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.

scholarly journals Deformation Responses and Mechanical Mechanism of Existing Tunnel due to New Building Construction

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Haifeng Guo ◽  
Dong Ma ◽  
Aijun Yao
Keyword(s):  
Large Scale ◽  
Earth Pressure ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Building Construction ◽  
Tunnel Structure ◽  
Total Stress ◽  
Foundation Pit ◽  
Loading Mode ◽  
Total Settlement

This study mainly investigated the variation law and mechanical mechanism of surrounding earth pressure and deformation of an existing tunnel, caused by dewatering, foundation excavation, building loading, and groundwater recovery. According to different dewatering schemes, two modes were established: nonisolated dewatering unloading-loading mode and isolated dewatering unloading-loading mode. Through large-scale similar materials model test, the variation law of deformation and surrounding earth pressure of adjacent tunnel under complex unloading-loading conditions was preliminarily revealed. Based on the size of the prototype project, the test results were further verified by the numerical simulation. The mechanical mechanism of tunnel deformation in different construction stages was analyzed after the comparative study. The results show that the tunnel structure deformation, vertical and horizontal displacement, and torsion occur in the process of building construction. In the nonisolated dewatering unloading-loading mode, the decrease or rise of the groundwater level significantly reduces (maximum 27.85%) or increases (maximum 35.19%) the surrounding earth pressure of the tunnel. The decrease or increase of the horizontal total stress was much greater than that of the vertical total stress, which leads to the deformation of tunnel structure. The vertical displacement of the tunnel is generally settlement, which mainly occurs in the stage of dewatering and building loading, accounting for 83.21%–100.00% and 25.11%–40.34% of the total settlement, respectively. In the stage of foundation pit excavation and groundwater recovery, the tunnel rises. In the horizontal direction, the tunnel moves towards the foundation pit, mainly in the excavation stage, accounting for 82.77%–86.30% of the maximum value. Due to the uneven change of displacement field and stress field of soil outside the foundation pit, the tunnel torsion occurs. In the isolated dewatering unloading-Loading mode, the change of groundwater has little effect on the tunnel. In the stage of excavation and construction load, the variation law of tunnel surrounding earth pressure and deformation is similar in the two modes.

The Influence of Engineering Pile on the Bottom Upheaval of Foundation Pit

2012 ◽  
Vol 193-194 ◽  
pp. 624-632
Author(s):  
Xi Zhen Zhang ◽  
Quan Mei Gong ◽  
Shun Hua Zhou
Keyword(s):  
Element Model ◽  
Correction Method ◽  
Inhibitory Effect ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Pile Spacing ◽  
Deformation Control ◽  
Pile Diameter ◽  
Pile Length

In foundation pit engineering, the presence of pile plays an important role on the pit stability and deformation control. The bottom upheaval of deep foundation pit is a key criterion of judging the foundation stability and deformation. This paper built the 3D finite element model to analyze the influence of different factors (pile diameter, pile length and pile spacing) on the bottom upheaval, and concluded that: when pile length and pile spacing is constant, changing the pile diameter can hardly affect the bottom upheaval; as the pile length increased, the inhibitory effect to the bottom upheaval grew stronger with a gradually decreased growth rate; increasing pile spacing can significantly reduce the bottom upheaval, and the smaller the pile spacing, the smaller the upheaval. The concept of upheaval inhibition rate was defined to evaluate the influence of different factors of pile layout on the bottom upheaval. A correction method of calculating the bottom upheaval of foundation pit with engineering pile was proposed. An engineering instance of Shanghai Natural History Museum foundation pit was studied, and the result showed that the bottom upheaval calculated by the correction method is less than the upheaval calculated by method of residual stress, which was more close to the monitoring data. The influence of engineering pile on bottom upheaval of foundation pit should not be neglected where a large number of piles were present in deep foundation pit.

scholarly journals The Study for Longitudinal Deformation of Adjacent Shield Tunnel Due to Foundation Pit Excavation with Consideration of the Retaining Structure Deformation

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2103
Author(s):  
Xinhai Zhang ◽  
Gang Wei ◽  
Chengwu Jiang
Keyword(s):  
Great Influence ◽  
Shield Tunnel ◽  
Additional Stress ◽  
Deformation Model ◽  
Burial Depth ◽  
Longitudinal Deformation ◽  
Foundation Pit ◽  
Structure Deformation ◽  
Retaining Structure ◽  
The Impact

