The Boundary Element Method for Pile-Soil Interaction

In this paper, several mathmatical models for the pile- soil interaction are outlined. The Boundary Element Method is one of the very effective methods for the reasonable models of elasticity and elastoplasticity. The major of this paper is concerned with the Boundary Element Method for the pile-soil interaction, including general methods and calculating formulation of static and dynamic analysis of the pile and pile groups. Some results of analysis are also given.

Dual-Mode Terahertz Extended Interaction Oscillator Driven by a Pseudospark-Sourced Sheet Electron Beam

A terahertz dual-mode extended interaction oscillator (EIO) driven by a pseudospark-sourced sheet electron beam (SEB) was presented.The major advantages of the newly developed circuit include 1) high-density SEB interacting with the TM_(11) and TM_(31) modes,respectively,and 2) high output power of over 1 kW at the subterahertz frequency range.Two different types of 2π modes and their output characteristics were studied,and the circuit was optimized to ensure efficient outputs of two standing-wave modes.The three-dimensional (3D) particle-in-cell (PIC) simulation predicts the maximum output power of 1.3 kW with the 3-dB bandwidth of ~0.5 GHz at 303 GHz when operating at the TM_(11)mode,and 3.18 kW with the 3-dB bandwidth of ~0.85 GHz at 364 GHz when operating at the TM_(31)mode.

Innovative Techniques Unveiled in Advanced Sheet Pile Curtain Design

This thorough review explores the complexities of geotechnical engineering, emphasizing soil-structure interaction (SSI). The investigation centers on sheet pile design, examining two primary methodologies: Limit Equilibrium Methods (LEM) and Soil-Structure Interaction Methods (SSIM). While LEM methods, grounded in classical principles, provide valuable insights for preliminary design considerations, they may encounter limitations in addressing real-world complexities. In contrast, SSIM methods, including the SSI-SR approach, introduce precision and depth to the field. By employing numerical techniques such as Finite Element (FE) and Finite Difference (FD) analyses, these methods enable engineers to navigate the dynamics of soil-structure interaction. The exploration extends to SSI-FE, highlighting its essential role in civil engineering. By integrating Finite Element analysis with considerations for soil-structure interaction, the SSI-FE method offers a holistic understanding of how structures dynamically interact with their geotechnical environment. Throughout this exploration, the study dissects critical components governing SSIM methods, providing engineers with tools to navigate the intricate landscape of geotechnical design. The study acknowledges the significance of the Mohr-Coulomb constitutive model while recognizing its limitations, and guiding practitioners toward informed decision-making in geotechnical analyses. As the article concludes, it underscores the importance of continuous learning and innovation for the future of geotechnical engineering. With advancing technology and an evolving understanding of soil-structure interaction, the study remains committed to ensuring the safety, stability, and efficiency of geotechnical structures through cutting-edge design and analysis techniques.

Advanced Sheet Pile Curtain Design: Case Study of Cotonou East Corniche

This paper delves into the critical aspects of sheet pile walls in civil engineering, highlighting their versatility in soil protection, retention, and waterproofing, all while emphasizing sustainability and efficient construction practices. The paper explores two fundamental approaches to sheet pile design: limit equilibrium methods and numerical techniques, with a particular focus on finite element analysis. Utilizing the robust PLAXIS 2016 calculation code based on the finite element method and employing a simplified elastoplastic model (Mohr-Coulomb), this study meticulously models the interaction between sheet pile walls and surrounding soil. The research offers valuable insights into settlement and deformation patterns that adjacent buildings may experience during various construction phases. The central objective of this paper is to present the study’s findings and recommend potential mitigation measures for settlement effects on nearby structures. By unraveling the intricate interplay between sheet pile wall construction and neighboring buildings, the paper equips engineers and practitioners to make informed decisions that ensure the safety and integrity of the built environment. In the context of the Cotonou East Corniche development, the study addresses the limitations of existing software, such as RIDO, in predicting settlements and deformations affecting nearby buildings due to the substantial load supported by sheet pile walls. This information gap necessitates a comprehensive study to assess potential impacts on adjacent structures and propose suitable mitigation measures. The research underscores the intricate dynamics between sheet pile wall construction and its influence on the local environment. It emphasizes the critical importance of proactive engineering and vigilant monitoring in managing and mitigating potential hazards to nearby buildings. To mitigate these risks, the paper recommends measures such as deep foundations, ground improvement techniques, and retrofitting. The findings presented in this study contribute significantly to the field of civil engineering and offer invaluable insights into the multifaceted dynamics of construction-induced settlement. The study underscores the importance of continuous evaluation and coordination between construction teams and building owners to effectively manage the impacts of sheet pile wall construction on adjacent structures.

