运用ANSYS对板桩墙支护模型的计算分析

运用ANSYS弹塑性有限元应用软件,对深基坑支护工程的板桩墙支护体系模型进行了分析探讨,得到了悬臂板桩墙支护模型的土体位移等值线图、主动土压力云图、墙土接触处的裂缝深度、不同土体材料的沉降影响区域半径。并求证了拉锚式支护结构的锚固力F对控制支护土体变形的有利影响。计算结果表明,ANSYS有限元程序将在深基坑支护工程的设计、施工中提供有效依据。     

Deformation analysis of reinforced soil retaining walls—simplistic versus sophisticated finite element analyses

Over the last two decades, different kinds of modular block have been increasingly used in the geogrid-reinforced soil retaining walls. The simulation of such wall behavior, which involves interactions between different structural components and backfill soils, requires a rigorous numerical procedure. Finite element is usually a preferred method, but this procedure, especially the soil constitutive models, is of different degrees of sophistication. It is always an issue of how simple or sophisticated should an analysis be conducted in replicating the actual behavior. In this article, a full-scale test wall was used to validate simplistic and sophisticated finite element analyses. Different types of finite element and material models were used in the two kinds of analysis to differentiate the level of simplicity or sophistication. The results obtained from stress-deformation analyses are presented and compared. It is shown that for wall construction that involves static loading conditions, simplistic nonlinear elastic and sophisticated elastoplastic analyses produced close and acceptable results.     

Analytical and 3D numerical modelling of full-height bridge abutments constructed on pile foundations through soft soils

The scope of this paper is the analysis of full-height bridge abutments on pile foundations, installed through soft soils, with a commercially available finite element software and soil model. Well-documented centrifuge test data were used as reference. Excess pore pressures developed in the clay layer, vertical and horizontal movements of the soft clay, pile displacements and bending moments, and abutment wall bending moments were chosen for comparison, since they are the most critical parameters for observation and design. Additionally, the validity of an analytical method (SIMPLE), which was proposed to analyse the piled abutments subjected to nearby surcharge loading, is discussed. This soil-structure interaction problem has been investigated over the last three decades, using either field or centrifuge tests, accompanied by FE analyses. Special modelling techniques and advanced soil models were used in these numerical studies to establish the most representative field behaviour. However, since the codes or techniques used in these advanced FE analyses are neither very practical nor easily accessible, it is difficult to employ them consistently in design. Thus, the results of this study are intended to provide some guidelines for designers, and to bring insight about the interacting mechanisms into the design process.     

基坑开挖时邻近桩基性状的数值分析

基坑开挖时尤为关注的问题是土体侧向移动对邻近桩基的不利影响,土体的侧向移动使邻近桩基产生侧向位移和附加应力及弯矩,甚至可能使上部建筑物功能失效。采用土工有限元软件Plaxis 8.2对内支撑排桩支护基坑开挖过程进行数值模拟,分析了基坑开挖时对邻近桩基的各种影响因素,包括单排桩、双排桩在不同开挖深度、支护桩的刚度、桩基刚度、桩基距基坑开挖面距离、桩身的约束和桩长条件下桩身水平位移和弯矩的变化特性。     

Analysis of soil–pile–structure interaction in a two‐layer ground during earthquakes considering liquefaction

This study is conducted with a numerical method to investigate the seismic behaviour among certain soils, single piles, and a structure. A series of numerical simulations of the seismic behaviour of a single‐pile foundation constructed in a two‐layer ground is carried out. Various sandy soils, namely, dense sand, medium dense sand, reclaimed soil, and loose sand, are employed for the upper layer, while one type of clayey soil is used for the lower layer. The results reveal that when a structure is built in a non‐liquefiable ground, an amplification of the seismic waves is seen on the ground surface and in the upper structure, and large bending moments are generated at the pile heads. When a structure is built in a liquefiable ground, a de‐amplification of the seismic waves is seen on the ground surface and in the upper structure, and large bending moments are generated firstly at the pile heads and then in the lower segment at the boundary between the soil layers when liquefaction takes place. Copyright © 2007 John Wiley & Sons, Ltd.     

