Development and application of a new physical simulation system for coal and gas outburst

A physical mechanics simulation experiment is one of the important technical methods to study the inoculation mechanism and development laws of coal and gas outburst. A new type of coal and gas outburst simulation system has been developed, aiming at developing an advanced experimental design scheme with the help of existing advanced monitoring technology, combined with specific gas geology conditions, to realize the simulation of coal and gas outburst phenomenon in complex scenes, and to promote the study of coal and gas outburst mechanism. The physical mechanics simulation system consists of following seven parts: stress loading subsystem, test chamber subsystem, power traction subsystem, gas pressure control subsystem, induced equipment subsystem, simulated roadway subsystem, and measurement and control subsystem. The design of each subsystem has been improved to different degrees, and the whole system has formed a landmark innovation. The simulation system has the following characteristics: ① the high load loading and unloading function of the three-axis synchronous continuous non-uniform loading technical equipment is improved. The specimen loading is done by 10 independent indenters in X, Y, and Z directions. The size of the experimental chamber is 400 mm × 400 mm × 1200 mm, the maximum load strength is 25 MPa, and the maximum closed gas pressure is 6.0 MPa. Each of the above 10 indenters can operate asynchronously or synchronously for loading or unloading tasks according to instructions, and horizontal stress loading and unloading layered processing function is implemented. ② An integrated process of systematic sample preparation, sample packing, sealing, and loading has been formed completely. The experimental chamber is designed as a new type of split structure, and the dynamic traction system is used to assist the experimental chamber to complete the molding, stress loading and material handling, and the translation amount of the chamber structure is controlled accurately. ③ The four kinds of technologies for inducing coal and gas outburst are integrated and applied in the same simulation platform, and some equipment functional innovations are realized, such as the test chamber, the pressure relief window, etc. Many kinds of technology and equipment have been successfully developed, as original innovation products, the dynamic technology and the drilling equipment have been verified by the experimental simulation. ④ The design innovation of key device structure is realized. The problems of stress concentration and high pressure gas leakage under synchronous loading are solved by the design of double-layer steel plate chamber structure. The experimental efficiency is improved by the structural optimization of the launching cavity, the safety of the simulation system is significantly improved by the design of the pipe end structure, a combination of soft and hard material pipe structure, and the variable diameter drilling technology has achieved the engineering application of the Rouleauxs triangle theory. ⑤ Simulation test precision is generated by multivariate information. Advanced data acquisition systems (stress, gas pressure, temperature, etc.) and monitoring technology equipment including acoustic emission and high-speed cameras are used to achieve multi-data monitoring of coal and gas outburst. ⑥ The reliability of the experimental system has been verified by laboratory simulation. Through the case simulation of the “3·22 accident in Pingdingshan”, the overall test of the system function is completed, and the influence law of fault structure on in-situ stress, gas pressure and temperature in the process of coal and gas outburst is discovered in a new way. It is proved that the physical mechanics simulation system is reliable and could provide a platform to support the research on the coal and gas outburst mechanism.