Seismic impact of mainshock-aftershock sequences on underground caverns: A case study of dynamic response

•Seismic response under single mainshock and single mainshock-aftershock is analyzed.•The sensitivity dominant index of caverns under mainshock-aftershock is expounded.•The NDR of underground cavern under multiple mainshock-aftershock is analyzed.•The evolution law of underground cavern is revealed under multiple aftershocks. At present, the seismic research of underground caverns mainly focuses on the mainshock effect, but ignores the aftershock hazard, and fails to fully consider that the cumulative damage after multiple earthquakes will reduce safety reserves of underground caverns. Therefore, based on incremental dynamic analysis method, this study selects real seismic records to construct single mainshock-aftershock sequence. The seismic response of underground cavern under single mainshock and single mainshock-aftershock is compared, and the sensitivity dominant index and seismic stress path of underground caverns under mainshock-aftershock is also expounded. Taking the Yingliangbao (YLB) hydropower caverns which experienced Luding MS6.8 earthquake as the research background. The mainshock-aftershock sequences with multiple aftershocks are constructed based on the real earthquake records in YLB area. The nonlinear dynamic response (NDR) of underground cavern under multiple mainshock-aftershock sequences is revealed. The results indicate that the residual displacement is more suitable as an evaluation index of the NDR of underground caverns under mainshock-aftershock than the peak displacement and yield zone volume. The residual displacement of underground cavern is related to the number of earthquake excitations, and multiple aftershock excitations will further increase the residual displacement of surrounding rock. The results can enrich the stability analysis and seismic design of underground caverns under mainshock-aftershock.