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.

Reliability analysis of anti-pull piles under excavation

The impact of excavation on the reliability of anti- pull piles is studied, and three cases of reliability analysis, named reliability of ultimate limit state （ULS）, reliability of serviceability limit state （SLS） and reliability of system （SYS） are studied. The reduction factor of the pile capacity is used to calculate the reliability indices for the three cases. The ratio ξ of the pile capacity of SLS to the pile capacity of ULS has a significant influence on the reliability indices of SLS and SYS. The mean value μξ of the ratio ξ： is considered as a random variable to study the reliability indices of SLS and SYS. The numerical example demonstrates that the excavation depth and the excavation diameter are proved to have significant influences on the reduction factor of the pile capacity and the reliability indices. The reliability indices decrease with the increase in the excavation depth, and the excavation diameter has a considerable influence on the reliability index when the excavation is relatively deep. In addition, μξ has a significant influence on the reliability indices of SLS and SYS. For a more accurate estimation of μξ, further research should be conducted to study μξ.

Analysis and design of axially loaded piles in rock

Despite significant advancements in in situ test techniques,construction practices,understanding of rock joint and rock mass behaviours,and numerical analysis methods,the design of bored concrete cast-insitu piles in rock is still largely based on the assessment of bearing capacity.However,for many of the rock conditions encountered,the bearing capacity of piles is a nebulous concept and a figment of the designer’s imagination.Even if it can be reasonably quantified,it has little,if any,significance to the performance of a pile in rock.The load carrying capacity of even low strength rock(in most situations)is far in excess of the strength of the structure(for example,a building column)transmitting the load.Unsatisfactory performance of a pile in rock is usually a displacement issue and is a function of rock mass stiffness rather than rock mass strength.In addition,poor pile performance is much more likely to result from poor construction practices than excessive displacement of the rock mass.Exceptions occur for footings that are undermined,or where unfavourable structure in the rock allows movement towards a free surface to occur.Standards,codes of practices,reference books and other sources of design information should focus foundation design in rock on displacement rather than strength performance.Ground investigations should measure rock mass stiffness and defect properties,as well as intact rock strength.This paper summarises the fundamental concepts relating to performance of piles in rock and provides a basis for displacement focused design of piles in rock.It also presents comments relating to how piles are modelled in widely used commercial finite element software for soil-structure interaction analysis,within the context of the back-analysis of a pile load test,and proposes recommendations for pile analysis and design.

Probabilistic limit state design methodof the axial resistance of post grouting pile

The reliability of post grouting pile axial resistance was studied by proposing a design method for its probabilistic limit state,which is represented by the partial coefficients of load,end,and side resistance.The hyperbolic,modified hyperbolic,and polynomial models were employed to predict the ultimate bearing capacity of test piles that were not loaded to damage in field tests.The results were used for the calculation and calibration of the reliability index.The reliability of the probabilistic limit state design method was verified by an engineering case.The results show that the prediction results obtained from the modified hyperbolic model are closest to those obtained through the static load test.The proposed corresponding values of total,side,and end resistance partial coefficients are 1.84,1.66,and 2.73 when the dead and live load partial coefficients are taken as 1.1 and 1.4,respectively.Meanwhile,the corresponding partial coefficients of total,side,and end resistance are 1.70,1.56,and 2.34 when the dead and live load partial coefficients are taken as 1.2 and 1.4,respectively.

Optimum Design of Jacket Platforms Considering Structure-Pile-Soil Interaction

This paper proposes an optimum design model for the offshore jacket platform considering multidesign criteria, multi-design constraints and the structure-pile-soil interaction, and gives an optimum design procedure in which the proposed optimum design model is used together with structural analysis software SAP91 and optimum algorithm software OPB1. The Chengbei (#)11 offshore platform, which lies in the Shengli oilfield, is designed by use of the above optimum design model. The results show that the optimum design model is stable, and it depends on neither the optimization algorithm nor initial values of design variables. All values of the objective function converge to the same minimum value, and the speed of convergence is high, showing that the proposed optimum design model is reasonable.

