Circular plates on Pasternak elastic foundations

This study deals with the geometrically nonlinear axisymmetric static and transient response of cylindrically orthotropic thin circular plates resting on Pasternak elastic foundations subjected to uniformly distributed loads. Clamped and simply-supported plates with radially movable and immovable edges have been considered. The von-Kármán type nonlinear governing equations have been solved using orthogonal point collocation method in the space domain and Newmark-β scheme in the time domain. The maximum transient response to step loads has also been predicted from static response. The influence of the foundation parameters on the response has been investigated.     

Analysis of Beams on Pasternak Foundation Using Quintic Displacement Functions

Geotechnical and Geological Engineering - Beams supported by elastic foundations one of the complex soil-structure interaction problems and analysis carried out using the concept of “beam on...     

弹—粘塑性地基上的弹性梁的有限元分析

本文分析了弹-粘塑性地基上弹性梁的计算原理,给出了利用有限单元法解决该问题的具体公式和程序实现方法,并通过数值解的例子说明了在基坑工程中弹-粘塑性地基对支护体系的影响。     

Rigid Foundations Resting on an Elastic Layered Soil

A rigid foundation of arbitrary shape resting on a stratified half space (soil), with specific geometrical and elastic properties for its horizontal layers, is examined under the action of a vertical load placed anywhere on the foundation area. On the basis of a purely analytical treatment of the deformability of the soil surface, i.e. without using a finite element discretization of the layered soil mass, a general method is developed in order to determine the contact soil pressures and the resulting settlements through an easily implemented numerical procedure. The possible presence of “inactive” foundation parts not being in contact with the soil surface is taken into account. Parametric studies are performed showing the influence of the variability of the soil layers, as well as of the vertical load location, on the contact pressures developed. In this context, for the cases of a rectangular and a circular foundation the area borders for the location of a vertical load are determined, either for the development of compressive soil pressures all over the footing (core), or for allowing the existence of some inactive part without contact with the soil (zero contact pressure), not exceeding the half of the total foundation surface (limit core).     

基础板厚度对减小不均匀沉降的算例分析

对弹性地基上不同刚度的基础板,利用弹性地基上梁的计算方法进行了不同集中荷载工况下的变形计算。根据计算结果,分析了基础刚度对于弹性地基上基础的最大沉降的影响以及刚度对于基础整体变形的影响。     

Prestressed Foundation Beams on Elastic Layered Soil

This paper develops a systematic procedure concerning the determination of the interaction of an arbitrary multistory frame with the elastic layered foundation soil by making use only of the soil surface deformational characteristics. The paper focuses on the response of the foundation beam through which the frame rests on the ground, showing the need for prestressing the beam in order to ensure better functionality. The investigation addresses the dual goal of excluding the undesirable cracked state of the beam and reducing its structural height together with the overall amount of reinforcement needed. A set of soil layered profiles is considered and it is investigated to what extent the required prestressing force depends not only on the soil deformational properties at hand, but also on the method of analysis used. The results are compared for both the elastic half-space and the Winkler’s method, taking into account either the whole structure stiffness, or the stiffness of the foundation beam only, as it is usually considered in practice.     

传递矩阵法分析中心集中荷载下圆形刚性板

采用传递矩阵法分析横观各向同性地基上的刚性圆板，分析竖向的弹性模量Ev、水平向的弹性模量Eh、竖直面上的剪切模量Gv以及Eh和Ev的比值n、Gv和Ev的比值m、水平向应力引起的正交水平向应变的泊松比Uh、竖直向应力引起的水平向应变的泊松比Uvh对沉降和基底反力影响；同时采用成层地基进行分析，将其计算结果与常规方法中采用对弹性模量和泊松在计算深度内按深度加权平均的计算结果进行比较。     

复合地基物理模型及圆板-复合地基系统分析

将非散体材料复合地基（水泥搅拌桩、粉喷桩等）模拟成各向异性弹性体。根据圆柱体柱坐标的极点条件，取样条函数为复合地基的位移函数，而外部土体用半解析函数来模拟。最后对圆板-成层复合地基系统进行了分析。     

A Research for Large Plate Foundation on Silt

It is necessary to consider the bearing capacity and displacement of the silt with 76~82% water content, when power transmission towers are contucted. Fall scale experiments have been carried out for the above reasons. The results of the experiments have shown that the large plate foundation method for the tower is the most efficient safety economic and easy to be constructed. The foundation is stable and the settlement is uniform.     

淤泥地基大板基础的试验研究

在淤泥地基上建造高耸输电铁塔,必须考虑地基的承载力与沉降变形.本文介绍了在含水量ω=76～82%的淤泥地基上,采用大板为基础建造铁塔,通过原型试验结果证明,选用此方案是可行的,不仅使地基达到了稳定,沉降均匀,确保了上部建筑的安全;而且施工简便,经济可靠,为在软土地基上建造这类高耸建筑物提供了新的技术途径.     

