Analysis On The Characteristics Of Longitudinal Stress Of Primary Support In Tunnel Construction Of Mining Method

In the large-scale tunnel construction in our country,the design and construction of the weak surrounding rock tunnel have been puzzling the tunnel builders all the time.At the beginning of a tunnel as the main bearing structure,the domestic and foreign research on tunnel construction problems are concentrated in the tunnel junction and lateral support for supporting and count two lining of tunnel inspection is only confined to the tunnel horizontal and ring structure,and for the security support structure of a vertical support tunnel rarely consider and check the implementation of the project,often due to the longitudinal force caused the initial support safety hazards caused by circumferential crack.In this paper,three-dimensional numerical simulation of construction process for ANSYS shotcrete longitudinal safety,through the simulation and comparison of the different rock mass,different sections,different support time,different length of the step of various working conditions,and analysis the settlement regularity of longitudinal stress,and the reinforcement according to the "standard" railway tunnel reinforcement provisions conclusions are drawn as follows:The simulation results are analyzed by longitudinal force,and the reinforcement is found:(1)the longitudinal force and the circumferential settlement of the third grade surrounding rock are smaller,so the longitudinal safety of the structure is not considered;(2)the longitudinal stress of the initial arch and the arch at the fourth and fifth grade surrounding rock is larger,and the reinforcement is needed;(3)the compressive stress of the initial branch increases with the increase of the hoop to the convergent deformation;(4)it is very important to start an extra machine at the beginning of the time,and there is a great difference in longitudinal stress between the different support time;(5)under the same buried depth,the longitudinal force between the double line and the single track is the same magnitude;in shallow ground,the stress of the vault and arch bottom of the long step method is several times of that of the short step method;in the deep buried case,the opposite is the opposite;Since the initial section is a thin shell structure,the effect of shear stress on the structure is more unfavorable,so the longitudinal stress and shear stress are not considered in the stress analysis and reinforcement.