STRENGTH DECAY LAW OF GLAUBERITE SALT ROCK WITH WATER AND TEMPERATURE

This paper studies the strength decay law of the glauberite salt rock of Guankou formation of Cretaceous in Southwest China under actions of water and temperature. It simulates the immersion test of glauberite salt rock sample in distilled water at a temperature of 30~70℃ by a home-made test device. During the 40-day immersion,we test the uniaxial compressive strength,elastic modulus,P-wave velocity,and failure mode of the glauberite salt rock. We summary the changes of the rock parameters with time and temperature before and after water immersion through the curves of the parameters versus the time or the temperature. We analyze the characteristics of rock microstructure changes before and after soaking by polarizing microscope. We examine the influence of composition,structure,time,temperature and other factors on the strength attenuation of the glauberite salt rock. We put forward some valuable conclusions. They are a new supplementary research results of the influence of water and temperature on the strength of glauberite salt rock. The rock strength decays sharply with increasing soaking time. After 7 days of immersion,the rock strength decays 50% to 72% of the initial strength. After 16 days of immersion,the rock strength decays 21%to 47% of the initial strength. After soaking for 30 to 40 days,the rock strength decays to 10% of the initial strength. The test data proves the same attenuation law of strength parameters such as uniaxial compressive strength,elastic modulus,and P-wave velocity of glauberite salt rock over immersion time. The dissolution and corrosion of the soluble components in glauberite salt rock are the fundamental factors affecting the strength decay of salt rock. The solubility of minerals such as glauberite,anhydrite,and gypsum in glauberite salt rock is slightly affected by temperature in the test temperature range of 30~70℃. Under the same immersion time,the strength difference between each immersion temperature is less than 10% of the initial strength. The immersion time can attenuate the strength of glauberite salt rock by more than 90%. Therefore,we consider that the more important external factor that affects the strength attenuation of glauberite salt rock is the soaking time. The research results have deepened the understanding of the water-rock interaction of saline rock,especially glauberite salt rock,and also provide a data reference for the problems of saline rock and soil engineering.