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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 China.An 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 fills.In recent years,air-boosted vacuum preloading has been developed to overcome these limitations;however,this method still requires more data to verify its performance.In 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 data.Then,a series of FE parametric analyses was performed to assess key factors,i.***.the air injection pressure,the injection spacing,and the characteristics of cyclic injection,which affect the performance of the air-boosted vacuum preloading.The 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 cycles.Based 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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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 UT.The 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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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 lines.Tunnels are being overlapped to an ever-increasing degree.This 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 forms.With 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 asymmetrical.Furthermore,the crown and bottom produce approximately0.38 mm and 1.26 mm of contraction,respectively.The 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 tunnel.Compared 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 tunnel.The 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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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 construction.In 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 test.The 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 conditions.The results show that the engineering characteristics of transparent clay are similar to those of soft clay in Binhai,Tianjin and satisfy visibility requirements.Two 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≥2.0.Additionally,the normalized thresholds of the relative displacement and support force ratio are 3%-6%and 0.2-0.4,respectively.Owing 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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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 fills.In 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,China.With 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 one.Ten 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 positions.The 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 phase.According 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 phase.An 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 method.For 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 consolidation.The 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 better treatment effect not only in decreasing t

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

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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 foundation.Safety control is pivotal to ensuring the safety of adjacent structures.In 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 environment.The AHP was adopted to determine key influencing factors based on the weight of each influencing factor.The FEM was used to quantify the impact of the key influencing factors on the surrounding environment.In 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 calculated.It was found that the excavation depth and the distance between the foundation pit and the bridge foundation were fundamental factors.For the FEM,the FE baseline model was calibrated based on the case of no bridge surrounding the foundation pit.The consistency between the monitoring data and the numerical simulation data for a ground settlement was analyzed.FE simulations were then conducted to quantitatively analyze the degree of influence of the key influencing factors on the bridge foundation.Furthermore,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 analyzed.The most hazardous construction condition was also determined.Finally,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 can provide some beneficial references for enginee

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

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西藏地区无导爆索光面爆破技术研究与应用

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四川水利 2024年第2期45卷 132-135页

作者：耿东红吴绍平雷花洋中国水利水电第九工程局有限公司贵阳550081

西藏地区交通不便,导爆索等爆破器材供应受到限制,且传统的光面爆破难以形成平整光面,这给该地区隧道的爆破施工带来了诸多困难。因此,研究在无导爆索情况下改进传统光面爆破技术进行爆破施工非常必要。文章以西藏地区某水电工程前期隧... 详细信息

西藏地区交通不便,导爆索等爆破器材供应受到限制,且传统的光面爆破难以形成平整光面,这给该地区隧道的爆破施工带来了诸多困难。因此,研究在无导爆索情况下改进传统光面爆破技术进行爆破施工非常必要。文章以西藏地区某水电工程前期隧道施工为例,研究了无导爆索光面爆破技术。该研究用雷管代替导爆索来引爆炸药,采用不耦合装药方式,把竹片放置在每个炮孔的炸药上方,起爆瞬间生成的爆轰波与同时生成的高温高压气体的威力能被竹片大大消减,与传统的光面爆破相比能有效保证爆破后形成平整稳定的光面,对隧道爆破具有重要意义。

关键词：导爆索光面爆破成本控制爆破技术

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注气加载路径对增压式真空预压法加固吹填软土的效果分析

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岩石力学与工程学报 2023年第8期42卷 2058-2067页

作者：雷华阳方庆峰刘景锦王磊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

采用增压式真空预压法加固处理吹填软土时,其加固效果会受到注气压力和注气时间的影响。利用不同注气压力和注气时间组合条件的室内模型试验,研究注气加载路径对增压式真空预压法加固吹填软土的效果影响,试验中考虑恒压力–恒时间、恒... 详细信息

采用增压式真空预压法加固处理吹填软土时,其加固效果会受到注气压力和注气时间的影响。利用不同注气压力和注气时间组合条件的室内模型试验,研究注气加载路径对增压式真空预压法加固吹填软土的效果影响,试验中考虑恒压力–恒时间、恒压力–变时间、变压力–恒时间以及变压力–变时间4种注气加载路径。试验结果表明,增压式真空预压法对土体的加固效果总是优于常规真空预压法,且当采用变压力–变时间的注气加载路径时,土体的加固效果最佳。与恒压力–恒时间的注气加载路径相比,采用变压力–变时间的注气加载路径可使土体的表面沉降增大9.25%,排水量增大9.35%,平均含水率降低13.91%,平均十字板剪切强度增大20.59%。注气压力和注气时间的逐级递增可有效地防止黏粒向排水板处聚集,促使排水板与增压板之间土体孔隙数量的增多,增大土体的渗透性,提高深层土体的加固效果。

关键词：土力学吹填软土增压式真空预压注气压力注气时间加固机制

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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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黏土结构性对孔压静力触探结果的影响分析

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水文地质工程地质 2023年第5期50卷 80-88页

作者：加瑞赵栋雷华阳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

针对目前黏土结构性对孔压静力触探结果的影响及其机理尚不是很清楚的问题,首先在ABAQUS软件中对结构性剑桥模型进行了程序实现,然后建立了孔压静力触探贯入结构性黏土的数值模型,通过数值计算分析了黏土结构性对孔压静力触探结果的影... 详细信息

针对目前黏土结构性对孔压静力触探结果的影响及其机理尚不是很清楚的问题,首先在ABAQUS软件中对结构性剑桥模型进行了程序实现,然后建立了孔压静力触探贯入结构性黏土的数值模型,通过数值计算分析了黏土结构性对孔压静力触探结果的影响。数值计算结果表明:(1)黏土的结构性会导致锥尖周围土体的偏应力增大,由于锥尖附近土体的结构性损伤,最大偏应力出现在距锥尖一定距离的右下方;(2)表征结构性强度的参数——初始结构屈服应力p’_(yi)越大,锥尖阻力qc越大,而表征结构性损伤速度的参数——结构性对流动法则影响参数ω越大,q_(c)值越小;(3)p’_(yi)值越大,贯入停止时的超静孔隙水压力u越大,而ω值越大,贯入停止时的u值越小;(4)经验圆锥系数N_(kt)随p’_(yi)增大明显减小,随ω的增大略有减小。因此,黏土的结构性强度及其损伤会明显影响孔压静力触探的测量结果,基于锥尖阻力q_(c)估算结构性黏土的不排水抗剪强度su时应采用考虑结构性影响的经验圆锥系数N_(kt),否则将会低估结构性黏土的s_(u)。研究结果可为孔压静力触探结果的分析和应用提供参考。

关键词：黏土结构性孔压静力触探结构性剑桥模型锥尖阻力经验圆锥系数

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