a portable testing device for directly measuring developed lateral pressure induced on a material by a vertical applied pressure while the lateral expansion is adjustable . the testing device comprises a thin - walled cylindrical sleeve - like receptacle which is capable of lateral expansion in response to a vertical applied force on the material contained in the receptacle . the sleeve is provided with a slit formed in the wall thereof which extends between the upper and lower ends thereof to define first and second side edge portions . apparatus is provided for preventing and / or adjusting lateral movement of the first side edge portion as the vertical applied force is applied to the material contained in the receptacle . a pressure sensing cylinder is connected to the second side edge portion and has a fluid pressure gauge operatively connected thereto for sensing the developed lateral stress .