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 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.

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 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 Effect of Wetting-Drying Cycle on the Deformation and Seepage Behaviors of Rock Masses around a Tunnel

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Qingzhen Guo ◽  
Haijian Su ◽  
Hongwen Jing ◽  
Wenxin Zhu
Keyword(s):  
Rock Mass ◽  
Principal Stress ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Tunnel Excavation ◽  
Cycle Number ◽  
Simulation Results

Water inrush caused by the wetting-drying cycle is a difficult problem in tunnel excavation. To investigate the effect of the wetting-drying cycle on the stability of the tunnel surrounding rock, physical experiments and numerical simulations regarding the process of tunnel excavation with different wetting-drying cycle numbers were performed in this study. The evolutions of stress, displacement, and pore water pressure were analyzed. With the increase in cycle number, the pore water pressure, vertical stress, and top-bottom approach of the tunnel surrounding rock increase gradually. And the increasing process could be divided into three stages: slightly increasing stage, slowly increasing stage, and sharply increasing stage, respectively. The failure process of the surrounding rock under the wetting-drying cycle gradually occurs from the roof to side wall, while the baseplate changes slightly. The simulation results showed that the maximum principal stress in the surrounding rock mass of the tunnel increases, while the minimum principal stress decreases. Furthermore, the displacement of the rock mass decreases gradually with the increasing distance from the tunnel surface. By comparing the simulation results with the experimental results, well consistency is shown. The results in this study can provide helpful references for the safe excavation and scientific design of a tunnel under the wetting-drying cycle.

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

Numerical Simulation Analysis of Isolation Pile-Steel Shotcrete Combined Support of Deep Foundation Pit Excavation

2014 ◽  
Vol 638-640 ◽  
pp. 507-511
Author(s):  
Chong Ma ◽  
Xin Gang Wang ◽  
Bin Hu ◽  
Hong Bing Zhan
Keyword(s):  
Numerical Simulation ◽  
Geotechnical Engineering ◽  
Rapid Development ◽  
Engineering Problem ◽  
Simulation Software ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Support Design ◽  
Deep Foundation Pit ◽  
Design And Construction

The rapid development of deep foundation pit engineering, has become an important part of the urbanization construction, which brings deep excavation support of geotechnical engineering problem research also became a major issue. This paper uses the international well-known geotechnical engineering numerical simulation software FLAC3D, through 3D finite difference numerical calculation and analysis, to better simulation calculation and analysis of deep foundation pit construction site condition, forecast after excavation of the deep foundation pit deformation displacement and dangerous position, analysis of deep foundation pit excavation process isolation pile - steel shotcrete combined support effect. Three dimensional numerical model analysis and calculation in deep foundation pit engineering design and construction scheme optimization with economy is convenient wait for a obvious advantages, can for deep foundation pit excavation of deep foundation pit support design and construction to provide effective basis.

Comparison and Analysis of Influence of Soil Deformation on the Speeds of Execution for Deep Foundation Pits

2013 ◽  
Vol 353-356 ◽  
pp. 159-162
Author(s):  
Li Liu ◽  
Hong Ru Zhang ◽  
Rui Yu Zhang
Keyword(s):  
Numerical Simulation ◽  
Soil Deformation ◽  
Deep Excavation ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Total Displacement ◽  
Rapid Construction ◽  
Test Points ◽  
Variation Tendency

The excavation of deep foundation pit by numerical simulation is researched in this paper. Different locations of soil are selected to be as test points. Under two velocities, the law of total displacements that reflect the test points in the same locations is discussed. The variation tendency of the pore pressure under the rapid construction and tendency of the volume change under the normal construction are compared. The soil is divided to three parts in numerical simulation: the side, the bottom I and the bottom II of the foundation. The numerical results are as follows: the total displacement of the rapid construction is double for ones of the normal construction, which is on the side and the bottom I of deep foundation pit. Under the different drainage conditions, the soil on the side of deep excavation experiences the dilatancy, and then the shear-contraction, and then the dilatancy; the soil on the bottom II of deep excavation experiences the dilatancy and then the shear-contraction. The soil on the bottom I experiences the dilatancy under the normal construction; but it experiences the dilatancy and then the shear-contraction under the rapid construction.

Theoretical prediction of rutting in flexible pavement subgrades

1992 ◽  
Vol 29 (5) ◽  
pp. 765-778 ◽  
Author(s):  
D. V. Ramsamooj ◽  
R. Piper
Keyword(s):  
Pore Water ◽  
Critical State ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Permanent Deformation ◽  
Flexible Pavement ◽  
Load Test ◽  
Model Parameters ◽  
Silty Clay ◽  
Rate Of Development

The theoretical model for predicting the cyclic response of soils is extended to handle the generation and dissipation of pore-water pressures and to predict the rutting of the subgrade of a flexible pavement. The model utilizes multiyield surfaces and the concepts of critical state mechanics to predict the permanent deformation of the subgrade under vehicular loading. The theoretical solution also considers the effects of the drainage characteristics of the subgrade soil on the rate of development of the permanent deformation. Experimental verification of the model concepts are presented for a drained cyclic load test on Ottawa sand and for undrained cyclic loading on Newfield clay using published experimental data. An illustrative example is given for the prediction of rutting in a silty clay subgrade. The model parameters for the silty clay are obtained from triaxial and consolidation tests. These parameters are then put into a computer program that determines the rut depth, pore-water pressure, and the ratio of the vertical deformation and the rut depth as functions of the number of vehicular loads for a flexible pavement for various conditions of drainage ranging from undrained to fully drained. The role of the coefficient of consolidation of the subgrade in controlling the rate of development of the rut depth is highlighted. Key words : critical state soil mechanics, multiyield surfaces, rutting, silty clay subgrade, drainage, vehicular loading.

Sign in / Sign up

Export Citation Format

Share Document