Experimental Study on Mix Proportion Parameter Optimization of Cement Anchoring Material

To prevent major deformation of surrounding rock and improve the stability of unstable rock mass, this study optimized the ratio of cement anchoring material based on the orthogonal design method and rock mechanics tests. Using the six influencing factors of coal ash content, sodium silicate content, ettringite content, naphthalene sulfonate content, water–cement ratio, and sand–cement ratio, a total of 18 sets of material matching schemes was designed. Compressive strength and pull-out force tests were carried out. The results are as follows: the compressive strength of the test piece between 43 and 55 MPa; the bond stress between the bolt and the anchoring agent range is from 103 to 136 kN; and the adhesion stress between the anchoring agent and the rock masses range is from 76 to 112 kN. The main order and degree of influence of various factors affecting the bond stress and the adhesion stress of the anchoring material were determined by range analysis and analysis of variance. The results showed that the amount of coal ash had a clear controlling effect on the bond stress, and the water–cement ratio, sand–cement ratio, and sodium silicate dosage had a significant influence on the bond stress. Moreover, the amount of sodium silicate had the greatest influence on the adhesion stress, and the water–cement ratio had the second largest influence on the adhesion stress. The amount of naphthalene sulfonate had the least influence on the adhesion stress. The above experimental data and results were subjected to multiple linear regression analyses, and the empirical equations of the mechanical indexes of the test pieces and the proportion parameters of the anchoring materials were obtained to guide the engineering support design. The engineering application showed that the optimized anchorage material could be applied to further improve the safety of the surrounding rock anchoring system.