Large-section tunnel combined yielding structure and method crossing upper-soft lower-hard stratum

The invention discloses a combined yielding structure and method for a large-section tunnel spanning an upper-soft and lower-hard stratum, the yielding structure comprises an inner-layer arch frame mounted on the surface of the large-section tunnel, an outer-layer arch frame is arranged between the inner-layer arch frame and a tunnel rock wall, a layer of elastic deformation body is arranged between the outer-layer arch frame and the inner-layer arch frame, and the elastic deformation body is arranged between the outer-layer arch frame and the inner-layer arch frame. The outer-layer arch frame and the inner-layer arch frame are in staggered connection through an elastic deformation body; a plurality of hydraulic devices are evenly arranged on the outer layer arch frame, and reinforcing yielding devices are arranged on piston rods of the hydraulic devices. The construction method comprises the steps S1-S4. Through the synergistic effect of the reinforcing and yielding devices, the new Austrian method supportin