Study On Mechanical Character And Structure Design Method Of Assembled Wind-proof Open-cut Tunnel For High-speed Railway In Gobi Windy Area

As the main wind-resistant structure of the high-speed railway in the Gobi gale area,the wind-resistant open-cut tunnel was used for the first time at 30 km wind area and100 km wind area along the second Lan-Xin railway.The wind-resistant open-cut tunnel is mainly subjected to wind load in the windy area,which is different from the load of traditional open-cut tunnel.At present,theoretical studies on wind-resistant open-cut tunnel structure system,calculation method of wind load and structural design are very lacking.Therefore,research on these key technologies in the Gobi gale area has a great practical significance for supporting the construction of the second Lan-Xin railway in the Gobi Desert.Based on the second Lan-Xin high-speed railway project,this paper uses data investigation,theoretical derivation,numerical simulation,indoor test and field test to systematically study on wind-resistant open-cut tunnel structure system,calculation method of wind load and structural design of wind-resistant open-cut tunnel in the Gobi windy area,and has achieved the following results:(1)Based on the natural environmental conditions such as drought and less rain,the study makes clear that the segment prefabricated arch structure is used for the wind-resistant open-cut tunnel in the Gobi gale area.Based on the stress characteristics of this kind of tunnel,the convenience of construction and the transportation conditions,the mode of circumferential segment and longitudinal length of the precast structure are determined.By studying the characteristics of contact net force,sand-proof and lighting requirements during the service stage,the size and the opening method of wind-resistant open-cut tunnel are determined.The structure system of wind-resistant open-cut tunnel in the Gobi gale area is constructed.(2)The load composition of the wind-resistant open-cut tunnel in embankment type,the cutting type and the general type in the Gobi gale area is studied.Base on the indoor wind tunnel experiment and the numerical simulation,the wind load distribution characteristics and variation law of the wind-resistant open-cut tunnel in the Gobi gale area are clarified.A correction calculation method of wind load is proposed and the wind load calculation method for wind-resistant open-cut tunnel in Gobi windy area is established.Compared with the field test,the correctness of this method is verified.(3)Based on the results of indoor test for tensile resistance,compressive resistance,shearing resistance,bending resistance,the mechanical properties of different arch joint and wall bottom joint are proved.The mechanical model of rigid joint is established,and the failure mode and criterion of joint are put forward.(4)The method for calculating the stiffness of rigid joint for the assembled wind-resistant open-cut tunnel in the Gobi windy area is established.The main load of wind-resistant open-cut tunnel is calculated by using the correction calculation method of wind pressure,so as to create a structure calculation model and provide a structural safety assessment method.The stiffness varies according to the different joint connection method,so the calculation model for each situation is established and compared with the field test,which verified the correctness of the calculation models.The structure design method for the assembled wind-resistant open-cut tunnel in the Gobi gale area is established.