Abstract：Based on the theory of confined concrete，the composite shaft linings of inner steel plate cylinder and high strength reinforced concrete have been adopted to solve the difficult problem of supporting coal frozen shafts penetrating through thick soil cover of 600–800 m. Through model experiments，the mechanical characteristics of such shaft linings are studied. The test results indicate that the concrete¢s deformational capacity and compressive strength increase greatly in triaxial compression stress state in inner steel plate cylinder；and the shaft lining is fairly plastic when it fails，and the brittleness defect of high strength concrete is improved. If the shaft linings of high strength reinforced concrete，which are used in site now，have been changed to the composite shaft linings of inner steel plate cylinder and high strength reinforced concrete，and the load bearing capacity of shaft lining will be increased greatly，and the supporting problem of the frozen shaft in the special deep alluvium will be reasonably solved. The main factors affecting load bearing capacity of this shaft lining are the concrete compression strength，the ratio of lining thickness to inner radius，the thickness of inner steel state and the reinforcement ratio. Increasing concrete compressive strength has a remarkable effect on the load bearing capacity of shaft lining. If concrete compression strength increases 10 MPa，the load bearing capacity of shaft lining will increase about 13.8 percent. Moreover，increasing reinforcement ratio has small effect on the load bearing capacity of shaft lining. Therefore，single outer row steel bar is used in practical engineering to economically and reasonably design shaft lining. Finally，a formula to calculate the load bearing capacity of the composite shaft linings of inner steel plate cylinder and high strength reinforced concrete was obtained according to the theory and experimental results. These results have provided a basis for similar engineering practice when designing this kind of shaft lining structure.
