EXPERIMENTAL STUDY ON THE DILATANCY OF ROCK SALT FROM AN UNLOADING PATH

Abstract

As underground storages produce gas, rock salt would always be in unloading paths. The
dilatancy behavior of the surrounding rock salt has a great significance for the stability and tightness of the
storages. This study investigated dilatancy properties of the rock salt from unloading paths where the confining
pressure decreased progressively while the axial pressure was kept fixed. The results showed that: the initial
confining pressure value has a rare influence on the dilatancy of the rock salt; an increasing axial pressure can
promote the dilatancy of the rock salt; a slower unloading rate and higher temperature would accelerate the
dilatancy rate and augment the total volumetric expansion. Compared with the results from conventional
loading paths, the compression-dilatancy point is independent of the loading types and remain unchanged in
cyclic loading tests. An empirical model to predict compression-dilatancy point was proposed. This model has
a certain degree of the engineering significance for designing the operating gas pressure and predicting the
dilatancy deformation of the surrounding rock, including porosity variation and permeability.