For the past half century, the research on boundary conditions on the detonation wave resulting in a velocity deficit or detonation failure mainly focused on the rough-walled or acoustically absorbing condition in one/two-dimensional models. In this paper, experiments on gaseous detonation propagation are conducted in the tube fully blocked by the non-rigid obstacles, under 20 kPa with the explosive gas of C2H2 + 2.5O(2) + nAr. The polypropylene membrane (PET) is selected as the non-rigid obstacle in this paper. The detonation wave behavior is to decelerate, accelerate, and overdrive prior to reaching a stable state once passing through the PET obstacles. When the initial pressure decreases or the layers of PET obstacle increases, the detonation wave will transit from a velocity deficit mode to a failure mode after deceleration occurs. With the PET layers increasing, the velocity minimum decreases continuously from 0.61 v(CJ) (m = 1) to 0.23 v(CJ) (m = 8). The propagation mode is associated with the average diameter of the hole after passing through the PET obstacles. The detonation wave will diffract when the average diameter decreases. In addition, the Mach reflection degenerates to the expansion wave and self-ignition ceases. As the shock is reflected from the tube wall, the initial regular reflection changes to a Mach reflection and auto-ignition forms again. For the multi-PET obstacles, the velocity after obstacles fluctuates more violently. The instability is regarded as the critical factor in the deceleration and acceleration. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.