scholarly journals A Precise Prediction of Tunnel Deformation Caused by Circular Foundation Pit Excavation

2019 ◽  
Vol 9 (11) ◽  
pp. 2275 ◽  
Author(s):  
Huasheng Sun ◽  
Lingwei Wang ◽  
Shenwei Chen ◽  
Hengwei Deng ◽  
Jihua Zhang
Keyword(s):  
Engineering Practice ◽  
Foundation Pit ◽  
Retaining Structures ◽  
Soil Stiffness ◽  
Circular Excavation ◽  
Nonlinear Constitutive Model ◽  
Bending Strain ◽  
Precise Prediction ◽  
Path Dependent ◽  
Reasonable Choice

In comparison with tetragonal retaining structures, circular retaining structures have an advantage in terms of controlling the deformation caused by foundation excavation, and are a reasonable choice in engineering practice. Many results have been obtained regarding the effect of tetragonal excavation on the deformation of an adjacent tunnel. Nevertheless, a sufficient understanding of the circular excavation’s effect on the deformation of an adjacent tunnel is currently lacking. Therefore, this study focused on the problem of precise predicting tunnel deformation below a circular excavation. A numerical model was established to calculate the tunnel deformation caused by the circular excavation. An advanced nonlinear constitutive model, known as a hypoplasticity model, which can capture path-dependent and strain-dependent soil stiffness even at small strains, was adopted. The models and their associated parameters were calibrated by centrifuge test results reported in the literature. The deformation mechanism was revealed, and the calculated results were compared with those obtained with a square excavation and the same excavation amount. The differences between the deformations caused by these two types of excavation shapes were analyzed. It was found that under equal excavation area conditions, the excavation-induced deformations of the metro tunnel below a circular excavation were approximately 1.18–1.22 times greater than those below a square excavation. The maximum tunnel tensile bending strain caused by the circular excavation was 32% smaller than that caused by the square excavation. By comparing with the measured results, it is proved that the proposed numerical method can provide effective reference for engineers to analyze soil-structure problems.

Geotechnical Engineering Practice of Multi-Forms of Composite Support of Deep Foundation Pit

2013 ◽  
Vol 838-841 ◽  
pp. 690-696
Author(s):  
Qin He Huang
Keyword(s):  
Geotechnical Engineering ◽  
Engineering Practice ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Double Row ◽  
Deep Foundation Pit ◽  
Composite Support ◽  
Surrounding Environment ◽  
The Cost

A project in Xiamen setting three basement, the surrounding environment is more complex.the depth of the foundation pit is 11.0-16.1m, considering the duration, cost, environment and other factors, different positions of the foundation pit is respectively realized by adoption of double-row piles, pile-anchor retaining, pile-strut bracing structure and other forms of support, excavation practice proved that this composite support effectively support the pit, facilitate the construction, and the cost is relatively low.

Monitoring and Analysis for the Deformation of SMW Retaining Structures in Subway Station

2014 ◽  
Vol 580-583 ◽  
pp. 1249-1253
Author(s):  
Jiang Tao Xia ◽  
Shao Fei Zhang ◽  
Hua Rong Shen ◽  
Ze Jun Liu ◽  
Shi Qing Huang
Keyword(s):  
Early Stage ◽  
Horizontal Displacement ◽  
Ground Subsidence ◽  
Subway Station ◽  
Deep Soil ◽  
Foundation Pit ◽  
Retaining Structures ◽  
Soil Mixing ◽  
Wall Structures ◽  
Soil Excavation

The monitoring is carried out for deformation of the soil-mixing-wall structures used in Baijihu subway station. The horizontal displacement of deep soil is obtained, as well as the ground subsidence around the edges of the foundation pit. Their variation rules under the influence of some factors, such as soil excavation and support settings etc, is analyzed. The results show that during the process of SMW construction, it is necessary to monitor the horizontal displacement of deep soil and the ground subsidence around the edges of the foundation pit, especially during the early stage of excavation.

Analysis on Dynamic Response of the Foundation Pit Supporting Structure under Vehicle Loads

2013 ◽  
Vol 790 ◽  
pp. 638-642
Author(s):  
Hong Zhi Qiu ◽  
Ji Ming Kong ◽  
Yin Zhang
Keyword(s):  
Dynamic Response ◽  
Axial Force ◽  
Effective Means ◽  
Numerical Results ◽  
Engineering Practice ◽  
Foundation Pit ◽  
Supporting Structure ◽  
Half Wave ◽  
Sinusoidal Load ◽  
Vehicle Loads

Using ABAQUS software analyzed the dynamic response of foundation pit supporting structure under vehicle loads. The vehicle load was simplified as a half-wave sinusoidal load, in order to analyze the influence of internal force and displacement of pile-anchor supporting structure under the vehicle loads, the position of half-wave sinusoidal load and the size of radian frequency were considered. Loading location away from the supporting structure is more nearly and the displacement value of support piles is greater, the greater the axial force of the bolt; with the increasing of radian frequency, the horizontal displacement value of supporting piles increased, on the contrary, the axial force of bolt reduced. A practical engineering was studied here. analysis of the monitoring data and compared with the numerical results, the analysis showed that the experimental results and numerical results are in good agreement, and the numerical method can be used as an effective means of research. The conclusion of the study has significance on engineering practice.

