Study On The Law Of Ground Surface Settlement Of Earth Pressure Balance Shield Construction In Weak Geology

Shield construction has become the main means of urban subway construction, in which the earth pressure balance (EPB) shield is the common construction method in the current weak geology. The ground surface settlement of earth pressure balance shield will seriously affect and even endanger the personal safety of people,the urban traffic and underground pipeline use, therefore, during the research of the ground surface settlement, so as to better control of ground surface settlement is an important research direction of metro construction.In this paper, the current research status and results of surface settlement caused by earth pressure balance shield construction are summarized. This paper expounds the working principle applicable scope, the development process and the mechanism of deformation of EPB shield caused by soil surface settlement.Combined with Foshan Rail Transit Line No.2 bay landing interval project, according to the peck formula fitting horizontal surface settlement curve, determine that the reasonable value range of the width coefficient K of the horizontal ground surface settlement curve in the interval shield construction is 0.4-0.6.And the influence of the jacking force, the thickness of the covering soil and the grouting on the shield construction is also determined. According to the results of the prediction, monitoring and measuring points are arranged.Finite element numerical simulation is used to simulate the process of shield tunneling, analysis of ground surface settlement during shield tunneling, and the data were compared with the monitoring data and Peck theory, focuses on the analysis of the settlement of shield tunneling in the first 30 meters, longitudinal surface settlement with time variation, the center line of the tunnel cross section settlement changes and effects on surface settlement of shield parameters. The results show:The lateral surface settlement is in accordance with the Peck settlement curve, the maximum longitudinal section of the longitudinal section occurs at the position of about 5 rings from the front of the excavation face. In the end, the settlement of the 10 rings of the excavation face tends to be stable. But the settlement is smaller than the measured value. According to the analysis results, in the soft geology, we should use the control of the jacking force, the timely grouting and other measures to reduce or control the surface subsidence in the construction process of the shield. To differentiate between primary and secondary monitoring area, by strengthening special sections encryption monitoring point arrangement and monitoring frequency to timely observation.