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Model-scale tests to examine water pressures acting on potentially buoyant underground structures in clay strata

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第3期14卷 861-872页

作者： Zhisheng Ren Qixian Lu Kaiwen Liu pengpeng ni Guoxiong Mei School of Civil Engineering Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Guangdong Key Laboratory of Oceanic Civil EngineeringGuangdong Research Center for Underground Space Exploitation TechnologySun Yat-sen UniversityGuangzhou510275China Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education College of Civil Engineering and ArchitectureGuangxi UniversityNanning530004China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China Key Laboratory of High-speed Railway Engineering(MOE) School of Civil EngineeringSouthwest Jiaotong UniversityChengdu610031China

Throughout the service life, underground structures are subjected to transient and sustained hydrostatic pressures. The reservoir impoundment results in an increase in water level, as well as hydraulic gradient,which can endanger the uplift performance of infrastructure. In uplift design, a reduction factor is often suggested for buoyant force acting on underground structures in clays due to the time lag ***, the mechanism of pore pressure generation in clays is not fully understood. This investigation presents a novel U-shaped test chamber to assess the pore pressure generation with time in the horizontal branch subjected to an increase in reservoir level in the left vertical branch. A mathematical model is developed to explain the time lag effect of pore pressure generation. The test program also involves the evaluation of uplift pressure acting on foundation model in the right vertical branch due to adjacent reservoir impoundment. It is found that the time lag effect of pore pressure generation in clays can be observed irrespective of hydraulic gradient, but a higher hydraulic gradient can lead to a faster response in pore pressure sensors. A reduction factor of 0.84-0.87 should be considered to reduce the conservatism of uplift design.

关键词： Buoyant force Reservoir impoundment Pore pressure generation Reduction factor Uplift pressure Time lag effect

Performance of a deep top-down zoned pit-in-pit excavation close to existing metro lines through winter

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Frontiers of Structural and Civil Engineering 2024年第11期18卷 1680-1697页

作者： Wenxin CAO Pengjiao JIA pengpeng ni Wen ZHAO Cheng CHENG Fei WANG School of Resources and Civil Engineering Northeastern UniversityShenyang 110819China School of Rail Transportation Soochow UniversitySuzhou 215131China School of Civil Engineering Sun Yat-sen UniversityZhuhai 519082China South China Engineering Co. Ltd.China Railway No.5 Engineering Group Co.Ltd.Dongguan 523160China

Though a comprehensive in situ measurement project,the performance of a deep pit-in-pit excavation constructed by the top-down method in seasonal frozen soil area in Shenyang was extensively *** measured excavation responses included the displacement of capping beam and retaining pile,settlement of ground surface,and deformation of metro *** on the analyses of field data,some major findings were obtained:1)the deformations of retaining structures fluctuated along with the increase of temperature,2)the deformation variation of retaining structures after the occurrence of thawing of seasonal frozen soil was greater than that in winter,although the excavation depth was smaller than before,3)the influence area of ground settlement was much smaller because of the features of seasonal frozen sandy soil,4)the displacement of metro line showed a significant spatial effect,and the tunnel lining had an obviously hogging displacement pattern,and 5)earth pressure redistribution occurred due to the combined effects of freezing-thawing of seasonal frozen soil and excavation,leading to the deformation of metro *** influence area of ground settlement was obviously smaller than that of Shanghai soft clay or other cases reported in literatures because of special geological conditions of ***,the deformation of metro lines was significantly lager after the thawing of the frozen soil,the stress in deep soil was redistributed,and the metro lines were forced to deform to meet a new state of equilibrium.

关键词： deep excavation metro line ground surface settlement deformation seasonal frozen soil

A modified back analysis method for deep excavation with multi-objective optimization procedure

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1373-1387页

作者： Chenyang Zhao Le Chen pengpeng ni Wenjun Xia Bin Wang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Guangdong Research Center for Underground Space Exploitation Technology School of Civil EngineeringSun Yat-sen UniversityGuangzhou510275China Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) Zhuhai519000China Jiangsu Provincial Transportation Engineering Construction Bureau Nanjing210004China

