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Structural characteristics and variable mass permeability of fall column broken rock mass

Suo Jie, Qin Qirong, Li Zhenhua

Archives of Civil Engineering

2024

Vol. 70, nr 1

459--472

In order to analyze the relationship between the configuration characteristics, variable mass permeability characteristics and the catastrophe mechanism of falling column process, The influence of the permeability was studied by diffraction instrument, And using the seepage test system of the fall column, The seepage instability process of variable mass broken rock mass is analyzed, The findings suggest that, The proportion of coarse particles accounted for 89.86%, Fine particles accounted for 10.14%, Broken rock particles is better, Low compression performance; The fall column, under strong hydrodynamic conditions, Due to its strong characteristics of migration and loss with water flow, It is easy to induce the subsidence column protrusion water disaster; As the ratio between coarse and fine aggregates increases, Porosity and permeability are both increased; When the axial displacement does not change, With the increasing circumference pressure, The permeability of the broken rock samples is decreasing; The fitting of the seepage velocity of the broken rock mass to the pore pressure gradient follows the Forchheimer relationship, The seepage of the broken rock mass belongs to the category of non-Darcy flow under the triaxial stress; The instability of the subsidence column fracture rock mass presents three seepage instability forms: initial seepage stage, seepage mutation stage and piping stage in different stages.

Monte Carlo simulation of polarization of light back-scattered from randomly rough surfaces

Jiang Yuxiang, Li Zhenhua

Optica Applicata

2023

Vol. 53, nr 1

65--85

Laser detection devices obtain target information from back-scattered light, such as lidar. The recognition rate can be improved by analyzing intensity and polarization of echo signal. In this paper, Monte Carlo method is used to generate a large number of randomly rough surfaces to simulate targets. Every rough surface is discretized into a large number of micro-surface elements. Stokes parameters of back-scattered light are calculated by numerical integration. Incident light is p-, s-, 45° linearly polarized light and right-hand circularly polarized light, respectively. Numerical results show that when s- and p-linearly polarized light incident on a metal rough surface, back-scattered light appears circularly polarized component. Metal rough surface resembles a wave plate with phase difference, with the fast axis parallel or perpendicular to the 45° direction. When linearly polarized light is incident on dielectric rough surface, back-scattered light has no circularly polarized component. Experimental data are consistent with the numerical results. The above research provides a new basis for laser detection device to identify metal targets from the environmental background.