<p>En-echelon joints are widely distributed in rock masses and play a critical role in engineering stability. While previous studies have mainly focused on shear behavior under constant normal load or constant normal stiffness conditions, the response under dynamic disturbances remains insufficiently understood. In this study, the shear behavior of en-echelon joints under dynamic normal load (DNL) conditions is investigated through laboratory experiments and numerical simulations, with particular emphasis on the effects of joint inclination and loading amplitude. The results show that shear strength is governed by the combined effects of normal constraint effects, bearing capacity of rock bridges, and crack development. Joint inclination controls the dominant failure mechanism, where negative-angle joints reach peak strength during the coalescence stage, and positive-angle joints are governed by the interlocking stage. DNL promotes secondary crack development, leading to accelerated damage evolution and an overall reduction in shear strength compared with CNL conditions. Furthermore, rock bridges play a decisive role in stress transfer and failure development. Variations in crack development and stress redistribution give rise to five typical failure patterns, reflecting different combinations of crack coalescence paths and interlocking structures. These findings provide new mechanistic insights into the shear behavior of en-echelon jointed rocks under dynamic disturbance and offer a theoretical basis for stability assessment and reinforcement design in rock engineering.</p>