Coupled Numerical Analysis of Tunnel Excavation in Saturated Soft Clay under High Groundwater

2011 ◽  
Vol 368-373 ◽  
pp. 2533-2536
Author(s):  
Hua Yuan ◽  
Hai Tao Wan ◽  
Zhi Liang Zhao
Keyword(s):  
Soft Clay ◽  
Three Dimensional ◽  
Bending Moment ◽  
High Water ◽  
Shield Tunnel ◽  
Deep Soil ◽  
Tunnel Excavation ◽  
Axial Forces ◽  
Reduction Effect ◽  
Saturated Soft Clay

A coupled numerical simulation of a river-crossing shield tunnel excavation in saturated soft clay with high groundwater has been performed using a three-dimensional finite difference model, which takes into account variation of soil permeability with stress, anisotropy of permeability, reduction effect of joints on segment bending stiffness and the hardening process of synchronized grouting material. Groundwater seepage conditions around the tunnel, bending moment, axial forces and strength safety factor of tunnel segment as well as deep soil displacement during tunnel diving are investigated numerically. The analyses provide valuable information concerning the mechanical behavior of tunnel segment and hydrological field in soil around tunnel during advancing. The result also is benefited to control groundwater for river-crossing tunnel in soft clay under high water table.

scholarly journals An Improved Method for Predicting the Greenfield Stratum Movements Caused by Shield Tunnel Construction

2019 ◽  
Vol 9 (21) ◽  
pp. 4522 ◽  
Author(s):  
Tan ◽  
Zhang ◽  
Zhang ◽  
Zhu ◽  
Tu
Keyword(s):  
Three Dimensional ◽  
Elastic Half Space ◽  
Shield Tunnel ◽  
Theoretical Formula ◽  
Tunnel Construction ◽  
Underground Structures ◽  
Underground Engineering ◽  
Shield Tunneling ◽  
Deep Soil ◽  
Contour Maps

Shield tunneling is becoming the preferred construction scheme for metro construction because of its advantages of fast construction speed and small disturbance. However, limited by process defects, the stratum movements induced by the construction of shield tunnels still affects the safety of nearby underground structures and aboveground buildings. Therefore, the reliable prediction of stratum movements is important. Described in this paper is an analysis method of the Greenfield stratum movements (Greenfield is an area of land that has not yet had buildings on it, stratum movements means the movement of various soil layers) caused by shield tunnel construction combining an elastic half-space model of mirror source–sink method with the use of modified analytical method. Based on the theoretical formula in this paper, not only can the curve of surface settlement trough be calculated, but also the three-dimensional displacement field of deep soil can be obtained. By comparing vertical and horizontal contour maps of Greenfield stratum movements, good consistency between theoretical formula results and centrifugal test results are shown. This solves the defects and limitations of existing two-dimensional formulas; furthermore, based on this, it is convenient to evaluate the effect on the other skewed underground structures through the elastic foundation beam and other similar methods; therefore, this paper can provide a wide guidance and service for the design and construction of underground engineering in the future.

scholarly journals Analysis of Structural Response of Subway Shield Tunnel Lining under the Influence of Cavities

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Yufeng Shi ◽  
Zhaoyang Chen ◽  
Duqiang Wei ◽  
Tao Zhang ◽  
Xuming Zhou ◽  
...  
Keyword(s):  
Structural Response ◽  
Bending Moment ◽  
Tunnel Lining ◽  
Structural Safety ◽  
Shield Tunnel ◽  
Cavity Depth ◽  
Stiffness Reduction ◽  
Lining Structure ◽  
Reduction Effect ◽  
Single Cavity

The existence of cavities behind the shield tunnel lining can cause cracking, broken pieces, water leakage, and other problems, which reduces the durability and safety of the shield tunnel segment structure. In order to clarify the mechanism of cavity damage, a more systematic study of the effects of cavities on the shield tunnel lining structure from the angle, depth, and the number of cavities is carried out using model tests and numerical simulations without considering the effects of the stiffness reduction effect at the tunnel segment joints and groundwater seepage in this paper. The findings show that the bending moment value and the cavity angle value are approximately linear with the increase of single cavity angle, and the bending moment at the vault arch is reversed when the angle of the cavity behind the arch is greater than 30°. With the increase of single cavity depth, the axial force and bending moment at the cavity increase, and the distribution of bending moment remains unchanged, and the bending moment tends to be stable and unchanged beyond a certain depth. With the increase of single cavity angle and depth, the structural safety coefficient of the segment decreases, and the degree of influence is angle value > depth value. The existence of multiple cavities intensifies the influence of each cavity on the segment, especially when there are cavities behind the top and bottom of the vault; the bending moment value of the top of the vault increases by 22.53% compared with that of the single cavity condition.

