Deep foundation pit excavation is a basic and key step involved in modern building construction.In order to ensure the construction quality and safety of deep foundation pits,this paper takes a project as an example t...Deep foundation pit excavation is a basic and key step involved in modern building construction.In order to ensure the construction quality and safety of deep foundation pits,this paper takes a project as an example to analyze deep foundation pit excavation technology,including the nature of this construction project,the main technical measures in the construction of deep foundation pit,and the analysis of the safety risk prevention and control measures.The purpose of this analysis is to provide scientific reference for the construction quality and safety of deep foundation pits.展开更多
Municipal civil engineering is the key content of municipal construction,and the construction scale is usually large.The quality of the project plays an important role in the development of urban economy.Due to the ra...Municipal civil engineering is the key content of municipal construction,and the construction scale is usually large.The quality of the project plays an important role in the development of urban economy.Due to the rapid increase of high-rise buildings,skyscrapers and underground buildings,the construction technology of deep foundation pit support has gradually become an indispensable construction technology.Therefore,the selection of foundation pit support construction technology is crucial in ensuring that whether the foundation is firm and stable,and whether the subsequent construction activities can be carried out smoothly.In view of this,the article discusses the application of deep foundation pit support construction technology in municipal civil engineering,aiming to provide reference for subsequent projects.展开更多
Based on analyses of the theories of groundwater unsteady flow in deep well dewatering in the deep foundation pit, Theis equations are chosen to calculate and analyze the relationship between water level drawdown of c...Based on analyses of the theories of groundwater unsteady flow in deep well dewatering in the deep foundation pit, Theis equations are chosen to calculate and analyze the relationship between water level drawdown of confined aquifer and dewatering duration. In order to reduce engineering cost and diminish detrimental effect on ambient surrounding, optimization design target function based on the control of confined water drawdown and four restriction requisitions based on the control of safe water level, resistance to throwing up from the bottom of foundation pit, avoiding excessively great subsidence and unequal surface subsidence are proposed. A deep well dewatering project in the deep foundation pit is optimally designed. The calculated results including confined water level drawdown and surface subsidence are in close agreement with the measured results, and the optimization design can effectively control both surface subsidence outside foundation pit and unequal subsidence as a result of dewatering.展开更多
A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missin...A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missing. To guarantee the safety of pit excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, should be 1 m below the pit bottom, while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem. The Yangtze River levee is notably close to the pit, and its deformation caused by dewatering should be controlled. A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer. The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d, which is larger than the values from numerical simulation（horizontal hydraulic conductivity K_H = 16 m/d and vertical hydraulic conductivity K_V = S m/d）. The difference between K_H and K_V indicates the anisotropy of the aquifer. Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes. The results show that though the first scheme could meet the dewatering requirements, the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰, respectively, greatly exceeding the limited values. Meanwhile, the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level, and 27 recharge wells are set along the levee, can control the deformation of the levee significantly.展开更多
In view of the characteristics of soft soil deep foundation pit for the construction and geotechnical characteristics of the special medium,it is difficult to calculate theoreti- cally accurately structural deformatio...In view of the characteristics of soft soil deep foundation pit for the construction and geotechnical characteristics of the special medium,it is difficult to calculate theoreti- cally accurately structural deformation of the foundation pit,so in the course of excavation on the construction of the information is particularly important.The analysis and compari- son of several popular non-linear forecasting methods,combined with the actual projects, set up a grey theoretical prediction model,time series forecasting model,improved neural network model to predict deformation of the foundation pit.The results show that the use of neural network to predict with high accuracy solution,it is the foundation deformation prediction effective way in underground works with good prospects.展开更多
The thinking of co evolution is applied to the optimization of retaining and protecting structure for deep foundation excavation, and the system of optimization of anchored row piles for deep foundation pit has been a...The thinking of co evolution is applied to the optimization of retaining and protecting structure for deep foundation excavation, and the system of optimization of anchored row piles for deep foundation pit has been already developed successfully. For the co evolution algorithm providing an evolutionary mechanism to simulate ever changing problem space, it is an optimization algorithm that has high performance, especially applying to the optimization of complicated system of retaining and protecting for deep foundation pit. It is shown by many engineering practices that the co evolution algorithm has obvious optimization effect, so it can be an important method of optimization of retaining and protecting for deep foundation pit. Here the authors discuss the co evolution model, object function, all kinds of constraint conditions and their disposal methods, and several key techniques of system realization.展开更多
