Parallel Shield Tunnels Research Articles

Bending performance of Y-shaped joints of subway station built by enlarging two parallel shield tunnels

Based on the characteristics of the Y-shaped joint of a subway station built by enlarging two parallel shield tunnels, a bending mechanical model of the segmental joint was proposed. The model was used to characterize the cracking and crushing of concrete, the yielding of the bolt, and the damage of the segmental joint. Theoretical equations were derived for the bending stiffness of the joint under various forms of joint opening. Bending experiments were conducted on full-scale models of the joints under different structural configurations. The results demonstrated that the nonlinear properties of the joint structure were evident under loading and that the bending stiffness of the joint initially increased and then decreased. The computed values were in good agreement with the experimental results for the pre-embedded connector joint when lc was 0.5 times the height of the compression zone, where lc was the effect depth of the compressive deformation of the outer edge of the concrete. The axial force had a great influence on the bending stiffness. The mechanical performance of the joint was influenced not only by the change in the stress–strain curve of the concrete from the rising stage to the descending stage but also by the structural morphology of the rotational angle of the joint.

Study on the effect of excavation sequence of three-hole shield tunnel on surface settlement and segment deformation

In order to study the influence of excavation sequence of three-hole parallel shield tunnel on surface settlement and segment convergence, an improved “three-stage analysis method” was proposed to calculate the surface settlement of three-hole parallel shield tunnel. Based on Peck's existing theory, this method deduced the ground settlement formula under the three-hole parallel condition, and can calculate the ground settlement more accurately. Based on the engineering background of a shield tunnel section in Jiangsu Province, a three-dimensional model of a three-hole parallel shield tunnel was established by using Flac3d software, and the three-hole parallel shield tunnel was simulated under four working conditions: right–center–left, right–left–center, right–left–right and right–center (reverse)–left. This paper analyzed the influence of tunnel excavation sequence on surface settlement, soil displacement and deformation of tunnel segments. The construction sequence was optimized based on the above influencing factors. It was found that Case 4, S-type sequential excavation, produced the least ground settlement. The surface settlement value caused by S-type excavation sequence was only 11.41 mm, and the convergence value of the segments generated by S-type excavation sequence was relatively small. Considering the economic factors such as construction efficiency and benefit, the S-shaped excavation sequence was better. The new calculation method of tunnel surface settlement and the optimal sequence of tunnel construction proposed in this paper can provide reference for actual construction.

Experiments on the seismic performance of Y-shape joints of subway stations built by enlarging two parallel shield tunnels

To improve the seismic performance of subway stations built by enlarging two parallel shield tunnels, joints of special structures between prefabricated open-loop segments and cast-in-site main station structures were proposed. Experiments on the low-frequency cyclic loading of full-scale models of joints under different structural configurations werecarriedout. The seismic performance, such as the load–displacement hysteresis curves, skeleton curves, structural ductility, strength degradation, energy dissipation, strain of the cable-stayed bars and failure modes, were studied. The results showed that compared with the pre-embedded connector joint, the pre-embedded steel plate joint had advantages in terms of the mechanical stability, intensity, stiffness, energy dissipation capacity and ductility performance. However, the relative displacement between the segment and wall column of the pre-embedded steel plate joint was larger than that of the pre-embedded connector joint. Both types of joints had a full hysteretic circle, good ductility nature, energy dissipation ability, and stable elastic and elastic–plastic deformation. The cable-stayed bars did not yield in the stretch area when the joints failed. Both of the joints could meet the performance requirements of strong joints and weak components.

Analysis of experimental data on the effect of double-line parallel shield tunneling on the deformation of adjacent buildings

Recent years have witnessed increasingly complex circumstances like shield passing buildings and underground structures at close range in urban tunnel design and construction. This paper has analyzed the short-distance side-crossing masonry structure engineering of the shield tunnel of Zhengzhou Metro Line 5. Using field measurement method, surface settlement, settlement and distortion of masonry structure during the construction process of double-line parallel shield tunnels successively superimposed and side-passed through the existing masonry structures, were studied. According to finding, when the construction of the double-line tunnel was completed, the maximum value of surface settlement still occurred near the centerline of the first tunnel. It was expected to make reasonable calculations and assessments for the safety of masonry structures after shield crossing construction and provide reference for similar projects in future.

