Study on Deep Well Dewatering Optimization Design in Deep Foundation Pit and Engineering Application

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.

Optimization of dewatering schemes for a deep foundation pit near the Yangtze River, China

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.

Research of deformation prediction method of soft soil deep foundation pit

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.

Co-Evolution Optimization of Anchored Row Piles for Deep Foundation Pit

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.

Numerical simulation and land subsidence control for deep foundation pit dewatering of Longyang Road Station on Shanghai Metro Line 18

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.

Construction Technology and Safety Risk Control Measures of Deep Foundation Pit Excavation

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.

Accident Analysis and Emergency Response Effect Research of the Deep Foundation Pit in Taiyuan Metro

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.

Deep Foundation Pit Excavations Adjacent to Disconnected Piled Rafts: A Review on Risk Control Practice

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 existing disconnected piled raft. More focus is given to geotechnical aspects. The review begins with achievements to ensure excavation performance requirements, and follows to discuss the complex soil structure interaction involved among the fundamental components: the retaining wall, mat, piles, cushion, and the soil. After bringing consensus points to practicing engineers and decision makers, it then suggests possible future research directions.

Elastic-plastic analysis for pile-anchor supporting system of deep foundation pit

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.

Construction Technology of Deep Foundation Pit Support in Municipal Civil Engineering Foundation Construction

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.

Numerical Simulation and Field Monitoring Analysis for Deep Foundation Pit Construction of Subway Station

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.

基于某复杂地层深基坑降水开挖数值模拟分析

本文以长春某深基坑项目为例,利用Midas GTS NX软件对施工过程进行模拟。研究降水开挖对地表沉降、坑底隆起、围护结构的变形影响以及分析不同桩径、降水对基坑开挖的影响。结果表明,围护结构最大变形与最大地表沉降随开挖深度不断增大,最大变形位置与开挖深度之比分别为0.72和0.63;富水砂层地区基坑降水开挖后地表沉降、围护结构变形降水关系占比较大;适当改变桩径可以减小围护结构的水平变形,此次建模也验证模型的准确性。

某档案馆建设对邻近既有供水隧洞安全影响分析

为分析某档案馆建设及运行对邻近既有供水隧洞安全的影响,采用MIDAS GTS构建三维有限元模型进行分析,模拟了档案馆从施工到运行的全过程对邻近既有供水隧洞安全的影响。结果表明,项目施工及运行过程中,对既有供水隧洞在各方向上的位移量均小于规范允许值,满足安全要求。

基于三维地质模型的深基坑土方开挖管理研究

建设项目弃土的资源化利用可有效降低施工企业的成本,同时按照弃土的工程特性进行预处理并分类填筑施工,可有效降低弃土边坡的稳定风险。基于岩土工程勘察成果,建立工程场地范围内的三维地质模型,通过模型分析及计算,对拟开挖的土石方按照岩性及工程位置进行工程量计算及统计,结合工程位置和土体的工程特点,合理组织施工,提高施工效率;加强开挖过程中土质的分类和管理,可有效控制弃土的综合成本,同时为合理组织弃土的预处理与回填施工提供依据。

基于BIM技术的基坑智能监测技术研究

基坑边坡的不安全性常导致工程事故发生,深基坑作为建设工程施工危险部位重大专项,确保基坑的安全监测和报警的及时性非常重要。文章基于BIM技术如何实现快速高效及时报警进行了分析。通过智能传感器采集数据进行无线传输至云平台,平台解析数据与BIM基坑模型自动匹配,对测点部位的位移、土压力进行动态监测,当超过预警值后自动传输报警信息,为工程危险源的及时处理提供决策依据。文章基于BIM技术的深基坑监测技术通过在天柱山管廊项目进行应用,取得了良好的安全经济效益。

复杂特殊条件下地下室深基坑施工技术研究

为保证地下室深基坑施工质量及安全,重点探究复杂特殊条件下的施工技术手段势在必行。基于此,本文对复杂特殊条件下地下室深基坑施工的特点进行分析,从多方面阐述复杂特殊条件下地下室深基坑施工技术要点,并提出了施工监测方案。希望通过本文研究,为相关人员提供参考借鉴,不断提升复杂特殊条件下地下室深基坑施工技术水平。

拉森钢板桩在软土地层深基坑支护中的应用

拉森钢板桩作为一种低碳环保、可回收的建筑材料,在各类建筑中发挥着重要的作用。以蕲春县某河道整治项目为例,选取了基坑支护工程中2个典型剖面,介绍了拉森钢板桩在软土地层中的应用,并将天汉软件设计计算结果、MIDAS GTS NX数值模型分析结果与基坑监测结果进行对比分析,三者得到的支护结构位移、受力数值较为一致,表明天汉深基坑设计软件的客观合理性及可靠性非常高,施工前可以用MIDAS GTS NX数字模拟来预测及引导施工。

深基坑施工对周边土体变形的影响分析

珠江三角洲有不良的地质情况与特殊岩土的特点,深基坑在开挖的过程中势必对地上结构、土体变形、城市交通设施造成一系列影响,故分析地下深基坑开挖施工时周边土体变形及其环境的动态变化,相应调整各项施工工序及施工参数,以确保工程安全、优质、快速。本文依托空港大道(白云五线-机场)工程,结合深基坑明挖施工现场监测结果,如基坑附近地表沉降、围护结构水平位移,结合明挖法施工过程建立有限元数值模型与实际监测数据对比从而有效地将施工控制在安全范围之内,并总结相关规律与对周边土体变形的影响因素,为同类型的地下工程施工提供参考和借鉴。

地铁车站深基坑开挖变形监测方案研究

为了保障地铁车站深基坑开挖过程中的施工安全与质量,本文以某地铁车站工程项目为例,详细规划了深基坑开挖变形监测的内容,包括围护结构位移、周边地表沉降、支撑轴力变化等关键指标。随后,阐述了监测实施方法及测点布置策略,包括高精度控制网的建立、监测初始值的精确测定与复核,以及具体监测步骤的执行。最后,对监测结果进行了深入分析,揭示了变形规律与潜在风险。研究结果表明,通过科学合理的监测方案,能够有效控制深基坑开挖引起的变形,为施工安全与进度管理提供了重要依据,同时验证了本文监测方案的有效性与实用性。