In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to ...In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled.展开更多
To investigate the effect of deep foundation pit excavation on the stability of retaining structure, a subway stationin the city of Jinan was selected as a project, and a FLAC3D-based three dimensional model was devel...To investigate the effect of deep foundation pit excavation on the stability of retaining structure, a subway stationin the city of Jinan was selected as a project, and a FLAC3D-based three dimensional model was developed fornumerical simulation. The horizontal displacement of the retaining structure, the axial force of the support, andthe vertical displacement of the column were studied and compared to the collected data from the field. The findingsindicate that when the foundation pit is excavated, the maximum deformation of the retaining structure progressivelydecreases from the top, the distortion of the retaining structure gradually rises, and the final maximumdeformation is around 17 meters deep. In each layer of support, the largest axial force support is located in thefirst reinforced concrete support;the uplift of the pit bottom caused by soil unloading plays a primary role in thevertical displacement of the column, and the column exhibits an upward trend under all construction conditions.When compared to the measured data, the generated findings are comparable and the fluctuation trend is extremelyconsistent. The findings of this article may give technical direction for the development of subway stationswith a comparable engineering basis.展开更多
Taking the deep foundation pit accident occurring at a station of metro Line 2 in Taiyuan as an example,the influence of the seepage and inrush of the foundation pit on the retaining structure and surrounding environm...Taking the deep foundation pit accident occurring at a station of metro Line 2 in Taiyuan as an example,the influence of the seepage and inrush of the foundation pit on the retaining structure and surrounding environment were studied under the geological conditions of the confined aquifer on the east coast of Fenhe River.The causes of deep foundation pit accident were also analyzed systematically based on the monitoring data,and various emergency measures were proposed to control the occurrence of secondary accident for deep foundation pit.The results showed that the occurrence of inrush for foundation pit was mainly caused by the insufficient dewatering.The development of the accident was effectively controlled by the adding of the dewatering wells,local grouting of retaining structure to stop seepage,surface grouting to reinforcement and uplift soil.The successful experience can provide some guidance to the construction of similar projects in the proposal.展开更多
Foundation pit excavation engineering is an old subject full of decision making. Yet, it still deserves further research due to the associated high failure cost and the complexity of the geological conditions and/or t...Foundation pit excavation engineering is an old subject full of decision making. Yet, it still deserves further research due to the associated high failure cost and the complexity of the geological conditions and/or the surrounding existing infrastructure around it. This article overviews the risk control practice of foundation pit excavation projects in close proximity to <span style="font-family:Verdana;">existing</span><span style="font-family:Verdana;"> disconnected piled raft. More focus is given to geotechnical aspects. The review begins with achievements to ensure excavation performance </span><span style="font-family:Verdana;">requirements,</span><span style="font-family:Verdana;"> and follows to discuss the complex </span><span style="font-family:Verdana;">soil structure</span><span style="font-family:Verdana;"> interaction involved among the fundamental components</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">: </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">the retaining wall, mat, piles, cushion, and the soil. After bringing consensus points to practicing engineers and </span><span style="font-family:Verdana;">decision makers</span><span style="font-family:Verdana;">, it then suggests possible future research directions.</span></span></span></span>展开更多
By using numerical analysis methods to simulate the deep excavation,a lot of analyses are established on the basis of two-dimensional plane strain,ignoring the fact that foundation pit possesses three dimensions. For ...By using numerical analysis methods to simulate the deep excavation,a lot of analyses are established on the basis of two-dimensional plane strain,ignoring the fact that foundation pit possesses three dimensions. For soil constitutive relation,people always take linear and nonlinear model,without considering the plastic behavior of soil. Using plastic-elastic hardening model to simulate constitutive relation of soil characteristics,the authors carried out mechanical analysis for pit excavation and support. The results show that the analysis for the stress state of pile anchor system is an effective way which provides theoretical basis for calculation of soil displacement.展开更多
为探究地铁深基坑施工安全风险因素动态作用规律,科学预防施工安全事故,针对目前缺乏因素系统识别、因果关系量化和动态推理分析等共性问题,提出一种基于决策试验和评估实验室(Decision Making Trial and Evaluation Laboratory DEMATEL...为探究地铁深基坑施工安全风险因素动态作用规律,科学预防施工安全事故,针对目前缺乏因素系统识别、因果关系量化和动态推理分析等共性问题,提出一种基于决策试验和评估实验室(Decision Making Trial and Evaluation Laboratory DEMATEL)与模糊认知图(Fuzzy Cognitive Map,FCM)的地铁深基坑施工安全风险分析方法。首先,通过理论分析与文献梳理,采用扎根理论识别风险因素;其次,结合专家调研与量化分析,利用DEMATEL方法分析风险因素的因果关系;再次,将DEMATAL决策矩阵转化为FCM模型的交互作用矩阵,展开风险因素的预测与诊断推理分析;最后,选取案例进行实证,验证模型方法的可用性与有效性。结果显示:因素X_(1)(人员安全风险意识)对其他因素的影响程度最高;因素X_(1)(人员安全风险意识)、X_(8)(安全施工组织设计方案)和X_(7)(施工安全风险管理措施)是排名前3的关键风险因素;完善安全施工组织设计方案是最有效的管控对策。展开更多
文摘Deep foundation pit excavation is a basic and key step involved in modern building construction.In order to ensure the construction quality and safety of deep foundation pits,this paper takes a project as an example to analyze deep foundation pit excavation technology,including the nature of this construction project,the main technical measures in the construction of deep foundation pit,and the analysis of the safety risk prevention and control measures.The purpose of this analysis is to provide scientific reference for the construction quality and safety of deep foundation pits.