Simplified analytical solution for stress concentration ratio of piled embankments incorporating pile–soil interaction

Piled embankments have been extensively used for high-speed rail over soft soils because of their effectiveness in minimizing differential settlement and shortening the construction period.Stress concentration ratio,defined as the ratio of vertical stress carried by pile heads(or pile caps if applicable)to that by adjacent soils,is a fundamental parameter in the design of piled embankments.In view of the complicated load transfer mechanism in the framework of embankment system,this paper presents a simplified analytical solution for the stress concentration ratio of rigid pile-supported embankments.In the derivation,the effects of cushion stiffness,pile–soil interaction,and pile penetration behavior are considered and examined.A modified linearly elastic-perfectly plastic model was used to analyze the mechanical response of a rigid pile–soil system.The analytical model was verified against field data and the results of numerical simulations from the literature.According to the proposed method,the skin friction distribution,pile–soil relative displacement,location of neural point,and differential settlement between the pile head(or cap)and adjacent soils can be determined.This work serves as a fast algorithm for initial and reasonable approximation of stress concentration ratio on the design aspects of piled embankments.

Pile-clayey soil interaction analysis by boundary element method

This paper is an attempt to solve the soil-pile interaction problems using the boundary element method（BEM）.A computer package called PGroupN,which deals mainly with the analysis of the pile group problem,is employed in this study.Parametric studies are carried out to assess the impacts of the pile diameter,pile length,ratio of spacing to diameter and the thickness of soil stratum.The external load is applied incrementally and,at each increment,a check is made that the stress state at the pile-soil interfaces does not violate the yield criteria.This is achieved by specifying the limited stresses of the soil for the axial pile shaft capacity and end-bearing resistance.The elements of the pile-soil interface yielded can take no additional load,and any increase in load is therefore redistributed between the remaining elements until all elements have failed.Thus,by successive application of loading increments,the entire load-displacement relationship for the pile group is determined.It is found that as the applied load reaches the ultimate bearing capacity of the pile group,all the piles will share the same amount of load.An exception to this case is for the center pile in a group of 9 piles embedded in clay,which is not consistent with the behaviors of the other piles in the group even if the load reaches the ultimate state.For the 4 piles group embedded in clay,the maximum load carried by the base does not exceed 8% of the load carried by each pile with different diameters.This low percentage ascertains that the piles embedded in cohesive soils carry most of the load throughout their shafts.

钢板桩加固岸坡变形与桩土相互作用机理研究

针对航道开挖过程中护岸边坡板桩变形及桩土相互作用机制,通过选取典型断面进行现场试验的方法,对板桩结构位移、土压力及临近土体变形等关键物理量参数进行监测,并结合理论计算方法对板桩结构及后方岸坡土体稳定性进行了详细分析,探究了复杂地质条件下桩后土体变形与主动土压力的内在关联,得到了部分有益结论。板桩护岸后方边坡土体水平位移随开挖进行逐渐增加,边坡达到平衡状态时不同深度土体位移约为0.8~1 mm,板桩桩顶水平位移变化量约为1.2 mm。航道开挖过程中板桩主动侧土压力随开挖的进行逐渐减小,不同埋深位置桩侧土压力减小值约为1 kPa,与理论计算结果比较发现现场试验结果均较小,说明上述理论计算方法对于本试验结构形式而言土压力计算略偏保守。

Seismic Response Analysis of Portal Water Injection Sheet Pile

To further the study on the newly developed portal water injection sheet pile under static loads, in this paper, by adopting the nonlinear calculation module of FEM software ANSYS, a model for the interaction between the soil and the sheet piles is set up, and the seismic response analysis for this type of space-retaining structure is performed. The effects of the embedded depth and the distance between the front pile and the back pile on the dynamic characteristics of the portal water injection sheet pile are studied.

