# Experimental Study of the Mechanical Properties of a Flexible Grid Filling Body
## 6 Analysis of the Shear Strength Characteristics of the Flexible Grid Filling
However, the increased amplitude was different, and the tensile strength, shear strength, cohesion, and internal friction angle strengthening coefficient of the flexible grid filling body in different dimensions were greater than its elastic modulus strengthening coefficient, indicating that the tensile and shear strength of the filling body was greatly increased after adding the flexible grid to the filling body, whereas the increase in the compressive strength was relatively small. That is, the flexible grid mainly improved the tensile and shear strength of the filling body and prevented its brittle failure, thereby increasing its toughness, ductility, and crack resistance to better meet the engineering production. Surface failure characteristics during the flexible grid filling body test  
The uniaxial compression test, uniaxial tensile test, and the shear test of the flexible grid filling body were recorded and screenshot, as shown in Figure 19, and the surface failure characteristics of the flexible grid filling body were analyzed. As shown in Figure 19a, there was no crack on the surface of the specimen in the early stage of the uniaxial compressive loading (before 1 min), after which a vertical crack began to appear in the middle of the surface of the specimen, and with continuous loading, the vertical crack gradually expanded and extended to the bottom, developing into a larger crack, accompanied by more vertical parallel cracks until the end of the test. As shown in Figure 19b, there was no crack on the surface of the specimen in the early stage of the uniaxial tensile loading (before 10 s), after which a small vertical penetrating fracture began to appear in the middle of the specimen surface, and with continuous loading until the end of the test, the penetrating vertical fracture gradually expanded, but no other associated fractures were generated. As shown in Figure 19c, there were no cracks on the surface of the specimen in the early stage of shear loading (before 1 min), after which an oblique shear crack began to appear in the middle of the specimen surface, developing into a crack, and with continuous loading, the shear crack gradually expanded, and more shear fractures were associated with it until the end of the test. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Ash-to-Sand** & **Grid Dimensions** & **Spacing/mm** & \(\xi_{T}\) & \(\xi_{Q}\) & \(\xi_{E}\) & \(\xi_{C}\) & \(\xi_{\varphi}\) \\ \hline \multirow{8}{*}{1:4} & \multirow{4}{*}{One-dimensional} & 20 & 1.3613 & 1.7000 & 1.1690 & 1.8114 & 1.9020 \\  & & 30 & 1.4563 & 1.8667 & 1.1206 & 1.9543 & 2.0520 \\  & & 40 & 1.5618 & 2.0056 & 1.0763 & 2.0971 & 2.2020 \\  & & 50 & 1.1397 & 1.4500 & 1.0266 & 1.5257 & 1.6020 \\  & & 20 & 1.5618 & 2.0056 & 1.1753 & 2.0971 & 2.2020 \\  & & 30 & 1.6674 & 2.1444 & 1.1267 & 2.2400 & 2.3520 \\  & & 40 & 1.7729 & 2.2833 & 1.0822 & 2.3829 & 2.5020 \\  & & 50 & 1.3508 & 1.7278 & 1.0329 & 1.8114 & 1.9020 \\  & & 20 & 1.7729 & 2.2833 & 1.1797 & 2.3829 & 2.5020 \\  & & 30 & 1.8995 & 2.4222 & 1.1331 & 2.5257 & 2.6520 \\  & & 40 & 1.9846 & 2.5611 & 1.0882 & 2.6686 & 2.8020 \\  & & 50 & 1.5618 & 2.0056 & 1.0402 & 2.0971 & 2.2020 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Strengthening coefficient of the flexible grid filling body with different dimensions and spacings. Failure mode of the flexible grid filling body  
The specimens of the flexible grid filling with different dimensions and spacings were photographed after the uniaxial compression test, uniaxial tensile test, and shear test, as shown in Figures 20-22, and their failure mode was analyzed. Figure 19: The surface failure characteristics of the flexible grid backfill during the tests; (**a**) uniaxial compression test, (**b**) uniaxial tensile test, and (**c**) shear test. Figure 20: Failure modes of the specimens with different dimensions and spacings of the flexible grid backfill after the uniaxial compression tests.