On the basis of elaborating the adsorption and migration properties of bentonite colloids in deep geological repository of high-level radioactive waste, a comprehensive review and summary of the co-migration experiments, interaction mechanisms and simulations of bentonite colloids and nuclides are summarized. The results show that the adsorption and mobility of the bentonite colloids are significantly affected by the concentration of the colloids, the ionic strength of groundwater and pH. The existing studies are difficult to evaluate the adsorption capacity of the bentonite colloids for nuclides and the migration capacity of the colloids themselves. The laboratory dynamic column tests and the in-situ dipole flow field tests both focus on the promotion of the mobile colloids and the blocking effects of filter colloids on the migration of the nuclide. There is a lack of examples of the co-migration of long-distance colloids and nuclides. The co-migration effects of the bentonite colloids and nuclides are controlled by the adsorption-desorption effect of the colloids and the filtering effect of the colloids, rarely considering the blocking effect of the medium. The dual permeability model and double-porosity model can simulate the co-migration breakthrough curves of the bentonite colloids and nuclides under specific conditions, but the fracture system considered is simple, and the competitive adsorption effect of the nuclides is not considered. For this reason, some suggestions for further experimental and theoretical researches are put forward.

In order to study the seismic wave field characteristics of large deeply-buried underground caverns, the input methods for obliquely incident earthquakes in deeply-buried underground caverns are proposed by converting the site seismic response into the equivalent load acting on the artificial boundaries. It is suitable to reflect the incident direction, the multi-incident surfaces and the inconsistency of near-field obliquely incident earthquakes. According to the dynamic interaction characteristics between interlayers in interbedded rock mass under seismic action, a dynamic contact analysis method considering the seismic deterioration effect and the bond-slip characteristics of interface is also established. Consequently, a dynamic response analysis method for a deeply-buried underground cavern in interbedded rock mass under obliquely incident seismic waves is constructed and applied to the seismic damage evolution process analysis of the underground powerhouse of Azad Pattan Hydropower Station. The simulated results reveal that the obliquely incident earthquake aggravates the seismic reaction of lining structure, which mainly lies in the amplitudes of the displacement and stress fluctuations. Some areas at the upper side wall and the arch of the linings in the main powerhouse are damaged to the most severe degree. After considering the dynamic contact, the seismic response of caverns near interface further increases, and the evident seismic deterioration effect and shear slip failure occur at interface. The dislocation between interlayers is more obvious, and the maximum dislocation displacement tends to be stable at 5.9 cm. Besides, the seismic damage characteristics and failure modes of the lining structures of the underground powerhouse in interbedded rock mass are discussed from the transverse and longitudinal angles.

In the traditional non-coaxial theories, linear assumption is usually made between non-coaxial plastic strain rate and non-coaxial stress rate, and they are always in the same direction, which is inconsistent with the real non-coaxial deformation characteristics of soils. In order to make up for this defect, firstly, it is proved by the mathematical derivation that the total stress rate can be decomposed into the sum of the component stress rates in six orthogonal directions, and then it is revealed that the non-coaxial stress rate defined in the traditional non-coaxial theories is composed of multiple orthogonal components. For each orthogonal component of the non-coaxial stress rate, based on the generalized plastic mechanics, the corresponding nonlinear loading mechanism is established by defining the loading strength index, plastic modulus and plastic flow direction explicitly, and the total non-coaxial plastic deformation is regarded as the sum of the plastic deformation induced by each component, thus a generalized non-coaxial theory is established. The stress-strain relationship of elastoplastic model for soils based on the generalized non-coaxial theory is derived. The numerical tests for model evaluation show the rationality of the generalized non-coaxial theory, which preliminarily indicates that the new theory can provide a broader theoretical basis for the establishment of non-coaxial model for soils.

The clinker ash is a kind of granular waste produced after the combustion of coal. It has been used in slope and foundation engineering as backfill materials. The single-particle crushing tests on the clinker ash from six different origins are carried out. The results indicate that the clinker ash particles own much lower single-particle strength than the natural sands and exhibit larger crushability. A series of drained triaxial shear tests are performed on the clinker ash to examine the effects of particle shape, degree of compaction and effective confining pressure on its shear characteristics. An increase in the degree of compaction strengthens the initial stiffness and the peak shear strength of the clinker ash. Compared to the natural sands, the clinker ash possesses larger peak friction angle and provides higher bearing capacity as foundation materials. As the effective confining pressure increases, the peak friction angle of the clinker ash gradually decreases. The results suggest that both the particle shape and the single-particle strength are important factors affecting the shear strength of the clinker ash. In addition, several particle shape parameters of the clinker ash are decided using the digital image analysis method. The clinker ash has smaller roundness and sphericity indexes due to its complex particle shape. The analysis results show that the critical state friction angle is well correlated with the particle shape parameters. A general and new particle shape index is employed to correlate with the relevant parameters associated with the critical state and its position.

Particle shape and gradation are the important factors affecting the movement of debris particle flows (such as landslides, debris flows, rock slides, etc.). The random generation method based on the Voronoi tessellation creates polyhedral particles with different aspect ratios and gradations. The potential particle algorithm is introduced to consider the contact effect between particles. The parameters of the contact model of discrete element are determined according to the indoor tests. For the item parameters, numerical experiments are carried out on the collapse characteristics of the particle column considering the gradation and morphology. The research results show that: (1) The normalized stacking height of the particle column decreases with the decrease of the aspect ratio and the median diameter (d₅₀) of the particles, and the normalized run-out distance increases with the decrease. (2) The relative angle of repose under different working conditions during the accumulation process is in the range of 61.49°~64.99°, and the change rule is consistent with the change of the normalized accumulation height. (3) The normalized energy dissipation range under different working conditions is between 27.1%~35.5%, and the rotational kinetic energy only accounts for 8.20%~9.05% of the translational kinetic energy. (4) The normalized kinetic energy has a negative correlation with the particle coordination number, and the particle coordination number reaches the minimum when the normalized kinetic energy reaches its peak. (5) In the process of collapse, the strong chain is generally distributed in the middle and lower areas of the sliding accumulation body, forming the "arch effect" of the transmission of the force chain. The increase in the median particle size (d₅₀) and the slenderness ratio will reduce the number of strong chains, and the paths of contact force transmission will be small and concentrated, thereby restricting the movement of particles during the accumulation process.