Experimental modeling of adjacent parallel shield tunnels subjected to train-induced vibration loads

Previous studies have performed numerical simulations of adjacent parallel shield tunnels under train-induced vibration loads. However, few experimental studies have been performed for the interaction mechanisms. In this study, experimental modeling is conduced to explore the interaction of adjacent parallel shield tunnels subjected to different train-induced vibration loads. A new Hilbert-Huang transform (HHT) is applied to obtain the instantaneous responses of tunnels. The results show that the acceleration of the tunnel follows the trend of the train load curve. The peak accelerations of the tunnels experience a unimodal distribution along the train speed, while the dominant frequencies of the tunnels follow a bimodal distribution. The interaction between the adjacent parallel tunnels is significant. The transform of the vibration loads to the adjacent tunnel is through the soil below the tunnel. The farther away from the train load is, the greater the train speed corresponding to the dominant frequency peak.

Experimental study on the vibration damping of two parallel shield tunnels connected by an assembled transverse passage

Transverse passages are ubiquitous in urban subways, and they pose serious mutual threats to the two adjacent tunnels they connect. In this paper, the frequency sweep loads were applied in model tests and the influence mechanism of integral transverse passage (ITP) was studied by using the one-third octave of the frequency response function (FRF). Subsequently, a new assembled transverse passage (ATP) was proposed and its vibration attenuation effect was studied. The results showed that, when the frequency sweep load is applied to one tunnel, the adjacent tunnel is more susceptible to a load that has a central frequency of 12.5–80 Hz due to the existence of ITP. The closer the loading frequency is to 31.5 Hz, the greater the impact on the adjacent tunnel becomes. When an ATP is used, the vertical acceleration level (VAL) of the tunnel to which the load is applied will increase by 1.3 dB, while that of the adjacent tunnel will decrease by 7.2 dB, and the transverse passage will decrease by 8.7 dB. Compared to the ITP, when the lining structure of an adjacent tunnel is closer to the ATP, the reduction in the vibration response of the structure is more pronounced, and the vibration response is reduced over a larger central frequency range.

Numerical Simulation of Site Deformation Induced by Shield Tunneling in Typical Upper-Soft-Lower-Hard Soil-Rock Composite Stratum Site of Changchun

In China, with the rapid development of subway construction, the site deformation induced by subway construction is an interesting and hot issue in civil engineering. Focusing on the mechanism and characteristics of site deformation induced by parallel shield tunnel construction in typical soil-rock composite strata of Changchun region, and relying on the subway tunnel between Northeast Normal University Station and Gongnong Square Station, which belongs to the Changchun Metro Line 1, the tunnel construction process is simulated using FLAC3D software. In this paper, the numerical modeling and parameters for shield tunneling are described in detail, and the mechanism and characteristics of site deformation induced by shield tunneling are discussed systematically. Furthermore, the influence of construction parameters on site deformation, including construction sequence, tunnel spacing and earth chamber pressure, are studied. The results can provide reference for similar projects in the future.

Ground Displacement Analysis of Double-tube Parallel Shield Tunnels

Ground Displacement Analysis of Double-tube Parallel Shield Tunnels

Analysis on the influence of double-line large diameter shield tunnel orthogonally underpassing tunneling on railway track group

In the process of urban traffic construction and reconstruction, the number of new tunnels crossing existing railways is increasing day by day.Based on the reconstruction project tunnel of Xiangyang Road in Weifang city underpassing Jiaoji Railway passenger dedicated line and Jiaoji Railway, the outer diameter of shield tunnel is 10.7 m, and the minimum cover soil thickness is 10.5 m, and the crossing length is 60 m. The three dimensional numerical simulation analysis was carried out to study the influence of the construction of the double-line parallel shield tunnel on the existing railway track group. The results show that the final settlement of the ground settlement of the railway subgrade centerline is “bimodal shape”; the maximum value of ground subsidence in the centerline of shield tunnel is -2.29mm, and the longitudinal influence range of shield construction is approximately 20 meters in front of the face to 40 meters in the rear. This study provides a reference for the implementation of similar double-line shield tunnel underpass railway engineering.

Performance of constructing a double-deck subway station by combining the shield method and cavern–pile method

A method of constructing a double-deck subway station by combining two parallel shield tunnels and the cavern–pile method is presented. Taking the practical engineering of the Beijing subway as the background, numerical simulations were carried out to study enlarging construction. Mechanical and deformed performances for opening segments, important nodes, and main components of the station structure were investigated. Subsequently, a comparative analysis was performed to investigate the effects of side piles. Finally, an economic investigation was conducted to validate the practicability of the present method. This paper systematically demonstrates the applicability of the proposed method through a three-dimensional numerical simulation. The results show that it is safe and feasible to create a double-deck subway station by enlarging two parallel shield tunnels using the cavern–pile method.

