## 6 Discussion
### Smectite Delhydration and Rehydration within Bentonite  
Table 7 shows the buffer volume and compression caused by dehydration and rehydration herein. The radial compression value of bentonite was 2.485 cm in the 0 W state. The compression may be because the smectite dehydration induces temporary overpressure within the buffer material. Then, the excess pore pressure may dissipate into the backfill/or fracture and cause bentonite consolidation and compression. However, smectite rehydration occurs because of the low buffer temperatures. Swelling pressure during rehydration may cause volume expansion recovery of the smectite. The recovery of the smectite volume depends on the balance between the swelling pressure of the smectite and the confining stress exerted by the surrounding host rock on the EBS. A literature review indicated that the horizontal confining stress from the surrounding host rock is approximately 11.43-16.55 MPa [51] and the bentonite dry density is 1533-1692 kg/m\({}^{3}\) (density at water saturation 1983-2086 kg/m\({}^{3}\)), yielding a swelling pressure of 4.5-16 MPa [67]. Therefore, further investigation of the smectite swelling pressure and the confining stress of the surrounding host rock could provide further insights into bentonite consolidation and compression as well as smectite volume expansion. [PERSON] [6] indicated that soil mechanics adopt a special basic stress principle: the so-called effective pressure concept proposed by [PERSON]'s theory of consolidation. It denotes that the effective or particle pressure is the difference between the total stress and pressure in the pore water. For most soils, the changes in shear strength and volume only depend on the effective stress. However, this is incorrect for highly plastic clay mainly because describing the transfer of grain pressure at the particle contact is difficult. Moreover, unless the pressure reaches several hundred MPa, no real contact occurs between the minerals [6]. [PERSON]'s theory of consolidation and expansion has obvious physical significance for soils containing nonexpansive clay mineral particles, such as illite and kaolinite. Therefore, the total pressure of the water-saturated clay of nonexpansive clay mineral particle type increases, which is similar to the generation of pore pressure. However, if drainage is allowed, the pressure is subsequently transferred to the particle network for compressing and densifying the particle network. The same process occurs in smectite-rich clay, causing the distance between some layer sheets and interlayer spacings to decrease, consequently increasing the repulsive force between the interlayers. Unloading has the opposite effect; that is, the water in the interlayer space and on the surface of the laminated lamellar crystal substrate is absorbed by an extremely strong hydration potential, causing expansion [6]. Furthermore, [PERSON] [6] indicated that all changes in the microstructure composition are related to the shear-induced slip within and at the contact of adjacent lamellae stacks. This sliding occurs under constant volume conditions or simultaneously with consolidation in all soils. The accumulated time-dependent strain is called creep. The creep phenomenon of smectite clay is stronger than that of nonexpandable clay, but it possesses the same random distribution sliding characteristics, which occur when the energy barrier is overcome; stochastic mechanics are used to explain these creep phenomena. The reliable theoretical formulas of creep and creep rate as functions of stress and clay density should be derived. The concept that all materials shear through the initiation of the potential barriers on the microstructure scale is used. The potential barrier is represented by a variety of bonds and forms a type of spectrum. Therefore, the energy spectrum is not a material constant and changes with strain and time.