# A Comprehensive Safety Analysis Study for Concrete Core Dams
## 5 The Influence of Elastic Modulus to Concrete Diaphrag Wall  
For the reason the diaphragm wall is located in the clay core wall of the original dam, the maximum depth is 41.80 m. When the conventional concrete is used and wall elastic modulus is higher, large deformation and stress concentration will occur under the water load. The tensile stress generated the wall cracks. Thereby it affects seepage effect. Due to the importance of low elastic modulus concrete in similar reinforcement projects, and the cutoff wall of this project subjects to change in the elastic modulus, so it is focused for different elastic modulus impacts on the cutoff wall for calculation and analysis. The analysis results are given as a reference for similar reinforcement projects. Parameters required for finite element calculation are adopted from similar projects at home and abroad. Similar material nonlinear stress-strain parameters use the Duncan-Chang nonlinear constitutive model with a total of eight model parameters, which can be determined by a conventional triaxial specimen. Dam and foundation material parameter values are selected based on geological drilling data. The calculation of material parameters is listed in Table 5.  
The result is analyzed by comparing the SDAP software from the China Institute of Water Resources and Hydropower Research with FEM software under the case of check flood level, as shown in Table 6.  
From SDAP software calculation results, the maximum tensile stress in the diaphragm wall is 0.92 MPa with the elastic modulus of 2500 MPa, respectively, while the maximum tensile stress in the diaphragm wall is 2.01 MPa with the elastic modulus of 5000 MPa, and it appears around 83.70 m elevation. In CCDDCR, the cutoff wall stress changes with the elastic modulus. When the elastic modulus is greater than 3000 MPa, the stress variation in the cutoff wall is significant. For this reason, less than 3000 MPa of elastic modulus is suggested. From Figures 8-12, it can be seen that the effect of a concrete anti-seepage wall with low-elastic-modulus material on seepage prevention in a reinforced earth-rock dam is clear. It can be concluded that this type of concrete material is appropriate for reducing seepage during the process of reinforcement.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Working Conditions**} & \multirow{2}{*}{\
\begin{tabular}{c} **Li Zheng Software with** \\ **Seepage Pressure** \\ \end{tabular} } & \multicolumn{2}{c}{**FEM**} \\ \cline{3-4}  & & **Considering Osmotic Pressure** &
\begin{tabular}{c} **Without Considering** \\ **Osmotic Pressure** \\ \end{tabular} \\ \hline Design flood level (124.33 m) & 1.49 & 1.5375 & 1.7625 \\ Check flood level (125.12 m) & 1.49 & 1.5125 & 1.7375 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Contrast Table of safety factor \(F\).  
Figure 13: The Maximum shear strain diagrams.  
Different analysis keys exist for different dam types. For the concrete dam, the deformation or stress is the key content, while the seepage is the most important factor for the earth-rock dam. Therefore, the seepage analysis is carried out in this paper. The seepage analysis also reflects the deformation and stress of the concrete wall. A large amount of seepage indicates a large area of deformation or stress.  
There are many factors influencing the stability of earth-rock dams, including the structures made of soils and the concrete ones. For the structures of soils, the permeability coefficient is the most important factor, while the elastic modulus is the key for concrete structures. The cut-off wall composed of concrete is the research object of this paper. Therefore, the seepage situation of the earth-rock dam is analyzed based on the elastic modulus of the cut-off wall.