ANALYSIS OF PILED RAFT SYSTEMS IN LAYERED SOIL

This paper presents a method of analysis for piled raft systems constructed in layered soils. The method presented takes account of the interactions of the raft, piles and soil without the cost of a full three-dimensional rigorous analysis. This is done by the use of finite layer methods for the analysis of the soil and finite element methods for the raft. Examples are provided in the paper for piled rafts constructed on layered soils, and results are presented for bending moments in the raft and loads in the piles.     

Influence of spatial variability of soil friction angle on sheet pile walls’ structural behaviour

The uncertainty in terms of soil characterisation is studied to assess its effect on the structural behaviour of extended structures as sheet pile walls. A finite element model is used. This integrates a numerical model of the soil–structure interaction together with a stochastic model that allows characterising the soil variability. The model serves in propagating the variability and the system parameter uncertainties. Discussion is mainly focused on two points: (1) testing the sensitivity of the structural behaviour of a sheet pile wall to different geotechnical parameters and (2) assessing the influence of spatial variability of soil properties on the structural behaviour by identifying the most sensitive geotechnical parameter and the most significant correlation length values. The findings showed that in assessing the sheet pile wall’s structural behaviour, there are spatial variability parameters that cannot be considered negligible. In this study, soil friction angle is found to be an important parameter.     

2D Numerical Simulations of Soil Nail Walls

In practice, numerical simulations of soil nail walls are often carried out to assess the performance and stability. In the present study, implications of the use of advanced soil models, such as hardening soil model and hardening soil with small-strain stiffness model to simulate the behavior of in situ soil on the overall response of simulated soil nail wall have been studied, and compared with respect to the analysis using conventional and most prevalently used Mohr-Coulomb soil model. Further, influence of the consideration of bending stiffness of soil nails on the simulation results has been examined. Results of the simulations indicated that the use of advanced models is desirable for cases of soil nail walls constructed in soft soils and when lateral wall displacements are critical to the adjoining structures. Incorporation of bending stiffness of nails is found important from the consideration of facing failure modes of soil nail walls.     

考虑流变与固结效应的桩筏基础-地基共同作用分析

土的流变性与地基固结的综合作用,导致了上部结构与地基变形的时效性,并呈现出明显的非线性,对桩筏基础与地基共同作用的工作机理及其工作性能产生重要影响。为此,采用弹黏塑性流变模型考虑土的流变特性,通过有限元方法数值求解Biot耦合固结方程,对桩筏基础与地基共同作用的时间效应问题进行了非线性数值分析。通过算例计算,对加载后桩筏基础荷载分配和沉降特性及下覆土层中孔隙水压力的扩散和消散规律进行了探讨。研究表明,地基孔隙水压力的增长和消散不仅具有Mandel-Cryer效应,而且依赖于土的流变变形,尤其在排水条件较差时更为明显。因此,在分析桩筏基础内力变形的时效性时必须考虑土的流变性与地基的固结作用的联合效应。     

Dynamic interaction between the soil and an anchored sheet pile during seismic excitation

A subdomain approach for dynamic soil–structure interaction is proposed for the linear elastic seismic analysis of an anchored sheet pile, retaining a horizontally layered soil on rigid bedrock. A hybrid solution technique is used, employing a finite element formulation for the generalized sheet pile, a thin layer formulation for the soil and a direct stiffness formulation for the tieback; the displacement vectors of the sheet pile and the soil are decomposed, using the eigenmodes of the sheet pile and the propagating or decaying modes in the soil. The discretization can be limited to the interface(s), where pointwise continuity of the displacements is enforced, whereas a weak variational formulation is used for the stress equilibrium. The solution technique is illustrated by means of a numerical example, where the harmonic response of a flexible anchored sheet pile is considered and compared to the case where no tieback is present. Copyright © 2002 John Wiley & Sons, Ltd.     

Numerical modeling of dredging effect on berthing structure

Piles and diaphragm wall-supported berthing structure on marine soils are loaded laterally from horizontal soil movements generated by dredging. The literature on the adequacy of the finite element method modeling of berthing structure to analyze their behavior during dredging is limited. This paper describes a finite element approach for analyzing the lateral response of pile and diaphragm wall during dredging. Piles are represented by equivalent sheet-pile walls and a plane strain analysis using the finite element method is performed. Results from the finite element method are compared with full-scale field test data. Full-scale field test was conducted on a bearing structure to measure the lateral deflection on pile and diaphragm wall for their full length using inclinometer during dredging in sequence. The finite element method results are in good agreement with full-scale field results. Conclusions are drawn regarding application of the analytical method to study the effect of dredging on piles and diaphragm wall-supported berthing structures.     

