Research On Pavement Settlement Caused By Shield Tunnel Passing Through Existing Urban Road

With the rapid development of economy and society,the problem of urban traffic congestion is becoming more and more serious,and the construction of shield tunnels has become an important part of urban construction.Due to the limited space,it is inevitable that the existing road will be penetrated underground during construction.When the soil settlement caused by excavation is too large,the pavement will crack,collapse or bulge and damage by grouting,affecting the safe use of the road.In this thesis,FLAC3 D finite different software is used to establish a simulation model for tunnel construction.Given at the construction process of the Jinxi Tunnel under the Taiyuan Southwest Ring Road passing through an existing road in a city,the excavation steps and supporting methods are established in conjunction with the actual situation of the project.The influence of different factors on the pavement settlement caused by excavation was discussed,and the correctness of the model was verified by comparing the measured settlement and the simulated value.The applicability of the Peck formula to the prediction of pavement settlement was further analyzed.The main conclusions are as follows:(1)Settlement curve of the three-section is groove-shaped and has a high degree of coincidence with the normal distribution curve.The settlement at the bottom of the groove,above the vault is the largest.The road surface settlement showed a gradual increase trend,but the difference was less than 5mm,which meet the requirements of the road surface design code;(2)The influence of soil conditions on the road surface settlement is unobvious.Only if the proportion of silty clay is too large,the settlement of road surface will show a slight increase trend;(3)The excavation footage and excavation diameter and Pavement stiffness have little effect on the settlement groove width,but have a greater impact on the road surface settlement.2m is the most reasonable.The larger the excavation diameter,the greater the pavement settlement.The greater the stiffness,the smaller the difference in settlement at each point;(4)Traffic load has an effect on the settlement groove width and road settlement.With the increase of the load,the settlement groove width and the pavement settlement show a significant increase trend;(5)Based on the Peck empirical formula,it is obtained that the formula is still applicable when the shield tunnel with a diameter of 12.14 m is under construction: the key parameter in the formula is the width K of the settlement channel,it is between 0.2 and 0.52,The formation loss rate is between 0.1 and0.24,and the maximum control standard for pavement settlement is-35.1mm.