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Analysis of ground deformation development and settlement prediction by air-boosted vacuum preloading

Journal of Rock Mechanics and Geotechnical Engineering 2022年第1期14卷 272-288页

作者： Shuangxi Feng huayang lei Cheng Lin Department of Civil Engineering Tianjin UniversityTianjin300354China Key Laboratory of Coast Civil Structure Safety of the Ministry of Education Tianjin UniversityTianjin300354China Key Laboratory of Comprehensive Simulation of Engineering Earthquake and Urban-Rural Seismic Resilience China Earthquak AdministrationTianjin300354China Department of Civil Engineering University of VictoriaVictoriaBCV8P 5C2Canada

Vacuum preloading has been widely used to improve soft soils in coastal areas of *** increasing amount of evidence from field operations has shown that conventional vacuum preloading is prone to clogging in prefabricated vertical drains(PVDs)and demands a large volume of sand *** recent years,air-boosted vacuum preloading has been developed to overcome these limitations;however,this method still requires more data to verify its *** this study,a field test for air-boosted vacuum preloading was conducted,and a large-strain two-dimensional(2D)finite element(FE)model was developed and validated against the field test ***,a series of FE parametric analyses was performed to assess key factors,*** air injection pressure,the injection spacing,and the characteristics of cyclic injection,which affect the performance of the air-boosted vacuum *** results showed that the ground settlement and lateral displacement of the soils increased due to an increase in the injection pressure,a decrease in the injection spacing,or increases in the number and duration of the injection *** on the parametric analyses,an empirical formula for ground settlement prediction was proposed and compared with a case history reported in the literature,showing good agreement.

关键词： Air-boosted vacuum preloading Field test Numerical modeling Settlement Soft soils Ground improvement

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Model test and discrete element method simulation of shield tunneling face stability in transparent clay

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Frontiers of Structural and Civil Engineering 2021年第1期15卷 147-166页

作者： huayang lei Yajie ZHANG Yao HU Yingnan LIU School of Civil Engineering Tianjin UniversityTianjin 300350China Key Laboratory of Coast Civil Structure Safety(Tianjin University) Ministry of EducationTianjin 300350China Key Laboratory of Earthquake Engineering Simulation and Seismic Resilience of China Earthquake Administration(Tianjin University) Tianjin 300350China

The stability of the shield tunneling face is an extremely important factor affecting the safety of tunnel *** this study,a transparent clay with properties similar to those of Tianjin clay is prepared and a new transparent clay model test apparatus is developed to overcome the“black box”problem in the traditional model *** stability of the shield tunneling face(failure mode,influence range,support force,and surface settlement)is investigated in transparent clay under active failure.A series of transparent clay model tests is performed to investigate the active failure mode,influence range,and support force of the shield tunneling face under different burial depth conditions,whereas particle flow code three-dimensional numerical simulations are conducted to verify the failure mode of the shield tunneling face and surface settlement along the transverse section under different burial depth *** results show that the engineering characteristics of transparent clay are similar to those of soft clay in Binhai,Tianjin and satisfy visibility *** types of failure modes are obtained:the overall failure mode(cover/diameter:C/D£1.0)and local failure mode(C/D≥2.0).The influence range of the transverse section is wider than that of the longitudinal section when C/D≥***,the normalized thresholds of the relative displacement and support force ratio are 3%-6%and 0.2-0.4,*** to the cushioning effect of the clay layer,the surface settlement is significantly reduced as the tunnel burial depth increases.

关键词： shield tunneling face stability transparent clay model test numerical simulation

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Influencing factors and control measures of excavation on adjacent bridge foundation based on analytic hierarchy process and finite element method

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Frontiers of Structural and Civil Engineering 2021年第2期15卷 461-477页

作者： Shuangxi FENG huayang lei Yongfeng WAN Haiyan JIN Jun HAN Department of Civil Engineering Tianjin UniversityTianjin 300354China Coast Civil Structure Safety of Education Ministry Tianjin UniversityTianjin 300354China Key Laboratory of Comprehensive Simulation of Engineering Earthquake and Urban-rural Seismic Resilience CEATianjin 300354China China Railway 16th Bureau Group the 5th Engineering Co. LTDTangshan 064000China

