Experimental study on the sealing plug structure of underground lined caverns for compressed air energy storage

The underground-lined cavern represents a pivotal element within the framework of broader compressed air energy storage (CAES) systems. Due to the sealing requirements during construction and operational periods, every subterranean cavern requires one or more sealing plugs. Ensuring the plugs' effective sealing capability hinges critically upon controlling the interface engineering mechanics characteristics at the plug-to-surrounding rock contact surface. To address this challenge, an innovative approach was adopted: indoor simulated compression tests were conducted on plugs featuring cylindrical, arched, conical, and wedge-shaped structures. These tests measured deformation, separation degree at the plug-rock interface, and ultimate load-bearing capacity for each design. To enable the identification of the most suitable plug structure for sealing artificial-lined caverns in compressed air energy storage systems. Results indicate that the wedge-shaped plug exhibits optimal load-bearing capacity, achieving a 200 % increase over other configurations to 96.92 MPa, thereby better utilising surrounding rock support. This design also most effectively maintains deformation coordination between the plug and rock interface, reducing contact surface deformation to under 2 mm and separation to 3.33 mm – both values lower than those of other plug configurations. These findings provide theoretical support for plug design in underground lined storage caverns, holding significant engineering implications. • It was found that the sealing efficacy of sealing plugs in compressed air energy storage (CAES) lined caverns is fundamentally governed by the interfacial geomechanical properties at the plug-rock interface. • In response to this characteristic, this study employs simulation testing methods to investigate the load-bearing capacity of sealing plugs with different structural forms and the interface deformation between plug and the surrounding rock. • Based on the test results, the failure modes of different types of sealing plugs were revealed, and the structural form of sealing plugs used in underground lined rock caverns for compressed air energy storage was proposed. • The study elucidates the deformation characteristics and stress transfer mechanisms at the interface between sealing plugs and surrounding rock formations. • The findings provide reliable experimental data and theoretical foundations for the structural design of sealing plugs in Compressed Air Energy Storage (CAES) systems.