FEM for Stability Analysis Against Overturning of Portal Water Injection Sheet Pile

Portal water injection sheet pile (PWISP), as a retaining wall, appeared in seashore engineering in 2000. Although there have been many systematic methods addressing the issue, there are very few focusing on the new structure because of the difficulties in defining the earth pressure between the two piles. A new method is proposed in this paper to obtain the earth pressure between the PWISPs. Stability analysis against overturning follows as a consequence. Using Finite Element Analysis (FEA) software ANSYS, both the nonlinear characteristics of the soil and those of the contact elements are taken into account to obtain the earth pressure distribution on the contact surface. Based on the results of the FEA, Rankin’s theory and the slip plane theory, the formula of the earth pressure on the inner surfaces between the piles is given. Assuming the PWISP as the analysis object and the earth pressure as an outside force acting upon it, the equation of stability against overturning of the PWISP is presented. Finally, some parameters are discussed about the stability of the PWISP against overturning, such as the embedded depth of the front pile, the distance between the two rows of piles, the internal friction angle and the cohesion of the earth. The results show that the increase of the cohesion and the internal friction angle will decrease the distance and the embedded depth, and therefore enhance the stability against overturning. Specifically, when the distance is 1/3-2/3 of the maximal excavation depth, the two rows of piles give the best performance in stability.

板桩码头浚深改造遮帘桩效应有限元数值分析

使用PLAXIS-3D有限元软件构建板桩码头浚深改造工程的三维模型,并进行数值模拟与分析,探讨遮帘式板桩码头在港池浚深改造中的作用及其产生的效果,研究地基土层、板桩墙、锚碇墙、桩基结构及遮帘桩在不同阶段的土体位移、结构弯矩、土压力分布等关键参数。结果表明,首排遮帘桩处的土体水平位移减小33.1%,弯矩小幅度减小,说明其提高了结构稳定性。

The mechanical response of piles with consideration of pile-soil interactions under a periodic wave pressure

The pile-soil interaction under wave loads is an extremely complex and difficult issue in engineering. In this study, a physical model test is designed based on the principle of the gravity similarity to obtain time histories of wave forces of unsteady regular waves, and to measure the magnitude and the distribution of wave forces acting on the piles. A numerical model and relevant numerical methods for the pile-soil contact surface are adopted based on the principles of elastic dynamics. For a practical project, the time histories of wave forces on the piles are obtained through physical model tests. The deformations of the piles in the pile-soil interactions and the distribution of the bending moment on the piles are studied. It is shown that, with the increase of the period of wave pressures, the absolute value of the horizontal displacement of the piles increases, the embedment depth of the piles increases, and the scope of influence of soils increases. The change of the bending moment on the piles is consistent with that of its theoretical results, and the proposed numerical method can very well simulate the properties of the piles.

W波段新型带状注扩展互作用振荡器的设计

设计了一种W波段新型带状注扩展互作用振荡器。为了进一步提升扩展互作用振荡器的功率水平,提出了一种适配于带状注的新型工字形间隙高频结构,通过高频特性计算分析,采用工字形间隙的多间隙谐振腔比传统矩形间隙谐振腔具有更大的有效特性阻抗,表现出更强的功率输出潜力。最终设计了一种七间隙单腔振荡器电路,仿真结果表明在直流电压为45.2kV、电流为1.4A的带状注驱动下,电路稳定输出功率5.6kW,电子效率为8.8%。

AVEVA Instrumentation Engineer在仪表系统设计中的应用研究

本文分析AVEVA Instrumentation软件功能模块Engineer在仪表系统设计中的应用。重点探讨借助AVEVA Instrumentation软件实现跨专业、跨软件的数据交互开发及仪表专业清单文件、数据表的模板定制。

20万吨级卸荷式板桩码头数值分析

京唐港#36泊位为20万吨级通用散货泊位,采用卸荷式板桩码头结构型式,这是世界上迄今为止设计最大的板桩码头。对于卸荷式深水板桩结构,原有的规范已不再适用,给结构设计带来了一定的困难。基于ABAQUS有限元平台,利用开发的土和结构相互作用软件,对该20万吨级板桩码头初步设计方案进行了三维数值模拟,研究了卸荷式板桩结构的卸荷机理和土与结构的相互作用规律,得到了码头结构的内力和变形等关键设计参数,揭示了码头前墙上的土压力随墙体变形的变化规律,为结构的设计和优化提供了技术支撑。