scholarly journals The Responses of an End-Bearing Pile to Adjacent Multipropped Excavation: 3D Numerical Modelling

2019 ◽  
Vol 5 (3) ◽  
pp. 552 ◽  
Author(s):  
Dildar Ali Mangnejo ◽  
Naeem Mangi
Keyword(s):  
Soft Clay ◽  
High Stress ◽  
Three Dimensional ◽  
Bending Moment ◽  
Small Strain ◽  
Ground Movement ◽  
Stress Regime ◽  
Moment Capacity ◽  
Negative Skin Friction ◽  
End Bearing Pile

It is well recognised that superstructure load is transferred to surrounding soil through piled foundation. Consequently, the high stress regime (stress bulb) is generated surrounding of the pile. On the other hand, the excavation in the ground inevitably results in the ground movement due to induced-stress release. These excavations are sometimes inevitable to be constructed adjacent to existing piled foundations. This condition leads to a big challenge for engineers to assess and protect the integrity of piled foundation. This research presents three-dimensional coupled consolidation analyses (using clay hypoplastic constitutive model which takes account of small-strain stiffness) to investigate the responses of an end-bearing pile due to adjacent excavation at different depths in soft clay. The effects of excavation depths (i.e., formation level) relative to pile were investigated by simulating the excavation near the pile shaft (i.e., case S) and next to (case T). It was revealed that the maximum induced bending moment in the pile after completion of excavation in all the cases is much less than the pile bending moment capacity (i.e. 800 kNm). Comparing the induced deflection of the end-bearing pile in the case T, the pile deflection in case S is higher. Moreover the piles in cases of S and T were subjected to significant dragload due to negative skin friction.

scholarly journals Settlement simulation of soft clay in the subway under dynamic load based on Midas GTS NX

2021 ◽  
Vol 237 ◽  
pp. 03011
Author(s):  
Quan Cao ◽  
Yu Hang
Keyword(s):  
Finite Element ◽  
Dynamic Load ◽  
High Speed ◽  
Large Population ◽  
Soft Clay ◽  
Three Dimensional ◽  
Element Model ◽  
Structural Safety ◽  
Finite Element Software ◽  
Saturated Soft Clay

The subway has become the main way for people to travel nowadays. The saturated soft clay area has a large population and subway construction is the most extensively distributed. The saturated soft clay foundation will settle under the dynamic load of the subway train, which will affect the service life and structural safety. To study the settlement characteristics of soft clay under the dynamic load of the subway, a three-dimensional dynamic finite element model was established based on the finite element software Midas GTS NX, and the soft clay under the normal design speed (80 km/h) and the high-speed (120 km/h) were compared and analyzed. The research results show that the higher the train speed, the larger the lateral influence range of the surface settlement trough, but the settlement decreases with the increase of the subway running speed. The settlement of the subway line after one year of operation is about 45mm, and the settlement after 20 years is about 58mm. The growth rate of the settlement prediction curve decreases gradually, and the settlement increment is very small for a long time in the later period of operation.

scholarly journals A Comparative Study of Protective Schemes for Shield Tunneling Adjacent to Pile Groups

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Penglin Li ◽  
Yuquan Lu ◽  
Jinxing Lai ◽  
Houquan Liu ◽  
Ke Wang
Keyword(s):  
Ground Deformation ◽  
Three Dimensional ◽  
Bending Moment ◽  
Shield Tunnel ◽  
Physical Parameters ◽  
Deep Hole ◽  
Pile Groups ◽  
Control Effect ◽  
Shield Tunneling ◽  
Reinforcement Scheme

