<p>The interlayer has a significant influence on rock failure under blasting, and understanding the blast-induced crack propagation process in natural rock mass is a key factor to improve and predict rock failure. In this paper, the influence of vertical interlayer on rock fracturing was investigated by using both caustic experiment and numerical simulation. The results reveal that the reflected waves originating at the interlayer markedly distort the caustic spot morphology, which first suppresses and then promotes the growth of oppositely propagating crack. And upon reaching the interlayer, the crack is either rapidly arrested or deflected along the rock-interlayer interface. Moreover, based on the numerical simulation results, for the interlayer thickness ranging from 10 to 25&#xa0;mm, the peak value of transmitted blast waves decrease by 57-68%, indicating that the obstruction to blast energy transmission becomes stronger with increasing interlayer thickness. However, the influence of interlayer on rock failure decreased as the distance between the borehole and the interlayer increases. When the ratio of the interlayer-to-borehole distance to the borehole diameter reaches 8.75 in our study, the influence of the interlayer on rock failure becomes negligible. Besides, for the rock mass containing vertical interlayer, confining pressure can induce a strong tensile stress along the maximum principal stress direction, particularly around the borehole and the rock-interlayer interface. This leads to crack initiation primarily along the maximum principal stress direction. Moreover, unloading stress waves emanating from the borehole considerably intensify the stress field when interacting with the blast waves, resulting in complicated fracturing of rock mass. These findings revealed the mechanism of crack fracture in layered rock masses, which provides valuable insights for optimizing blasting parameters in engineering practice.</p>