Abstract: A base beneath a specimen of a specimen cell for triaxial testing includes sealingly interconnected upper and lower covers. The upper cover is perforated, and has a downwardly opening first receiving groove receiving a porous ceramic plate, and a first pressure hole communicated with the first receiving groove. The lower cover has an upwardly opening second receiving groove, and a second pressure hole communicated with the second receiving groove. A non-permeable film is disposed between the upper and lower covers to span the first and second receiving grooves. A guide tube interconnects the first and second pressure holes so that pore air flows to the second receiving groove to provide an upward pressure beneath the film and the ceramic plate. Thus, the pressure difference across the ceramic plate can be reduced to be nearly zero.