Shield tunneling adjacent to pile groups is always an unavoidable problem in urban metro construction. A case was found in the project of Tianjin Metro Line 7, where a shield tunnel would be constructed near the existing pile groups of Shiyou Bridge. The whole shield tunnel is close to pile groups, and the minimum distance is only 0.8 m. Therefore, four kinds of protective schemes are proposed in this paper. It is vital to select an appropriate protective scheme to guarantee the safety during the tunnel construction. In this study, the main mechanical characteristic and physical parameters of site soil were obtained through laboratory tests. Besides, the three-dimensional finite element method was carried out to compare and analyze the effectiveness of the protective schemes in mitigating the effects of tunneling on adjacent pile groups. The results show that the deep-hole grouting scheme has better control effect on the lateral deformation and bending moment of piles, while the pile foundation underpinning scheme has better effectiveness on reducing the settlement of bridge structure and ground deformation. Finally, the deep-hole grouting reinforcement scheme will be adopted to ensure the shield passing through the pile groups smoothly.

scholarly journals Effects of Water Inrush from Tunnel Excavation Face on the Deformation and Mechanical Performance of Shield Tunnel Segment Joints

2017 ◽  
Vol 2017 ◽  
pp. 1-18 ◽  
Author(s):  
Tingsheng Zhao ◽  
Wen Liu ◽  
Zhi Ye
Keyword(s):  
Mechanical Performance ◽  
Coupling Effect ◽  
Water Inrush ◽  
Bending Moment ◽  
Sharp Decrease ◽  
Shield Tunnel ◽  
Cross Sectional ◽  
Tunnel Excavation ◽  
Water Head ◽  
Control Criterion

Water inrush from the excavation face often occurs in the current shield construction of metro tunnels. In this study, the discontinuity of shield tunnel lining and the interaction between the tunnel segments, the grouting layer, and the surrounding rock are considered. Based on the 3D nonlinear contact theory, a hybrid model of the shield tunnel is constructed. Considering the fluid-solid coupling effect of water and soil, the influences of different water head differences on the mechanical performance and deformation of segments and joints in the shield tunnel are studied. The water gushing from the excavation face leads to vertical convergence of the cross-sectional area of the shield tunnel, and joint opening and dislocation result in sharp decrease of the waterproof capacity of joints. Meanwhile, the stress in the vicinity of segment joints increases sharply, and local cracks occur in the segment lining. The axial force, shear force, and bending moment in the joint bolt are also significantly increased. Based on the current metro standard and the computational results in this study, an emergency control criterion is put forward by means of controlling the discharge of water: the water head difference over the excavation face is required less than 4.6 M.

Influence of Tunnel Excavation on Adjacent Rigid-Flexible Pile Bearing Horizontal Loads

2013 ◽  
Vol 353-356 ◽  
pp. 1648-1652
Author(s):  
Shao Kun Ma ◽  
Yan Zhen Huang ◽  
Xiao Bing Zhou ◽  
Xin Chen ◽  
Jian Xing He
Keyword(s):  
Shear Force ◽  
Three Dimensional ◽  
Bending Moment ◽  
Longitudinal Shear ◽  
Horizontal Load ◽  
Constant Length ◽  
Tunnel Excavation ◽  
Soil Stiffness ◽  
Transverse Bending ◽  
Flexible Pile

In order to investigate the influence of tunnel excavation on adjacent rigid-flexible pile bearing horizontal load，many three-dimensional numerical analysis were conducted by altering the pile-soil stiffness resulted from the change of elastic modulus, radius, and length of pile. Many useful conclusions can be drawn. The longitudinal shear force and transverse bending moment of pile increase with the increment of longitudinal horizontal loads and pile-soil stiffness ratio for the pile of constant length. Therefore, different measures must be executed to protect adjacent piles with different stiffness during tunneling. This study can provide some references for the design and construction of tunnel.

scholarly journals Neck Vertebral Level-specific Forces and Moments Under G-x Accelerative Loading

2021 ◽  
Vol 186 (Supplement_1) ◽  
pp. 625-631
Author(s):  
Yuvaraj Purushothaman ◽  
John Humm ◽  
Davidson Jebaseelan ◽  
Narayan Yoganandan
Keyword(s):  
Three Dimensional ◽  
Spinal Column ◽  
Bending Moment ◽  
Element Model ◽  
Whole Body ◽  
Shear Forces ◽  
Male And Female ◽  
Axial Forces ◽  
Impact Acceleration ◽  
Three Dimensional Finite Element

