Microstructural Variation of Clay during Land Subsidence and the Correlation between Macroscopic and Microscopic Parameters

Abstract

The nonlinear deformation, visco-elasto-plasticity and other macroscopic properties of soil are the concentrated manifestations of its microstructural state. In order to study the microstructural characteristics and variations of the clay under the action of additional stress caused by groundwater exploitation, borehole sampling was carried out on the clay layers at different depths in a typical land subsidence area. Consolidation tests, freeze-drying, ion sputtering, and scanning electron microscope (SEM) were conducted in order to scan and analyze the microstructure of the test samples at different scales. The Particles and Cracks Analysis System (PCAS) was used to quantify the microscopic parameters, the variations of the microstructural parameters with consolidation loads at different sizes were revealed, and the correlation between the macroscopic and microscopic parameters were discussed. The results show that: (1) the microstructural characteristics of soils with different buried depths have directivity, to a certain extent; (2) as the consolidation load increases, the average unit area and average form factor of the soil microstructure generally decrease, the structural arrangement of the unit gradually tends to be orderly, and the average pore area, apparent void ratio and the number of pores generally show a decreasing trend; (3) under the action of a consolidation load, when the microstructure at a relatively large scale is basically stable, the microstructure at a smaller scale will continue to adjust; (4) the apparent void ratio has a good linear regression relationship with the conventional void ratio, and the apparent void ratio has a good exponential growth relationship with the compressibility.

An Experimental Study on the Microstructure Evolution of Soil under Lateral Consolidation Compression

“…At this time, the pores were smaller, the soil particles were more intimately coupled and the arrangement was more directed, which improved the homogeneity of the pores. Similar results have also been presented by Di et al [43], who proposed that, under the initial consolidation stress, structural units are compressed and structurally adjusted, and the shape becomes oblate.…”

“…Furthermore, the area of the micropore group was almost within In addition, the authors discovered that, at the initial stages of consolidation, particle damage is greater, and growth is more obvious, whereas at the later stage, particle shape and pore shape are more stable, and the curve is flatter. This demonstrates that recombination and aggregation occur among structural units under the consolidation pressure, and the degree of homogeneity of the pore tends to approach with time [43]. This conclusion is supported by the results of equivalent diameter and plane porosity.…”

Study on the effect of microwave irradiation improvement on the long-term stability of expansive soil

“…Average form factor describes the shape of the pore, with a value between 0 to 1. The larger the value, the smoother the shape of pore, and vice versa (Di et al, 2022). It can be seen from Fig.…”

Determining Effective Threshold Range of Image Pixel Values for Municipal Waste-Contaminated Clay

“…The microstructure and pixel threshold value of municipal waste-contaminated clay notably affect the assessment of its engineering characteristics. In many previous studies, the fractal dimension and apparent void ratio are commonly used parameters for analyzing the microstructure of soil [15][16][17][18][19]. The fractal dimension can be used to quantitatively describe the complexity of the particle shape profile, and the change in the apparent void ratio directly reflects the soil deformation [20,21].…”