Analysis of pile‐raft foundations under complex loads in layered soils

Considering there is hardly any concerted effort to analyze the pile‐raft foundations under complex loads (combined with vertical loads, horizontal loads and moments), an analysis method is proposed in this paper to estimate the responses of pile‐raft foundations which are subjected to vertical loads, horizontal loads and moments in layered soils based on solutions for stresses and displacements in layered elastic half space. Pile to pile, pile to soil surface, soil surface to pile and soil surface to soil surface interactions are key ingredients for calculating the responses of pile‐raft foundations accurately. Those interactions are fully taken into account to estimate the responses of pile‐raft foundations subject to vertical loads, horizontal loads and moments in layered soils. The constraints of the raft on vertical movements, horizontal movements and rotations of the piles as well as the constraints of the raft on vertical movements and horizontal movements of the soils are considered to reflect the coupled effect on the raft. The method is verified through comparisons with the published methods and FEM. Then, the method is adopted to investigate the influence of soil stratigraphy on pile responses. The study shows that it is necessary to consider the soil non‐homogeneity when estimating the responses of pile‐raft foundations in layered soils, especially when estimating the horizontal responses of pile‐raft foundations. The horizontal loads and the moments have a significant impact on vertical responses of piles in pile‐raft foundations, while vertical loads have little influence on horizontal responses of piles in pile‐raft foundations in the cases of small deformations. The proposed method can provide a simple and useful tool for engineering design. Copyright © 2013 John Wiley & Sons, Ltd.     

Parametric studies of DDC-induced deflections of sheet pile walls in soft soils

This paper presents a thorough finite element (FE) parametric study of sheet pile wall deflections caused by deep dynamic compaction (DDC). In this study, the effects of several parameters which may affect the wall deflections were investigated. These parameters are (1) wall embedment length; (2) tamping distance; (3) impact energy per blow; (4) blow counts; (5) soil types on the supporting side of sheet pile walls; and (6) wall stiffness. The effects of these parameters were quantified and discussed, and the factors that help to reduce wall deflections were identified. A series of figures which depict the effects of these parameters were generated. Finally, some suggestions and recommendations for design and construction were reached.     

钢板桩挡墙主动土压力分布的形状效应

采用有限元数值试验,研究帽型钢板桩的截面形状对墙后主动土压力分布规律的影响。首先,对室内缩尺模型试验进行数值模拟,对比实测数据验证数值模型的有效性;然后,建立钢板桩挡墙数值模型,模拟该挡墙在不同位移模式下土压力变化和分布的规律,与平板挡墙计算结果进行对比,分析钢板桩截面形状对土压力分布的影响,进一步探讨形状效应的可能影响因素及机制。分析结果表明,钢板桩的截面形状影响墙后主动土压力的分布形式,影响程度与位移模式有关;墙体平动和绕墙底转动情况下,钢板桩挡墙凸出部分的主动土压力值大于凹处,但墙体绕墙顶转动情况下差异不明显;主动土压力的形状效应由土拱效应引起,截面高宽比对其影响显著,墙土摩擦角影响有限。     

土钉墙数值模拟在干船坞坞墙中应用探讨

从减少基坑开挖过程中坞墙位移和控制坞壁渗水角度出发,利用数值模拟分析,探讨在深基坑开挖中得到广泛应用的普通土钉墙和用于船坞坞室基坑开挖中的复合土钉墙技术,将联合劲性水泥土搅拌桩的复合土钉墙用于干船坞的坞墙结构。从工程探讨角度,研究土钉联合劲性水泥土搅拌桩、预应力锚杆的复合土钉墙在干船坞这一特定条件下的应用问题,并通过分析模拟结果,为干船坞坞墙设计施工过程中安全问题提出一些注意点     

A novel computational approach for large deformation and post‐failure analyses of segmental retaining wall systems

