Dynamic Response Of Underground Tunnel Under Plane Charge Explosion

As the military capabilities of various countries continue to increase,the surface-to-air missile system has gradually become an important deployment of the modern strategic system by virtue of its combat mobility,precision strikes and powerful lethality.In military warfare,the impact of explosive waves caused by missile attacks is the main factor that causes damage to the structure.In reality,large-scale missile tests not only have huge security risks,but also have high cost and it is difficult to conduct actual drills.Therefore,the research on the anti-blast protection of the structure is worthy of further discussion.In this paper,the finite element analysis software ANSYS/LS-DYNA is used to model and analyze the underground tunnel under the action of explosion,to study and analyze the structural damage under different working conditions,and to study the impact of different covering soil thickness and different cavity size on the explosion stress wave The influence of propagation,analysis of the effect of the stress wave generated by blasting under different charges on the rock mass and the damage law;the establishment of three different working conditions of numerical models to study the impact of the height,span and thickness of the underground tunnel lining structure on the explosion stress For the influence of waves,corresponding treatment methods are proposed for the damage patterns.What I obtained are as follows:(1)The formation and propagation law of explosion stress wave in free field,i.e.in air are analyzed theoretically.The simplification of peak overpressure of explosion shock wave is theoretically described.Based on the damage characteristics of shock wave on building structure,the specific anti explosion protection measures are summarized.(2)Based on ANSYS/LS-DYNA,the numerical simulation of plane charge explosion free field impact test is established to study the rationality of plane charge explosion with covering soil thickness of 1 m,1.5 m and prototype cavity.The simulation results show that the change of pressure amplitude of cavity charge is caused by multiple oscillation reflection of air wave after cavity blasting,and the flatness of blasting pressure waveform of cavity charge is good,which indicates the plane of cavity The charge can form a plane pressure wave with long duration.The results show that the planeness of explosion wave under multi-layer charge is better than that of single-layer charge,and the effect of continuous explosion on underground tunnel structure is better than that of single-layer charge.It is proved that plane charge is effective and reliable to simulate long-lasting explosion effect.(3)This paper analyzes the plastic strain,velocity,acceleration and displacement of the vault,,arch shoulder and arch bottom of the underground tunnel under three different high span ratio conditions(P1,P2,P3)with the same charge quantity,analyzes the damage mode of lining structure and the damage state of the easily damaged part,compares and studies the failure mechanism of various types of structures under different explosion conditions,and compares their structural characteristics The results show that under the same charge and the same supporting conditions,appropriately reducing the span and height of the tunnel lining structure can reduce the damage of the tunnel under the action of explosion waves.(4)The changes of speed,acceleration and displacement in the X direction and Y direction of each element of the lining structure are studied..The dynamic response of underground tunnel under plane charge explosion is analyzed when the lining thickness is 30cm,40cm and 50cm,and the damage modes of lining structure under different working conditions are compared.(5)Using the P-I curve of the concrete lining structure and the structural damage diagram in the numerical simulation,combined with the study of the influence of the lining vault,arch shoulder and arch bottom on its P-I curve,the damage and destruction degree of the tunnel is studied.The results show that the damage shown in the P-I curve is consistent with the conclusion of the structural damage map.