Influence Of Tunnel Construction Research Articles

Study on the Influence of an Under-Crossing Parallel Double-Line Shield Tunnel on the Existing Tunnel Structure

Extra care should be taken when new tunnels pass through an existing tunnel. If it is not handled properly, this will affect the operation safety of the existing line, and bring security risks to the train’s operation. In order to study the impact of an under-crossing parallel double-line shield tunnel on the existing shield tunnel structure, the influence of tunnel construction on the deformation of overlying strata was analyzed, and the formula for estimating the formation settlement at depth Z below the surface, caused by the excavation of a double-tunnel parallel tunnel, was deduced. Then, a series of three-dimensional finite element numerical simulations were carried out. We analyzed and systematically studied the adverse effects of the tunnel structure of Guangzhou subway Line 5, caused by the tunneling of subway Line 18, evaluated its structure and operational safety, and provided suggestions for site construction. This research demonstrates the following conclusions. (1) The tunnel structures of subway Line 5 and Line 18 are mainly in the strongly weathered argillaceous siltstone stratum, and lightly weathered argillaceous siltstone stratum, respectively, and the stratum where the Line 18 tunnel is located is relatively safe. (2) According to three-dimensional finite element numerical simulation analysis, during the shield-tunneling process of subway Line 18, the maximum X horizontal displacement, the maximum Y horizontal displacement, and the maximum Z vertical displacement of the tunnel structure in subway Line 5 are 1.09, 3.50, and 4.55 mm, respectively. It is considered that the impact of the shield-tunnel penetration of subway Line 18 on the tunnel structure of subway Line 5 is relatively controllable, and does not affect the structure and operational safety. (3) It is suggested that settlement monitoring should be strengthened within the range of 12 m (about 1.5 tunnel diameter D). before and after the excavation axis of the underpass tunnel, and it is necessary to carry out local reinforcement treatment, to prevent adverse effects on the operation of the existing tunnel.

Mechanical Properties of Sheet Pile Cofferdam during Adjacent Open Cut Tunnel Construction near Lake Bottom

In water-related projects, the application of steel sheet pile cofferdams is becoming more and more widespread, and the influence of tunnel construction on the mechanical properties of adjacent cofferdams is important. In this study, the object of research was the mechanical properties of large-span steel sheet pile cofferdams. The open-cut tunnel project was located in Suzhou Yinshan Lake, China. According to the actual construction steps of the tunnel foundation pit, assuming that the soil was a small strain hardening soil model, combined with on-site monitoring data, a three-dimensional elastoplastic finite difference model was established. The results show that during tunnel construction, the maximum settlement of the cofferdam appeared at 0.27~0.53 m on the side of the foundation pit; the maximum horizontal displacement of the steel sheet pile occurred at the pile bottom of foundation pit side, and the seepage gradually increased during construction, eventually resulting in water gushing at the bottom of the foundation pit. After the completion of tunnel construction, the settlement value of the cofferdam presented a pattern that first increased and then decreased from the side of the foundation pit to the side of the adjacent lakeside; the steel cofferdam tilted toward the side of the foundation pit, with a maximum inclination angle of 3.37°. It should be pointed out that as the construction progressed, the axial force of the tie rods in the steel cofferdam changed from a U-shaped distribution to a V-shaped distribution. This study could provide a reference for the impact of tunnel foundation pit construction on adjacent steel cofferdam and could also provide a reference for the safety research of open-cut tunnel construction.

Influences of double-track shield tunnel construction on settlements of adjacent ground and buildings in a soft soil area

The influence of the shield tunnel construction on the adjacent grounds and buildings is a fundamental issue for the safe construction and regular service of the shield tunnel in the soft soil area. In order to investigate the influences of the double-track shield tunnel construction between the Tongde Road Station and the Shiqi Station of the Ningbo Metro Line 5 on the adjacent grounds and buildings, a dynamic 3D finite element model of shield tunneling is established. After comparing the simulated and monitered settlements of the ground surface and adjacent building, the influences of the tunnel construction on the adjacent ground surface and building are thereafter explored. The results show that when the excavation is completed, the subsidence tank deviates from the direction of the upward tunnel with an inverted trapezoidal shape, and the final cross-sectional influence area is less than 3 times the tunnel diameter from the center of the double-track tunnel axis. After the excavation of the ascending line, the surface settlement does not increase, but the width of the settlement groove increases. The settlement generated before the arrival of the downstream line accounts for 67% of the final cumulative settlement. The building inclines along the direction of shield tunneling as the shield reaches the building, while the building inclines along the opposite direction of shield tunneling as the shield leaves the building. The settlements at both sides of the building are reduced by 83%, compared with those at the middle part. After the two lines are connected, the settlements of the building shows a U shape distribution, and the maximum settlement occurring at the middle building is 0.5 m from the tunnel.

Study on the influence of tunnel construction on existing tunnel below by above-crossing tunnel

During the construction of the above-crossing tunnel, the surrounding rock of the existing tunnel will be disturbed in different degrees due to the different spacing between the upper tunnel and the existing tunnel. In order to study the regular pattern between the surface deformation of the existing tunnel surrounding rock and the tunnel spacing, the surrounding rock deformation of 10 groups of existing tunnels with different spacing is studied by numerical simulation based on the project of the upper loop section of Chongqing rail transit line 9. The results show that the uplift deformation of the vault of the existing tunnel will be caused by the construction of the upper double-track tunnel, and the final deformation of the existing tunnel is in the shape of “M“. The maximum displacement of the existing tunnel decreases first and then increases with the increase of the transverse distance of the upper crossing tunnel, but the maximum displacement of the existing tunnel does not change much; As the vertical distance between the new tunnel and the existing tunnel increases, the maximum displacement of the existing tunnel decreases linearly within the 3L vertical distance. It gradually stabilized after 3L, indicating that the existing tunnels beyond 3L are almost unaffected by new tunnels.

