scholarly journals Temporal-Spatial Characteristics of Ground and Pile Responses to Twin Shield Tunneling in Clays

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Minghong Sheng ◽  
Jingjing Gao ◽  
Panpan Guo ◽  
Rihong Cao ◽  
Yixian Wang
Keyword(s):  
Three Dimensional ◽  
Horizontal Displacement ◽  
Pile Group ◽  
In Situ Monitoring ◽  
Fe Method ◽  
Shield Tunneling ◽  
Spatial Characteristics ◽  
Axial Forces ◽  
The Difference ◽  
Horizontal Displacements

This paper investigates the temporal-spatial characteristics of ground displacements as well as vertical and horizontal displacements and axial forces in existing piles induced by twin shield tunneling in clays. To that end, a case study and three-dimensional (3D) finite element (FE) analysis were performed. Based on the in situ monitoring data from the presented twin tunneling case history with existing piles beneath, the adopted 3D FE method was validated to be competent to yield reasonable simulation results. The validated 3D FE method was then used to analyze the effects of the distance between the tunnel and the pile, the distance between tunnel faces, and the pile length on the horizontal and vertical displacements and axial stresses in piles. It was found that the horizontal displacement distribution forms along the pile shaft for the front piles are similar to that for the back piles, whereas the magnitudes of the horizontal displacements of the front piles are slightly larger than that of the back piles. The interactions between piles in the pile group provide protection of the middle piles in the pile group against twin tunneling effects. With a reduction in the distance between the tunnel and the pile, the pile displacements and stresses increase nonlinearly. With an increase in the distance between tunnel faces, the maximum positive pile displacements and the maximum and minimum axial pile stresses increase, while the maximum negative pile displacements and the difference between the maximum and minimum axial pile stresses decrease.

Numerical Analysis of the Influence of Shield Tunneling to Adjacent Loaded Piles

2012 ◽  
Vol 538-541 ◽  
pp. 548-551
Author(s):  
Feng Bin Zhu
Keyword(s):  
Numerical Analysis ◽  
Case History ◽  
Pile Foundation ◽  
Pile Group ◽  
Single Pile ◽  
Bending Moments ◽  
Shield Tunneling ◽  
Railway Line ◽  
Axial Forces ◽  
Horizontal Displacements

Suzhou Light Railway Line 1 is used as a case history to investigate the effects of the non-homogeneity of soil, distance to the tunnel and cushion cap on the pile foundation performance including horizontal displacements, settlements, axial forces and bending moments. According to behaviors of the single pile and pile group under different concentrated loads, it is concluded that with tunneling, the loaded pile foundation will rotate toward to the tunnel and their bearing capacity is influenced significantly.

scholarly journals Study of the Construction Sequence of Overlapping Tunnels by the Shield Tunneling Method: A Case Study of the Longest Overlapping Tunnel in China

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhiyong Yang ◽  
Yaowen Ding ◽  
Yusheng Jiang ◽  
Kuanda Fang ◽  
Linwei Dong ◽  
...  
Keyword(s):  
Working Conditions ◽  
Radial Stress ◽  
Three Dimensional ◽  
Vertical Displacement ◽  
Tunnel Lining ◽  
Shield Tunneling ◽  
Construction Sequence ◽  
Tunneling Method ◽  
The Difference ◽  
Small Change

In this study, the reasonable construction sequence of an overlapping tunnel shield is investigated. Taking the overlapping tunnel of Tianjin Metro Line 5 as the background, a three-dimensional numerical model was established using Flac3D software to study the influence of the “first up and then down” and “first down and then up” construction sequences of the overlapping tunnel on the surface settlement, stratum displacement, lining radial stress, and displacement. The research results show that the shape and width of the final settlement tank on the ground under the two conditions are basically the same, and the difference between the maximum cumulative settlements is small. The accumulated ground settlement caused by the first up and then down construction sequence is 1.8 mm larger than that caused by the first down and then up sequence. The difference between the two working conditions on the vertical displacement of the stratum mainly occurs in the middle stratum of the upper and lower tunnels, and the proportion of the strata in the uplifted state and subsidence state is different. The construction sequence has little effect on the radial stress on the lining of the upper and lower tunnels. Under these two conditions, the excavation of the second tunnel causes a small change in the radial stress of the preceding tunnel lining, both within 4.2%. Under the working condition of first down and then up, the construction of the second tunnel causes the lining of the preceding tunnel to rise by 7.2∼9.2 mm. Under the condition of first up and then down, the construction of the second tunnel causes the lining of the preceding tunnel to sink again by 9.1∼10.4 mm. By comparing the effects of the two working conditions on the stratum and the tunnel lining, it is recommended that the construction be carried out in the order of first down and then up.

