## 1 Introduction
Therefore, in order to reduce the impact load acting on the inner lining structure and reduce the vibration of the structure, a certain thickness of low-density material can be backfilled between the inner lining structure and the surrounding rock to form a composite structure with more than two layers, which can improve the internal force and deformation of the inner lining structure [23; 24]. To obtain the propagation law of the compression wave generated by the explosion in the inhomogeneous stratigraphic medium, [PERSON] [25] carried out an explosion test for a large ratio circular composite structure in the medium stiff stratigraphic medium, and found that the peak pressure of the compression wave on the wavefront was unequal in intensity, and most of the energy of the compression wave was transferred to the stiffness of the medium. When the stress wave propagates to the composite structure containing the foam concrete backfill layer, the foam concrete layer can significantly reduce the peak stress [26; 27; 28; 29; 30]. [PERSON] [31; 32] conducted an elastic-plastic dynamic study on the multi-layer circular structure with a foam concrete backfill layer in the rock by using the calculation program, and analyzed the dynamic test and numerical calculation results of the composite structure under the action of plane shock wave load, and discussed the dynamic characteristics of the underground multi-layer circular structure and the influence of the backfill layer thickness on the dynamic response of the structural system. The optimum thickness of foam concrete layer for the wave clipping vibration reduction, and the optimum wave impedance ratio of both the surrounding rock and the backfill material, were given. The anti-explosion and seismic performances of the high-resistance concrete structure were investigated by using the plane loading test under the condition of high pressure, and the stress, deformation and vibration characteristics of the surrounding rock, backfill layer and reinforced concrete lining were obtained. By analyzing the interaction mechanism among the three different types of structures, it was found that the composite circular structure with a soft backfill layer possessed excellent explosion and impact resistance properties. At present, due to the limitations of test cost and test technique, the research on the damage characteristics and damage mechanisms of underground engineering structures under the condition of plane charge explosion loading mainly focuses on \"the small-scalephysical similarity model tests\". Although these tests can provide some references for the anti-explosion design of underground engineering, there is no clear certainty whether the macroscopic damage characteristics and damage mechanisms between the model tests and the prototype tests are consistent. In this paper, the prototype tests of the anti-explosion performance of the high-performance reinforced concrete structure, the C30 reinforced concrete structure and the C30 reinforced concrete structure with a foam concrete backfill composite structure in the rock medium are carried out by using the field high-pressure plane charge loading test technology, with a total charge of 384 kg. The damage characteristics and damage mechanisms of the three types of structures are investigated by observing the macro damage phenomenon and analyzing the dynamic responses of the specific structure.