Experimental study on surface protection support using polymer thin spray-on layer

The Thin Spray-on Layer (TSL) is widely used in seal engineering of mine. TSL with high bearing capability is a new method to replace the metal mesh in the roadway support of underground coal mines, which has the advantages of fast development, automation and applicability of geo-conditions. Based on the deformational process of TSL in soft rock roadway, the support theories of TSL are analyzed. It shows that TSL coheres and repairs the surrounding rock surface to form a bonding layer, which has a confinement effect on the deformation of deep rock mass. Under the condition of large deformation of surrounding rock, TSL forms a thin shell structure, which produces supporting effect. Experiments were conducted to compare the support effects of different surface protection methods using large-scale briquette coal pillar samples and a newly developed polymer TSL material. The results show that the confining effect of TSL is greater than that of the metal mesh, and the bearing capacity of the sample is increased by 28.3%. The residual strength of the TSL specimen is also higher, and the energy dissipation of the system increases by 44.1%. The support effect of TSL thin shell structure is experimentally studied for the first time on different rock mass. The results showed that the TSL shell structure reduced surface rock deformation by bearing compressive stress, and the bearing capacity of lignite and sandstone samples increased by 44.6% and 20.4%, respectively, while energy dissipation increased by about 2 times. The numerical method was used to analyze stress distribution of TSL and mechanism of surrounding rock deformation in the experiments, and results were compared with experimental observations. This study provides a theoretical basis for the practice of TSL support engineering and an experimental research method for predicting the effect of TSL support in underground coal mine roadway.