Mechanical Properties And Reliability Analysis Of Concrete-filled Steel Tube Support Structure Expansive Soil Tunnel Under Wetting-drying Circulation

With the rapid development of the tunnel construction scale and speed,the tunnel is inevitable to pass through the complicated condition stratum during the construction of the tunnel,such as expansive soil.Due to the fact that the traditional support methods can not meet the practical needs,the safety and stability of the tunnel are prominent.And the new expansive soil tunnel surrounding rock supporting technology needs to be studied urgently.Concrete-filled steel tube arch because of its good mechanical properties has been applied in underground engineering such as mine,etc.And the effect of controlling deformation has been remarkable.However,the research on the concrete-filled steel tube supporting technology of expansive soil tunnel is still in its infancy.In this context,the following research work has been carried out,and some useful conclusions have been obtained.Firstly,the destruction mechanism of the expansive soil tunnel and the theoretical analysis of the concrete-filled steel tube supporting technology are studied in this paper.Based on the engineering background of a tunnel in Guangxi Gui Gui railway,the model test of the expansive soil tunnel under the condition of wetting-drying circulation is carried out.Displacement and stress evolution law of the surrounding rock in the excavation process,rainfall and wetting-drying circulation are analyzed.It provides the basis for the design and construction safety of the expansive soil tunnel.Concrete-filled steel tube support structures are subjected to stress and influence factors,which cannot be fully analyzed by theoretical research and model tests.Based on the large finite element analysis software of ABAQUS,studied the different cross section forms of mechanical properties of concrete-filled steel tube support structure,and compared with the traditional support structures.Then expounds the concrete-filled steel tube support effect.Studies have shown that compared with traditional I-beam arch supporting structure,concrete-filled steel tube support structure has strong carrying capacity and good supporting effect.The results can provide reference for the design of tunnel support.In addition,the reliability calculation method based on continuous medium is adopted in this paper.The thickness of the steel tube wall and the expansion angle of the concrete-filled steel tube support structure are taken as random variables.Firstly,using ABAQUS to obtain a series stress value of the supporting structure on a random variable,and to fit a single change function.After that combine all the random variables.Accordingly,the expression of the stress value of the supporting structure on random variables is obtained.The reliability of the bearing capacity of concrete-filled steel tube support structure is evaluated,and the corresponding reliability index is calculated.