## 4 Improved Neural Network Prediction
### Optimization Prediction of Cementing Material Ratio  
Figure 9a shows the predicted strength results of CTB samples with different DA contents. The GM content was 2.5% and the SH content was 1%. The following conclusions could be drawn from Figure 9a: (i) when the Q dosage was 3.5-5.5%, and the DA content was 15-21%, the mechanical strength of CTB samples exceeded 2 MPa; (ii) with the increase of the DA content, the backfill strength gradually increased. When the DA and Q contents were 21% and 3.5%, respectively, the maximum strength value reached 2.4691 MPa. When the DA and Q contents were 15% and 5.0%, respectively, the minimum strength of the backfill was 2.0468 MPa; (iii) the compressive strength of the backfill showed a decreasing trend with the increase of the Q content.  
Given that our sample size was small, our study had some limitations in predicting data results. The quicklime content of 4.5-5.5% basically conformed to the experimental regularity. However, when the Q content was less than 4.5%, further confirmatory experimental studies were needed. Considering that DA has no cost as a solid waste, increasing the dosage could greatly reduce the cost of cementitious materials without affecting the comprehensive performance of CTB samples. Given that the low activity of the DA required excitation under good conditions, the quantity of the DA content was 19% and the Q content was 4.5% or 5.0%.  
Figure 9b shows the predicted results of SH dosage, with 4.5% or 5.0% Q, 19% DA, and 2.5% GM. When the Q content was 4.5% and 5.0%, the compressive strength of the CTB samples increased with the increase of the SH content. In addition, when the SH content was greater than 0.7%, the CTB's strength acquisition exceeded 2.3 MPa.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test No.** & **Experimental Value/MPa** & **Predicted Value/MPa** & **Relative Error/\%** \\ \hline DA-1 & 1.83 & 1.8297 & \(-\)0.02 \\ DA-2 & 2.429 & 2.4288 & \(-\)0.01 \\ DA-3 & 2.045 & 2.0457 & 0.04 \\ DA-4 & 2.135 & 2.1346 & \(-\)0.02 \\ DA-5 & 2.245 & 2.2450 & 0.00 \\ DA-6 & 2.068 & 2.0716 & 0.18 \\ DA-7 & 1.701 & 1.7043 & 0.19 \\ DA-8 & 2.056 & 2.0898 & 1.64 \\ DA-9 & 2.087 & 2.1055 & 0.89 \\ \hline \hline \end{tabular}
\end{table}
Table 5: A summary of experimental values and predicted results.  
Figure 9: Predicted strength curves of CTB samples: (**a**) desulfurization ash and (**b**) sodium hydroxide.  
Considering the existence of certain safety and wealth coefficients, the strength of CTB samples was greater than 2.3 MPa to meet the requirements of mine safety production. When the Q contents were 4.5% and 5.0%, the DA dosage was 19% and the SH amount was greater than 0.7%. The costs of cementitious material were calculated as follows:  
\[350\times(4.5\text{--}5.0)+900\times 2.5\%+2100\times 0.7\%+110\times(72.8\text{--}73.3)=(133.58 \text{--}134.78)\,\forall/\text{ton}.\]  
In summary, the developed DA excitation formula not only satisfies the actual mining intensity requirements, making full use of DA; but also reduces the cost of backfill and mining, and improves the economic benefits of mining. The developed formula also responded to the country's mining policy of green mining.