By selecting the ratio of the cumulative maximum deformation of the retaining structure to the excavation depth as the control parameter of the retaining structure deformation, this paper established a sidewall unloading model which can consider the deformation of the retaining structure and the spatial effect of foundation pit excavation. Meanwhile, the impact region of the sidewall was divided to calculate the distribution of additional stress caused by foundation pit excavation. On this basis, through introducing the collaborative deformation model for rotation and dislocation of a shield tunnel, this paper studied the longitudinal deformation of the adjacent shield tunnel due to foundation pit excavation. Moreover, several engineering cases were given to verify the reliability of the proposed method, and the influencing factors were analyzed. The following conclusions were obtained: the axial horizontal displacement of the shield tunnel by the side of the foundation pit was normally distributed, and the calculated value was in good agreement with the measured value; the longitudinal deformation of the shield tunnel was mainly induced by the unloading effect of the sidewall of the foundation pit, which was parallel and closed to the tunnel; the soil excavation in the vicinity of the buried depth of the tunnel would result in a significant increase in longitudinal deformation; with the increase in the retaining structure deformation of the foundation pit, the longitudinal deformation of the adjacent shield tunnel and its influence scope also increased; the longitudinal deformation of the shield tunnel decreased with the increase of clearances between the foundation pit and tunnel; and finally, the excavation of the foundation pit had a great influence on the shallowly buried shield tunnel nearby, and the effect of foundation pit excavation on the tunnel decreased with the increase of the burial depth of the shield tunnel.

Horizontal Displacement of GFRP Bars and PC Strand Combination of Technology Supporting Piles

2014 ◽  
Vol 580-583 ◽  
pp. 420-423
Author(s):  
Xiu Hua Li ◽  
Yan Yan Gao ◽  
Chen Xi Yue ◽  
Chun Qing Hu
Keyword(s):  
Experimental Data ◽  
Field Test ◽  
Energy Method ◽  
Pile Foundation ◽  
Horizontal Displacement ◽  
Engineering Practice ◽  
Foundation Pit ◽  
Gfrp Bars ◽  
Composite Pile

GFRP bars and PC strand composite pile is a new supporting piles, according to the engineering field test and analysis of experimental data prove that there is a significant effect on the control aspects of the horizontal displacement of supporting piles. Principle energy method can calculate the horizontal displacement of pile foundation pit in theory, by comparing the size of the horizontal displacement of the supporting piles of ordinary reinforcement, to demonstrate the feasibility of using GFRP bars and PC strand combination of techniques to reduce the horizontal displacement of excavation, provide reference for future engineering practice.

Finite Element Analysis and Investigation of Double-Row Piles Supporting Structure

2013 ◽  
Vol 838-841 ◽  
pp. 779-785
Author(s):  
Liang Gu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Distribution ◽  
Maximum Shear Stress ◽  
Horizontal Displacement ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Double Row ◽  
Element Analysis ◽  
Supporting Structure

The double-row piles supporting structure is a new type of supporting and protecting for deep foundation excavation. It is widely used to in design of deep foundation pit. Now how to simply and effectively design the structure of double-row piles is in a research and discuss stage. Using the Midas GTS finite element method, the displacement and stress distribution of double-row piles in the different stages of excavation are obtained, and the horizontal displacement and stress distribution of double-row piles in the different stages of excavation are calculated. The results of Midas GTS finite element analysis as follows: (1) after the excavation of foundation pit, the horizontal displacement of pile-top is maximum. The horizontal displacement decreases gradually with depth increases. And the displacement of front row piles is larger than that of back row piles; (2) the maximum shear stress is at the distance 5m to the foundation basement. The higher bending moment at the pile-top and the distance 10m to the foundation basement are consistent with the actual monitoring date. (3) the results of finite element analysis is close to the Richard software and actual monitoring data. It is show that using the finite element analysis to analyze the double-row piles supporting structure with is veritable and credible.

Determination of Spacing between Anchored Piles in Row for Deep Foundation Pit

2012 ◽  
Vol 204-208 ◽  
pp. 2736-2739
Author(s):  
Guang Qian Du ◽  
Shi Jie Wang ◽  
Yan Ting Qin ◽  
Chang Zhi Zhu
Keyword(s):  
Strength Criterion ◽  
Strength Analysis ◽  
Soil Arching ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Pile Spacing ◽  
Soil Arch ◽  
Uniformly Distributed Loads

Based on the pile - anchor structure soil between piles,the unified strength theory is introdued in the strength analysis of soil arching between the piles, and parabolic soil arching computational model is uniformly distributed loads ,which are given to meet the soil between piles arch static equilibrium conditions and intensity of conditions , pile spacing formula. Compared with calculations based on the pile spacing of the Mohr-Coulomb strength criterion , the proposed method can consider the contribution of the intermediate principal stress on the strength of the soil arch , the results are more in line with the actual characters of the supporting structure .

