The utility model discloses a bury central ditch's weak surrounding rock tunnel supporting construction deeply, big hunch foot including tunnel section, it is provided with loop -locked preliminary bracing steelframe entirely to encircle foot department greatly, the hunch foot department of encircleing the foot greatly is provided with the shaped steel bracing, and the steelframe connected node department of the arch wall and the foot of a wall executes does arch wall and foot of a wall lock foot anchor pipe, it lays and buries central ditch deeply to encircle underfooting end greatly, bury the outer inverted arch steelframe of central ditch excavation influence scope deeply and add inverted arch lock foot anchor pipe. The utility model discloses increasing the shaped steel bracing encircleing foot department, addding lock foot anchor pipe at the inverted arch steelframe that buries deeply beyond the central ditch excavation influence scope, the vertical connecting reinforcement of steelframe of foot of a wall scope adopts cross arrangement, improves the stability of preliminary bracing, design exquisite, construction easy operation, the effect easily obtains the assurance.