| China's development is inseparable from infrastructure construction,traffic engineering construction is an important part of infrastructure construction,tunnels play an important role in the transportation field,and the environment is harsh,the probability of accidents during the construction process is high,and it has become the transportation field One of the most concerned focal points in China.During tunnel construction,there are often appear constructions such as up-crossing,down-passing,and overlapping with existing tunnels.However,less research has been done on the construction of a new tunnel between two existing tunnels in the loess area,especially When the two existing tunnels on both sides and the new tunnel on the center line each have a certain angle,the research is less,so it is necessary to carry out research on this.The main purpose of this article is to use numerical simulation software to study the performance of new tunnels in various aspects when a new tunnel is established between two existing tunnels under specific conditions,and to summarize the changes in the new tunnels in all aspects.More importantly,To study the horizontal displacements,vertical displacements,and maximum principal stresses and minimum principal stresses of each key point of the two existing tunnels during the excavation of a new tunnel under different conditions,and compare the displacement and stress conditions of the existing tunnels under each condition,then the most reasonable parameters are selected for construction.The main analysis contents are as follows:(1)Investigate the topographic changes of the tunnel site and the engineering characteristics of the loess,fully understand the physical and mechanical parameters of the loess,and provide sufficient conditions for subsequent modeling analysis.(2)During the construction process,the loess is prone to collapse accidents along the joint surface,and the tunnel needs to be reinforced in advance.The reinforcement effect is mainly achieved through large pipe sheds and small ducts.The issues that need to be considered when constructing large pipe sheds and small pipes are: selection of material diameter,determination of drilling diameter and drilling angle,slurry ratio and grouting precautions.(3)Take the step excavation as an example,analyze the change of the maximum unbalanced force and the distribution of the plastic area during the excavation of the new tunnel.At the same time,summarize the settlement of the stratum and the initial lining vault,and the deformation of the step and the palm surface.(4)Simulate the displacement of the two existing lines during the excavation of the new tunnel on the center line,and determine the most dangerous line and the dangerous section of the line.(5)A variety of project status are combined for the new tunnel with different excavation methods,different excavation feet and different strengths of the initial lining concrete,the single factor method is used to compare and analyze the stress and displacement performance of the dangerous section under these project status to determine the most suitable project status and parameters.The research results of this paper not only guide the project,but also provide reference for the project under similar conditions in the loess area. |
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