Abstract: The most significant challenge for the dam construction industry is overcoming the existing technical limitations and proposing strategies to make dam construction more cost-effective. Roller-compacted concrete dams have gained attention due to their ease and speed of construction as well as lower costs compared to conventional concrete dams. In this study, the mechanical performance of RCC dams with different shapes was modeled using the ABAQUS software. After validating the numerical model, the results indicated that the maximum stress in the dams is related to their foundation, necessitating special measures to reinforce this area. Among the evaluated geometries, shape buttressed design, with columns having side walls without slopes, is an ideal option for optimizing the design of RCC dams due to its relatively low maximum stress. In addition to structural and functional criteria, this geometry increases the visual and architectural appeal of the dam. The findings can assist engineers and decision-makers, enabling them to make better-informed decisions regarding the cross-sectional geometry of dams.

Keywords: Roller-Compacted Concrete Dam, Finite Elements, Gravity Dam, ABAQUS

Introduction

A dam plays an important role in providing a wide range of economic, environmental, and social benefits. The roller-compacted concrete (RCC) dam refers to concrete that is constructed using the same cheap and fast construction techniques and machinery as earth dams, while it has the same strength and durability as concrete dams. These dams are well-known because of their fast construction process, low engineering cost, strong environmental compatibility, and good heat generation control. Finite element (FE) modeling is widely accepted as a powerful tool for conducting comprehensive studies and evaluating the behavior of structural elements under various loading conditions. The finite element method is an effective method for estimating the seismic, thermal, and structural behavior of roller concrete gravity dams when appropriate boundary conditions are available. In this research, the performance of RCC dams with different shapes was studied in Abaqus software using the finite element method, and the results were compared with Zheng et al.’s research. Also, the results related to stress and strain were presented to them, and the best-optimized cross-section was selected.

Methodology

Considering the capabilities of Abaqus software in analyzing complex problems, as well as the ability of this software to provide regular and accurate meshing in a way that minimizes the error phenomenon, this software was chosen to perform finite element simulations. Zhang et al. (2019) research was considered as the selected paper to validate the finite element simulation process and also to continue research to investigate changes in the structure and model of the roller-compacted concrete dam. For the concrete part that was modeled volumetrically, the node spacing was set to 0.01 mm, which resulted in 20,850 eight-node 3D elements of type C3D8R. For the soil part that was modeled volumetrically, the node spacing was set to 0.02 mm, which resulted in 15,375 eight-node 3D elements of type C3D8R.

Results and Discussion

The volume parameter was considered as the objective function, and the strain energy parameter was considered as the control function to optimize analysis. After performing the optimization analysis and reducing the model volume by approximately thirty percent by the software, under the same loading conditions, the maximum stress value was 6.98 MPa at the toe of the dam. While before optimization, the maximum stress value at the same point was 10.68 MPa, which had a maximum stress value of 34.5 percent. The displacement of the dam crest was 34.27 mm in the horizontal direction and 12.71 mm in the vertical direction. In the undeformed dam, the maximum displacement of the crest of the dam was 18.648 mm in the horizontal direction and 20.17 mm in the vertical direction. The reason for the reduction in displacement in the vertical direction was due to a thirty percent reduction in the volume of the model, which led to a reduction in weight and, as a result, a thirty-two percent reduction in the subsidence of the dam. In contrast, it was observed that by optimizing the shape of the dam structure to reduce the volume, the horizontal displacement of the dam had almost doubled, but it should be noted that this displacement was due to an increase in the flexibility of the dam against the applied forces and not a decrease in its resistance because an increase in the stresses created in the dam had not occurred. Based on the results obtained, which indicated a thirty percent reduction in the dam volume without loss of its resistance, several models were designed using Abaqus software and based on the optimized design. The maximum stress value was at the interface between the dam base and the foundation. The maximum horizontal displacement occurred at the dam crest, while the minimum displacement was observed at the connection to the foundation. The optimized design shape No. 4, due to its relatively low maximum stress, can be considered a suitable option for the optimization of roller-compacted concrete dams.

Conclusion

The results showed that

1- The numerical model validation showed that the use of finite element simulation with Abaqus software to investigate the static behavior of RCC dams is generally appropriate and effective.

2- The maximum stress in dams is related to their foundation, and special measures are required to strengthen this part.

3- Buttressed design, with mechanical performance similar to the best options, is a suitable option for optimizing the design of RCC dams and increase the architectural appealing of it.

4- Costs can be reduced by reducing the volume of concrete by 30% while the dam's resistance does not change.