Research progress of confined concrete support theory and technology for underground engineering

With the rapid development of underground engineering in China and the continuous expansion of construction scale, a large number of complex conditions are faced in the construction process such as high stress, extremely soft rock, strong mining and fault fracture zone, which lead to serious surrounding rock deformation and control difficulties.The engineering practice shows that, combined support is the inevitable choice to control surrounding rock effectively under complex conditions.As the last line of defense for combined support, the lack of bearing capacity of arch leads to frequent roof fall and collapse.Confined concrete (CC) support has the characteristics of high bearing capacity, good plasticity and toughness, and excellent economic performance.In recent years, it has been widely used in mine roadways and traffic tunnels.Many researchers have done a lot of research in laboratory test, theoretical research, design method and field construction.In the aspect of indoor test, a large number of mechanical properties tests of CC arches and basic components are carried out, which provide the basis for the bearing capacity calculation theory and design method of CC arch.In the aspect of theoretical research, the calculation model of internal force of arch is established, and the calculation and design method of CC support strength is formed by combining the compressive bending strength criteria of CC components.In terms of design method, the overall selection design, concrete core design, grouting hole and exhaust hole design, joint design, arch spacing and longitudinal connection design are studied.In the aspect of field construction, two kinds of construction methods, mine roadway composite construction and traffic tunnel mechanized construction, have been formed, and a set of key technologies and equipment have been developed.This paper summarizes the above research contents, and prospects the design, construction and acceptance criterion formulation of confined concrete system in different engineering fields in the next step.At the same time, the future developments of design, construction and acceptance standard of confined concrete system and its application in different engineering fields such as traffic, water conservancy and municipal engineering are prospected. © 2020, Editorial Office of Journal of China Coal Society. All right reserved.