Real-time prediction of excavation-induced displacement of retaining pile during the deep excavation process is crucial for construction *** paper proposes a modified back analysis method with multi-objective optimization procedure,which enables a real-time prediction of horizontal displacement of retaining pile during *** opposed to the traditional stage-by-stage back analysis,time series monitoring data till the current excavation stage are utilized to form a multi-objective ***,the multi-objective particle swarm optimization (MOPSO) algorithm is applied for parameter *** optimized model parameters are immediately adopted to predict the excavation-induced pile deformation in the continuous construction *** achieve efficient parameter optimization and real-time prediction of system behavior,the back propagation neural network (BPNN) is established to substitute the finite element model,which is further implemented together with MOPSO for automatic *** proposed approach is applied in the Taihu tunnel excavation project,where the effectiveness of the method is demonstrated via the comparisons with the site monitoring *** method is reliable with a prediction accuracy of more than 90%.Moreover,different optimization algorithms,including non-dominated sorting genetic algorithm (NSGA-II),Pareto Envelope-based Selection Algorithm II (PESA-II) and MOPSO,are compared,and their influences on the prediction accuracy at different excavation stages are *** results show that MOPSO has the best performance for high dimensional optimization task.

关键词： Multi-objective optimization Back analysis Surrogate model Multi-objective particle swarm optimization(MOPSO) Deep excavation

Model test and numerical simulation of a new prefabricated double-row piles retaining system in silty clay ground

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Underground Space 2023年第6期13卷 262-280页

作者： Ruisong Wang Hao Yang pengpeng ni Chenyang Zhao Chengchao Guo Huihuan Ma Pu Dong Huqing Liang Mengxiong Tang School of Civil Engineering Sun Yat-sen UniversitySouthern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Guangdong Key Laboratory of Oceanic Civil EngineeringGuangdong Research Center for Underground Space Exploitation TechnologyZhuhai 519082China Beijing Urban Rail Transit Construction Engineering Co. LtdBeijing 100088China BeSTDR Infrastucture Hospital Zhumadian 463400China School of Architecture and Civil Engineering Huizhou UniversityHuizhou 516008China Guangzhou Municipal Construction Group Co. LtdGuangzhou 510275China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China

This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay *** model test and numerical simulation are conducted to study the system behavior upon *** horizontal displacement(δ_(h)),Von Mises stress(δ_(M)),strain(ε),ground surface settlement(δ_(v)),and earth pressure are systematically ***,the monitoring data of 13 excavation cases supported by double-row piles retaining system are presented and *** experimental results can basically match the numerical results,and the maximumδ_(M),maximum bending moment(M_(max)),maximum horizontal displacement(δ_(hm))of structural members are all less than the tolerance *** ground surface settlement model of double-row piles retaining system consists of three zones,i.e.,rebound influence zone,primary influence zone and secondary influence *** dhm values are 0.07%–1.42%of the excavation depth(He).The maximum ground surface settlement(δ_(vm))is generally less than *** ratio ofδ_(vm)=δ_(hm)varies between 0.09 and 0.76,with an average value of *** observed earth pressure on the retained side of front pile(paf)is about 0.53–0.57γH below the excavation *** the excavation surface,p_(af)decreases dramatically when getting closer to the ground surface.

关键词： Prefabricated recyclable structure Double-row piles retaining system Physical model test Numerical simulation Deformation

深圳滨海大道改造工程超宽坑中坑降水与开挖响应实例分析

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隧道建设（中英文） 2023年第12期43卷 2026-2035页

作者：韩辉王锐松倪芃芃中铁四局集团有限公司安徽合肥230041 中山大学土木工程学院广东珠海519082

为探究超宽坑中坑降水与开挖过程中基坑变形和地下水的变化特征,采用实测分析方法对围护结构侧移、地表沉降、周边建筑物沉降及地下水与潮汐水之间的关系进行分析。同时,利用ABAQUS有限元软件建立考虑潮汐补水的三维流固耦合模型,研究... 详细信息

为探究超宽坑中坑降水与开挖过程中基坑变形和地下水的变化特征,采用实测分析方法对围护结构侧移、地表沉降、周边建筑物沉降及地下水与潮汐水之间的关系进行分析。同时,利用ABAQUS有限元软件建立考虑潮汐补水的三维流固耦合模型,研究基坑降水和开挖过程中地下连续墙的侧移规律,并验证分段降水控制和换撑措施对墙体变形的控制效果。主要结论如下:1)基坑开挖过程中,围护结构最大侧移为29.5 mm,南北墙顶均向坑外侧移,地表沉降最大为29.4 mm,立柱、周边建筑物竖向位移量均小于6.5 mm;2)潮汐补水和降雨导致南北两侧坑外水位降落分别约-1.0 m和-1.5 m;3)在坑中坑降水和开挖深坑阶段,采用分段降水控制和钢支撑换撑使墙体最大侧移减小约29%和21%。