Numerical analysis of soil deformation behind the reaction wall of an open caisson induced by horizontal parallel pipe-jacking construction

2015 ◽  
Vol 52 (12) ◽  
pp. 2008-2016 ◽  
Author(s):  
Yang Sun ◽  
Jing-bo Su ◽  
Xiao-he Xia ◽  
Zheng-liang Xu
Keyword(s):  
Reaction Force ◽  
Soil Surface ◽  
Horizontal Displacement ◽  
Element Model ◽  
Deformation Analysis ◽  
Burial Depth ◽  
Maximum Displacement ◽  
Obvious Effect ◽  
Simple Loading ◽  
Pipe Jacking

The disturbance of the soil behind the reaction wall of an open caisson can affect the efficiency and safety of jacking operation and control. This study focuses on the deformation of the soil mass behind the reaction wall used to support the jack. The stress–strain relationship of the soil behind the reaction wall was analysed, providing a theoretical basis for determining the most unfavourable combination of reactive forces using a computational model. A three-dimensional finite element model for this problem was developed, and a simple loading scenario was implemented. In addition, the mechanism of the deformation of the soil induced by horizontal parallel pipe jacking was also analysed. The results showed that for the soil behind the reaction wall of the open caisson, the uplift deformation of the soil surface increased initially and later gradually decreased, eventually achieving stability. The reaction force had a relatively obvious effect on the deformation of the soil within the range of the reaction wall burial depth and the horizontal displacement of the soil along the length of the reaction wall. The maximum displacement occurred near the axis of symmetry of the reaction wall. In addition, to consider the cyclic characteristics of the reaction force, the shakedown theorem is introduced to the deformation analysis of the soil and compared with the results obtained from simple loading. It was shown that the two deformation analysis methods have certain scopes of application, depending on the individual engineering requirements.

scholarly journals TRANSMISSION OF RANDOM WAVES THROUGH PILE BREAKWATERS

1986 ◽  
Vol 1 (20) ◽  
pp. 169 ◽  
Author(s):  
Clifford L. Truitt ◽  
John B. Herbich
Keyword(s):  
Random Waves ◽  
Pile Spacing ◽  
Transmission Coefficients ◽  
Pile Diameter ◽  
Model Pile ◽  
Incident Waves ◽  
Good Agreement ◽  
Monochromatic Waves

Several previous investigators have conducted experiments leading to expressions for predicting the transformation of waves passing through closely-spaced pile breakwaters. The present study extends those earlier experiments using monochromatic waves to the case of a spectrum of random waves. Records of incident waves and of waves after transmission through a model pile breakwater were compared to determine a coefficient of transmission. Results are presented for several cases of pile spacing and pile diameter. Good agreement is found between observed transmission coefficients and those predicted using the expression proposed by Hayashi et al. (1966).

Piled Raft Structure Finite Element Analysis of Composite Foundation Settlement in Da XI Passenger Dedicated Line

2014 ◽  
Vol 937 ◽  
pp. 438-443
Author(s):  
Xiao Tong Ma ◽  
Guang Long Liu
Keyword(s):  
Finite Element ◽  
Composite Foundation ◽  
Foundation Settlement ◽  
Pile Spacing ◽  
Finite Element Software ◽  
Piled Raft ◽  
Pile Diameter ◽  
Foundation Treatment ◽  
Pile Length ◽  
Passenger Dedicated Line

Composite foundation settlement of piled raft structure in Da Xi passenger dedicated line is analyzed by the large finite element software MIDAS/GTS and established calculation model of foundation treatment. The problem of pile-soil contact is highlighted in the trail and analyzes the settlement nephogram and pile-soil stress nephogram. On this basis the foundation settlement factors was analyzed systematically that focus on the elastic modulus of pile, pile spacing, pile diameter and pile length in foundation treatment, especially for the characteristics parameters of contact element. Result shows that increasing the pile modulus, pile diameter, pile length and decreasing the pile spacing is all conducive to reducing settlement. The best advice is got that the pile diameter should be not more than 0.5m, pile length not more than 27m and the pile spacing be around 2m.

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.

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