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- 저자 : Xiedong Zhang (검색결과 3 건)
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Yingqi Liu,Xiedong Zhang,Jiali Li,Zhihua Zhang,Hang Zhang 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1
Tunnels excavated through weak rock masses using the Shallow Tunneling Method (STM) call for rigid lining support to withstand and constrain the mobility of the unstable rock where its performance needs to be assessed with field measured data in case of potential failure. For fear of any further hazards after the occurrence of a rock fall at chainage km 86,685 m in the Longsheng Tunnels, the monitoring plan was specially modified to accurately obtain the relative vertical and horizontal displacements of the steel rib component in the arch-shaped composite rigid primary lining that was simply placed on the heading. In this paper, the weak rock masses’ interaction with the rigid lining is treated as unknown distributed loads divided into radial and tangential directions, where the influence line theory is applied to better understand the response of the lining so as to facilitate a displacement-based back analysis for unknown rock mass loads and the resultant stress outcome. By comparing the back analyzed stress outcome with the measured one, the proposed performance assessing method for the unclosed arch-shaped lining was proven to be time efficient with acceptable accuracy, which is of considerable application potential and can provide a reference for similar engineering.
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3D Discrete Element Method Modelling of Tunnel Construction Impact on an Adjacent Tunnel
Lin Wu,Xiedong Zhang,Zhihua Zhang,Weichen Sun 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.2
Closely-spaced side-by-side mechanized twin tunnels are commonly used in urban metro transit systems. The aim of this paper was to investigate the influence of tunnel construction on an adjacent existing tunnel using the 3D discrete element method (DEM) and propose a new method to protect the existing tunnel. The first tunnel at the left side was initially included in the DEM model. The construction of the second adjacent tunnel at the right side was then modelled in phases. Displacement, stress variation, porosity variation, and coordination of surroundings of the first tunnel were investigated. The results showed that the excavation of the second tunnel had a great negative impact on the existing tunnel surroundings when the distance of twin tunnels was less than the diameter of the tunnel. The maximum horizontal displacement occurred at the angle of 45° and was equal to 103 mm. The influenced area of the existing tunnel is the surroundings between the tunnel crown and the spring line on the second tunnel side near the tunnel lining. The composite reinforcement method consists of pasted fiber reinforced plastic (FRP) sheet method and grouting in a specific area; thus, the structure safety and the normal operation of the existing tunnel nearby can be guaranteed. The protective method can give reference for similar project.
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Mohammad Daddow,Xiedong Zhang,Hongsheng Qiu,Zhihua Zhang 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.6
This paper presents an optimization model for the problem of optimal scheduling of tamping actions on ballasted tracks. The model extends an existing one in the literature by including the unused life costs for track sections in the objective function and introducing available workforce constraints in the model. The aim is to obtain an optimal schedule for tamping actions minimizing the total cost in a finite time horizon using global optimization. The results of numerical study show that consideration of track layout in the problem leads to a significant increase in the total number of tamping actions and the amount of unused life for track sections. It is also found that it is important to use a big value for available workforce in the problem in order to reduce the total cost. The proposed model presents a more realistic solution for the studied problem than the existing work in the literature.
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