## 2 Construction of Cemented Soft Rock Dams
After vibratory rolling, the test section was cured for 90 days and then the cemented sand and gravel with soft sandstone contents of 50%, 60%, and 70%, respectively, were subjected to in situ direct shear tests between the bulk alone, the bulk and slurry-rich cemented sand and gravel, and the bulk and the concrete interface. The typical shear stress-displacement relationship curves and shear cross-sections are shown in Figures 2 and 3, and the test results are provided in Table 2.  
Figure 2: Shear stress–displacement curves of typical measurement points. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Sandstone** & \multicolumn{2}{c}{**Shear Failure Strength**} & \multicolumn{2}{c}{**Residual Strength**} & \multicolumn{2}{c}{**Shear Strength**} & \multicolumn{1}{c}{**Shear Mode**} \\ \cline{2-7}
**Content** & \(f\) & _c\({}^{\prime}\)_ **(MPa)** & _f\({}_{R}\)_ & _c\({}_{R}\)_ **(MPa)** & _f\({}_{R}\)_ & \(c\) **(MPa)** & **Shear Mode** \\ \hline
50\% & 1.10 & 0.38 & 0.81 & 0.24 & 0.81 & 0.18 & Dominated by mixed failure \\ \hline
60\% & 1.08 & 0.34 & 0.81 & 0.30 & 0.85 & 0.11 &
\begin{tabular}{c} Dominated by mixed failure and \\ supplemented by surface shear failure \\ Dominated by shear failure along \\ the surface \\ Shear failure along the cemented body \\ on the surface \\ \end{tabular} \\ \hline
70\% & 1.02 & 0.26 & 0.91 & 0.24 & 0.87 & 0.09 &
\begin{tabular}{c} Shear failure along the cemented body \\ on the surface or along the surface \\ Mixed failure or shear failure of the cemented body on the surface \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of the in situ direct shear test results of the test sections. Figure 3: The typical failure of the shear piers: (**a**) soft sandstone contents of 50% between the bulk alone; (**b**) soft sandstone contents of 60% between the bulk alone; (**c**) soft sandstone contents of 70% between the bulk alone; and (**d**) soft sandstone contents of 60% between the bulk and the concrete interface. The test results showed that the relationship curves of shear stress to displacement for the cemented sand and gravel mixed with sandstone had an obvious linear increasing stage and a peak strength, the shear failure friction coefficient, \(f^{\prime}\), was between 0.99 and 1.10 MPa, and the cohesion, \(c^{\prime}\), ranged from 0.26 to 0.53 MPa, indicating that the shear parameters met the stress demands for low-to-medium dams and the sliding stability demand for the Jinijigou cemented material dam with soft rock. In terms of the trend, as the sandstone aggregate content increased, \(f^{\prime}\) decreased from 1.10 MPa to 0.99 MPa, and \(c^{\prime}\) decreased from 0.53 MPa to 0.26 MPa, i.e., the shear failure strength of the layer and contact surface gradually decreased. Since the mixed failure mode corresponding to several sandstone contents basically dominated at the layer and contact surfaces, the shear strength and single-point friction shear strength at the shear surface did not change significantly, with the shear friction coefficient being\(f\) = 0.72\(\sim\)0.91 MPa and cohesion being \(c\) = 0.05\(\sim\)0.18 MPa, which were low. The cemented sand and gravel exhibited a high residual strength after shear failure, accounting for 60-80% of the peak strength, indicating that the cemented sand and gravel still had a high shear resistance after the shear failure at the layer or contact surface, hence indicating that the cemented sand and gravel had a strong ability to withstand the risk of catastrophe. (3) Dam stress and sliding stability analysis considering each weak sliding surface. The results of the stress analysis of the dam (Figure 4) showed that the stress of the dam below the elevation of 402.00 m decreased from 1.32 MPa at the bottom to 0.75 MPa at the top, both of which are less than the allowable compressive stress of C8 cemented sand and gravel (2 MPa).