Study On Dynamic Response And Long-term Settlement Of Curved Tunnel Under Vibrati On Load Of Train In Silty Strata

The long-term cumulative settlement of the subway shield tunnel will affect the normal operation and structural safety of the subway.Among them,the vibration load generated during the train operation has a great influence on the settlement.Therefore,it is of great theoretical and practical significance to study the dynamic response and long-term settlement of the tunnel structure and surrounding soil under the vibration load of the train.In this paper,the first phase of the Zhengzhou Metro Line 1 project is used as the research background.The field response,numerical simulation,and theoretical calculation are used to study the dynamic response and long-term accumulation of the vibration load of the train in the silty formation to the curved tunnel structure and surrounding soil.The effect of settlement.The specific research contents are as follows:(1)Through post-construction on-site monitoring of the curved shield tunnel under the vibration load of the train in the silty soil layer,the cumulative settlement values of the straight section and the curved section shield tunnel are compared,indicating that the settlement of the curved section has increased on average compared with the straight section 30%,and the shortterm settlement value of the tunnel is far less than the long-term cumulative settlement value;the maximum change in horizontal displacement of the track bed is 1.95mm;the maximum change in the convergence displacement of the segment is 2.6mm,both of which meet the deformation requirements of the code,and the cumulative settlement value on site is considered to be monitored on site It is the sum of two factors: train vibration load and postconsolidation.(2)A method for applying the vibration load of the train in a curved tunnel is proposed.The dynamic response of the tunnel with different radius of curvature and the surrounding soil layer are analyzed and compared.The numerical simulation and theoretical calculation values are compared with the on-site monitoring results to verify the reliability of the numerical model.Sex.The results show that the dynamic response and long-term cumulative settlement value of the soil around the curved tunnel decrease with the increase of the distance from the tunnel axis and the turning radius.The main influence range of the dynamic response is at 0-15 m at the bottom of the tunnel.When the turning radius of the tunnel is increased to a straight line,the maximum decreases are 84.6% and 44.2% respectively;the maximum value of the liquefaction coefficient ζ of the underlying soil layer under the tunnel is less than 1,indicating that the curved tunnel is not prone to liquefaction under the vibration load of the train,and The liquefaction of soil layer decreases with increasing depth;(3)By changing the thickness of the tunnel segments,the super elevation form of the track,and the running speed of the train,the dynamic response and long-term settlement of the tunnel structure and surrounding soil layer under combined conditions are studied.The study found that monitoring points with the same position characteristics have similar response characteristics;the dynamic response of the tunnel structure mainly has two response frequencies(high frequency and low frequency).In actual engineering,appropriate measures should be taken according to the actual response frequency of the tunnel structure to avoid two The frequency is similar or the same between the two,causing resonance;the vehicle speed is 80km/h,the lining thickness is 300 mm,and the super elevation is changed from external to internal descending.The dynamic response of the soil at the bottom of the tunnel is reduced by 54.5%;compared with the train The calculated long-term settlement values of the tunnel at running speeds of 40km/h,60km/h,and 80km/h are reduced by an average of 27.0% and 13.7%.It is recommended that the speed of the train should be maintained at 60~80km/h when passing through the curved tunnel.