Study On Surface Subsidence Law Of Asymmetric Three-Cabin Pipe Gallery Underground Excavation Construction

The urban underground comprehensive pipe gallery project is one of the popular infrastructure projects in large cities.Its construction purpose is to standardize and clean up the city's ground,improve the city's image,and improve the efficiency of city's operation.Reviewing the literature,it is found that there is little research and analysis about the asymmetric three-cabin underground pipe gallery which has a special crosssectional form.Based on the project of Underground Pipe Gallery of Beijing New Airport Expressway,this paper analyzes the Surface Subsidence laws of the asymmetric three-cabin pipe gallery during the excavation process by using empirical formula calculation,numerical simulation models and comparison of monitoring data.The main research works are as follows :(1)For the special section form of the three-cabin pipe gallery,superimposing the Peck formula of the surface settlement caused by each pipe gallery to attain the total surface settlement Peck formula of the pipe galleries.Then use the data from site to carry out the linear regression fitting and correction of the Peck formula to obtain the Peck formula that can be estimated under the similar geological conditions.(2)Establishing a three-dimensional numerical model and comparing the monitoring results to verify the reliability of the model.There are four stages for analysis of the ground settlement law during the excavation of the pipe gallery.Then we found that the settlement of the upper step was greater than that of the down step.In addition,the settlement of the middle tunnel excavation is greater than that of the side tunnel excavation.The ground settlement of the asymmetric pipe gallery also shows asymmetricity.The larger the excavation cross section is,the larger the surface settlement will be.The ground settlement caused by stratum strength,grouting reinforcement area strength and lining strength were studied by using different parameters.It found that the surface settlement was approximately inversely proportional to the size of the three.(3)The pipeline gallery construction scheme was optimized by studying the aspects of construction sequence and construction spacing.We found that the offset distance of the mid-side hole is inversely proportional to the surface settlement,and it of the excavation of the mid-side hole has little effect on the surface settlement.The maximum ground settlement and settlement range of the side cave first is smaller than that of the left cave,and the maximum settlement and settlement range of the left cave first surface is less than that of the middle cave.The later excavated pipe gallery will enhance the stress of the supporting structure of the former one.The first supporting structure of the middle cave bears the largest bending moment,the first supporting structure of the left cave bears the second largest bending moment,and the first supporting structure of the side cave bears the largest bending moment.