The traditional humidity stress field theory cannot perfectly describe the time-dependent relationship between the swelling state and humidity state when simulating the swelling process of anhydrite rock mass. Based on this theory

the swelling tests on anhydrite rock mass were designed to investigate the swelling with different initial humidities and soaking time. In addition

tensile strength tests were carried out after swelling. The testing results showed that with the increase of initial humidity

the duration time of swelling

the maximal axial swelling strain

and the maximal lateral swelling stress increased. The water absorption rate and crystallisation water rate of anhydrite increased at the end of the test

while the free water rate was close to zero. Under the same initial humidity

with the increase of soaking time

the water absorption rate exhibited a rapid increase first and then slowly grew. The crystallisation water rate gradually increased to the water absorption rate

while the free water rate decreased to close to zero. With the increase of water absorption rate

the maximum axial swelling strain

the maximum lateral swelling stress and the tensile strength increased. Therefore

this study proposed the time-dependent humidity state equations and the time-dependent swelling constitutive model according to the testing results.