Pore-water pressure response in saturated intact specimens of Berea sandstone, Salem limestone, Vermont marble and Barre granite to undrained increase in all-round stress, was measured in a specially designed triaxial cell. Dense intact rock specimens exhibited values of Skempton's B coefficient near one at small effective all-round stresses. However, as effective stress increased, B coefficient rapidly decreased. Based on the measurements, corrected for the compressibility of the pore-pressure measuring system, the values of B at effective stress of 1600 lb/in2. were in the range of 0·33-0·69. The rapid decrease in porepressure response at the effective all-round stress range of 0-500 lb/in2 is attributed to closure of crack-type pores and the corresponding decrease in compressibility of the rock skeleton. It is concluded that Bishop's expression for the B coefficient with appropriate values of the compressibility of the rock skeleton can predict the pore-pressure response in rocks with interconnecting pores. The major problem in computation lies with the proper choice of values for the compressibility of the rock skeleton.
ASJC Scopus subject areas
- Geotechnical Engineering and Engineering Geology
- Earth and Planetary Sciences (miscellaneous)