scholarly journals The application of land subsidence control technologies caused by deep foundation pit dewatering

2020 ◽  
Vol 382 ◽  
pp. 775-780
Author(s):  
Jinbao Liu
Keyword(s):  
Land Subsidence ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Integrated Design ◽  
Good Effect ◽  
Information Control ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Control Technologies

Abstract. In order to analyze land subsidence caused by the dewatering of a deep foundation pit in Shanghai, numerical analysis, field testing, automatic monitoring and other technologies are applied to research land subsidence control technologies, covering the whole process during the design, construction and operation of foundation pit dewatering systems. The key technologies are applied to a typical metro station foundation pit in Shanghai, such as the integrated design of foundation pit dewatering and a waterproof curtain, information control, groundwater artificial recharge, etc. The measured data of groundwater level, pore water pressure and land subsidence show a good effect on land subsidence prevention and control.

scholarly journals Numerical Simulation of Seepage and Deformation in Excavation of a Deep Foundation Pit under Water-Rich Fractured Intrusive Rock

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Changfeng Yuan ◽  
Zhenhui Hu ◽  
Zhen Zhu ◽  
Zijin Yuan ◽  
Yanxiang Fan ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Inrush ◽  
Risk Level ◽  
Silty Clay ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit

Water is one of the major risk sources in the excavation of deep-large foundation pits in a water-rich area. The presence of intrusive broken diorite porphyrite in the stratum aggravates the risk level of deep foundation pits. Based on a geological survey report and design documents of parameter information, MIDAS/GTS software was used to perform the numerical simulation of an engineering example of a deep foundation pit project of ultradeep and water-rich intrusion into the broken rock station of subway line 4 in a city. The simulation results show the characteristics of seepage path evolution, seepage aggregation areas and points, and the effect of seepage on the deformation of a deep foundation pit during the whole construction of this deep foundation pit. The results show that with the precipitation-excavation of the deep foundation pit, the pore water pressure at the bottom of the foundation pit follows a distribution of three “concave” shapes. High-permeability pressure zones are found around the foundation pit, intruding broken diorite porphyrite zones, and middle coarse sand zones. With further excavation of the foundation pit, the seepage pressure in the middle part of the foundation pit gradually decreases, and the two “concave” distributions in the middle gradually merge together. After excavation to the bottom of the pit, the pore water pressure at the bottom is distributed in two asymmetrical “concave” shapes, and the maximum peak of pore water pressure is found at the intrusion of fractured porphyrites prone to water inrush. The four corners of the foundation pit are prone to form seepage accumulation zones; therefore, suffosion and piping zones are formed. The surface settlement caused by excavation is found to be the largest along the longitudinal axis of the deep foundation pit, whereas the largest deformation is found near the foundation pit side in the horizontal axis direction of the foundation pit. With the excavation of the deep foundation pit, the diaphragm wall converges to the foundation pit with the maximum deformation reaching about 25 mm. After the first precipitation-excavation of the deep foundation pit to the silty clay and the bottom of the pit with the largest uplift, with further precipitation-excavation of the deep foundation pit, the uplift at the bottom of the deep foundation pit changes only slightly.

scholarly journals Analysis of Seepage Characteristics of a Foundation Pit with Horizontal Waterproof Curtain in Highly Permeable Strata

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1303
Author(s):  
Chenghua Shi ◽  
Xiaohe Sun ◽  
Shengli Liu ◽  
Chengyong Cao ◽  
Linghui Liu ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Theoretical Calculation ◽  
Calculation Method ◽  
Design Method ◽  
Water Pressure ◽  
Water Inflow ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Seepage Characteristics

At present, jet-grouted horizontal waterproof curtain reinforcement has become an essential method for deep foundation pit groundwater control. However, there is still a lack of an effective theoretical calculation method for horizontal waterproof curtain reinforcement, and there is little research on the seepage laws of foundation pits under different horizontal waterproof curtain conditions. Based on Darcy’s seepage theory, theoretical analysis models of deep foundation pit seepage were established considering the effect of a horizontal curtain in a highly permeable formation. Through the established models, the calculation method of the water inflow and the water pressure under the condition of a horizontal curtain was derived. Then through indoor tests, the reliability of the theoretical calculation method was verified. Furthermore, the established theoretical calculation method is used to analyze the influence of various factors on the water inflow and the water pressure, such as the ratio of hydraulic conductivity of the horizontal curtain to surrounding soil, thickness, and reinforcement position of the horizontal curtain. It is found that the hydraulic conductivity ratio has the most significant influence on the seepage characteristics of the foundation pit. Finally, the design method was applied to an example of the horizontal waterproof curtain of the foundation pit, which is located at Juyuanzhou Station in Fuzhou (China). The water inflow per unit area is 0.36 m3/d in the foundation pit, and this implies that the design method of the horizontal waterproof curtain applied for the excavation case is good and meets the requirements of design and safety.