The Vertical and Horizontal Displacements of Cross-river Twin-tunnels Surroundings Induced by Tunneling

2018 ◽  
Author(s):  
Lin Wu ◽  
Zhihua Zhang ◽  
Xiedong Zhang ◽  
FaJin Lin
Keyword(s):  
Three Dimensional ◽  
Great Influence ◽  
Scale Model ◽  
Soil Arching ◽  
Tunnel Excavation ◽  
Large Cities ◽  
Vertical Displacements ◽  
The Difference ◽  
Twin Tunnels ◽  
Horizontal Displacements

<p>Twin-tunnels are widely constructed in large cities because of their many advantages. The first tunnel (named tunnel_1) constructed before a period time than the second tunnel (named tunnel_2) which is to reduce the disturbance between twin-tunnels. In this paper, a three-dimensional scale model of twin-tunnels is established utilizing the discrete element method (DEM) with PFC3D, this model aims to investigate the difference of the vertical displacements and the horizontal displacements of the surroundings in construction process. The numerical results indicate that the peak vertical and horizontal displacements of the surroundings around tunnel_2 are larger than those around tunnel_1. The vertical and horizontal displacements of particles decrease with the distance from the out edge of the twin-tunnels shield lining increases. The existence and evolution of soil arching during tunneling process exert great influence on the stress state and deformation of twin-tunnels surroundings. The peak horizontal displacements are larger in the lateral points of twin-tunnels, while the peak vertical displacements are larger in the vault and bottom points, the tunnel excavation leads the particles around the twin-tunnels move to new location to achieve new equilibrium state. The peak vertical and horizontal displacements occur in own tunnel excavation process, whereas the adjacent tunnel construction affects the displacements as well. The excavation and existence of tunnel_1 have magnified effect on the vertical and horizontal displacements of tunnel_2.</p>

Ground Deformation Rule Induced by Shield Tunneling Construction

2011 ◽  
Vol 90-93 ◽  
pp. 670-675
Author(s):  
Xin Jiang Wei ◽  
Yang Zhou ◽  
Gang Wei ◽  
Jie Hong
Keyword(s):  
Ground Deformation ◽  
Three Dimensional ◽  
Analytical Calculation ◽  
Horizontal Displacement ◽  
Tunnel Construction ◽  
Shield Tunneling ◽  
Dimensional Solution ◽  
Ground Loss ◽  
Good Agreement ◽  
Ground Displacements

In this paper, Ground deformation in shield tunneling construction is researched. It is put forward that ground deformation is caused by three reasons, which are ground loss, the positive thrust and the friction. By solving the three-part respectively, the three-dimensional solution formula can be obtained after superposing these. This method is used to calculate the tunnel construction phase at any point in the level of vertical settlement and horizontal displacement. As shown in analytical calculation, the predicted ground displacements of this method are in good agreement with the measured values.

scholarly journals Comparison on the Horizontal Behaviors of Lattice-Shaped Diaphragm Wall and Pile Group under Static and Seismic Loads

2016 ◽  
Vol 2016 ◽  
pp. 1-17
Author(s):  
Jiu-jiang Wu ◽  
Qian-gong Cheng ◽  
Hua Wen ◽  
Yan Li ◽  
Jian-lei Zhang ◽  
...  
Keyword(s):  
Numerical Study ◽  
Soft Soil ◽  
Horizontal Displacement ◽  
Pile Group ◽  
Diaphragm Wall ◽  
Deformation Pattern ◽  
Soil Core ◽  
Acceleration Amplification ◽  
The Difference ◽  
Bridge Foundation

Lattice-shaped diaphragm wall (hereafter referring to LSDW) is a new type of bridge foundation, and the relevant investigation on its horizontal behaviors is scant. This paper is devoted to the numerical study of the comparison on the static and seismic responses of LSDW and pile group under similar material quantity in soft soil. It can be found that the horizontal bearing capacity of LSDW is considerably larger than that of pile group, and the deformation pattern of LSDW basically appears to be an overall toppling while pile group clearly shows a local bending deformation pattern during the static loading process. The acceleration response and the acceleration amplification effects of LSDW are slightly greater than that of pile group due to the existing of soil core and the difference on the ability of energy dissipation. The horizontal displacement response of pile group is close to that of LSDW at first and becomes stronger than that of LSDW due to the generation of plastic soil deformation near the pile-soil interface at last. The pile body may be broken in larger potential than LSDW especially when its horizontal displacement is notable. Compared with pile group, LSDW can be a good option for being served as a lateral bearing or an earthquake-proof foundation in soft soil.