Design and construction of scour protection for deep-water group pile foundation structures of two pylons in the Sutong Bridge project

Sutong Bridge,as a world-record cable-stayed bridge with its main span exceeding 1 000 m constructed in Yangtze River estuary region in China,is located at a site with complicated hydrologic conditions and poor geotechnical conditions and therefore,scour protection will be a decisive factor for ensuring smooth and successful construction of this bridge.This paper,starting from structural description of deep-water group pile foundation,analyzes impact to the bridge safety introduced by scour and its protection and further presents different solutions of scour protection for foundation structures of this bridge.

滑坡稳定性评价及治理工程设计软件Slope Designer

主要介绍了Slop eDesigne r1.2的设计开发思路和主要功能。该软件是基于Windows面向对象技术开发的滑坡稳定性评价与治理工程设计的一体化工程软件,采用Visual C++进行程序设计,包括稳定性分析子模块和抗滑桩设计子模块2部分,可对地震作用、暴雨等不同工况下的滑坡进行稳定性评价和推力计算,并能够对(锚拉)抗滑桩(弹性桩、刚性桩)的弯矩、剪力及侧应力进行计算,最后根据内力计算结果完成配筋计算。在三峡库区兴山县二里半滑坡的应用研究表明,该软件具有很好的工程实用性。

Dynamic response of a slope reinforced by double-row antisliding piles and pre-stressed anchor cables

Large-scale shaking table tests were conducted to study the dynamic response of a slope reinforced by double-row anti-sliding piles and prestressed anchor cables. The test results show that the reinforcement suppressed the acceleration amplification effectively. The axial force time histories are decomposed into a baseline part and a vibration part in this study. The baseline part of axial force well revealed the seismic slope stability, the peak vibration values of axial force of the anchor cables changed significantly in different area of the slope under seismic excitations. The peak lateral earth pressure acting on the back of the anti-sliding pile located at the slope toe was much larger than that acting on the back of the anti-sliding pile located at the slope waist. The test results indicate an obvious load sharing ratio difference between these two anti-slide piles, the load sharing ratio between the two anti-sliding piles located at the slope toe and the slope waist varied mainly in a range of 2-5. The anti-slide pile at the slope waist suppressed the horizontal displacement of the slope surface.

Research on pile performance and state-of-the-art practice in cold regions

A pile foundation is commonly adopted in geotechnical engineering to support structures, and its application has been extended to cold-regions engineering. In past decades, a host of scholars investigated pile behaviors and proposed design guidelines for seasonally frozen ground or permafrost. This paper reviews the research with respect to pile performance and engineering practice in cold regions, organized as follows:(1) creep tests and bearing capacity,(2) frost-jacking hazards,(3) laterally loaded piles,(4) dynamic responses,(5) refreezing due to concrete-hydration heat, and(6) improved countermeasures and design methods. We first summarize previous research and recent progress; then, predict the development trend of pile foundations in cold regions and recommend further research.

Optimization Mathematical Model of Pile Forces for Offshore Piled Breasting Dolphins

An optimization mathematical model of the pile forces for piled breasting dolphins in the open sea under various loading conditions is presented. The optimum layout with the well distributed pile forces and the least number of piles is achieved by the multiplier penalty function method. Several engineering cases have been calculated and compared with the result of the conventional design method. It is shown that the number of piles can be reduced at least by 10%～20% and the piles' bearing state is improved greatly.

Bearing Behaviors of Stiffened Deep Cement Mixed Pile

A series of investigations were conducted to study the bearing capacity and load transfer mechanism of stiffened deep cement mixed （SDCM） pile. Laboratory tests including six specimens were conducted to investigate the frictional resistance between the concrete core and the cementsoil. Two model piles and twenty-four full-scale piles were tested to examine the bearing behavior of single pile. Laboratory and model tests results indicate that the cohesive strength is large enough to ensure the interaction between core pile and the outer cement-soil. The full-scale test results show that the SDCM piles exhibit similar bearing behavior to bored and cast-in-place concrete piles. In general, with the rational composite structure the SDCM piles can transmit the applied load effectively, and due to the addition of the stiffer core, the SDCM piles possess high bearing capacity. Based on the findings of these experimental investigations and theoretical analysi , a practical design method is developed to predict the vertical bearing capacity of SDCM pile.

