| With the growing needs of people's life and the current social imbalance,urban traffic congestion is a pressing problem,and the construction of subway leading to the airport is imminent.However,the speed and construction period of the metro line have certain criteria for the selection of shield machine.To meet the needs of the rapid subway line,the construction of large-diameter shield machine has become the main method of modern subway construction.Shield method is widely used because of its rapid construction speed and small impact on ground traffic and buildings.However,due to the limitation of geological conditions and construction technology,the influence on the surface subsidence is unavoidable.How to control the settlement of the construction process of the mudstone formation by the large diameter shield machine is an important problem facing the shield construction.Taking the Airport South Station Tianfu International Airport of Chengdu metro line 18 as the engineering background,according to the engineering geological conditions of the mudstone strata in Chengdu,a 8.65-meter large-diameter earth pressure shield shield machine was used to excavate the tunnel and collect the tunneling parameters and monitoring data.To study the effect of changes in the construction parameters of large shields on the surface settlement in mudstone formations.Mainly through the following aspects of analysis:(1)To investigate and study the special geological conditions of the Chengdu Metro Line 18,the main geological conditions for the selected line are moderately weathered mudstone and a few sandstone formations,and both hybrid formations.(2)Based on the construction of the large-diameter shield machine used,the theoretical data and basic construction techniques of the shield were calculated based on data from other researchers.The basic parameters of the large shield excavation and the basic elements of surface settlement control are selected by the analysis of the first 100 rings of large shield excavation.(4)Analyze the data actually monitored at the site,draw and analyze the actual curve of surface settlement,and obtain the cause and mechanism of surface settlement during construction along the large shield.According to the 100-ring large shield excavation parameters,35 data were randomly selected in the geologically uniform section,and the correlation degree between the large shield excavation parameters and the ground settlement was determined by using the grey correlation analysis to analyze the different construction parameters(The effect of thrust,speed,torque,grouting volume,grouting pressure,and earth pressure on surface settlement.At the same time,combining the curve of each construction parameter during the construction process of the shield with the cumulative settlement curve of the actual monitoring,the parameters of the excavation of the large shield construction in the shale formation are optimized to provide a certain reference value for the follow-up project.(4)Using the Midas finite element software to perform dynamic numerical calculations on the construction process of the shield tunnelling project,and comparing the calculation results of the settlement curve with the actual settlement curves monitored,the results show that the finite element software can be used to simulate the actual settlement.As a result,when the modelling is in line with the actual situation of the project,it is more concise and accurate.The variation trend is similar to the actual result.It provides dynamic simulation for the later excavation construction,predicts the construction monitoring of the shield in advance,and controls the surface settlement. |
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