Pressure measurements were conducted under shock-loaded particle layers laid on the end wall of a vertical shock tube. The Mach number of the incident shock wave was 1.33. In order to reduce the uncertainty regarding the particles' arrangement, sized spherical particles were carefully set in regular array in the test section of the shock tube. The repeatability of the pressure measurements under the particle layer was much improved by using these regularly arranged particle layers. It was also found that the gas pressure transiently exceeded the pressure behind the reflected shock wave for the relatively small number of layers.