Defocus ramp correction in spot-scan imaging

1992 ◽  
Vol 50 (1) ◽  
pp. 130-131
Author(s):  
Kenneth H. Downing
Keyword(s):  
Computer Control ◽  
Three Dimensional ◽  
Sufficient Accuracy ◽  
Objective Lens ◽  
Electron Crystallography ◽  
Contrast Transfer Function ◽  
Tilt Axis ◽  
Specimen Height ◽  
The Difference ◽  
Envelope Functions

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.

Analysis of the horizontal structure of a measurement and control geodetic network based on entropy

2013 ◽  
Vol 62 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Maria Mrówczyńska
Keyword(s):  
Geodetic Network ◽  
The State ◽  
Observation System ◽  
Optimum Number ◽  
Optimum Structure ◽  
Horizontal Structure ◽  
The Difference ◽  
And Control ◽  
Measurement And Control ◽  
Horizontal Displacements

Abstract The paper attempts to determine an optimum structure of a directional measurement and control network intended for investigating horizontal displacements. For this purpose it uses the notion of entropy as a logarithmical measure of probability of the state of a particular observation system. An optimum number of observations results from the difference of the entropy of the vector of parameters ΔHX̂ (x)corresponding to one extra observation. An increment of entropy interpreted as an increment of the amount of information about the state of the system determines the adoption or rejection of another extra observation to be carried out.

The iron content of iron superoxide dismutase: determination by anomalous scattering

1983 ◽  
Vol 218 (1210) ◽  
pp. 119-126 ◽  
Keyword(s):  
Superoxide Dismutase ◽  
Iron Content ◽  
Three Dimensional ◽  
Anomalous Scattering ◽  
Total Iron Content ◽  
Iron Site ◽  
Iron Superoxide Dismutase ◽  
Density Map ◽  
The Difference ◽  
Electron Density Map

The number of iron atoms in the dimeric iron-containing superoxide dismutase from Pseudomonas ovalis and their atomic positions have been determined directly from anomalous scattering measurements on crystals of the native enzyme. To resolve the long-standing question of the total amount of iron per molecule for this class of dismutase, the occupancy of each site was refined against the measured Bijvoet differences. The enzyme is a symmetrical dimer with one iron site in each subunit. The iron position is 9 ņ from the intersubunit interface. The total iron content of the dimer is 1.2±0.2 moles per mole of protein. This is divided between the subunits in the ratio 0.65:0.55; the difference between them is probably not significant. Since each subunit contains, on average, slightly more than half an iron atom we conclude that the normal state of this enzyme is two iron atoms per dimer but that some of the metal is lost during purification of the protein. Although the crystals are obviously a mixture of holo- and apo-enzymes, the 2.9 Å electron density map is uniformly clean, even at the iron site. We conclude that the three-dimensional structures of the iron-bound enzyme and the apoenzyme are identical.

scholarly journals Analysis of Turn-to-Turn Fault on Split-Winding Transformer Using Coupled Field-Circuit Approach

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1314
Author(s):  
Cunxiang Yang ◽  
Yiwei Ding ◽  
Hongbo Qiu ◽  
Bin Xiong
Keyword(s):  
Low Voltage ◽  
Short Circuit ◽  
Three Dimensional ◽  
Great Influence ◽  
Normal Operation ◽  
Transient Field ◽  
Axial Forces ◽  
Leakage Field ◽  
Characteristics Analysis ◽  
Split Winding

The turn-to-turn faults (TTF) are also inevitable in split-winding transformers. The distorted leakage field generated by the TTF current results in large axial forces and end thrusts in the fault windings as well as affecting other branch windings normal operation, so it is of significance to study TTF of split-winding transformers. In this paper, the characteristics analysis of the split-winding transformer under the TTFs of the low voltage winding at different positions are presented. A 3600 KVA four split-windings transformer is taken as an example. Then, a simplified three-dimensional simplified model is established, taking into account the forces of the per-turn coil. The nonlinear-transient field-circuit coupled finite element method is used for the model. The leakage field distribution under the TTFs of the low voltage winding at different positions is studied. The resultant force of the short-circuit winding and the force of the per-turn coil are obtained. Subsequently, the force and current relationship between the branch windings are analyzed. The results show that the TTF at the specific location has a great influence on the axial windings on the same core, and the distorted leakage magnetic field will cause excessive axial force and end thrust of the normal and short-circuit windings. These results can provide a basis for the short-circuit design of split-winding transformer.

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