scholarly journals Mechanical and Deformation Characteristics and Optimization of Support Parameters for Superlarge-Span Tunnel: A Case Study from Laohushan Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Yanbin Luo ◽  
Jianxun Chen ◽  
Zhou Shi ◽  
Shaoqiang Zhang ◽  
Weiwei Liu ◽  
...  
Keyword(s):  
Stable State ◽  
Structural Safety ◽  
Measuring Point ◽  
Highway Tunnel ◽  
Engineering Economy ◽  
Tunnel Design ◽  
New Construction ◽  
Technical Specifications ◽  
Secondary Lining ◽  
Primary Support

In the new construction or reconstruction of expressway projects, the number of highway twin tunnels with eight lanes is increasing. However, there are no corresponding design support parameters and measures in the current technical specifications for tunnel design and construction in China. In Laohushan superlarge-span highway tunnel with single hole and four lanes, the deformation behavior and mechanical characteristics of support structures are measured and analyzed. The monitoring results indicated that the deformation of tunnel structure mainly experienced three stages: rapid deformation, slow deformation, and stable deformation, and finally reached a relatively stable state; the structure stress of primary support and secondary lining increases sharply at first and then tends to be stable gradually with the gradual construction of each excavation part in the tunnel; the stress of each measuring point at the steel rib is less than the yield limit of steel rib (235 MPa), and the support structure is safe and stable in the process of tunnel construction. Then, the structure safety of primary support under different support parameters is simulated and calculated by numerical simulation with Grade IV rock mass, and the reasonable support parameters for Laohushan highway tunnel are studied considering the structural safety and engineering economy. It is suggested to use the H175-type steel sets with a distance of 80 cm and C25 shotcrete with a thickness of 26 cm. The results could provide reference for similar tunnel projects and provide a basis for the design specification and construction standards for superlarge-span tunnels.

scholarly journals New Construction Technology of a Shallow Tunnel in Boulder-Cobble Mixed Grounds

2020 ◽  
Vol 2020 ◽  
pp. 1-20 ◽  
Author(s):  
Tong Liu ◽  
Yujian Zhong ◽  
Zhihua Feng ◽  
Wei Xu ◽  
Feiting Song ◽  
...  
Keyword(s):  
Surrounding Rock ◽  
Construction Technology ◽  
Construction Process ◽  
Tunnel Excavation ◽  
Supporting System ◽  
Highway Tunnel ◽  
Bulk Medium ◽  
New Construction ◽  
Secondary Lining ◽  
Design And Construction

As a typical granular bulk medium, problems are common in boulder-cobble mixed grounds, such as easy collapse and instability and difficult effective support for large-section tunnel excavation. Tunnels constructed in BCM grounds are rare still, and there is a big gap between the design and construction of tunnels. Based on the Nianggaicun highway tunnel crossing the BCM grounds, the construction technology of tunnel in BCM grounds is studied by means of literature investigation and field survey. Here are the main conclusions: the overall deformation of surrounding rock is quite small; the pressure distribution of surrounding rock is small and loose pressure is dominant, and the safety reserve of secondary lining is large. The deformation process of surrounding rock concentrates on the construction stage. During the construction process, there are many problems, such as serious overexcavation, difficulty of bolt penetration, and continuous rock fall. In this paper, a three-bench complementary cyclic excavation method is proposed, which replaces the original CD and CRD methods. Meanwhile, the supporting system is optimized. The results show that the disturbance of surrounding rock is reduced, while the safety of construction process and the reliability of structure are increased. The new excavation method and optimized supporting system are expected to fill the gap between design and construction of tunnel in BCM grounds and provide reference for construction of such tunnels in the future.

