The Influence of Rate of Change in Confining and Pore Pressure on Values of the Modulus of Compressibility of the Rock Skeleton and Biot’s Coefficient

Abstract

This work discusses the results of a study of the influence of rates of change of confining pressure on the result of a drained compressibility tests intended to determine the modulus of compressibility of a rock skeleton Ks. A series of cyclical compressibility tests was performed on samples of sandstone soaked in kerosene, for various rates of compression and decompression of the pressure liquid filling the cell and the pore volume of the sample. The studies showed that the deformability of the tested sample was directly proportional to the rate of change of the confining pressure. As a consequence, the value of the Ks modulus and Biot coefficient α decreased with increasing sample load rate. This phenomenon should be attributed primarily to equilibration of the liquid pressure inside the high-pressure cell with the liquid pressure in the sample pore space, caused by filtration of the pore liquid. These phenomena prove that the filtration process impacts the values of the modulus of compressibility of the rock skeleton Ks and of Biot coefficient α determined on the basis of the experiment. This is significant in the context of the use of Biot equations as constitutive equations for a porous rock medium.

Comprehensive review of geomechanics of underground hydrogen storage in depleted reservoirs and salt caverns

“…Lastly, damage strain can occur which can initiate microcracks and lead to the failure of rocks [162,163]. Few rocks also show anisotropic elastic deformation which needs to be accounted for effectively using appropriate constitutive formulations [164,165,166]. This particular stage must be avoided to ensure the safety of UHS technology.…”

Comparison of the Compressive and Tensile Strength Values of Rocks Obtained on the Basis of Various Standards and Recommendations

“…Geotechnical laboratory tests are also necessary, e.g., in the initial phase of designing facilities for underground storage of energy carriers, e.g., in salt caverns [2]. One of the problems that occurs is the correct determination of the mechanical properties of the rocks forming the rock mass in which energy carriers are stored [3]. Studies are usually aimed at determining the strength values of material constants, usually of compressive strength and, more rarely, of tensile strength.…”