This study investigates the 3D effects introduced by the end walls for an aspect ratio 1 in ramp-induced shock wave boundary layer interactions. The simulations are performed using symmetry boundary condition in spanwise at free-stream Mach numbers in three dimensions. The simulations are done using an in-house compressible supersonic solver “OpenSBLIFVM”[1]. Two free stream Mach numbers 2.5, and 3 are utilised in the current work, the simulated results are compared with the aspect ratio 1 simulations of Mangalagiri and Jammy [2]. The inflow is initialized with a similarity solution; its Reynolds number based on the boundary layer thickness is adjusted such that the Reynolds number at the starting of the ramp is kept at 3×105 for all simulations. From the results, it is evident that the introduction of sidewalls resulted in a shorter centerline separation length when compared with the 2D simulations. This is contradictory to the results at Mach 2 by [2]. The vortex observed at Mach 2 by Mangalagiri and Jammy [2], in the central separation region, has vanished with increasing the free-stream Mach number. Also, the topology of interaction has changed from owl-like separation of the second kind to the first kind when the freestream Mach number has increased from 2 to 2.5. It can be concluded that, the topology of interaction is key to the increase or decrease of the central separation length when compared to 2D.