Grouting is a widely used and effective method to enhance the strength of soft

fractured surrounding rock and maintain engineering stability. In order to evaluate the impacts of grouting on mechanical properties and fracture damage of coal and rock

uniaxial compression tests were conducted on samples before and after ultrafine cement grouting. Digital image correlation and acoustic emission technologies were employed to monitor damage evolution and crack growth in coal and rock. The process of crack tip grouting expansion was discussed using fracture mechanics theory. The results show that: 1) Compared to intact coal samples

the strength increase post-grouting. Coal samples with more cracks exhibit lower strength

potentially due to stress concentration at crack tips. 2) Post-grouting

internal pores in the coal sample are filled

reducing brittleness and enhancing plasticity and deformation resistance. However

grouting minimally affects post-peak deformation

and the cementation between grout and coal is suboptimal. 3) The failure of intact coal samples primarily exhibits a single high-strain concentrated zone. In grouted coal samples

grouting enhances the isotropic of the mechanical properties failure lacks a in distinct strain concentrated zone

and strain evolution is relatively disordered. 4) The horizontal displacement damage factor Dw is proposed to characterize the damage evolution degree of coal under uniaxial load

the horizontal displacement damage variable is defined

and the damage piecewise constitutive model for uniaxial compression coal sample is established.