Plate Load Tests of Composite Foundation Reinforced by Concrete-Cored DCM Pile

The concrete-cored deep cement mixing (DCM) pile is a new kind of composite pile created by inserting precast core pile into the DCM column socket and has only been used in a few projects to date. The bearing mechanism of concrete-cored DCM pile composite foundation has not been investigated systematically. In this paper, plate load tests (PLT) on single pile composite foundation were conducted in Nanjing–Changzhou expressway, Xinhua district in Jiangyin city and Nanjing surrounding (NS) expressway. Following the results of the PLT, a comparison of ultimate bearing capacity between composite foundation reinforced by concrete-cored DCM pile and DCM column was made. During the PLT process, the vertical stress of surrounding soil and DCM column socket was measured using pressure cells. The vertical stress of precast core pile was obtained using steel stress gauge welded onto the reinforcement. Based on the vertical stress of surrounding soil, DCM column socket and precast core pile, the skin friction and load sharing ratio were obtained. The variation in surrounding soil properties depending on the installation of concrete-cored DCM pile was also analyzed using the results from cone penetration tests (CPT) taken in NS expressway. With the analysis of results for stress tests and CPT, the bearing mechanisms of composite foundation reinforced by concrete-cored DCM pile are obtained.     

A Simple Method for Analysis of Point Anchored Rockbolts in Circular Tunnels in Elastic Ground

Summary. A simple analytical method for the analysis of point anchored rockbolts is presented in this paper. The solution has been derived for elastic ground and rockbolts, for plane strain conditions, and for tunnels with circular cross section. The method provides accurate results for the rockbolts’ loads and displacements and explicitly includes the connection of the rockbolts to the surrounding ground. The addition of such details to a Finite Element numerical model is critical; otherwise the solution obtained may be dependent on the discretization used and on the stiffness of rockbolts and ground. As an alternative to including details of the rockbolt head and anchor point in the numerical model, which could be computationally very expensive, an equivalent spring constant is proposed. The spring constant is obtained by matching numerical with analytical results for a simple case, but keeping the geometry, material properties, and discretization unchanged.     

Bearing Capacity of Shallow Foundation on Two Clay Layers by Numerical Approach

Natural soils are often deposited in layers. The estimation of the bearing capacity of the soil, using conventional bearing capacity theory based on the properties of the top layer, introduces significant inaccuracies if the thickness of the top layer is comparable to the width of the rigid footing placed on the soil surface. Saturated normally consolidated and lightly overconsolidated clays indicate that under undrained condition the cohesion of soil mass increases almost linearly with depth. A few theoretical studies have been proposed in the literature to incorporate the variation of cohesion with depth in the computation of the ultimate bearing capacity of strip and circular footings. In this paper, after reviewing previous works, numerical computations using the FLAC code (Fast Lagrangian Analyses of Continua) are reported to evaluate the two layered clays effect on the bearing capacity beneath rigid strip footing subject to axial static load. The results of the bearing capacity relating to the relative thickness of the top layer, the strength ratio of the soil two-layered clays and the rates of the increase of soil cohesion with depth are presented in Tables and graphs. The obtained results are compared with previous published results available in the literature.     

Analysis of Error Caused by Replacing Spherical Shell with an Elastic Plate Model in Studying Bending Deformation of the Lithosphere

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An Effective Method for Free Vibration of Plate on Elastic Half Space

The vibration analysis of a plate on an elastic foundation is an important problem in engineering. It is the interaction of a plate with the three-dimensional half space and the plate is usually loaded from both the upper and lower surfaces. The contact pressure from the soil can not be predefined. According to Lambs solution for a single oscillating force acting on a point on the surface of an elastic half space, and the relevant approximation formulae, a relation between the local pressure and the deflection of the plate has been proposed. Based on this analysis, the reaction of the soil can be represented as the deformation of the plate. Therefore, the plate can be separated from the soil and only needs to be divided by a number of elements in the analysis. The following procedure is the same as the standard finite element method. This is a semi-analytical and semi-numerical method. It has been applied to the dynamic analysis of circular or rectangular plates on the elastic half space, at low or high frequency vibration, and on rigid, soft or flexible foundations. The results show that this method is versatile and highly accurate.     

某工程塑料排水板法加固软弱地基试验研究

通过对广州美的厂房地基处理工程进行试验和研究,分析了塑料排水板法处理深厚软弱地基的工程特点,并为同类工程的设计提供了一定的依据。     

Effectiveness of Random Field Approach in Serviceability Limit State Analysis of Strip Foundation

Geotechnical and Geological Engineering - This work conducts a probabilistic inquiry on how the variability of the parameter defining soil deformability affects the settlement of the foundation...     

水平荷载下单片地下连续墙基础的应变楔模型分析法

近年来单片地下连续墙被广泛运用于桥梁工程和高层建筑中,但其大部分研究均集中于单片地下连续墙的竖向承载性能试验研究和理论分析,只进行了少量单片墙的水平承载性能试验研究.通过应变楔模型把墙与土之间复杂的三维接触特性简化为一维的弹性地基梁中所需土体的参数,然后按照弹性地基梁的理论计算墙的内力和变形,利用室内模型试验实测数据验证了该算法的合理性.可为类似工程提供依据.     

利用低应变检测曲线判断桩基质量

随着建筑业的迅速发展,采用桩基处理的工程越来越多,而施工及土层等复杂因素导致桩身质量问题普遍存在,因此检测桩基质量问题显得十分重要。运用低应变无损检测方法进行检测,在现场原始资料准确无误前提下,可以检测桩身质量问题。根据在沈阳施工中见到的不同桩身质量问题,结合时域及频域计算分析,总结出完好桩、轻微缺陷桩、明显缺陷桩三种类型桩的典型曲线反应特征,借此曲线类型可做检测新区时参考。