Investigating Influence of Metro Jet System Hydration Heat on Artificial Ground Freezing Using Numerical Analysis

With the development of urban subway system, intersection is sometimes inevitable during the construction of underground tunnels. When a tunnel to be excavated is underneath an existing subway station, the support wall of the station that lies on the way of the tunnel is often required to be partially dismantled to facilitate the construction of the tunnel. To ensure safety of the existing station and the tunnel, both metro jet system (MJS) using cement paste and artificial ground freezing (AGF) techniques can be applied and sometimes combined to stabilize the area under the influence of tunnel construction. However, when two techniques are combined, the hydration heat from the cement paste will bring an increase in the active freezing time. By taking advantage of an existing project, a preliminary numerical simulation is performed to evaluate the influence of hydration heat on a 100-day ground freezing process with considering the effect of ambient temperature, thermal insulation, and the timing of the initiation of the freezing after MJS treatment. Simulation results show that the active freezing time can be reduced by 53 and 3 days with thermal insulation at the end sections in summer and winter, respectively. Hydration heat leads to an increase of the active freezing time from 14 to 15 days, and the effect of timing for the initiation of artificial ground freezing is insignificant on the active freezing time. Subsequently, consistent with the construction plan and site condition, using the ambient temperature from the previous year, a numerical simulation is also performed to simulate the soil temperature variation during the releasing of hydration heat and the freezing followed. The simulation results show that 52-day active freezing time is required for the formation of a frozen soil wall which met the requirement for further tunneling.

The influence and calculation method of ground settlement induced by tunnel construction in sand

ABSTRACT In order to study the influence of tunnel construction on ground settlement in sand, the distribution and variation characteristics of ground settlement during tunnel construction were explored through model tests. The results showed that during tunnel construction in sand, the variations of surface settlement and ground settlement at different ground depths were basically the same at the same monitoring section. The distribution and variation characteristics of the ground settlements along the width and length directions of the tunnel were basically the same. The ground loss increased in power function from the surface to the underground. The maximum ground settlement and the width coefficient of the settlement trough were strongly positively correlated with the ground loss. Based on the experimental study and statistical analyses, the relation between ground loss and ground surface loss at different burial depths was established. The calculation of an equation of ground loss at different depths was put forward, and the calculation of an equation of the width coefficient of ground settlement trough was modified, both of which enable the calculation for ground settlement in an arbitrary position above the tunnel during tunneling.

Evaluation of a Tunnel Underpass Building Scheme in Yunnan Province

Side-crossing residential buildings in tunnel construction may lead to building subsidence, structural damage by tension and affect the use of buildings. Aiming at the structural damage caused by the side-crossing structure of Re Shuitang Tunnel NO.1, by simulating the influence of tunnel construction on the building, it is concluded that the surrounding rock above the tunnel will be deformed when the tunnel crosses the building. The maximum horizontal displacement is 0.64 mm and the maximum vertical displacement is 4.43 mm. According to the analysis results, the surrounding rock above the tunnel should be strengthened in time, and attention should be paid to the impact of blasting on residential buildings, so as to ensure the safety of buildings and provide reference for future construction.

地下水向雪山隧道的排泄对台湾北部水资源的影响

The Hsueh-Shan tunnel is the fifth longest road tunnel in the world. During the excavation, the tunnel encountered several events of groundwater inrush, causing serious delay of the construction. Data on groundwater discharge to the tunnel were gathered from the monitoring system and their spatial and temporal variations were analyzed. The results of the integrated analysis of groundwater discharge and local precipitation indicated that the discharge increased rapidly when the cumulative rainfall exceeded 85 mm. The groundwater level recession rate after a rainfall event was found to be independent of rainfall intensity. A hydrogeological conceptual model was developed to simulate the long-term groundwater discharge to the tunnel. Sensitivity analysis was first conducted to identify sensitive parameters, and then the calibration process was accomplished by the automated parameter estimation method. The calibrated model was then used to evaluate the potential impact of tunnel excavation on the Feitsui reservoir; the average percentage loss of inflow to the Feitsui reservoir from 2006 to 2010 is estimated to be 1.74 %. The developed model can provide a tool for evaluating the regional hydrogeologic setting and the influence of tunnel construction on water resources.

Numerical Analysis of the Influence of Tunnel Construction on High-Voltage Transmission Tower

Coal mining often results in settlement of tower foundation and stress change of tower. The influence of tunnel construction on above tower is similar to the influence of coal mining on above tower. Therefore, it is necessary to analyze the settlement of tower foundation and stress of tower. Some reinforcement measures have been taken to the foundation of tower before tunnel construction. The settlement of tower foundation and stress of tower is analyzed by ABAQUS finite element software. The analyses show that the settlement of tower foundation and stress of tower are within the range of the allowable, during tunnel construction. These show that the safety of the tower can be guaranteed after reinforcement.

Influence of Tunnel Excavation on Adjacent Underground Pipeline

Based on nonlinear finite element method, the influence of tunnel construction on adjacent underground pipeline is studied. It is shown that remarkable settlements occurred above tunnel working surface due to tunnel excavation, and soil bulged below tunnel working surface due to load-off. The inhomogeneous deformation of pipeline become more serious when the distance between tunnel working surface and pipeline become shorter. So it is important to keep enough distance between tunnel working surface and pipeline. The deformation of pipeline become less when the radius of tunnel decreased. It is also find that there is no obvious influence on settlement of pipeline with different materials of pipeline. The settlement of pipeline can be reduced and stability of tunnel can be enhanced evidently by local excavation above tunnel working surface. Therefore, local excavation above tunnel working surface can be prior used to protect underground pipeline if allowable.