关键词：坑中坑变形特性地下水变化工程实测有限元分析

基于YIG调谐的四通道宽带微波接收前端设计

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电子技术（上海） 2024年第8期53卷 36-37页

作者：倪鹏鹏扬州船用电子仪器研究所江苏225000

阐述一种基于YIG调谐的四通道宽带微波接收前端设计方案,通过仿真实验验证,该设计方案的宽带微波接收前端不但具有较强的抑制干扰的能力,同时可提高ECM、ESM等系统的兼容能力。

关键词：微波信号 YIG调谐宽带接收前端设计

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基于微波通信技术的分离式天线调试系统设计

电子技术（上海） 2024年第8期53卷 42-43页

作者：倪鹏鹏扬州船用电子仪器研究所江苏225000

阐述一种基于微波通信技术的分离式天线调试系统设计方案,通过单片机、微波传输链路和高速数字信号处理器芯片完成对分离式天线信号的采集、传输、分析等功能,并利用测量参数进一步检测和调试分离式天线的性能。

关键词：微波通信单片机天线调试性能检测 DSP

预应力CFRP加固断丝PCCP的试验与仿真研究

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水利学报 2021年第6期52卷 739-749页

作者：翟科杰方宏远郭成超倪芃芃付兵李斌中山大学土木工程学院广东广州510275 郑州大学水利科学与工程学院河南郑州450001 广东省地下空间开发工程技术研究中心广东广州510275 广东省海洋土木工程重点实验室广东广州510275 南方海洋科学与工程广东省实验室(珠海) 广东珠海519082 暨南大学力学与建筑工程学院广东广州510632

针对预应力钢筒混凝土管(PCCP)断丝问题,提出一种创新的加固技术,即外部缠绕预应力碳纤维布(CFRP)加固。利用一根长6 m、内径1.4 m的PCCP管道,选取不同截面进行对比试验,对所提加固方法效果进行了验证。之后,基于有限元方法(FEM),建立... 详细信息

针对预应力钢筒混凝土管(PCCP)断丝问题,提出一种创新的加固技术,即外部缠绕预应力碳纤维布(CFRP)加固。利用一根长6 m、内径1.4 m的PCCP管道,选取不同截面进行对比试验,对所提加固方法效果进行了验证。之后,基于有限元方法(FEM),建立了预应力CFRP加固断丝PCCP三维模型,并将仿真结果与试验进行了对比评估,分析了CFRP预应力水平和层数对管道受力性能的影响。研究结果表明,经预应力CFRP加固后的管道承载能力明显提高;断丝与加固对管道的影响范围有限,约为其宽度的3倍;断丝15%的管道经2层、4层和6层预应力为10%的CFRP加固后,承载能力可分别提高65.6%、103.1%和162.5%。

关键词： PCCP CFRP 预应力加固足尺试验

滨海地区地下连续墙+抗拔桩组合式坑中坑现场实测分析

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建筑结构 2023年第S1期53卷 2771-2776页

作者：丁得志王锐松倪芃芃赵辰洋中铁四局集团有限公司合肥230041 中山大学土木工程学院珠海519082 南方海洋科学与工程广东省实验室(珠海) 珠海519082

为探究滨海地区超长“高低坑”基坑施工力学特性,基于深圳市滨海大道交通综合改造工程下沉隧道基坑,结合工程实测数据,分析了基坑施工过程中墙体侧移,地表沉降,支撑轴力,立柱及周边建(构)竖向位移的变化规律。研究结果表明:截至2022年12... 详细信息

为探究滨海地区超长“高低坑”基坑施工力学特性,基于深圳市滨海大道交通综合改造工程下沉隧道基坑,结合工程实测数据,分析了基坑施工过程中墙体侧移,地表沉降,支撑轴力,立柱及周边建(构)竖向位移的变化规律。研究结果表明:截至2022年12月,实测数据显示围护墙体最大侧移为29.6mm,地表最大沉降值为28.3mm,支撑最大轴力为8962.9kN,立柱支撑和周边建(构)筑物的最大沉降量分别为15.4mm和2.1mm,均小于设计控制值。基坑开挖期间,地下连续墙上部呈现逐渐向坑外(主动土区)倾斜的趋势,横向支撑处于受拉状态;基坑南北两侧高、低坑土方开挖对彼方墙身侧移的影响可忽略不计;本工程利用地下连续墙+抗拔桩结合的优势,有效降低了地连墙插入深度,墙体最小插入比仅为0.15。

关键词：降水开挖坑中坑地下连续墙+抗拔桩现场监测