Dynamic responses of a bituminous concrete core rockfill dam on layered overburden under seismic wave input

Abstract

The dynamic nonlinearity, overburden stratification characteristics and oblique incidence of seismic waves in soil greatly increase the difficulty of determining the free field of a dam foundation, which restricts seismic input accuracy. Based on the potential function theory, this paper constructs a transfer relationship between the wave amplitude matrix at the top layer of a dam foundation with overburden and the wave amplitude matrix at any layer and obtains the shear strain of the soil through Fourier inverse transformation. Then, the equivalent linearization method is adopted to depict the nonlinearity of the soil. An analytical calculation method for the free field of a dam foundation with layered overburden under inclined seismic waves is proposed. This method can not only forward the free field according to the incident wave in the deep part of the foundation but also directly invert the free field according to the seismic motion on the ground surface, and the inversion efficiency is high. Using a nonlinear viscous-spring boundary element developed by the authors, combined with the free field, a wave input method for a dam foundation with a layered overburden under inclined seismic waves is established. The maximum error between the numerical solution under wave input and the analytical solution is only 5%. The computational precision of the method is high. Finally, the dynamic responses of a bituminous concrete core rockfill dam on a layered overburden are studied. The results show that an upstream buoyancy and oblique incidence are the main reasons for a larger acceleration on the upstream side of the dam than on the downstream side. As the incident angle increases, the differential distribution becomes more significant, and the amplification coefficient of the anti-seepage system also increases. When the incident angle is 25°, the horizontal and vertical amplification coefficients at the top of the core wall increase by 12.8% and 25.2% compared to the vertical incidence, respectively. The accelerations of the dam are overestimated under uniform seismic input, and the amplification coefficients of the dam crest are overestimated by 52.3% and 39.8% compared with the wave input, respectively. The wave input reasonably solves the problem of seismic input for a dam foundation with layered overburden, considers the inclined seismic waves, and can reflect the seismic waves propagation characteristics. The wave method provides a solid foundation for the seismic safety of rockfill dams with layered overburden.