Many uncertain factors in the excavation process may lead to excessive lateral displacement or overlimited internal force of the piles,as well as inordinate settlement of soil surrounding the existing bridge *** control is pivotal to ensuring the safety of adjacent *** this paper,an innovative method is proposed that combines an analytic hierarchy process(AHP)with a finite element method(FEM)to reveal the potential impact risk of uncertain factors on the surrounding *** AHP was adopted to determine key influencing factors based on the weight of each influencing *** FEM was used to quantify the impact of the key influencing factors on the surrounding *** terms of the AHP,the index system of uncertain factors was established based on an engineering investigation.A matrix comparing the lower index layer to the upper index layer,and the weight of each influencing factor,were *** was found that the excavation depth and the distance between the foundation pit and the bridge foundation were fundamental *** the FEM,the FE baseline model was calibrated based on the case of no bridge surrounding the foundation *** consistency between the monitoring data and the numerical simulation data for a ground settlement was *** simulations were then conducted to quantitatively analyze the degree of influence of the key influencing factors on the bridge ***,the lateral displacement of the bridge pile foundation,the internal force of the piles,and the settlement of the soil surrounding the pile foundation were emphatically *** most hazardous construction condition was also ***,two safety control measures for increasing the numbers of support levels and the rooted depths of the enclosure structure were suggested.A novel method for combining AHP with FEM can be used to determine the key influencing aspects among many uncertain factors during a construction,which ca

关键词： deep foundation pit excavation adjacent bridge foundation influencing factors analytic hierarchy process finite element

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Laboratory model study of newly deposited dredger fills using improved multiple-vacuum preloading technique

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第5期9卷 924-935页

作者： Jingjin Liu huayang lei Gang Zheng Haizuo Zhou Xuelian Zhang School of Civil Engineering Tianjin University Tianjin 300072 China Key Laboratory of Coast Civil Structure Safety of Ministry of Education Tianjin University Tianjin 300072 China State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University Tianjin 300072 China

Problems continue to be encountered concerning the traditional vacuum preloading method in field during the treatment of newly deposited dredger *** this paper,an improved multiple-vacuum preloading method was developed to consolidate newly dredger fills that are hydraulically placed in seawater for land reclamation in Lingang Industrial Zone of Tianjin City,*** this multiplevacuum preloading method,the newly deposited dredger fills could be treated effectively by adopting a novel moisture separator and a rapid improvement technique without sand cushion.A series of model tests was conducted in the laboratory for comparing the results from the multiple-vacuum preloading method and the traditional *** piezometers and settlement plates were installed to measure the variations in excess pore water pressures and moisture content,and vane shear strength was measured at different *** testing results indicate that water dischargeetime curves obtained by the traditional vacuum preloading method can be divided into three phases:rapid growth phase,slow growth phase,and steady *** to the process of fluid flow concentrated along tiny ripples and building of larger channels inside soils during the whole vacuum loading process,the fluctuations of pore water pressure during each loading step are divided into three phases:steady phase,rapid dissipation phase,and slow dissipation *** optimal loading pattern which could have a best treatment effect was proposed for calculating the water discharge and pore water pressure of soil using the improved multiple-vacuum preloading *** the newly deposited dredger fills at Lingang Industrial Zone of Tianjin City,the best loading step was 20 kPa and the loading of 40-50 k Pa produced the highest drainage *** measured moisture content and vane shear strength were discussed in terms of the effect of reinforcement,both of which indicate that the multiple-vacuum preloading method has a

关键词： Model tests Vacuum preloading Ultra-soft soil Dredger fills Cost effectiveness

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Ground settlement and tunnel response due to twin-curved shield tunnelling in soft ground with small clear distance

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第8期16卷 3122-3135页

作者： Yao Hu Haoran Tang Yinggang Xu huayang lei Peng Zeng Kai Yao Yabo Dong State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu610059China Research Center of Tunneling and Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing100044China College of Environment and Civil Engineering Chengdu University of TechnologyChengdu610059China School of Civil Engineering Tianjin UniversityTianjin300350China School of Qilu Transportation Shandong UniversityJinan250002China Power China Sinohydro Bureau 7 Co. Ltd.Chengdu610213China

Twin curved tunnels are often encountered in shield tunnelling,where significant complexities in densely exploited underground space are *** this study,the ground settlement and tunnel deformation due to twin-curved shield tunnelling in soft ground were investigated using numerical simulation and field *** curvature radii of twin curved tunnels and subsequent effects of tunnel construction were considered to reveal the tunnelling effect on ground surface settlement and tunnel *** results show that the settlement trough yields one offset towards inside of curved shield *** location of settlement trough and maximum settlement were affected by curvature radius but except for the shape and width of settlement *** parallel twin-curved shield tunnelling could increase the offset of existing settlement trough and maximum ***,an empirical prediction of surface settlement trough due to twin-curved shield tunnelling with same tunnel diameters in soft clay was proposed,which was applicable to curvature radius less than 800 ***,a minimum radius of 600 m of curvature tunnel was proposed in terms of allowable convergence deformation of *** result could provide guidance on safety evaluation for twin curved shield tunnelling construction.

