Weakening Mechanism And Strengthening Design Of Confined Concrete With Cavity

With the increase of coal mining depth,the phenomena of high ground stress,complex geological structure and loose and fragmentation of surrounding rock of roadway increase gradually.The supporting methods of I-beam + bolt-mesh shotcrete or U-beam + bolt-mesh shotcrete often appear to be inadequate when facing this kind of roadway,while the restrained concrete supporting method is fast in this kind of roadway because of its advantages in supporting strength,stiffness and economy.Promotion and application.However,due to the complexity of underground engineering and the short application time of this technology in practical engineering,the corresponding construction technology has not formed a better unification,and the construction quality of constrained concrete arch is not high.Especially in the field pouring construction,there are some problems such as incomplete pouring,which make it difficult for the constrained concrete arch to reach the design strength and affect the mechanical properties of the constrained concrete arch.To give full play to it will result in insufficient support strength,which will lead to the destruction of support structure.Under this background,the following research is carried out through the combination of indoor test,numerical test and field test.(1)A series of experimental studies on core concrete with expansive agent and early strength agent were carried out,and the strain characteristics of steel tube surface and the bond characteristics between core concrete and steel tube under the condition of different amount of expansive agent added to confined concrete were clarified.The early strength of concrete standard test block and the strength of confined concrete component changed with concrete age under different amount of early strength agent added were obtained.(2)The numerical and laboratory tests of confined concrete members with cavity under axial,pure bending and eccentric compression are carried out.The failure characteristics and load-bearing capacity Weakening Mechanism of confined concrete members with cavity under different load forms are obtained,and the strength allowable reduction rate and the void ratio of member section are proposed.(3)The reinforcement design method of concrete members with cavity constraints is studied,and the influence rule of each reinforcement design method on members is clarified,and the optimal reinforcement plate design method suitable for different section sizes is obtained.(4)The strengthening design method and efficient pouring method suitable for confined concrete arch are designed.And it has been applied in the design of the support of the head chamber of belt conveyor in Wanfu Coal Mine,and good application results have been achieved.