Double-hole Tunnel Research Articles

Safety assessment of the construction of double track tunnels underneah exsiting railway tunnels

The ground disturbance caused by the tunnel construction will inevitably have an impact on the upper part of the constructed tunnel structure, and the railroad tunnel requires a very high level of control over the structural settlement deformation. For the problem of double-hole tunnel under the built tunnel, this paper takes Chongqing Mingyue Mountain Tunnel under the built Shanghai-Rong Railway Paihua Cave tunnel and Zheng-Yu Railway tunnel as the engineering background, and starts from the mechanism of ground loss caused by tunnel excavation, firstly, the settlement at the height of the existing tunnel strata is obtained through theoretical analysis, and the new Mingyue Mountain Tunnel under the Shanghai-Rong Railway tunnel is determined to be a more dangerous section. Further simulate and calculate the dynamic excavation process of the new double-hole tunnel underpass, and study the settlement deformation law of the Mingyue Mountain Tunnel underpassing the Hurong Railway Tunnel. According to the requirements of railroad tunnel for settlement deformation control, the new tunnel is determined to be constructed by step method to ensure the safety of railroad tunnel. The shortcomings of the theoretical calculation are analyzed to illustrate the important role of numerical simulation in the evaluation of tunnel underpass projects.

Analysis of the Stability of the Double-Hole Complementary Ventilation and Ventilation Network of the Tunnel Constructed by Drilling and Blasting Method

Currently, double-hole complementary ventilation is a mature ventilation method for operating tunnels, but how to carry out it in the construction tunnel poses a new challenge. Due to the desynchronization in the construction period of the double-hole tunnel, there is an instantaneous difference in the air flow demand between the two working faces. The study analyzes the impact of geometric parameters, specifically Lt (the distance from the traffic cross passage to the working face of the advance side tunnel), Lp (the distance between the pedestrian cross passage and the working face of the advance side tunnel), Ht (height of the upper step), and Lw (safe step distance of the double-hole working face) on ventilation network stability. The results show that with the increase of Lt and Lp, the Rm resistance of each branch changes non-uniformly, and the stability of the ventilation network is significantly different. Then, when Lt, Lp = 80 and 180 m, the air flow directions of the double-hole tunnel are the same. Finally, when Lt and Lp = 130 m, the air flow directions are inconsistent, which indicates that in the range of 80 m < Lt or Lp < 180 m, the cross-section size of the cross passage affects the stability of the ventilation network. However, when 2.5 m < Ht < 3 m, or 30 m < Lw < 50 m, the stability of the ventilation network is not affected, and the flow field of the double-holes does not interfere with each other. The conclusions obtained confirm that the double-hole complementary ventilation method is available in construction tunnels, and has potential for implementation.

An iterative FEM approach for tunnel shape optimization based on the concept of rational arch axis

The shape of tunnel is one of the major factors influencing its stability. Aiming at optimization design of tunnel shape, an iterative FEM approach is proposed based on the concept of rational arch axis, on which the structure is only subjected to axial compressive force without bending moment. In the proposed approach, the eccentricity of each lining node, which is the ratio between bending moment and axial force, is progressively calculated according to the current nodal position until it satisfies a predetermined criterion by continuously changing nodal coordinates. The rational arch axis of lining is then obtained and the optimal tunnel shape is thus determined. Two different tunnels, one with a circular initial shape and the other with a rectangular-like shape, and both with the same stratum and loading conditions, are employed to obtain their optimal shapes by using the proposed method. The optimal shapes obtained are identical and therefore the proposed approach is verified to be effective and robust. Furthermore, this method is applied to the optimization of the shape of a double-hole tunnel. The mechanical responses of tunnel lining and the stress distributions in surrounding rock-soil during the optimization process are investigated as well. The results show that the mechanical behavior of the optimal lining has been improved in terms of force and deformation characteristics, and the rock-soil around the tunnel can be retained in situ avoiding the stress concentration.