Segmental retaining wall (SRW) systems are commonly used in geotechnical practice to stabilize cut and fill slopes. Because of their flexibility, these systems can tolerate minor movements and settlements without incurring damage or crack. Despite these advantages, very few numerical studies of large deformations and post‐failure behavior of SRW systems are found in the current literature. Traditional numerical methods, such as the finite element method, suffer from mesh entanglement, thus are unable to simulate large deformations and flexible behavior of retaining wall blocks in SRW systems. To overcome the above limitations, a novel computational framework based on the smoothed particle hydrodynamics (SPH) method was developed to simulate large deformations and post‐failure behavior of soils and retaining wall blocks in SRW systems. The proposed numerical framework is a hybrid continuum/discontinuum approach that can model soil as an elasto‐plastic material and retaining wall blocks as independent rigid bodies associated with both translational and rotational degrees of freedom. A new contact model is proposed within the SPH framework to simulate the interaction between the soil and the blocks and between the blocks. As an application of the proposed numerical method, a two‐dimensional simulation of an SRW collapse was simulated and compared to experimental results conducted under the same conditions. The results showed that the proposed computational approach provided satisfactory agreement with the experiment. This suggests that the new framework is a promising numerical approach to model SRW systems. Copyright © 2014 John Wiley & Sons, Ltd.     

Strutted Excavation in Soft Soil Incorporating a Jet-Grout Base Slab: Analysis Considering the Consolidation Effect

The influence of the consolidation on a strutted excavation in soft soil is analysed using a computer code based on the finite element method. A base jet-grout slab is considered in order to improve stability against bottom heave failure and minimize wall displacements. The numerical model incorporates the Biot consolidation theory (coupled formulation of the flow and equilibrium equations) with soil constitutive relations simulated by the p–q–θ critical state model. Special emphasis is given to the analysis, during and after the construction period, of the pore pressures, shear stresses, stress levels and displacements in the ground, as well as strut compression loads, wall displacements and bending moments, earth pressures on the wall faces and compression loads and bending moments on the jet-grout slab. The safety factor against bottom heave is also evaluated from the finite element analysis considering formulations of the critical state soil mechanics, and also compared to values obtained with traditional methods that use limit equilibrium approach and bearing capacity fundamentals.     

Experimental and Numerical Study of Strip Footing Supported on Stabilized Sand Slope

The paper presents the results of laboratory model tests and theoretical analysis on the behavior of a strip footing supported on sheet pile wall-stabilized sandy slope and loaded vertically to failure. The parameters varied in the study include the height, stiffness and location of the sheet pile wall, the location of the footing relative to the slope crest and the relative density of sand. Two-dimensional plane strain finite element analyses was used to analyze a prototype strip footing on sandy slope with same conditions. The results indicate that the inclusion of sheet pile wall has significant effect in improving the response of the strip footing and the slope itself. The theoretical results confirm the experimental results of the model footing tests and show reasonable agreement. Based on the numerical and experimental results, critical values of the sheet pile wall parameters for maximum stabilizing effect are established.     

Probabilistic approach to the design of anchored sheet pile walls

Following a brief review of the physico-mechanical properties of soils, this work analyzes and comments upon some of the most frequently used approaches in anchored sheet pile wall design. The analysis highlights the conceptual differences between the various approaches, often leading, inevitably, to markedly diverging results. Although the probabilistic approach cannot be applied extensively, mainly because it is difficult to obtain statistical modelling of the soil mass, it nevertheless enables designers to avoid certain ambiguities that are present in the commonly used approach based on the Safety Factor. In addition, the probabilistic approach also permits handling of the calibrations required for the approaches to partial coefficients to be effective and applicable to different local conditions associated with the diversity of soils, different modes of construction, etc. Numerical results obtained for a simple probabilistic model lead to conclusions which are certainly not exhaustive but may contribute significant elements for reflection.     

On vertical dynamic stability and cross‐section optimization of closed‐ended hollow pile by considering soil compaction effects

This paper conducts a comprehensive study on the effects of expansion force after pile driving on the vertical vibration of the hollow pile. The initial radially inhomogeneous strain field of soil in disturbed soil region and dynamic shear modulus of remolded soil are constructed by applying the cylindrical cavity expansion method. The equation governing the incremental motion of the soil is consequently deduced on the basis of incremental deformations superposed on an underlying finite deformation. The longitudinal impedance of the top of the pile and the velocity response in frequency and time domains are also numerically studied. The relations between the expansion force after pile driving and the velocity response of the pile with different wall thickness are discussed accordingly. The results suggest that a pile has a better dynamical stability when the characteristics of the section are optimized and interacting force with soil medium gets smaller.