文摘Municipal civil engineering is the key content of municipal construction,and the construction scale is usually large.The quality of the project plays an important role in the development of urban economy.Due to the rapid increase of high-rise buildings,skyscrapers and underground buildings,the construction technology of deep foundation pit support has gradually become an indispensable construction technology.Therefore,the selection of foundation pit support construction technology is crucial in ensuring that whether the foundation is firm and stable,and whether the subsequent construction activities can be carried out smoothly.In view of this,the article discusses the application of deep foundation pit support construction technology in municipal civil engineering,aiming to provide reference for subsequent projects.
基金This paper is supported by the Hubei Construct Science Foundation of China (G200013).
文摘Based on analyses of the theories of groundwater unsteady flow in deep well dewatering in the deep foundation pit, Theis equations are chosen to calculate and analyze the relationship between water level drawdown of confined aquifer and dewatering duration. In order to reduce engineering cost and diminish detrimental effect on ambient surrounding, optimization design target function based on the control of confined water drawdown and four restriction requisitions based on the control of safe water level, resistance to throwing up from the bottom of foundation pit, avoiding excessively great subsidence and unequal surface subsidence are proposed. A deep well dewatering project in the deep foundation pit is optimally designed. The calculated results including confined water level drawdown and surface subsidence are in close agreement with the measured results, and the optimization design can effectively control both surface subsidence outside foundation pit and unequal subsidence as a result of dewatering.
基金financially supported by the doctoral fund of the Ministry of Education of Chinathe Nature Science Foundation of Jiangsu Province, China (Grant Nos. 20130091110020 and BE2015675)
文摘A deep foundation pit constructed for an underground transportation hub was excavated near the Yangtze River. Among the strata, there are two confined aquifers, between which lies an aquiclude that is partially missing. To guarantee the safety of pit excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, should be 1 m below the pit bottom, while that of the lower confined aquifer should be dewatered down to a safe water level to avoid uplift problem. The Yangtze River levee is notably close to the pit, and its deformation caused by dewatering should be controlled. A pumping test was performed to obtain the hydraulic conductivity of the upper confined aquifer. The average value of the hydraulic conductivity obtained from analytical calculation is 20.45 m/d, which is larger than the values from numerical simulation（horizontal hydraulic conductivity K_H = 16 m/d and vertical hydraulic conductivity K_V = S m/d）. The difference between K_H and K_V indicates the anisotropy of the aquifer. Two dewatering schemes were designed for the construction and simulated by the numerical models for comparison purposes. The results show that though the first scheme could meet the dewatering requirements, the largest accumulated settlement and differential settlement would be94.64 mm and 3.3‰, respectively, greatly exceeding the limited values. Meanwhile, the second scheme,in which the bottoms of the waterproof curtains in ramp B and the river side of ramp A are installed at a deeper elevation of-28 m above sea level, and 27 recharge wells are set along the levee, can control the deformation of the levee significantly.
基金the Educational Department of Liaoning Province Through Scientific Research Project(20060051)National Natural Science Foundation of China(50604009)Universities Excellent Talents Support Plan to Train Foundation of Liaoning(RC-04-13)
文摘In view of the characteristics of soft soil deep foundation pit for the construction and geotechnical characteristics of the special medium,it is difficult to calculate theoreti- cally accurately structural deformation of the foundation pit,so in the course of excavation on the construction of the information is particularly important.The analysis and compari- son of several popular non-linear forecasting methods,combined with the actual projects, set up a grey theoretical prediction model,time series forecasting model,improved neural network model to predict deformation of the foundation pit.The results show that the use of neural network to predict with high accuracy solution,it is the foundation deformation prediction effective way in underground works with good prospects.
基金National Natural Science Foundation of China( 5 986 80 0 1)
文摘The thinking of co evolution is applied to the optimization of retaining and protecting structure for deep foundation excavation, and the system of optimization of anchored row piles for deep foundation pit has been already developed successfully. For the co evolution algorithm providing an evolutionary mechanism to simulate ever changing problem space, it is an optimization algorithm that has high performance, especially applying to the optimization of complicated system of retaining and protecting for deep foundation pit. It is shown by many engineering practices that the co evolution algorithm has obvious optimization effect, so it can be an important method of optimization of retaining and protecting for deep foundation pit. Here the authors discuss the co evolution model, object function, all kinds of constraint conditions and their disposal methods, and several key techniques of system realization.