Stability analysis of full-section construction of staggered distance double-hole tunnel

In the staggered distance double-hole tunnel located on the slope of the mountain, the deformation of the surrounding rock and the supporting structure of the tunnel is complicated. The deformation stability of the tunnel entrance is one of the most difficult points of the tunnel. In order to clarify the deformation law of the full-section construction at the entrance of the staggered distance double-hole tunnel, the entrance section of the Georgia E60 Highway No. 3 tunnel under construction is used as the background, and the method of numerical simulation test is used to study the staggered distance double-hole tunnel, the influence of section construction on the deformation and stability of the side and front slopes of the tunnel entrance section and the support structure of the tunnel entrance section. The research results show that: For tunnels with full-section construction, excavation will cause certain deformations on the ground and the tunnel, and the stability of the left side support structure of the right line tunnel without rock column between the two tunnels is worse than that in other positions, on the whole, the construction plan is reasonable and feasible.

Study on Fire Smoke Distribution and Smoke Control in Extra-long Double-hole Tunnel

Abstract：
 Construction of tunnels, as one of the main methods to solve physical traffic barriers, However, It vulnerable to the threat of fire during the process of tunnel operation period. In response to such situation, this article explores the smoke distribution of extra-long double-tube tunnel and its impact on evacuation in the event of a fire. This paper take the Jieling tunnel as an example, and applies Accident Tree Analysis (ATA) method combined with Fires Dynamics Simulator (FDS）simulation software to study the changes of harmful factors such as tunnel smoke. According to the research, when a fire occurs in an extra-long double-tube tunnel, It is concluded that people are supposed to be guided to leave via the nearest cross-passages as soon as possible, In the end analysis the roles that air curtains could play in the control of smoke. It is recommended to open the air curtain so that in such condition people away from the cross-passages have enough time to escape.

Simulation and analysis of seismic response of parallel double-hole tunnel

In order to realize the seismic response analysis of the parallel double-hole tunnel, this paper takes the double-hole tunnel of an underground section of shenyang subway as the research object, USES midas-gts to establish a three-dimensional finite element numerical calculation model, and analyzes and discusses its seismic response. The results show that:Under the action of seismic wave, the maximum position of relative displacement of soil is usually at the soil boundary, and the maximum position of relative displacement of tunnel lining is usually at the tunnel entrance. Along the input direction of seismic wave, the maximum relative displacement of the tunnel is greater than the corresponding value of the other two directions.

Dynamic Response of Shallow-Buried Tunnels under Asymmetrical Pressure Distributions

Abstract Based on the similarity theory, two physical testing models (double-hole tunnel and single-hole tunnel) with a scale of 1:10 were designed and manufactured. A series of shaking table tests followed by numerical simulations was carried out to obtain the dynamic response characteristics of shallow-buried tunnels with asymmetrical pressure distributions. The similarities and differences in the dynamic response laws between double-hole tunnel and single-hole tunnel were studied. The effects of types of seismic wave (Wenchuan wave, Darui artificial wave, and Kobe wave), peaks acceleration excitation (0.1 g, 0.2 g, 0.4 g, and 0.6 g), excitation directions (horizontal and vertical directions), and excitation modes (unidirection and bidirection) on dynamic response laws of the tunnels were studied. The results show that the variation of acceleration multiplying factor (AMF) shows a nonlinear trend. The AMFs are different at different monitoring points. The type of seismic wave has a significant effect on the acceleration response, with Kobe wave being the most serious, followed by the Darui artificial wave and the Wenchuan wave. In bidirectional excitation, the AMFs are relatively larger than those of unidirectional excitation. A comparison between the numerical simulation and the shaking table tests in both acceleration time history and peaks acceleration shows that the results of the shaking table tests and numerical simulations are credible. The acceleration response of monitoring points near the existing slope is generally magnified. The residual strains are generated at the monitoring points. The variation trends of both tensile strain and compressive strain are opposite. The tensile strains are generally larger than the compressive strains. Many factors, such as the type of seismic wave, peaks of acceleration excitation, excitation direction, and excitation mode, have a significant influence on the dynamic strain response and acceleration response of the tunnels. The research results could promote the understanding of dynamic response characteristics of the tunnels.