Long-Term Safety Analysis of Tunnel Structure Based on the Performing Degree of Support Strength

2011 ◽  
Vol 261-263 ◽  
pp. 1220-1224
Author(s):  
Jin Xing Lai ◽  
Xiao Wei Liu ◽  
Fei Zhou
Keyword(s):  
Safety Analysis ◽  
Internal Force ◽  
Tunnel Structure ◽  
Load Bearing ◽  
Geological Conditions ◽  
Temporary Support ◽  
Tunnel Design ◽  
Secondary Lining ◽  
Primary Support

At present, the new Austrian tunneling method is basically used as the theoretical guidance for domestic tunnel design, which shows that the primary support is not progressed by durability design in the light of service life in the practical work generally acting as the temporary support structure during the period of construction. After the long-term tunnel operation, owing to the erosion of groundwater and the changes of internal stress and external load of surrounding rock, the reinforced of primary support system will be rusted; the bolt, grille arch frame and I-beam will be partially invalidated; the stress of tunnel structure system will be readjusted gradually from the original load-bearing state with dominant position of primary support into the load-bearing state by secondary lining. The Long-term safety analysis refers to the analysis of secondary lining internal force and safety coefficient by load structure model, and the long-term safety analysis of Qingshashan tunnel which is in season frozen zone with complex geological conditions is very necessary.

scholarly journals Test on Rigid-flexible Composite Anti-breaking Measure for Tunnels across Stick-slip Fault

2021 ◽  
Author(s):  
Cui Guang-yao ◽  
Song Bohan
Keyword(s):  
Seismic Intensity ◽  
Structural Safety ◽  
Tunnel Structure ◽  
Test Results ◽  
Tunnel Engineering ◽  
Stick Slip ◽  
Breaking Effect ◽  
Secondary Lining ◽  
Dislocation Layer ◽  
Primary Support

Abstract In this paper, based on the F8 stick-slip fault section of Longxi Tunnel in China, the effect of the anti-breaking measure of rigid-flexible composite (reinforcement of the secondary lining & construction of the reducing dislocation layer between the primary support and the secondary lining) is studied by using the method of indoor model test in order to improve the anti-breaking performance of the tunnel across stick-slip fault in the actual tunnel engineering. The test results show that the anti-breaking effect is limited by adopting structural strengthening measures to resist the influence of stick-slip dislocation on the tunnel structure and the anti-breaking effect is obvious by adopting the measures of reducing dislocation layer only. However, the structural safety of the tunnel with stick-slip fault in the strong seismic intensity area can be greatly improved by adopting the anti-breaking measure of rigid-flexible composite, and the structural safety factor can be significantly improved. The research results of this paper can provide a reference for the anti-breaking design of the tunnel across stick-slip fault in the high seismic intensity area.

scholarly journals Study on the Mechanical Behavior of Double Primary Support of Soft Rock Tunnel under High Ground Stresses and Large Deformation

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhe Liu
Keyword(s):  
Mechanical Behavior ◽  
Large Deformation ◽  
Design Method ◽  
Characteristic Curve ◽  
Soft Rock ◽  
Support Design ◽  
Deformation Amount ◽  
Secondary Lining ◽  
Rock Tunnels ◽  
Primary Support

Double primary support structures could effectively solve the problem of large deformation of surrounding rock for soft rock tunnels. However, the mechanical behavior of this new support structure is still incomplete, and the design method should be revised. Based on the theory of energy conversion, this paper analyzes the support characteristic curve of double primary support and puts forward the dynamic design method of double primary support. Considering that the secondary lining can be set after monitoring the deformation amount and deformation rate of the first primary support, its support parameters can be dynamically adjusted according to the actual situation. By applying the double primary support design method in the Maoxian tunnel of Chenglan Railway, the field monitoring results show that the double primary support has a significant effect on the energy release of surrounding rocks, greatly reducing the load acting on the secondary lining and ensuring the safety and reliability of the tunnel structure.

Mutual influence of long-span urban highway tunnel and rail transit construction

2021 ◽  
pp. 1-15
Author(s):  
Honglin Yu ◽  
Shiyang Liu ◽  
Chun Zheng ◽  
Yun Li ◽  
Jie Liu
Keyword(s):  
Mutual Influence ◽  
Vertical Displacement ◽  
Relative Displacement ◽  
Urban Rail Transit ◽  
Rail Transit ◽  
Railway Line ◽  
Long Span ◽  
Highway Tunnel ◽  
Urban Rail ◽  
Secondary Lining

