Numerical Simulation Of Mutual Influence Between Up-crossing Underground Street Construction And Existing Metro Tunnel

With the rapid and diversified development of urban underground engineering，It’s inevitable that the new building structures will cross the existing structures andmake effect on the old structures,such as changing the deformation or internal force.From the present research, we can find that the most common situation ofapproaching construction is that when the existing structures are metro tunnels. So inorder to ensure the safe operation of the subway, it’s very important to control thedeformation and force of the existing tunnels during construction. And when theimpact of tunnel is out of control, how to take measures to reinforce existingstructures economically and effectively is very urgent, and it has become a hot topicin this area.This paper is based on the approaching construction that a undergroundcommercial street up-cross the existing metro tunnel in Harbin. The geotechnicalspecial software MIDAS/GTS has been used to make a numerically simulated for theproject,and some related mechanical models have been established. The main contentsand achievements of the article are as follows:(1) According to the project specific conditions, The vertical distance betweenthe old and the new structure is mutative. In order to research the impact on the oldstructures with different vertical spacing, different models that the vertical distanceare respectively0.5m,2.5m,5.0m,7.5m have been established. The results show thatwith the increase of distance between new and old structure, the deformation of theold structure decreases，and the mainly deformation of the existing tunnels occurs inthe vertical direction.(2) Two different building programs of the new commercial street are taken inthe paper. The first program is that two rows of the street’s columns happen to pressthe tunnels vault, and the other one is that there are no columns pressing the tunnels,but just located near the waist of the tunnels. Juxtaposing the deformation and forceoccurred in the tunnels, the paper get a better building program for the newcommercial street.(3) In order to explore some other measures to reduce the impact on the existingtunnels, during approaching construction, we change some related parameters to getthe effective reinforcement measures. By respectively changing the soil’s elasticitymodulus that surround the existing tunnels and the elasticity modulus of the soilsandwiched between the old and new structures. And get the conclusion that whenchanging soil’s elasticity modulus that surround the existing tunnels, the existingtunnel’s deformation significantly reduce, on the other hand, when changing the elasticity modulus of the soil sandwiched between the old and new structures, existingtunnel structure deformation occurs only a little bit of change.(4) Through comparative analysis the deformation and force of the newstructure in the two different situation whether the subway tunnel under the newcommercial street is presence or absence, we can find that the old existing tunnels canalso produce some ignored impact to the new structures.The proximity phenomenon researched in this paper is very common in theunderground engineering. The conclusions can not only provides technical support forthe construction researched in this paper but also provide reference for future similarprojects.