## 3 Result and Analysis  
### Experimental Scheme and Results  
Given the low content of CaO in DA, it was mostly packed with dense sulfate material. The total hydration time was prolonged, and only the weak base environment was generated. The micro power from the Tangshan Iron and Steel Company showed weak acidity. When the slag powder has potential self-activity, it can more easily stimulate hydraulic activity in an alkaline environment than in acidic conditions. Consequently, a typical alkaline activator SH was added to the experiment in order to adjust the acid and alkaline range of the hydration environment which obtains the best excitation effect during the experiments. The tests used an orthogonal test design of four factors (Q, DA, GM, and SH) and three levels, with a cement-to-sand ratio of 1:8 and a slurry density of 73%. The dosage of GM and SH activators is determined based on the research and development results. At present, we have related patents for the preparation of gelling materials for desulfurization ash to replace gypsum. Due to the use of whole tailings and Q, the amount of individual activator is solemnly adjusted. To compare this with the new type of cementitious material, samples with the same glue-sand ratio and the slurry density were prepared by OPC 32.5R early strength cement. The test samples of DA residue formula were labeled as DA-1, DA-2, DA-3, and so on. Table 2 shows a summary of the experimental scheme and strength results. The mechanical strength gains of 14-day and 28-day cured DA samples were better than those of the OPC 32.5R cement reference group under the same conditions (Table 2). The UCS values of CTB samples at 14 and 28 days were 1.259 and 2.429 MPa, which were 2.03 and 2.23 times of CTB samples, respectively. The stope parameters of a single mine house during actual production were as follows: 40 m, length; 12 m, width; 50 m, extreme height; and 12.6 m, average mining thickness. Referring to the backfill strength design of the underground mines around the world, the 28-day strength acquisition \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Test No.**} & \multirow{2}{*}{**Q/\%**} & \multirow{2}{*}{**DA/\%**} & \multirow{2}{*}{**GM/\%**} & \multirow{2}{*}{**SH/\%**} & \multicolumn{2}{c}{**Slag**} & \multicolumn{2}{c}{**Stress/MPa**} & \multirow{2}{*}{**28-d Sinking**} \\  & & & & & & & **Powder/\%** & & **14-d** & **28-d** & **Rate/\%** \\ \hline DA-1 & 4.5 & 16 & 1.5 & 0 & 78 & 0.912 & 1.830 & 5.20 \\ DA-2 & 4.5 & 17.5 & 2.0 & 0.5 & 75.5 & 1.222 & 2.056 & 5.12 \\ DA-3 & 4.5 & 19 & 2.5 & 1.0 & 73 & 1.156 & 2.429 & 4.85 \\ DA-4 & 5.0 & 16 & 2.0 & 1.0 & 76 & 1.119 & 2.045 & 4.36 \\ DA-5 & 5.0 & 17.5 & 2.5 & 0 & 75 & 0.948 & 2.135 & 6.07 \\ DA-6 & 5.0 & 19 & 1.5 & 0.5 & 74 & 1.005 & 2.245 & 4.21 \\ DA-7 & 5.5 & 16 & 2.5 & 0.5 & 75.5 & 1.259 & 2.068 & 4.88 \\ DA-8 & 5.5 & 17.5 & 1.5 & 1.0 & 74.5 & 1.053 & 2.087 & 6.17 \\ DA-9 & 5.5 & 19 & 2.0 & 0 & 73.5 & 0.830 & 1.701 & 3.16 \\ \multicolumn{8}{c}{OPC 32.5R cement type} & \multicolumn{2}{c}{0.619} & \multicolumn{2}{c}{1.091} & \multicolumn{2}{c}{3.56} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: A summary of the experimental scheme and UCS test results. Figure 5: Photos of UCS test device (**a**) and broken CTB sample after UCS testing (**b**). of CTB samples must reach 2-2.5 MPa to meet the requirements of mine safety mining. Based on the relationship between the self-stabilization and height of CTB samples, and the relationship between the backfill body strength and maximum plastic zone width, the design strength of the 28-day cured CTB exceeded 2 MPa [56; 57; 58]. Therefore, when the mining thickness was less than or equal to the average thickness of 12.6 m, it could meet the safe and efficient mining requirements. By measuring the volume of the test blocks before and after de-molding, it was found that the 28-day shrinkage rate was mostly 5%, which was conducive to the realization of the roof grafting problem and the overall stability of the filling stop.