In order to analyze the mutual influence between the long-span highway tunnel and urban rail transit tunnel that is constructed at proximity, this paper established 3D finite element models based on Chongqing Zengjiayan Tunnel and the Metro Railway Line 9 and Line 10 projects to calculate and analyze the secondary lining stress, distribution and change law of deformation of Zengjiayan Tunnel and the Metro Railway Line Tunnel. The results show that: (1) The main risk of the Zengjiayan Tunnel is that the tunnel body might displace in the excavation and the surrounding rock stress could possibly change. The forces undertaken by the main structure of the cross-section are calculated and analyzed based on the shallow buried tunnel. Accordingly, the horizontal and vertical displacement limit and relative displacement meet the relevant specification; (2) Zengjiayan Tunnel over the lobby of Liyuchi Station, a transitional station of Line 9 and Line 10. The main risk is the displacement of the transitional channel in the excavation and changes in the stress on surrounding rocks, but the risk of self-structure excavation and support is under control.

Mechanics Analysis of Grade V Surrounding Rock Primary Support in Maanziliang Tunnel

2012 ◽  
Vol 164 ◽  
pp. 414-417
Author(s):  
Jia Ming Han
Keyword(s):  
Finite Element ◽  
Safety Factor ◽  
Surrounding Rock ◽  
Qinling Mountains ◽  
The Finite Element Method ◽  
Highway Tunnel ◽  
Geological Conditions ◽  
The Stability ◽  
Primary Support ◽  
Rock Section

Commonly used finite element strength reduction to calculate the safety factor of slope，to analyze the stability of the slope[1～3]. Recently it also proposed the methods to evaluate the safety factor for the stability of surrounding rock of underground chambers and supporting structural mechanics[4～6]. For Qinling Mountains of the complex geological conditions in the Maanziliang highway tunnel, this article use the finite element method from the bolt resist tension, bolt length, the force of sprayed layer of concrete to computing gradeⅤsurrounding rock section of primary support safety factor, to give evaluation to support mechanics of the Maanziliang tunnel.

The Bench Method Numerical Simulation of Soft Rock Tunnel

2013 ◽  
Vol 438-439 ◽  
pp. 949-953
Author(s):  
Hao Bo Fan ◽  
Jin Xing Lai ◽  
Dan Dan Hou
Keyword(s):  
Numerical Simulation ◽  
Measurement Data ◽  
Soft Rock ◽  
Simulation Method ◽  
Internal Force ◽  
Surrounding Rock ◽  
Supporting Structure ◽  
Highway Tunnel ◽  
Tunnel Design ◽  
Rock Tunnel

This paper based on Chaoyang tunnel by bench method excavation, using the finite element numerical simulation method, simulates the surrounding rock displacement of soft rock tunnel and the stress characteristics of supporting structure to get the various stages of tunnel surrounding rock stress, strain and the internal force changes of tunnel supporting structure. After the analyses of the numerical simulation results and field monitoring measurement data, the safety and rationality of the method are determined. The research provides certain reference for highway tunnel design and construction.

Energy-Saving and Economic Study of Natural Ventilation in City Tunnel

2012 ◽  
Vol 178-181 ◽  
pp. 92-97 ◽  
Author(s):  
Jin Feng Mao ◽  
Yu Liang Huang ◽  
Jun Zhou ◽  
Zhe Li Xing
Keyword(s):  
Energy Consumption ◽  
Energy Saving ◽  
Natural Ventilation ◽  
Economic Study ◽  
Equipment Investment ◽  
Longitudinal Ventilation ◽  
Highway Tunnel ◽  
Tunnel Design ◽  
Total Investment ◽  
Reduce Energy Consumption

City highway tunnel ventilation design is one of the key processes in whole tunnel design. The ventilation design has important influence in ventilation sanitation effect, equipment investment, operations energy consumption and operations cost. On the premise of safety and sanitation, if city tunnel adopts natural ventilation, this can reduce energy consumption, construction cost and operations cost. Combining practical conditions of a project, this paper evaluated three kinds of mechanical ventilation, and analyzed contrastively economic efficiency of the natural ventilation and the jet longitudinal ventilation. At last drew the conclusion that the natural ventilation can reduce the total investment by 30% and has obvious energy-saving efficiency, then put forward the pertinent suggestions to the ventilation construction of highway tunnel.

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