桩板墙桩土作用机理有限元分析

桩板墙是一种已得到广泛应用的新型支挡结构。该文采用数值分析方法对岩土体和桩共同作用下,桩上部岩土体剩余下滑力的作用形式、桩身传力方式、桩身内力的计算方法等进行了分析。得到了板桩墙能够显著改善桩后岩土体桩轴法线方向应力矢量的方向和分布特征,使桩后岩土体的桩轴法线方向的应力矢量分异减小;同时能够将上部坡体和下部锚固段岩土体连接成一个共同作用体,利用其自身强大抗弯能力,在阻止上部变形体出现过大的侧向变形的同时,协调两部分岩土体侧向变形;还能有效改善因开挖引起的坡脚应力集中现象和上部拉应力现象,避免岩土体因过大的应力集中而导致塑性破坏的认识。其分析方法和得到的认识,可为相关工程的优化设计提供参考。

遮帘式板桩码头工作机理初探

为了适应大吨位深水码头的发展要求,我国自主设计了一种新型板桩码头结构——遮帘式板桩码头,这种新型的码头结构由于前板桩墙后多了一排遮帘桩而使得整个结构的工作机理变得十分复杂。以数值模拟为手段,研究了遮帘桩与前墙的距离以及遮帘桩的刚度对码头工作性状的影响。结果显示,前墙内力受墙桩距离影响很大,墙桩距离决定着遮帘桩能否发挥替前墙挡土的作用,从而决定着结构是否稳定;墙桩距离增大会削弱自身对结构受力造成的影响;遮帘桩刚度越大越能有效的阻止土体变形,挡土效果越好。

W波段带状注扩展互作用振荡器的粒子模拟

设计了一种工作在W波段的振荡器。采用宽高比值为2的薄矩形电子注降低空间电荷效应,周期耦合腔慢波线作为高频结构以增加功率容量,阶梯渐变矩形波导作为输出结构,使输出结构与高频结构匹配连接减少反射。利用三维PIC粒子模拟程序进行数值模拟,分析慢波结构的周期数及周期长度对输出功率、频率及效率的影响。结果表明:当阴极电压为13.0～16.1kV时,谐振腔能正常工作;谐振腔周期数为9,阴极电压为15.7kV时输出功率和转换效率最大,输出峰值功率大于1.9kW,平均功率为980 W,频率为91.6GHz,转换效率达25%,输出频率随谐振腔周期长度的减小而增大。

甲烷在石墨烯和活性炭上的吸附

以研制新型吸附式天然气(ANG)吸附剂为目的,比较了甲烷在石墨烯和活性炭上的吸附平衡。首先,在温度区间273~293K、压力范围0~8MPa,测试甲烷在比表面积分别为300和2074m2·g-1石墨烯和活性炭上的吸附平衡数据。其次,应用格子理论导出的通用吸附等温方程,通过吸附平衡态能量分析及10-4-3相互作用势函数求解,确定甲烷分子在石墨烯平面和活性炭上的最大面密度、受到的壁面吸附作用势及其在吸附层内的作用能。结果表明,在相同温度下,吸附甲烷分子在石墨烯上吸附层内的相互作用能较其在活性炭上的大,甲烷分子在石墨烯平面上的集聚更为密集。提高石墨烯的比表面积将有效提高甲烷在其上的吸附容量。

板片空间结构关键理论及软件开发综述

结合SPSA软件剖析板片空间结构体系的有限元分析核心算法、共同工作问题、结构稳定问题、结构优化的关键理论问题。

X波段带状注速调管注波互作用系统的3维PIC模拟

带状注速调管是采用宽高比值很大的薄矩形注来降低空间电荷效应,采用特殊的高频结构来增加功率容量,从而使注波互作用效率得到提高的一种新型微波电真空器件。本文对工作在π模状态下的X波段带状注速调管三间隙腔进行了模拟计算,并对由该型腔体构成的注波互作用系统进行了3维PIC模拟,给出了初步的模拟设计结果。模拟结果表明:在电子注电压为415kV,电流为250A时,该速调管可以获得大于29.6MW的输出功率、34.3dB的增益以及29.6%的效率。