Laboratory evaluation of shear strength properties for cement-based grouted coal mass

Cement-based grouting has been widely used in underground coal mining to improve the overall quality of highly fractured rock masses. Due to the difficulties in obtaining characteristic specimens from highly fractured coal rocks, there are very limited laboratory studies investigating the effect of grout on the strength of coal. The purpose of this paper is to address this gap by examining the effects of grouting on fractured coal in terms of overall shear strength. Two failure modes associated with coal and grouted coal specimens have been identified. The results show the shear strength improvement of grouted coal specimens as indicated by the improvement of their peak and residual cohesion as well as friction angle when the amount of reinforcing grout increases. Linear regression models were constructed for the prediction of shear strength parameters based on grout percentages. These models can be used as a guideline for the preliminary design of pre-grouting applications.