| Loess is special in struction and engineering,there are no perfect secondary support design method for loess tunnel.Since Zhengzhou-Xi'an passenger dedicated railway line has been constructed,the design method for large cross-section tunnel must be settled as early as possible.The thesis is combined tightly with loess tunnel of Zhengzhou-Xi'an passenger dedicated railway line,for the object of perfecting design method, this paper research a preferable design method of large cross-section loess tunnel through the field measurement,in-site survey,theory analysis,numercial sumulation.This paper mainly consists of three parts: which are definition of tunnel depth; calculating surrounding rock pressure ; surrounding rock pressure distributing ; "load-structure"FEM calculating; secondary support construct time.For the definition of tunnel depth, base on the earth 's surface crack survey of loess tunnel,dudecing the cracking angel and analysing the destroy pattern, combining with the theory destroy pattern of Xie jiaxiu and K.Terzaghi the divisional depth has been done;Camparing the theory calculated result with the surrounding rock pressure that is in-site measurement,the theory calculated formulas have been maked sure; the paper make a statistical analysis of the surrounding rock pressure that is in-site measurement with the vertical and horizontal acpect,analysing the sacle of resistance force of surrounding rock,the active surrounding rock pressure distributing has been confirmed;The resistance coefficient has bend confirmed through in-site test, base on the four sorts surrounding rock pressure distributing,taking the "load-structure"FEM calculate the the secondary support, The paper gives the two sorts surrounding rock pressure distributing by the safety principle;At last ,the secondary support construct space distance has been done by analysing the measure data of arch crown settlement and level constringency of primary support. |
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