Field Test Study on Cantilever Circular Occluded Pile Supporting Structure

In order to explore the deformation of the pile body of the circular occluded pile retaining structure under earth pressure, this paper carries out on-site monitoring in combination with the actual project, and obtains the deformation characteristics and change rules of the occluded pile by measuring the strain and displacement of the pile body. The research conclusion can provide a certain reference value for the pile body design of bite pile in similar projects.

Dynamic and Field Analysis of Pile Driving in Cameroun

Complexity and implementation of design norms in Cameroon required a proven foreign expertise, but nowadays local engineers are mastering modern construction techniques. They are turning to pile foundations to solve the problem of construction sites on weak soils. The objective of this work is to present the trend of the country pile-driving capacity of some foundations design and construction companies. The proposed analytical method is based on Finite Element Method and on the theory of wave＇s propagation and transmission along the pile taking into account experimental data on the construction site. The proposed method is validated through recorded data during the construction of the Mungo Bridge in Cameroon, and obtained analytical results are in agreement with experimental results.

The Application of Pile Foundation Bearing-Retaining Wall Combination Structure in a Mountainous Urban High Fill Project

Pile foundation bearing-retaining wall combination structure is a new type of support structure developed in recent years.This article focuses on the characteristics,advantages,and application scope of the support structure,while combining a variety of algorithms,according to different geological conditions and slope stability,as well as summarizes the pile foundation bearing-retaining wall combination structure force analysis and design methods,taking a high-fill road project in Chongqing as an example.The application of this support structure under special conditions,such as thicker soil layer,steeper sliding surface,weak foundation,and limited slope release conditions,is presented,which illustrates the technical advantages of this support structure and proving that it has several other advantages,including clear force mechanism as well as economic and reasonable structure,thus providing reference for similar projects.

太原武宿国际机场T3航站楼主楼主体结构设计

太原武宿国际机场T3航站楼项目所在地抗震设防烈度高、地质条件复杂。T3航站楼主楼采用下部混凝土结构、屋盖大跨度钢结构的混合形式,并存在局部转换、扭转不规则、穿层柱、钢屋盖跨越下部混凝土结构单体形成连体等超限情况。对T3航站楼主楼的基础设计和下部混凝土结构消能减震设计进行了介绍,包括局部液化场地的地基处理、带板结夹层土层条件下锤击桩的设计、考虑承台作用的桩基水平承载力测试、减震与隔振方案的比选与确定等,并探讨了T3航站楼功能约束条件下的黏滞阻尼器不均匀布置对减隔震效果的影响情况,可为类似工程的设计提供参考。

液化场地大直径变截面单桩动力响应研究

为研究不同地震动强度下液化场地大直径变截面单桩的动力响应规律,基于振动台试验,选取5010波,在地震动强度0.10g~0.45g作用下,研究液化场地砂土孔压比和大直径变截面单桩桩顶水平位移、桩身弯矩、桩身加速度时程响应及桩基损伤等变化规律.试验结果表明:饱和砂土孔压比随着地震动强度的增大上升明显,地震动强度≥0.30g时,饱和砂土孔压比稳定值在0.9附近,此时砂土完全液化;在0.45g地震动强度作用下,桩身加速度、桩顶水平位移及桩身弯矩均达到最大;桩身不同位置处加速度峰值出现时刻均滞后于输入地震波加速度峰值出现时刻,且桩顶及变截面的加速度响应比桩端的响应更弱;不同地震动强度作用下,桩身弯矩最大值均出现在液化土层和非液化土层分界处,且变截面处弯矩小于土层分界面处;地震动强度达到0.30g时,大直径变截面单桩桩身发生损伤.因此,液化场地下大直径变截面桥梁单桩基础抗震设计时,应该重点考虑饱和砂土层分界处、变截面处的抗弯能力,以确保单桩桩身强度满足抗震要求.

