An Experimental Study on Fiber Reinforcement of a Polymer TSL Material

Thin spray-on liner (TSL) technology provides rapid and highly automated surface support for underground coal mine roadways. However, in deep roadways affected by high in situ stress, mining-induced disturbances, and fractured surrounding rock, conventional TSL materials require improved tensile–shear resistance, deformation compatibility, and support adaptability. Although fiber reinforcement is an effective method for enhancing polymer composites, systematic studies on the effects of fiber type and dosage in reactive polymer-based TSL materials remain limited. In this study, a commercially available two-component polyurea-silicate-based TSL matrix was reinforced with polyvinyl alcohol (PVA) fibers, polypropylene mesh fibers, and toughened polypropylene fibers at volume fractions of 0.25–1.50%. A stepwise experimental program, including uniaxial compression, variable-angle shear, tensile, circular-indenter buffered shear, and true triaxial tests, was conducted to evaluate the mechanical behavior and support-related performance of the fiber-reinforced TSL materials. The basic mechanical tests showed that the 0.75% toughened polypropylene fiber group maintained favorable compressive and shear resistance, achieving a cohesion of 8.65 MPa and an internal friction angle of 24.12°. PVA fibers exhibited higher tensile reinforcement efficiency at relatively low contents, with the 0.25% PVA fiber group reaching a peak tensile stress of 13.61 ± 1.00 MPa. The 1.0% PVA fiber group showed good deformation coordination, with a compressive strength of approximately 49.87 MPa. In the circular-indenter buffered shear test, the 1.0% PVA fiber group reached a peak load of 0.636 ± 0.055 kN and an absorbed energy of 3.118 ± 0.832 J at 10 mm displacement. Under true triaxial loading, the 1.0% PVA fiber group absorbed 311.4 J of energy at a displacement of 10 mm, approximately 5.5% higher than that of the 0.75% toughened polypropylene fiber group. Therefore, 1.0% PVA fiber reinforcement is recommended as the optimal reinforcement scheme for polymer-based TSL materials used in deep, fractured, and large-deformation coal mine roadways.