关键词： Shield tunnelling Curvature radius Ground settlement Tunnel deformation Numerical simulation

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Assessing the deformation response of double-track overlapped tunnels using numerical simulation and field monitoring

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第2期14卷 436-447页

作者： Yao Hu huayang lei Gang Zheng Liang Shi Tianqi Zhang Zhichao Shen Rui Jia School of Civil Engineering Tianjin UniversityTianjin300350China Department of Civil and Environmental Engineering National University of Singapore117576Singapore Key Laboratory of Coast Civil Structure Safety(Tianjin University) Ministry of EducationTianjin300350China Key Laboratory of Earthquake Engineering Simulation and Seismic Resilience of China Earthquake Administration(Tianjin University) Tianjin300350China State Key Laboratory of Hydraulic Engineering Simulation and Safety(Tianjin University) Tianjin300350China

The unprecedented rate of metro construction has led to a highly complex network of metro *** are being overlapped to an ever-increasing *** paper investigates the deformation response of double-track overlapped tunnels in Tianjin,China using finite element analysis(FEA)and field monitoring,considering the attributes of different tunneling *** respect to the upper tunneling,the results of the FEA and field monitoring showed that the maximum vertical displacements of the ground surface during the tail passage were 2.06 mm,2.25 mm and 2.39 mm obtained by the FEA,field monitoring and Peck calculation,respectively;the heaves on the vertical displacement curve were observed at 8 m(1.25D,where D is the diameter of the tunnel)away from the center of the tunnel and the curve at both sides was ***,the crown and bottom produce approximately0.38 mm and 1.26 mm of contraction,*** results of the FEA of the upper and lower sections demonstrated that the tunneling form has an obvious influence on the deformation response of the double-track overlapped *** with the upper tunneling,the lower tunneling exerted significantly less influence on the deformation response,which manifested as a smaller displacement of the strata and deformation of the existing *** results of this study on overlapped tunnels can provide a reference for similar projects in the future.

关键词： Double-track overlapped tunnels Deformation response Finite element analysis(FEA) Field monitoring Upper and lower tunneling

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Ground movement induced by triple stacked tunneling with different construction sequences

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第5期14卷 1433-1446页

作者： Yao Hu huayang lei Gang Zheng Liang Shi Tianqi Zhang Zhichao Shen Rui Jia School of Civil Engineering Tianjin UniversityTianjin300350China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu610059China Department of Civil and Environmental Engineering National University of Singapore117576Singapore Key Laboratory of Coast Civil Structure Safety of Ministry of Education Tianjin UniversityTianjin300350China Key Laboratory of Earthquake Engineering Simulation and Seismic Resilience of China Earthquake Administration Tianjin UniversityTianjin300350China State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin300350China

This study tried to explore the ground movement induced by triple stacked tunneling(TST) with different construction sequences. A case study in Tianjin, China was used to investigate the ground movement during the TST(upper tunneling(UT)). For this, a modified Peck formula was proposed to predict the surface settlement induced by TST. Next, three sets of finite element analyses(FEA) were used to compare the effects of construction sequences(i.e. UT, middle tunneling(MT), and lower tunneling(LT)) on vertical and lateral ground displacements. The results of Tianjin case and UT reveal that compared to a Gaussian distribution for a single tunnel, the surface settlement curve of triple stacked tunnels is a bimodal distribution. It seems that the proposed modified Peck formula can effectively predict the surface settlement induced by TST. The results of the three sets of FEA demonstrate that the construction sequence has a significant influence on the ground movement. Among the three construction sequences, the largest lateral displacement is observed in the MT and the smallest one in *** existing tunnel has an inhibitory effect on the vertical displacement. The maximum value of the lateral displacement occurs at the depth of the new tunnel in each construction sequence.

关键词： Triple stacked tunneling(TST) Ground movement Construction sequence Case study Surface settlement prediction Finite element analysis

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温度对CPTU在海底泥中测试结果的影响及修正方法

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天津大学学报（自然科学与工程技术版） 2019年第11期52卷 1194-1200页

作者：加瑞雷华阳冯双喜天津大学建筑工程学院天津300350 天津大学滨海土木工程结构与安全教育部重点实验室天津300350

温度改变会影响孔压静力触探(CPTU)的测量结果.利用CPTU调查了海底泥的特性,由于海底泥的锥尖阻力(qc)和侧壁摩阻力(fs)较小而且调查时海底泥和海水中的温差较大,fs大多数是负值且随深度逐渐减小.据此提出了在没有安装温度传感器的情况... 详细信息