ABSTRACT Introduction It is important to determine the local forces and moments across the entire cervical spine as dysfunctions such as spondylosis and acceleration-induced injuries are focused on specific levels/segments. The aims of the study were to determine the axial and shear forces and moments at each level under G-x accelerative loading for female and male spines. Methods A three-dimensional finite element model of the male head-cervical spinal column was developed. G-x impact acceleration was applied using experimental data from whole body human cadaver tests. It was validated with experimental head kinematics. The model was converted to a female model, and the same input was applied. Segmental axial and shear forces and moments were obtained at all levels from C2 to T1 in male and female spines. Results The time of occurrence of peak axial forces in male and female spines ranged from 37 to 41 ms and 31 to 35 ms. The peak times for the shear forces in male and female spines ranged from 65 to 86 ms and 58 to 78 ms. The peak times for the bending moment ranged from 79 to 91 ms for male and 75 to 83 ms for female spines. Other data are given. Conclusions All metrics reached their peaks earlier in female than male spines, representing a quicker loading in the female spine. Peak magnitudes were also lower in the female spines. Moments and axial forces varied differently compared to the shear forces in the female spine, suggesting that intersegmental loads vary nonuniformly. Effects of head inertia contributed to the greatest increase in axial force under this impact acceleration vector. Because female spines have a lower biomechanical tolerance to injury, female spines may be more vulnerable to injury under this load vector.

Additive Load Influence Analysis of Shield Tunneling Construction on Adjacent Piles

2012 ◽  
Vol 193-194 ◽  
pp. 1033-1037
Author(s):  
Gang Wei ◽  
Jie Hong ◽  
Xin Jiang Wei
Keyword(s):  
Distribution Curve ◽  
Thrust Force ◽  
Pipe Wall ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Shield Tunnel ◽  
Dimensional Problem ◽  
Shield Tunneling ◽  
Tunnel Excavation ◽  
Shield Tunnelling

The distribution regular of total additive load induced by bulkhead additive thrust, force of friction between shield and soil, and soil loss during shield tunnelling construction was studied. The analytical results show that, the distribution regular of additive load is closely related with the relative position of pile and shield, and it is a three-dimensional problem. Toward the shield tunnelling direction and perpendicular to the pipe wall, the additive load is changed from press to pull force along with the pass of shield excavation face. In addition, the value and influence bound of additive load in shield tunnelling direction is bigger than that of perpendicular to the pipe wall. Value of additive load in vertical direction is small. Direction of additive load close to the axes of pipeline is opposite with that of both ends and the force distribution curve is arch-shaped. It is proved by the comparison with the results of numerical simulation, centrifuge experiments and field measurement that the study on the influence due to shield tunnel excavation on neighboring piles is reliable through analytical analysis.

Numerical Analysis of New Shield Tunnel on Mechanical Behavior of Existing Parallel Tunnel

2012 ◽  
Vol 204-208 ◽  
pp. 1429-1434
Author(s):  
Xue Feng Li ◽  
Shou Ji Du ◽  
Ding Feng Zhang
Keyword(s):  
Numerical Analysis ◽  
Mechanical Behavior ◽  
Safety Concern ◽  
Bending Moment ◽  
Soil Mass ◽  
Shield Tunnel ◽  
Configuration Model ◽  
Tunnel Excavation ◽  
Parallel Tunnel ◽  
Plastic Zones

A three-dimensional numerical analysis was conducted to investigate the effects of a new shield tunnel excavation on the internal forces and deformation induced in an existing parallel tunnel and soil plastic zones around it. Special attention was paid to the influence of relative positions between two tunnels. The results of the analysis show that the relative positions affect the mechanical behavior of the existing parallel tunnel and the soil mass behavior around it. When a new tunnel is driven below or above an existing parallel tunnel, important increments are induced in deformation and bending moment in the lining of existing tunnel at its crown and springline, compared to that of induced by new tunnel excavation in horizontally parallel to the existing one. The plastic zones around tunnels also extend larger when tunnels are driven in vertically parallel than they are in horizontally parallel. For the safety concern, it is concluded that horizontally parallel configuration model between two tunnels should be adopted in practice.

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