scholarly journals Experimental Study on the Variation Law of Excess Pore Water Pressure at the Bottom of the Foundation Pit for Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Qizhi Hu ◽  
Qiang Zou ◽  
Zhigang Ding ◽  
Zhaodong Xu
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Confining Pressure ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Excess Pore Water Pressure ◽  
Accurate Expression ◽  
Excess Pore

The excavation unloading of deep foundation pits in soft soil areas often produces negative excess pore water pressure. The rebound deformation of soil on the excavation surface of the foundation pit can be predicted reliably through the accurate expression of relevant variation laws. In combination with the principle of effective stress and the general equation of unidirectional seepage consolidation, an equation for calculating the rebound deformation from the bottom in the process of foundation pit excavation unloading was obtained. Additionally, a triaxial unloading test was adopted to simulate the excavation unloading processes for actual foundation pit engineering. After studying the variation law of the excess pore water pressure generated by excavation unloading, it was found that the negative excess pore water pressure increased with increasing unloading rate, while the corresponding peak value decreased with increasing confining pressure. The equation for rebound calculation was verified through a comparison with relevant measured data from actual engineering. Therefore, it is considered that the equation can reliably describe the rebound deformation law of the base. This paper aims to guide the design and construction of deep foundation pits in soft soil areas.

Numerical simulation of deep foundation pit dewatering and optimization of controlling land subsidence

2010 ◽  
Vol 114 (3-4) ◽  
pp. 251-260 ◽  
Author(s):  
Nianqing Zhou ◽  
Pieter A. Vermeer ◽  
Rongxiang Lou ◽  
Yiqun Tang ◽  
Simin Jiang
Keyword(s):  
Numerical Simulation ◽  
Land Subsidence ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit

scholarly journals Establishment and practice of land subsidence control and management system for deep foundation pit dewatering in Shanghai

2020 ◽  
Vol 382 ◽  
pp. 755-759
Author(s):  
Xinlei Huang ◽  
Tianliang Yang ◽  
Jianzhong Wu ◽  
Jinxin Lin ◽  
Ye He
Keyword(s):  
Land Subsidence ◽  
Management System ◽  
Prevention And Control ◽  
Large Scale ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Whole Process ◽  
Control And Management ◽  
And Control

Abstract. At present, large-scale engineering construction activities, especially deep foundation pit dewatering, are important factors of land subsidence in Shanghai, which induces uneven land subsidence. To solve this problem, this paper puts forward a technical approach to prevention and control the land subsidence. Based on the practice of joint work by multiple administrative departments in Shanghai, this paper further combines the technology and management measures effectively, and summarizes the management system of land subsidence control for deep foundation pit dewatering. Meanwhile, this paper provides the key workflow, starting from the whole process control of construction project for feasibility demonstration, design, construction and completion. The practice shows that the whole process of deep foundation pit dewatering control and management provides a powerful guarantee for land subsidence prevention and control.

Coupled Numerical Simulation Research on Dewatering and Land Subsidence in Deep Foundation Pit

2013 ◽  
Vol 275-277 ◽  
pp. 1549-1552 ◽  
Author(s):  
Dong Dong Zhang
Keyword(s):  
Numerical Simulation ◽  
Land Subsidence ◽  
Coupled Model ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Simulation Research ◽  
Deep Foundation Pit ◽  
Space And Time ◽  
Design And Construction

With the construction of deep and large foundation pit, land subsidence disasters caused by dewatering in deep foundation pit become very serious. Using the coupled model of foundation pit dewatering and land subsidence and putting it into foundation pit dewatering construction, analyzes and summarizes the effect of land subsidence in space and time, which will provide references for the design and construction of foundation pit dewatering.

scholarly journals Comprehensive experimental study on prevention of land subsidence caused by dewatering in deep foundation pit with hanging waterproof curtain

2015 ◽  
Vol 372 ◽  
pp. 1-5
Author(s):  
T. L. Yang ◽  
X. X. Yan ◽  
H. M. Wang ◽  
X. L. Huang ◽  
G. H. Zhan
Keyword(s):  
Land Subsidence ◽  
Prevention And Control ◽  
Scientific Basis ◽  
Deep Foundations ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Soil Subsidence ◽  
Basic Features ◽  
And Control

Abstract. Land subsidence caused by dewatering of deep foundations pit has currently become the focus of prevention and control of land subsidence in Shanghai. Because of the reliance on deep foundation dewatering pit projects, two comprehensive test sites were established to help prevent land subsidence. Through geological environmental monitoring during dewatering of a deep foundation pit, the analysis of the relation between artesian water level and soil subsidence, some basic features of land subsidence caused by dewatering of deep foundation pits are elucidated. The results provide a scientific basis for prevention and control of land subsidence caused by dewatering in deep foundation pits.

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