A Quantitative Index Representing Crack Shapes and Corresponding Techniques

In order to quantificationally describe the soil cracks due to dry-wet cycles, the concept of gray level entropy is applied according to the physical significance of the information entropy to represent various shapes of cracks. Then a piece of simple and easy-to-use equipment for taking photos is used to monitor and record the crack propagation. A grayscale image and the corresponding gray level entropy are obtained automatically by a program. Test results showed that gray level entropy can quantificationally describe the shape of cracks reasonably well and evaluate the degree of crack development effectively.

Detection of Cracks in Clay Soil Using Quasi-3D Electrical Resistivity Tomography Method: Numerical and Experimental Study

Soil cracks affect the geotechnical characteristics of clay soils frequently used in engineered earth structures. In this work, numerical simulation and laboratory tests using Wenner- Schlumberger array of Electrical Resistivity Tomography (ERT) method are adopted to detect soil cracks in compacted clay soil. 3D numerical simulation showed that air-filled cracks have an anomalous high resistivity signature that can be differentiated from the background due to the high resistivity contrast between cracks and the surrounding soil. Depth, geometry, and extension of the simulated cracks are reasonably indicated. At the laboratory scale, quasi-3D ERT experiment was conducted. The results showed that soil resistivity is significantly affected by an artificially introduced crack as the crack forms a barrier that disturbs the flow of electricity in the soil. Similarly, depth, geometry, and extension of the crack are detected. Both numerical and experimental findings demonstrated that ERT method can effectively be used to identify cracking in clay soils. It is suggested that ERT, as a non invasive method, can be adopted with other traditional geotechnical methods for detecting cracks in clay soils.

Experimental and Numerical Analysis of Soil Cracking Characteristics under Evaporation

There are numerous cracks on soil surface in nature. These cracks are mainly formed by the continuous water loss and shrinkage of soil under evaporation. Cracks have an important effect on the properties of soil. The analysis of soil moisture movement and cracking characteristics under evaporation is of great significance to the engineering construction in the cracked soil area. In this work, an experimental study was conducted to investigate the development of soil cracks. Crack geometrical parameters were acquired at various developmental stages. According to this, the crack evolution characteristic was described qualitatively. The law of soil water movement was analyzed through the numerical simulation of evaporation effect on cracked soil. The relationship between soil moisture content and crack width was revealed, and the dynamic prediction of crack development under evaporation was realized. The results show that the development and evaporation process of soil cracks can be divided into three distinct stages, and the longer the stable evaporation time, the greater the development of cracks.

Soil cracking propagation due to dryness and its relation to suction

Investigation of Crack Intensity Factor is essential as it affects the mechanical and hydraulic behaviour of soils. Soil water coming from the wet seasons or from the water table, is removed by evaporation during the driest season. The loss of water provokes a significant increase in suction. When it exceeds the tensile strength of the soil, cracks occur that can modify the mechanical and mainly hydraulic properties of the soil, creating preferred paths for water infiltration. Little research is conducted on quantifying cracking in soil relating it to its hydraulic properties. This research aims to investigate the cracking of soils with focus on analysing its relation to water content and soil suction. Soils from a specific region in Brazil with clay predominance are collected and characterized. Unsaturated soil specimens are prepared and subjected to environmental real conditions in order to progressively check the consequences caused by the environment in soils with different clay content during four weeks. The Crack Intensity Factor is measured along the time through image processing. The water content is monitored through volume water content sensors. The measured results are evaluated to correlate crack intensity factor as function of weather variables and soil water content.

A review of genetic classification and characteristics of soil cracks

Soil cracks are one of the most important physical properties of soil. The formation of soil cracks is a result of interactions between the inner and external conditions of soil. Specifically, the inner conditions include physical and chemical properties of soil, and the external conditions refer to natural and anthropogenic factors. Previous studies of soil cracks mainly focus on the soil properties and the natural environment (NE), such as soil cracks produced by biotic and abiotic processes. Very few studies have focused on the soil environmental changes induced by other external conditions, such as geological processes and anthropogenic activity. To systematically illustrate the soil fissure, according to the characteristics of soil cracks, and considering the properties of soil preferential flow path, the geneses and the characteristics of soil cracks have been comprehensively analyzed and summarized in this study. Two major types of soil cracks have been proposed: one is the cracks caused by NE and the other is the cracks caused by anthropogenic activity. Additionally, based on the specific differences of these geneses, these two types of soil cracks have been further divided into six subtypes and fourteen sub-subtypes, respectively. In this article, a genetic classification method of soil cracks is systematically proposed, which provides a new approach for the related research of soil cracks.

Effect of Saline Soil Cracks on Satellite Spectral Inversion Electrical Conductivity

The dehydration cracking of saline soil is a kind of common natural phenomenon, and the cracks of saline soil will affect the satellite spectrum, and then affect the accuracy of satellite spectral inversion of electrical conductivity (EC). This study introduces the concept of crack rate (CR) to describe the crack information of saline soil, and quantifies the influence of saline soil crack on the EC of satellite spectral inversion. In 2014 and 2020, the satellite-ground synchronous observation experiments of soda-type inland saline soil and coastal chlorinated-type saline soil were carried out, and the CR of surface cracked saline soil was extracted by an image processing algorithm. For the saline soil spectrum data, the correlation analysis method is used to establish the best band combination that characterizes the relationship between the different saline soil spectrum data and salinity, and the EC inversion model is established using the BP neural network method. The results show that: after the CR is introduced, the determination coefficient (R2) for the EC of soda-type saline soil satellite spectral inversion increased from 0.59 to 0.67, with an increase of 14.42%, and the mean square error (MSE) reduced from 0.20 to 0.16, with a decrease of 19.49%. The R2 for the EC of coastal chlorinated-type saline soil satellite spectral inversion increased from 0.64 to 0.75, an increase of 17.73%, and the MSE decreased from 0.16 to 0.12, a decrease of 25.15%. The study proved the influence of the cracks in the saline soil on the satellite spectrum and provided a new way to improve the accuracy of the satellite spectrum inversion of the EC of the cracked saline soil.