Primary support structure of underground engineering

The preliminary bracing structure of the underground engineering comprises a side wall protection plate, two connecting openings are formed in the top face of the side wall protection plate, a buckle plate is arranged above the side wall protection plate, a groove is formed in the surface of the buckle plate, the top end of the side wall protection plate is located in the groove, and the top end of the side wall protection plate is located in the groove. A through hole is formed in the outer surface of the top end of the side wall protection plate, and a rotating shaft is rotationally connected into the through hole. According to the primary supporting structure of the underground engineering, side wall protection plates are attached to the inner wall of a foundation pit and inserted into soil in the foundation pit, buckle plates are buckled on the soil on the side of the foundation pit and inserted into the ground through insertion holes in cooperation with insertion nails so that the buckle plates can be pr