Experimental study on mechanical properties of hoop-disconnectable coupling in internal support system of excavation engineering

In order to improve the force way of the traditional disconnectable coupling in excavation engineering to further increase its security and stability, the design and development about the new hoop-disconnectable coupling are performed. Through axial compression tests, the mechanical properties of different specimens are studied. The main conclusions are drawn as follows: (1) the stiffness of the hoop-disconnectable coupling is higher than that of the traditional one; (2) under in the same load, the displacement of the traditional is larger; (3) under normal operation, the specimens can be reused; (4) when the ultimate bearing capacity is reached, the hoop-disconnectable coupling exhibits tiny brittle failure and after slipping, and it can continue to carry; (5) due to the clamping action of the bottom bolts, when the adjustable length is short, namely the larger contact area, the carrying capacity instead decreases; (6) under the axial compression, the pretension of bolts is essentially unchanged.