The permeability of a saturated porous medium is an important parameter in the field of water resources and geotechnical engineering. The geometric characteristics of a porous medium are key factors in the prediction of its permeability. In this paper, particles of different shapes are constructed by Cellular Automata (CA) random growth model, and particles with different surface characteristics are constructed by the spherical harmonic function. Then, porous media of different porosities, shapes, surface features, and particle size distributions are generated on the basis of the constructed particles. Three-dimensional Lattice Boltzmann Method is used for the pore-scale simulation of the seepage flow in a porous medium. The numerical results show that the effects of the particle shape and surface characteristics on the permeability are too obvious to be ignored. Using strict univariate analysis, the sensitivity of the various factors to the permeability, ordered from large to small, is as follows: porosity>particle size distribution>particle surface>particle shape. Based on numerical studies, a modified Kozeny-Carman (KC) formula is proposed by considering all the geometrical factors. All the parameters (the Wadell sphericity S w , Cox roundness R c , coefficient of non-uniformity C u , the curve coefficient of curvature C c , and effective particle size d 10 ) in it are easily obtained in engineering practice and the accuracy of the formula is verified. Although It has been proven that the KC formula is applicable to multi-dispersed spherical particles and non-spherical particles whose surfaces are not very rough, its applicability to rough particles is limited. The modified KC formula does not have this limitation; therefore, it has a wider scope of application than the conventional KC formula.

In this paper, the results of a series of experiments on wave-induced pore-water pressures around a mono-pile are presented. Unlike the previous study, in which the mono-pile was fully buried, the mono-pile in this study was installed at 0.6 m below the seabed surface. In this study, we focus on the pore-water pressures around the mono-pile and beneath the pile. The experimental results lead to the following conclusions: (1) the seabed response is more pronounced near the surface (in the region above 30 cm deep), and the rate of pore pressure attenuation gradually slows down. For the region below 0.3 m, the response is much smaller; (2) in general, along the surface of the pile, pore pressures increase as the wave height and wave period increase; (3) the spatial distribution of pore pressure near the pile will vary with different wave periods, while the wave height only has a significant effect on the amplitude; and (4) At z = −0.15 m, the pore pressure in front of the pile is the largest, while at the point 0.1 m below the bottom of the pile, the largest pore pressure occurs behind the pile.

Numerous studies have proven that natural particle-packed granular materials, such as soil and rock, are consistent with the grain-size fractal rule. The majority of existing studies have regarded these materials as ideal fractal structures, while few have viewed them as particle-packed materials to study the pore structure. In this study, theoretical analysis, the discrete element method, and digital image processing were used to explore the general rules of the pore structures of grain-size fractal granular materials. The relationship between the porosity and grain-size fractal dimension was determined based on bi-dispersed packing and the geometric packing theory. The pore structure of the grain-size fractal granular material was proven to differ from the ideal fractal structure, such as the Menger sponge. The empirical relationships among the box-counting dimension, lacunarity, succolarity, grain-size fractal dimension, and porosity were provided. A new segmentation method for the pore structure was proposed. Moreover, a general function of the pore size distribution was developed based on the segmentation results, which was verified by the soil-water characteristic curves from the experimental database.

Investigations into the Wenchuan earthquake (2008, China) demonstrated that landslides were concentrated in the near-fault areas, and numerous large-scale landslides occurred in slopes with weak interlayers. A mathematical model was established based on the shear beam theory, while a numerical model was developed based on the discrete element method which perfectly matched layer boundary theory. Through a theoretical analysis and numerical simulation, the dynamic response and failure modes of the slope with a weak interlayer under the near-fault ground motion were studied. It was found that a combined effect took place between the near-fault ground motion and the weak interlayer, causing the slope near a fault to be destroyed more easily. The coupling between the near-fault ground motion and the weak interlayer leads to a maximum amplification effect of the slope. The existence of a weak interlayer induces nonconforming vibration between the upper and the lower rock masses of the interlayer. The variation in the amplification effect along the slope elevation is related to the ratio of the input seismic period to the natural slope period. Under horizontal ground motion, weak interlayers will be subjected to impacting and shearing action. The failure mode of the slope with a weak interlayer under near-fault ground motion can be expressed as a trailing edge tension crack, as well as weak interlayer impacting and shearing failure.