温度改变会影响孔压静力触探(CPTU)的测量结果.利用CPTU调查了海底泥的特性,由于海底泥的锥尖阻力(qc)和侧壁摩阻力(fs)较小而且调查时海底泥和海水中的温差较大,fs大多数是负值且随深度逐渐减小.据此提出了在没有安装温度传感器的情况下考虑温度对CPTU在海底泥中测试结果影响的修正方法:首先通过室内温度校正试验获得qc和fs的温度校正系数;然后假设浅层海底泥的fs随深度线性增加,根据相关测量结果或经验估计“实际”的fs剖面;再根据测量和“实际”的fs剖面的区别估计地基中的温度剖面;最后根据温度剖面和温度校正系数对CPTU的测量结果进行温度修正.对本文CPTU测试数据的温度修正结果表明,如果不考虑温度的影响,CPTU在海底泥中的fs会被低估,其值会随深度减小甚至变为负值;在约3.5m深度处,海底泥的qt(考虑孔压修正的锥尖阻力)可能会被高估50%以上;海底泥的不排水抗剪强度(su)将会被高估,温度修正后CPTU所得su更接近于室内试验所得的su.在本文所建议的修正方法中,唯一不确定的参数是正常固结海底沉积物的fs随深度的增加率(α).本文通过反分析得出的α=0.2kPa/m,黏土矿物类型和沉积环境等因素可能会影响α的大小.实际中应该根据相关的测量数据确定α的大小,如果没有相关的测量数据,可以采用本文建议的α值.

关键词：孔压静力触探(CPTU) 海底泥温度修正方法地基温度

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盾构隧道开挖面失稳破坏机理及土拱效应研究综述

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太原理工大学学报 2022年第1期53卷 98-117页

作者：雷华阳刘敏天津大学建筑工程学院天津300354 天津大学滨海土木工程结构与安全教育部重点实验室天津300354

针对当前国内外盾构隧道开挖面失稳机理研究现状进行了系统概括和评述,并重点探讨开挖面失稳研究中的土拱效应问题。盾构隧道开挖面失稳机理包括失稳过程、失稳模式和失稳模型研究。盾构隧道开挖面失稳过程中土拱效应包括盾构开挖面失... 详细信息

针对当前国内外盾构隧道开挖面失稳机理研究现状进行了系统概括和评述,并重点探讨开挖面失稳研究中的土拱效应问题。盾构隧道开挖面失稳机理包括失稳过程、失稳模式和失稳模型研究。盾构隧道开挖面失稳过程中土拱效应包括盾构开挖面失稳破坏过程土拱效应演化研究和考虑土拱效应影响的盾构开挖面失稳模型研究两部分。在此基础上进一步提出基于土体三向压力时空变化规律揭示开挖面失稳破坏机理,进行开挖面失稳过程空间三维土拱效应演化规律,以及空间物理土拱演化及相应计算方法应用的未来研究方向及建议。

关键词：盾构隧道开挖面稳定性土拱效应

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不同硫酸钠含量条件下吹填超软土的力学特性试验研究

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天津大学学报（自然科学与工程技术版） 2020年第7期53卷 685-694页

作者：雷华阳屠慈科王磊李宸元天津大学建筑工程学院天津300354 滨海土木工程结构与安全教育部重点实验室(天津大学) 天津300354

吹填土中所含的丰富的可溶盐对其物理力学特性有着极大的影响.通过配置不同硫酸钠掺量的含盐吹填土试样,研究了可溶盐含量对吹填土强度及变形特性的影响,并利用SEM电镜扫描试验分析了吹填土微观结构特征的变化规律,从微观角度分析了其... 详细信息

吹填土中所含的丰富的可溶盐对其物理力学特性有着极大的影响.通过配置不同硫酸钠掺量的含盐吹填土试样,研究了可溶盐含量对吹填土强度及变形特性的影响,并利用SEM电镜扫描试验分析了吹填土微观结构特征的变化规律,从微观角度分析了其宏观力学特性的变化机理.研究结果表明:由于钠离子作用,土颗粒吸附水膜的厚度不断增大,粒间吸引团聚作用减弱,吹填土试样内部孔隙增大,结构更加疏松,宏观上表现为强度不断减小(最大降低幅度达44.1%),压缩性相应增大;随着含盐量的不断增加,由于硫酸钠的结晶及相关离子反应导致硫酸钙的生成,吹填土试样内部胶结作用有所增强,强度会出现约29.6%的增长,压缩性相应减小.而当含水量增大时,钠离子对土颗粒团聚作用的影响以及硫酸钠的结晶作用被弱化,硫酸钙对吹填土的增强作用对其力学特性有更显著的影响.试样内部开始有明显的粒间胶结物生成,粒间孔隙减小,颗粒团聚,形成了较明显的团粒结构,土骨架效应显著,宏观上呈现出抗剪强度不断增大(最大增幅约335.5%)、压缩性不断减小的变化特点.吹填土试样在可溶盐环境下的应力-应变关系呈现应变硬化特征.

关键词：吹填超软土含盐量力学特性微观结构

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