基金supported by the Researches on the Control of Confined Water Drawdown and Subsidence in Foundation Pit Projects (Project No. JS-KY16R009-1)this project is funded by Shanghai Metro Line 18 Development Co., Ltd.
文摘In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled.
基金supported by the National Natural Science Foundation of China(51774199).
文摘To investigate the effect of deep foundation pit excavation on the stability of retaining structure, a subway stationin the city of Jinan was selected as a project, and a FLAC3D-based three dimensional model was developed fornumerical simulation. The horizontal displacement of the retaining structure, the axial force of the support, andthe vertical displacement of the column were studied and compared to the collected data from the field. The findingsindicate that when the foundation pit is excavated, the maximum deformation of the retaining structure progressivelydecreases from the top, the distortion of the retaining structure gradually rises, and the final maximumdeformation is around 17 meters deep. In each layer of support, the largest axial force support is located in thefirst reinforced concrete support;the uplift of the pit bottom caused by soil unloading plays a primary role in thevertical displacement of the column, and the column exhibits an upward trend under all construction conditions.When compared to the measured data, the generated findings are comparable and the fluctuation trend is extremelyconsistent. The findings of this article may give technical direction for the development of subway stationswith a comparable engineering basis.
基金National Natural Science Foundation of China(No.51908516)Natural Science Foundation of Shanxi Province,China(No.201901D211207)。
文摘Taking the deep foundation pit accident occurring at a station of metro Line 2 in Taiyuan as an example,the influence of the seepage and inrush of the foundation pit on the retaining structure and surrounding environment were studied under the geological conditions of the confined aquifer on the east coast of Fenhe River.The causes of deep foundation pit accident were also analyzed systematically based on the monitoring data,and various emergency measures were proposed to control the occurrence of secondary accident for deep foundation pit.The results showed that the occurrence of inrush for foundation pit was mainly caused by the insufficient dewatering.The development of the accident was effectively controlled by the adding of the dewatering wells,local grouting of retaining structure to stop seepage,surface grouting to reinforcement and uplift soil.The successful experience can provide some guidance to the construction of similar projects in the proposal.
文摘Foundation pit excavation engineering is an old subject full of decision making. Yet, it still deserves further research due to the associated high failure cost and the complexity of the geological conditions and/or the surrounding existing infrastructure around it. This article overviews the risk control practice of foundation pit excavation projects in close proximity to <span style="font-family:Verdana;">existing</span><span style="font-family:Verdana;"> disconnected piled raft. More focus is given to geotechnical aspects. The review begins with achievements to ensure excavation performance </span><span style="font-family:Verdana;">requirements,</span><span style="font-family:Verdana;"> and follows to discuss the complex </span><span style="font-family:Verdana;">soil structure</span><span style="font-family:Verdana;"> interaction involved among the fundamental components</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">: </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">the retaining wall, mat, piles, cushion, and the soil. After bringing consensus points to practicing engineers and </span><span style="font-family:Verdana;">decision makers</span><span style="font-family:Verdana;">, it then suggests possible future research directions.</span></span></span></span>
文摘By using numerical analysis methods to simulate the deep excavation,a lot of analyses are established on the basis of two-dimensional plane strain,ignoring the fact that foundation pit possesses three dimensions. For soil constitutive relation,people always take linear and nonlinear model,without considering the plastic behavior of soil. Using plastic-elastic hardening model to simulate constitutive relation of soil characteristics,the authors carried out mechanical analysis for pit excavation and support. The results show that the analysis for the stress state of pile anchor system is an effective way which provides theoretical basis for calculation of soil displacement.
文摘为探究地铁深基坑施工安全风险因素动态作用规律,科学预防施工安全事故,针对目前缺乏因素系统识别、因果关系量化和动态推理分析等共性问题,提出一种基于决策试验和评估实验室(Decision Making Trial and Evaluation Laboratory DEMATEL)与模糊认知图(Fuzzy Cognitive Map,FCM)的地铁深基坑施工安全风险分析方法。首先,通过理论分析与文献梳理,采用扎根理论识别风险因素;其次,结合专家调研与量化分析,利用DEMATEL方法分析风险因素的因果关系;再次,将DEMATAL决策矩阵转化为FCM模型的交互作用矩阵,展开风险因素的预测与诊断推理分析;最后,选取案例进行实证,验证模型方法的可用性与有效性。结果显示:因素X_(1)(人员安全风险意识)对其他因素的影响程度最高;因素X_(1)(人员安全风险意识)、X_(8)(安全施工组织设计方案)和X_(7)(施工安全风险管理措施)是排名前3的关键风险因素;完善安全施工组织设计方案是最有效的管控对策。
