Design of a Plastic Concrete Cutoff Wall as a Remediation Plan for an Earth-Fill Dam Subjected to an Internal Erosion

Abstract

This paper deals with the procedure to determine the required mechanical properties of plastic concrete used to build a new cutoff wall as a remediation measure in an earth-fill dam constructed in a narrow canyon and subjected to internal erosion. The study includes a detailed three-dimensional numerical simulation of the staged construction and reservoir impoundment of the dam before and after the cutoff wall installation to consider the influence of the past loading history and upcoming static and seismic loading on the cutoff wall behavior. The static analysis uses the hyperbolic model by considering a two-phase approach for the core elements to simulate the construction pore-pressure generation and its consolidation effect. The dynamic analysis uses a nonlinear hysteretic model to consider the shear modulus reduction and damping ratio increase with the shear strain increase. A variety of preliminary mechanical properties are selected based on a procedure discussed in the paper and assigned to the plastic concrete to assess the cutoff wall responses. This assessment not only introduces the critical zones in the wall, where they experience high shear and axial strain but also help to finalize the mechanical properties, which are low-elasticity modulus with high tensile and shear strength. However, by using the conventional mix designs, it is not possible to produce such material, according to the laboratory test data collected from the literature. Therefore, polypropylene fibers are added to the mix design to obtain the required mechanical properties, whose test results are in the paper.