Three-dimensional numerical simulation of a mechanized twin tunnels in soft ground

The increase in transportation in large cities makes it necessary to construct of twin tunnels at shallow depths. Thus, the prediction of the influence of a new tunnel construction on an already existing one plays a key role in the optimal design and construction of close parallel shield tunnels in order to avoid any damage to the existing tunnel during and after excavation of the new tunnel.Most of the reported cases in the literature on parallel mechanized excavation of twin tunnels have focused on the effects of the ground condition, tunnel size, tunnel depth, surface loads, and relative position between the two tunnels on tunnel behaviour. The numerical investigation performed in this study, using the FLAC3D finite difference element programme, has made it possible to include the influence of the construction process between the two tunnels. The structural forces induced in both tunnels and the development of the displacement field in the surrounding ground have been highlighted.The results of the numerical analysis have indicated a great impact of a new tunnel construction on an existing tunnel. The influence of the lagged distance between the two tunnels faces has also been highlighted. Generally, the simultaneous excavation of twin tunnels causes smaller structural forces and lining displacements than those induced in the case of twin tunnels excavated at a large lagged distance. However, the simultaneous excavation of twin tunnels could result in a higher settlement above the two tunnels.

Effect Analysis of Double-Line Parallel Shield Tunnel Crossing Frame Structure Building Based on GTS

Considering the interaction of building-soil-tunnel, the grillage beams foundation frame building vertical crossed by Double-Line (DL) parallel shield tunnel was simulated by 3D MIDAS/GTS software. The results show that: after left-shield tunnel construction had done, during the passage of the right shield tunnelling, the differential settlement decreased gradually, settlement is slightly larger than the left when the right tunnel had ready crossed the building. Uneven settlement first increases, and then decreases gradually tends to zero. Lateral horizontal displacement changes little, and longitudinal horizontal displacement first increased and then decreases. The building’s maximum first principal stress exceeds the standard value, which may cause cracking. With the increase of L the distance from frame axis to the axis of the two tunnels, the first principal stress P1 and maximum shear strain MSmax tended to reduce in general. The maximum differential settlement between columns first increased and then decreased.

Evaluations of the behavior of the closely constructed parallel shield tunnel

Evaluations of the behavior of the closely constructed parallel shield tunnel

A study on methods of evaluating the influence of a parallel shield tunnel

A study on methods of evaluating the influence of a parallel shield tunnel

An experimental study on the behavior of the closely constructed parallel shield tunnels

An experimental study on the behavior of the closely constructed parallel shield tunnels

Study of ground-tunnel interactions of four shield tunnels driven in close proximity, in relation to design and construction of parallel shield tunnels

In Japan, K yoto City has constructed four subway tunnels that run closely each other. Problems accompanying the closely running tunnels are studied during the planning and design stages prior to construction. A variety of monitoring during the construction stage resulted in the collection of numerous data including the load transmission between tunnels and characteristic behavior of theground during the construction of four tunnels. Aiming at improving the method for the evaluation of the interaction of closely running tunnels, this study attempted to analyze and assess the behavior of the tunnels and the surrounding ground through such data obtained from the above project. This paper describes the characteristics of influence from the thrust of a succeeding tunnel to a preceding tunnel and the analytical expression of the mechanism of ground behavior during the construction of closely running tunnels.

IN-SITU MEASUREMENTS OF PARALLEL SHIELD TUNNELS IN POOR COHESIVE SOIL GROUND AND PSEUDO-THREE DIMENSIONAL ANALYSIS METHOD OF SEGMENT RINGS

IN-SITU MEASUREMENTS OF PARALLEL SHIELD TUNNELS IN POOR COHESIVE SOIL GROUND AND PSEUDO-THREE DIMENSIONAL ANALYSIS METHOD OF SEGMENT RINGS

Prediction of surface settlements due to parallel shield tunnels : Hisatake, M; Ito, T Proc eighth Asian regional conference on soil mechanics and foundation engineering, Kyoto, 20–24 July 1987V1, P293–296. Publ Japan: Japanese Society for Soil Mechanics and Foundation Engineering, 1987

Prediction of surface settlements due to parallel shield tunnels : Hisatake, M; Ito, T Proc eighth Asian regional conference on soil mechanics and foundation engineering, Kyoto, 20–24 July 1987V1, P293–296. Publ Japan: Japanese Society for Soil Mechanics and Foundation Engineering, 1987