Deep Foundation Pit Engineering Technology Research

2012 ◽  
Vol 256-259 ◽  
pp. 332-335
Author(s):  
Xiang Dong Zhang ◽  
Jin Wei Lv
Keyword(s):  
Rapid Development ◽  
Engineering Practice ◽  
Soil Test ◽  
Technology Research ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Engineering Technology ◽  
Deep Foundation Pit ◽  
Key Technology ◽  
Geotechnical Problems

Deep foundation pit engineering is a comprehensive geotechnical problems, has distinct regional. In recent years, it has become the hotspot in geotechnical engineering. The key technology of deep foundation pit engineering rapid development in recent years such as soil test, the design and construction of retaining and protecting, monitoring, dewater. The use of computers in the calculation theory and monitoring technology of deep foundation pit engineering makes two parts have changed in essential. This article discusses the soil test, retaining and protecting technology and principle, the monitoring and dewater of deep foundation pit engineering. The development of deep foundation pit engineering situation and the problems exist of the development of deep foundation pit engineering, which have important meaning to guide the engineering practice and discipline new fields of explore.

scholarly journals Tunnel Behaviour Caused by Basement Excavation in Clay

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Huasheng Sun ◽  
Jihua Zhang ◽  
Guodong Zhao ◽  
Hao Wang
Keyword(s):  
Permeability Coefficient ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Soil Permeability ◽  
Foundation Pit ◽  
Nonlinear Constitutive Model ◽  
Tunnel Diameter ◽  
Consolidation Time ◽  
Diameter Change

Many researchers have investigated the effect of basement excavation on tunnel deformation. However, the influence of consolidation on the interaction of basement-tunnel-soil is rarely considered or systematically studied in clay. In this study, three-dimensional coupled-consolidation finite element analyses were conducted to investigate the effect of consolidation on the tunnel response to excavation. An advanced nonlinear constitutive model was adopted, and numerical parametric investigations were conducted to study the effect of the excavation depth, tunnel stiffness, soil permeability coefficient, and consolidation time on the tunnel response. The results revealed that the basement excavation led to stress release, which caused tunnel heave. Owing to the dissipation of excess negative pore water pressure, the tunnel heave further increased to become approximately twice as large compared with that observed when the foundation pit excavation had just been completed. As the consolidation time increased, the longitudinal tunnel heave and tunnel diameter change caused by the foundation pit excavation gradually increased, but the growth rate was slower down. When the consolidation time changed from 50 days to 150 days, the maximum tunnel heave at the crown and the maximum tunnel diameter change increased by 1.18 and 1.48 times, respectively. The soil’s permeability coefficient did not have a significant effect on the tunnel heave at the crown nor on the tunnel diameter change. The results obtained by this study are expected to be useful as an engineering reference for the analysis of soil structure problems in clay.

scholarly journals Ground deformation mechanism due to deep excavation in sand: 3D numerical modelling

2021 ◽  
Vol 9 (6) ◽  
pp. 741-747
Keyword(s):  
Relative Density ◽  
Deformation Mechanism ◽  
Ground Deformation ◽  
Ground Movement ◽  
Soil Stiffness ◽  
Maximum Settlement ◽  
Hypoplastic Model ◽  
3D Numerical Modelling ◽  
Path Dependent ◽  
Underground Transportation

In densely built areas, development of underground transportation system often involves excavations for basement construction and cut-and-cover tunnels which are sometimes inevitable to be constructed adjacent to existing structure. Inadequate support systems have always been major concern as excessive ground movement induced during excavation could damage to neighbouring structure. A detailed parametric analysis of the ground deformation mechanism due to excavation with different depths in sand with different densities (Dr=30%, 50%, 70% and 90%) is presented. 3D finite element analyses were carried out using a hypoplastic model, which considers strain-dependent and path-dependent soil stiffness. The computed results have revealed that the maximum settlement decreased substantially when the excavation is carried out in the sand with higher relative density. This is because of reason that sand with higher relative density possesses higher stiffness. Moreover, the depth of the maximum settlement of the wall decreases as the sandbecome denser.The ground movement flow is towards excavation in retained side of the excavation. On the other hand the soil heave was induced below the formation level at excavation side. The maximum strain level of 2.4% was induced around the diaphragm wall.