嵌岩低桩承台锁口钢管桩围堰设计与施工技术

昌九高铁扬子洲赣江公铁大桥西支主桥为(48+144+320+144+48)m无砟轨道钢箱桁组合梁斜拉桥。桥塔墩位于通航河道内,桥位处河床覆盖层浅,基岩强度高,基础由大直径钻孔桩和矩形嵌岩低桩承台组成,承台采用锁口钢管桩围堰施工方案。G33号主墩围堰平面设计尺寸54.56 m×28.52 m,锁口钢管桩采用Q345B材质∅1020 mm螺旋钢管,长28 m,钢管桩之间采用C-T形锁扣连接;围堰设置4层内支撑,单层内支撑设3道对撑,内支撑四角设型钢斜撑;基底设置混凝土垫层参与围堰结构受力。围堰采用XR360旋挖钻机在岩层中引孔,孔内换填细砂后插打钢管桩,钢管桩壁内、外两侧换填砂采用高压旋喷注浆加固。围堰设置智能化监测系统,对围堰受力、变形等进行实时动态监控。实践证明,该桥围堰结构安全可靠、止水效果良好、施工快捷高效。

大倾角钢箱提篮拱桥总体设计

考虑施工技术、经济性和景观效果等方面,陕西蔡家坡渭河特大桥主桥采用(35+210+35) m大倾角钢箱提篮拱桥。该桥采用摩擦摆和环向钢丝绳阻尼支座综合减隔震约束体系,以降低结构的地震响应。拱肋为单室等宽钢箱截面,采用主、副拱肋2条悬链线,主、副拱肋共面,设计为横向内倾20°的大倾角,在提高桥梁景观效果的同时,又有效提高了结构的整体稳定性;拱肋设钢-混结合段连接拱脚与混凝土拱座。桥面系采用自重较轻的正交异性钢桥面板结构。吊杆采用抗拉强度1 860 MPa的环氧柔性钢绞线。基础采用Φ2.5 m的钻孔灌注群桩,以抵抗软弱地质条件下荷载的竖向及水平作用力。该桥总体采用先梁后拱的施工方案。整体及局部有限元分析结果表明,桥梁结构力学性能均满足规范要求,设计安全可靠。

考虑多失效模式的桩锚结构鲁棒性设计及经济性优化

目的 研究岩土力学参数的不确定性对桩锚支护体系的整体影响,探究经济性和鲁棒性共同作用的优化设计。方法 选取黄土地区工程案例,考虑支护桩隆起破坏、支护桩倾覆破坏、整体稳定性破坏三类破坏形式,使用蒙特卡洛及点估计法嵌套的方式求出不同设计组合下的失效概率及标准差;同时考虑优化设计的经济性,筛选出桩锚支护结构体系的鲁棒性优化设计方案。结果 随着桩长增加,主控模式由隆起破坏向整体稳定性改变,不同的几何参数对结构鲁棒性影响不同,优化后可以获得同时满足经济性、鲁棒性及可靠度要求的最佳设计方案。结论 在桩锚结构设计中考虑经济性优化及多失效模式的鲁棒性设计是必要的。

砾砂地层盾构切削大直径群桩的刀具研究

刀盘刀具是盾构机实现切削功能并保证其顺利推进的主要部件,合适的刀具选型与设计在保证盾构机成功切削大直径钢筋混凝土群桩的过程中至关重要。依托沈阳地铁4号线盾构切桩工程,结合盾构穿越砾砂地层的工程特点以及切削大直径钢筋混凝土群桩的工程需求,对刀盘刀具进行选型,采用LS-DYNA软件模拟不同刃宽、刃角及前角的贝壳刀切削钢筋的效果。将分析结果应用于该工程,通过对比切桩前后既有隧道沉降变化规律论证刀具选型设计的合理性,并根据切桩后的贝壳刀磨损规律及盾构机排出钢筋情况,评估刀盘刀具切削效果,从而优化刀盘的刀具布置。研究结果表明:盾构刀盘采用面板+辐条复合式直角刀盘,切桩刀具采用前角-45°零后角、5 mm刃宽、90°刃角的双面刃贝壳刀,可提升盾构切桩效果;盾构切桩过程中既有隧道的变形波动控制在1.1 mm内,切桩完成后既有隧道的最大沉降仅为1.96 mm,未对既有隧道造成明显影响;刀盘布置贝壳刀时,应增加高度为210 mm的贝壳刀数量,尤其需要避免单个辐条上仅有1把高度为210 mm贝壳刀的情况,可有效提高刀盘刀具切削钢筋的能力并降低崩刃风险。刀具选型设计结果成功应用于沈阳地铁4号线切桩工程,可为今后类似工程提供参考。