Soil Desiccation Cracking Research Articles

Monitoring and early detection of soil desiccation cracking using distributed fibre optical sensing

Desiccation cracking can significantly affect the hydro-mechanical behaviour of soil in various engineering applications. Characterising the evolution of desiccation-induced shrinkage strain in soils is a key step in understanding the cracking mechanism. This study presents a novel framework for monitoring and early detecting soil cracking by utilising the distributed fibre optical sensing (DFOS) technique based on optical frequency domain reflectometry (OFDR). DFOS-OFDR was integrated into a set of experimental testing to simultaneously monitor water content, crack pattern and strain state. OFDR with 1 με strain measurement accuracy was employed to monitor the initiation and propagation of cracks. The results reveal a strong correlation between the spatiotemporal evolution of soil strain and crack, confirming the efficacy and reliability of the proposed framework. During the drying process, the compressive strain induced by soil shrinkage increases first and starts to decrease when cracking is initiated. Further, DFOS-OFDR demonstrated promising results to predict the position of cracks. Compared to traditional strain monitoring methods with discrete measurements, DFOS-OFDR offers a non-destructive, accurate yet efficient, high-resolution and continuous technique for monitoring and early detection of soil desiccation cracking.

AI (ANN, GP, and EPR)-based predictive models of bulk density, linear-volumetric shrinkage & desiccation cracking of HSDA-treated black cotton soil for sustainable subgrade

ABSTRACT AI-based bi-input predictive models have been executed to forecast the bulk density, linear and volumetric shrinkages and desiccation cracking of HSDA-treated black cotton soil (BCS) for sustainable subgrade construction purposes. The BCS was characterised and classified as A-7 group soil with high plasticity and poorly graded condition. Sawdust ash was obtained by combusting sawdust and sieving through 2.35 mm aperture sieve. It was further activated by blending it with pre-formulated activator material (a blend of 8 M NaOH solution and NaSiO2 in 1:1 ratio) to derive waste-based HSDA. The HSDA was further used in wt % of 3, 6, 9, and 12 to treat the BCS. The treated samples were compacted in the standard proctor moulds, cured for 24 h and extruded. The desiccation tests were then performed on the prepared specimens by drying them at a temp of 102°C for 30 days and behavioural changes in weight, height, diameter, average crack development, etc., were taken throughout the period. Multiple data sets were collected for the references test, and treated specimens of 3, 6, 9, and 12% wt HSDA of the soil for 30 drying days. XRF and SEM tests were also conducted to determine the pozzolanic strength via the chemical oxide composition, three chemical moduli (TCM) and the microstructural arrangement of the experimental materials and the treated BCS. The XRF tests showed that the experimental materials had less pozzolanic strength, which improved with the treated blends thereby forming stabilised mass of BCS. Also, it showed the silica moduli of the TCM dominated the stabilisation of the soil with waste-based HSDA. SEM tests showed increased formation of ettringite and gels with the addition of the HSDA. The data collected was subjected intelligent models’ prediction using ANN, GP and EPR for the four outcomes; BD, CW, LS and VS of the HSDA-treated BCS. The models’ performance showed that EPR outclassed the other techniques in predicting BD and CW with accuracies of 98.2% and 92.7% and minimal error, while ANN outclassed the other techniques in predicting LS and VS with accuracies of 98.8% and 99.3% and minimal error, respectively.

Quantitative Response of Gray-Level Co-Occurrence Matrix Texture Features to the Salinity of Cracked Soda Saline-Alkali Soil.

Desiccation cracking during water evaporation is a common phenomenon in soda saline–alkali soils and is mainly determined by soil salinity. Therefore, quantitative measurement of the surface cracking status of soda saline–alkali soils is highly significant in different applications. Texture features can help to determine the mechanical properties of soda saline–alkali soils, thus improving the understanding of the mechanism of desiccation cracking in saline–alkali soils. This study aims to provide a new standard describing the surface cracking conditions of soda saline–alkali soil on the basis of gray-level co-occurrence matrix (GLCM) texture analysis and to quantitatively study the responses of GLCM texture features to soil salinity. To achieve this, images of 200 field soil samples with different surface cracks were processed and calculated for GLCMs under different parameters, including directions, gray levels, and step sizes. Subsequently, correlation analysis was then conducted between texture features and electrical conductivity (EC) values. The results indicated that direction had little effect on the GLCM texture features, and that four selected texture features, contrast (CON), angular second moment (ASM), entropy (ENT), and homogeneity (HOM), were the most correlated with EC under a gray level of 2 and step size of 1 pixel. The results also showed that logarithmic models can be used to accurately describe the relationships between EC values and GLCM texture features of soda saline–alkali soils in the Songnen Plain of China, with calibration R2 ranging from 0.88 to 0.92, and RMSE from 2.12 × 10−4 to 9.68 × 10−3, respectively. This study can therefore enhance the understanding of desiccation cracking of salt-affected soil to a certain extent and can also help to improve the detection accuracy of soil salinity.

Numerical Solution of Desiccation Cracks in Clayey Soils

This entry presents the theoretical fundamentals, the mathematical formulation, and the numerical solution for the problem of desiccation cracks in clayey soils. The formulation uses two stress state variables (total stress and suction) and results in a non-symmetric and nonlinear system of transient partial differential equations. A release node algorithm technique is proposed to simulate cracking, and the strategy to implement it in the hydromechanical framework is explained in detail. This general framework was validated with experimental results, and several numerical examples were published at international conferences and in journal papers.

