function of the displacement decay parameter γ and soil Poisson's ratio. A parametric study is performed to investigate the effects of the soil–pile system properties on the kinematic response of single piles. The results show that the dimensionless pile length controls the transverse kinematics of piles. In terms of the theory of beams on elastic foundation, the classification limits of the dimensionless pile length may be π ∕ 4 and π, respectively. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Capturing the two‐way hydromechanical coupling effect on fluid‐driven fracture in a dual‐graph lattice beam model          下载免费PDF全文

Ole Ivar Ulven  WaiChing Sun 《国际地质力学数值与分析法杂志》2018,42(5):736-767

Fluid‐driven fractures of brittle rock is simulated via a dual‐graph lattice model. The new discrete hydromechanical model incorporates a two‐way coupling mechanism between the discrete element model and the flow network. By adopting an operator‐split algorithm, the coupling model is able to replicate the transient poroelasticity coupling mechanism and the resultant Mandel‐Cryer hydromechanical coupling effect in a discrete mechanics framework. As crack propagation, coalescence and branching are all path‐dependent and irreversible processes, capturing this transient coupling effect is important for capturing the essence of the fluid‐driven fracture in simulations. Injection simulations indicate that the onset and propagation of fractures is highly sensitive to the ratio between the injection rate and the effective permeability. Furthermore, we show that in a permeable rock, the borehole breakdown pressure, the pressure at which fractures start to grow from the borehole, depends on both the given ratio between injection rate and permeability and the Biot coefficient.  相似文献   

Kinematic analysis of pile behavior for improvement of slope stability in fractured and saturated Hoek–Brown rock masses          下载免费PDF全文

C.B. Qin  S.C. Chian  C.Y. Wang 《国际地质力学数值与分析法杂志》2017,41(6):803-827

Because of a multitude of steep slopes being constructed adjacent to roadways, there is greater concern of landslide occurrence, particularly in instances where poor geomaterials are present. Installation of piles along the slope is one commonly adopted method. This paper presents the assessment of the stability of a rock slope with stabilizing piles based on kinematic analysis. The pile effect is introduced with a resultant lateral force and a moment. Upper bound solutions of the pile's lateral force are derived with a log‐spiral rotational failure mechanism. The slope performance based on the bearing capacity of surcharge loading is also discussed with consideration of pore water pressure. In order to substantiate the derived theoretical solutions, numerical analysis with optimization technique is carried out. Results demonstrate that rock materials with high quality are conducive to ensure slope stability. Reduced lateral force on the pile is produced with lower rock weight, slope height, and surcharge loading. Finally, the safety factor and stability coefficient are discussed to complete the evaluation of the slope stability. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

A new analytical model to study the influence of weld on the vertical dynamic response of prestressed pipe pile          下载免费PDF全文

Wenbing Wu  Guosheng Jiang  Shenggen Huang  Guoxiong Mei  Chin Jian Leo 《国际地质力学数值与分析法杂志》2017,41(10):1247-1266

This investigation is concerned with the mathematical analysis of a viscoelastic prestressed pipe pile embedded in multilayered soil under vertical dynamic excitation. The pile surrounding soil is governed by the plane strain model, and the soil plug is assumed to be an additional mass connected to the pipe pile shaft by applying the distributed Voigt model. Meanwhile, the prestressed pipe pile is assumed to be a vertical, viscoelastic, and hollow cylinder governed by the one‐dimensional wave equation. Then, analytical solutions of the dynamic response of the pipe pile in the frequency domain are derived by means of the Laplace transform and impedance function transfer method. Subsequently, the corresponding quasi‐analytical solution in the time domain for the case of the prestressed pipe pile undergoing a vertical semi‐sinusoidal exciting force applied at the pile top is obtained by employing the inverse Fourier transform. Utilizing these solutions, selected results for the velocity admittance curve and the reflected wave curve are presented for different heights of the soil plug to examine the influence of weld properties on the vertical dynamic response of prestressed pipe pile. The reasonableness of the theoretical model is verified by comparing the calculated results based on the presented solutions with measured results. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

基于ANSYS和响应面法的抗滑桩结构可靠性分析     

罗丽娟  张鹏  任翔  石娜  江冠 《工程地质学报》2015,23(3):454-461

在深入分析可靠度指标的几何意义和响应面法的基本思想的基础上,提出了基于ANSYS和响应面法的可靠度算法与步骤。分析了陕西省吴起县大路沟巨型黄土滑坡的工程地质条件,根据滑坡的工程地质勘察资料和滑坡治理工程的设计资料,建立了基于ANSYS的抗滑桩桩土体系有限元模型,经过自重作用下桩土结构有限元分析,验证了该有限元模型的有效性。在此基础上,选取滑体土重度、滑面土内聚力c和内摩擦角、滑面以下土的压缩模量Es;4个随机变量,基于响应面(中心复合设计CCD)法和通用有限元软件ANSYS平台,建立了抗滑桩的可靠度分析模型,并研制了对应算法。工程算例结果表明:当试验点数量N=25时,抗滑桩结构的失效概率Pf=0.35%,可靠度指标=2.70,从而验证了基于ANSYS和CCD响应面法建立抗滑桩可靠度计算模型及算法是可行的。  相似文献   

CFG桩复合地基在天津武清地区软土地基中的应用     

王响贵  曹胜利  刘立岩 《城市地质》2015,(Z2):82-85

CFG桩技术已在全国推广应用,但在天津武清软土地区应用不普遍。本文以天津武清开发区尚清湾花园高层建筑软土地基处理中CFG桩的应用为例,介绍了CFG桩在天津武清地区的适用条件和设计方法,并通过对CFG桩工程验收检测结果分析,验证了在该地区采用CFG桩复合地基的可行性。经济技术效益明显,应用效果良好。对在该地区的CFG桩施工过程中出现的问题加以总结并对原因进行分析,为今后在该地区应用CFG桩复合地基的设计、施工提供参考借鉴。  相似文献   

软土地区基坑开挖引起桩基质量问题的判定与处理          下载免费PDF全文

郭月亮  田少坤 《探矿工程》2015,42(6):59-62

软土地区在基坑开挖时常常引起桩基破坏等工程问题,特别是在沿海、沿江等软土地区发生较多。以江苏一个沿江电厂为工程实例,通过对桩基位移和桩身裂缝的数据统计分析,揭示了基坑开挖时桩基发生移位、倾斜甚至断桩的真实原因。通过桩基取心试验、超声波试验和开挖验证找到了产生桩身缺陷的原因。此外还结合工程实例,提出了桩基出现质量问题时,可采取补强注浆的方法进行补救和处理,实践证明提出的处理方法效果良好。  相似文献