Sensitivity Analysis of Hardfill Dams to Seismic Loading and Foundation Bearing Capacity

Hardfill dams represent a recent and cost-effective construction method in which locally available materials such as alluvial deposits, riverbed gravel, and excavation spoil are mixed with a low cement content to form the dam body. Compared with conventional roller-compacted concrete (RCC) gravity dams, hardfill dams require less rigorous material specifications and quality control, resulting in lower stresses within both the dam body and its foundation. Their symmetrical trapezoidal cross-section also provides favorable seismic performance. This paper presents a parametric sensitivity analysis of a 30 m high hardfill dam, examining the combined influence of horizontal seismic acceleration (0.1 g, 0.2 g, and 0.3 g) and foundation allowable bearing capacity (0.4, 0.6, and 0.8 MPa) on the required upstream and downstream slope inclinations. Nine models were first pre-dimensioned through rigid-body stability analysis following USACE criteria and then verified using plane-strain finite element models in SAP2000, with pseudo-static seismic loading. Results show that foundation bearing capacity is the governing parameter for the dam geometry, while seismic acceleration produces a proportional but less dominant effect on slope steepness. Gentler slopes consistently yield better stress distributions along the foundation, and significant discrepancies between rigid-body and elastic analyses arise when the foundation-to-dam stiffness ratio is low.