Doctor of Philosophy
School of Civil, Mining and Environmental Engineering
Although thin spray-on liners (TSLs) have been stated as a potential medium for surface support in underground mines since the late 1980s, their application in underground coal mines is still in the infant stage. This thesis aims to evaluate the feasibility of replacing the traditional steel mesh with innovative TSLs for underground coal mine roof support. In this study, beam enhancement capacity of a TSL and its performance in supporting cracked rock mass were investigated; the TSL and steel mesh in supporting buckling strata, guttering strata and strata with weak bedding planes were compared; the load bearing capacities of TSLs, TSL-concrete composite and steel mesh were compared; numerical modelling was conducted to simulate the performance of the TSL in underground coal mine roof support.
Beam enhancement is one of the TSLs support mechanisms proposed by Stacey (2001), however, research on this mechanism has been limited. As such, four-point bending tests on plaster beams with and without TSL reinforcement were conducted to evaluate the ability of the TSL in enhancing roof beams. Test results indicated that the plaster beam experienced a significant increase in strength after being bonded with the TSL, failure modes of the beams were also altered. Previous studies on TSLs have mainly focused on determining their basic mechanical properties and load bearing capabilities. The mechanism by which TSLs help to stabilise the ‘cracked’ roof or walls of an underground roadway is not completely understood. To gain a better understanding, a series of hydrostone plaster beams with different notch shapes were tested to failure in a four-point bending test, as expected failure in all cases propagated from the tip of the notch. To assess the effect a thin spray-on liner (TSL) has in resisting crack propagation from the tip, another series of beams was coated on the notched face with a 5 mm thick polymeric liner. Results in all cases showed that failure at the crack tip had been resisted and that failure of the beam initiated elsewhere. This ability of the thin polymeric liner to resist crack propagation suggests that the polymer acts as a composite with the beam, a relationship which traditional steel mesh does not have. In order to investigate the influence of TSL material penetrating into rock joints, a series of TSL reinforced notched beams with polymer filling in the notch were subjected to the four-point bending test. Results indicated that filling of the notch with polymer was able to change the failure mode of the beam.
Shan, Zhenjun, Geotechnical Assessment of Thin Spray-on Liners for Underground Coal Mine Roof Support, Doctor of Philosophy thesis, School of Civil, Mining and Environmental Engineering, University of Wollongong, 2017. https://ro.uow.edu.au/theses1/140