Research On The Deformation Law And Blasting Stability Of Excavation Of Synchronous Construction Transfer Metro Station In Soil-rock Combination Strata

In recent years,the development of urban rail transit in China has changed with each passing day.As of December 2021,the number of cities with rail transit in Chinese mainland has reached 50,with a total operation mileage of about 8939 km.During the14 th Five-Year Plan period,with the further improvement of rail transit network in major cities in China,the construction scale of transfer stations will gradually expand,more and more transfer station excavations will be built under complicated geological conditions,and the safety issue of their construction will become increasingly prominent.As far as excavation engineering is concerned,it is of great significance to research the deformation law and stability after excavation for the safety of construction.Therefore,based on the excavation of synchronous construction transfer metro station in soil-rock combination strata of Shenzhen as the background,this thesis researched the deformation law and blasting stability of excavation of synchronous construction transfer metro station in soilrock combination strata by monitoring and numerical analysis.The main works are as follows:(1)Based on the analysis of monitoring data during the construction of antecedent excavation of Shenzhen metro Liutang station,the time-space laws of horizontal displacement and settlement of pile top,horizontal displacement of pile shaft and ground surface settlement caused by excavation were obtained.(2)Relying on the excavation engineering of Shenzhen metro Liutang station,a three-dimensional numerical model of the excavation of synchronous construction transfer metro station in soil-rock combination strata was established by using the finite element numerical simulation software Midas GTS.At the same time,the reliability of the numerical model was verified by comparing with the monitoring data.According to the results of the numerical simulation,this thesis analyzed the time-space laws of deformation of diaphragm wall,ground surface settlement,bottom upheaval and deformation of uprightly post caused by excavation,especially by subsequently excavation.(3)Based on the time-space law of the deformation of excavation of synchronous construction transfer metro station in soil-rock combination strata,using the principle of single variable,through the numerical simulation to explore the effects of thickness of covering soil,depth of transfer node and excavation scheme,and obtained the optimal excavation scheme.(4)The numerical simulation was used to analyze the vibration characteristics of the retaining and protection structure of antecedent excavation under different blasting cutting forms and different blasting delay time,and the blasting cutting form that had the least effect on the stability of the retaining and protection structure of antecedent excavation and the delay time that met the requirement of blasting stability control were obtained.The results showed that: the deformation of excavation increased with the increase of excavation depth,but its growth rate decreased significantly when the excavation reached the rock stratum;after excavation,the deformation at the transfer node was the largest,the transfer node was the most dangerous part of the excavation;the thickness of covering soil and excavation scheme had a great effect on the deformation of excavation;in the range of rock strata,the depth of transfer node mainly affected the horizontal displacement of the lower part of the common retaining and protection structure;blasting by the cutting form of C was the most beneficial to the stability of the retaining and protection structure of antecedent excavation,and 110 ms delay blasting could ensure the stability and safety of the retaining and protection structure of antecedent excavation under blasting vibration.