The Research On The Transition Behaviors Of Mechanics During The Center Drift Method In Subway Station Construction

It is convenient to build the under-cut subway station by center drift method(CDM), which flexibly apply to varied soil condition and use for different forms of section and span. In recent years, the subway stations excavated by CDM are in the majority. This thesis is based on Xueyuanlu station of the 10th line in Beijing Metro. With the measures of the finite-difference numerical analysis and the site monitoring, the transition behaviors of mechanics during subway station excavated by CDM are synthetically studied, the main idears of this thesis are conducted as follows.(i) The rules of strucure distortion and stratum settlement during the excavation of the pilot tunnel. It is found that the settlement is related to the shape of pilot tunnel,the speed of excavation and the time of closure. Then, some measures of controlling settlement are taken by analyzing the proportion of settlement caused by each pilot tunnel excavation.(ii) The rules of adjustment of the bearing of initial support and the stress of ground rock. There is obvious transformation of ground stress during the pilot tunnel excavation, it indicate that the subsequent excavations alter the bearing of initial supports jetted anterior.(iii) The optimization studies of the backout of temporary supports (BOTS). Base on the theoretical calculation and the convenience of construction, finally, it consider that the lesser alteration of settlement, ground rock stess and the bearing of initial support will be the fine.(iv) The rules of structure distortion and stratum settlement caused by BOTS. Based on the theoretical calculation and the site monitoring, it conclude that the settlement during the first phase of BOTS account for nearly half of the whole settlement.(v) The rules of adjustment of the initial supports bearing and the ground rock pressure during the the BOTS. Based on the theoretical calculation and the site monitoring, it conclude that the alteration of initial sopports bearing is remarkble, and find that the differentiation between the academic and the practical, caused by the complexity of underground condition, is evident.