A Practical Swelling Constitutive Model of Anhydrite and Its Application on Tunnel Engineering

Figure 5

Introduction of two kinds of swelling strain-time model. The red line is the exponential model employed in [23]. The black line is the S-curve model employed in this paper. In the representation of the S-curve model, there are three clearly defined phases: ① the growth rate of swelling strain increases over time. This phase can be very short, for example, the data of No. 1 and No. 2 samples in Figure 3. ② Swelling strain increases rapidly, while the growth rate of it decreases over time. ③ The increase of swelling strain is relatively stable and is able to last a long time and will be close to a maximal swelling strain too. ① and ② Unstable phases of the growth rate of swelling strain, which is controlled by the combined effect of both the osmotic effect and hydration effect. ③ A relatively stable increase phase of swelling strain, of which the hydration effect is dominant.