Numerical Analysis on Influence of Subway Double-Hole Parallel Tunnel Deployment on Surrounding Soil Distortion

construction of near double-hole parallel tunnels frequently occurs in city subway evacuation. Studying the dynamical behaviors of the parallel tunnel construction, performing systematic numerical analysis and grasping mutual influences of different factors on the tunnel evacuation and different effects of surface sedimentation has important theoretical meaning and application value for the building technology of the parallel double-hole tunnel. This paper establishes a three-dimensional numeral model, analyzes influences of three main influence factors (tunnel distribution form, tunnel burying depth and tunnel gap) on the surrounding soil and surface sedimentation in double-hole tunnel synchronous evacuation. The conclusions indicate that the vertical distribution has the biggest influences on tunneling in horizontal distribution, vertical distribution and tilted distribution of two tunnels, followed by tilted distribution. The horizontal distribution has the minimal influence. With growth of the tunnel gap, the mutual influence between two tunnels will become smaller. With growth of the tunnel burying depth, the influences on tunneling will become bigger.

Numerical Analysis on Mutual Influences in Urban Subway Double-Hole Parallel Tunneling

mutual influence of the double-hole tunnel evacuation of urban subways is one of key issues involving the subway construction safety. The asynchronous one-direction evacuation, synchronous one-direction evacuation and opposite evacuation methods are frequently used in double-hole tunnel evacuation. This paper establishes three-dimensional numerical model by using the finite element analysis software MIDAS/GTS v2.01 and mainly studies the mutual influences of tunnels in the asynchronous one-direction evacuation and synchronous one-direction evacuation. The following conclusions are concluded based on computing. The preliminary conclusion is that the influential distance between the evacuation section of two tunnels is 3D (D is the tunnel diameter) in the parallel tunnel asynchronous evacuation, namely when the lagging distance is more than 3D, the lagging evacuation tunnel will not affect the advance evacuation tunnel section. The asynchronous evacuation of the vertical distribution tunnel is divided into the up tunnel first evacuation and down tunnel first evacuation. For up tunnel first evacuation, the influence range of the lagging distance is 5D. For down tunnel first evacuation, the influence range of the lagging distance is 1D. For up tunnel first evacuation on the slope, the influence range of the lagging distance is 5D. On the whole, the influence of two tunnels in up tunnel first evacuation is bigger than it in down tunnel first evacuation. The numerical analysis results will have important theoretical meaning and application value for building technology of the parallel double-hole tunnel.

Research of Surface Deformation with Metro Double Tunnels Construction and the Relative Position Change

With the rapid development of our economy, the urban traffic becomes increasingly busy. To ease traffic congestion, underground rail transportation is becoming one of the main modes of transportation in city. At present in order to relieve the traffic congestion most major cities in China are accelerating the construction of subway tunnels. The relative position change of metro double tunnels and construction of the sequence will affect the surface subsidence deformation and the interaction of the tunnel lining. It is more concerned about these issues in tunnel design. It is the main purposes, in this paper, to analyze the metro double tunnels surface deformation, which affect by the position changes of new construction double and the sequence of construction. From the numerical simulating results, in order to reduce surface subsidence and ensure the structural safety over the subway tunnel, it should try to make double-tunnels at the same horizontal plane in design. If the double tunnels could not be located at the same horizontal plane, the double-hole tunnel construction sequence of the deformation of the surface subsidence effects are obvious it is obvious that the double tunnels construction sequence differently make the deformation of the surface subsidence. To reduce the deformation of the surface subsidence, it should be first excavated the shallow tunnels and then excavated the tunnel buried deeply. The ideal distance of the double tunnels center is greater than 4 times the tunnel diameter. It can make the surface subsidence reduce to the minimum during the metro tunnel construction.