scholarly journals An Investigation of Effects and Safety of Pipelines due to Twin Tunneling

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Shao Yu ◽  
Riyan Lan ◽  
Junhui Luo ◽  
Zhibo Duan ◽  
Shaokun Ma
Keyword(s):  
Soil Parameters ◽  
Centrifuge Model Test ◽  
Burial Depth ◽  
Buried Pipelines ◽  
Soil Stiffness ◽  
Maximum Settlement ◽  
Dimensionless Analysis ◽  
Bending Strain ◽  
Calculation Results ◽  
Subway Tunnels

To efficiently and accurately predict the effects of twin tunneling on adjacent buried pipelines, the effects of upward and downward relative pipeline-soil interactions were considered. A series of numerical parametric studies encompassing 8640 conditions were performed to investigate the responses of a pipeline to twin tunneling. Based on the dimensionless analysis and normalized calculation results, the concept of equivalent relative pipeline-soil stiffness was proposed. Additionally, expressions for the relative pipeline-soil stiffness and relative pipeline curvature and for the relative pipeline-soil stiffness and relative pipeline settlement were established, along with the related calculation plots. Relying on a comparison of prediction results, centrifuge model test results, and field measured results, the accuracy and reliability of the obtained expressions for predicting the bending strain and settlement of adjacent buried pipelines caused by twin tunneling were validated. Based on the calculation method, the maximum bending strain and maximum settlement of pipelines can be calculated precisely when the pipeline parameters, burial depth, soil parameters, and curve parameters of ground settlement due to tunneling are provided. The proposed expressions can be used not only to predict the maximum bending strain and maximum settlement of pipelines caused by single and twin tunneling but also to evaluate the effects of single and twin tunneling on the safety of existing buried pipelines. The relevant conclusions of this article can also provide a theoretical basis for the normal service of buried pipelines adjacent to subway tunnels.

scholarly journals Reinforcement Effects of Isolation Piles on the Adjacent Existing Tunnel in Building Construction

2019 ◽  
Vol 2019 ◽  
pp. 1-21 ◽  
Author(s):  
Aijun Yao ◽  
Jian Lu ◽  
Yanfei Guo ◽  
Jiantao Zhang ◽  
Haifeng Guo
Keyword(s):  
Horizontal Displacement ◽  
Building Construction ◽  
Shield Tunnel ◽  
Engineering Practice ◽  
Burial Depth ◽  
Tunnel Structure ◽  
Reinforcement Effect ◽  
Foundation Pit ◽  
Pile Spacing ◽  
Pile Diameter

Similar material model test and numerical simulation method were used to study the reinforcement effect of isolation piles on the existing shield tunnel structure in the adjacent building construction for analyzing foundation pit excavation and new building construction approaching existing shield tunnel engineering. The numerical simulation orthogonal experiment was used to optimize four isolation pile parameters. The conclusions were obtained as follows: (1) Isolation piles could share horizontal load of the soil at the rear side of the support structure and reduce horizontal displacement of the soil. As a result, maximum horizontal displacement of the tunnel structure and differences in horizontal displacement between the tunnel structure roof and the floor after foundation pit excavation and building loading were decreased. The horizontal displacement and torsional deformation of the tunnel structure toward the direction of the foundation pit were controlled, and the increase in internal forces of the transverse tunnel structure was also restrained. (2) At the elevation above the tunnel roof, the increase in burial depth of the isolation pile top slightly affected the reinforcement effect on the tunnel structure. The increase in burial depth of the isolation pile bottom could improve the reinforcement effect. Thus, burial depth of the isolation pile bottom should be properly increased in the engineering practice. The reduction in pile spacing could improve the reinforcement effect. Accordingly, pile spacing should be properly selected in the engineering practice. With the increase of diameter of the isolation pile, the reinforcement effect of isolation piles increased obviously. (3) Pile diameter had the greatest influence on the reinforcement effect of isolation piles, followed by burial depth of the pile bottom, pile spacing, and burial depth of the pile top. Orthogonal experiments indicated the following optimal parameter values: a pile diameter of 1.2 m, a burial depth of the pile bottom of 2H, a pile spacing of 1.6 m, and a burial depth of the pile top of 0.75Z.

Design of Foundation Pit Retaining Structures

2019 ◽  
pp. 391-436
Author(s):  
Zhen-Dong Cui ◽  
Zhong-Liang Zhang ◽  
Li Yuan ◽  
Zhi-Xiang Zhan ◽  
Wan-Kai Zhang
Keyword(s):  
Foundation Pit ◽  
Retaining Structures
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