Deep learning based approach for the instance segmentation of clayey soil desiccation cracks

The identification of clayey soil desiccation cracks is an important practical issue in geotechnical engineering and engineering geology. The desiccation cracks can dramatically increase the hydraulic conductivity and deteriorate the mechanical performances of clayey soils. Traditionally, the analysis of soil desiccation cracks relies on visual inspection and image processing techniques, which lack automation and intelligence. Therefore, there is an increasing need for an automated algorithm to meet accuracy and efficiency requirements for various engineering scenarios. In this study, a state-of-the-art deep-learning algorithm, Mask R-CNN, was utilized for the clayey soil crack detection, localization and segmentation. A comprehensive dataset including 1200 annotated crack images of 256 × 256 resolution was prepared for the algorithm training and validation. The proposed Mask R-CNN algorithm achieved precision, recall and F1 score of 73.29%, 82.76% and 77.74%, respectively. Besides, the algorithm gained a mean localization accuracy (APbb) of 64.14% and a mean segmentation accuracy (APm) of 47.59%. The detection performance of the Mask R-CNN was also compared with that of the U-Net under three different scenarios. The test results have demonstrated the superiority of the Mask R-CNN over the U-Net algorithm in crack detection, localization and segmentation.

Desiccation Cracking Behavior of Sustainable and Environmentally Friendly Reinforced Cohesive Soils.

Desiccation cracking of cohesive soils is the development of cracks on the soil surface as a result of a reduction in water content. The formation of desiccation cracks on the cohesive soil surface has an undesirable impact on the mechanical, hydrological, and physicochemical soil properties. Therefore, the main aim of this study is to experimentally and numerically investigate eco-friendly soil improvement additives and their effect on the desiccation cracking behavior of soils. Improvement of soil crack resistance was experimentally studied by conducting desiccation cracking tests on kaolin clay. Biopolymer xanthan gum and recycled carpet fibers were studied as potential sustainable soil improvement additives. In addition, image processing was conducted to describe the effect of an additive on the geometrical characteristics of crack patterns. The results show that the soil improvement additives generally enhanced the soil strength and reduced cracking. Furthermore, a hydro-mechanical model was developed to predict the moisture transfer and onset of desiccation cracks in plain and amended kaolin clays. Data obtained show that the inception of the desiccation cracking and radial displacements were delayed in the improved soil specimens, which is in agreement with the experimental data.

3D characterization of desiccation cracking in clayey soils using a structured light scanner

To capture the 3D morphological features of drying soils, we explore the potential of using a structured light scanner. Bentonite clay is used for desiccation tests. Both 2D images and 3D scans are obtained at certain time intervals throughout the test. We develop a post-processing methodology to quantify the 2D and 3D features of soil cracking, including surface crack ratio, total volume, surface area, and fractal dimension. Experimental results validate that the structured light scanner enables 3D high-resolution and accurate scanning of the soil desiccation cracking patterns. The change of 3D soil volume is more influenced by the widening of desiccation cracks, with slower soil volume reduction corresponding to the moment when primary cracks propagate vertically downwards. The spatiotemporal evolution of 3D reconstructed model indicates that the soil surface shrinks first, more in the central region and less along the boundaries due to the boundary constraint, before crack initiates and propagates. Both surface area and fractal dimension increase monotonically before the evaporation stops, with both more susceptible to the change of crack depth rather than crack width. Through presenting a new approach for soil desiccation cracking analysis, this study is expected to provide new insights into the soil desiccation process.

Morphological description of desiccation cracks in soils: insights from the perspective of anisotropy

Morphological description of desiccation cracks in soils: insights from the perspective of anisotropy

Experimental Investigation on the Impact of Drying–Wetting Cycles on the Shrink–Swell Behavior of Clay Loam in Farmland

Soil shrink–swell behavior is a common phenomenon in farmland, which usually alters the process of water and solute migration in soil. In this paper, we report on a phenomenological investigation aimed at exploring the impact of drying–wetting cycles on the shrink–swell behavior of soil in farmland. Samples were prepared using clay loam collected from farmland and subjected to four drying–wetting cycles. The vertical deformation of soil was measured by a vernier caliper, and the horizontal deformation was captured by a digital camera and then calculated via an image processing technique. The results showed that the height, equivalent diameter, volume and shrinkage-swelling potential of the soil decreased with the repeated cycles. Irreversible deformation (shrinkage accumulation) was observed during cycles, suggesting that soil cracks might form owing to previous drying rather than current drying. The vertical shrinkage process consisted of two stages: a declining stage and a residual stage, while the horizontal shrinkage process had one more stage, a constant stage at the initial time of drying. The VG-Peng model fit the soil shrinkage curves very well, and all shrinkage curves had four complete shrinkage zones. Drying–wetting cycles had a substantial impact on the soil shrinkage curves, causing significant changes in the distribution of void ratio and moisture ratio in the four zones. However, the impact weakened as the number of cycles increased because the soil structure became more stable. Vertical shrinkage dominated soil deformation at the early stage of drying owing to the effect of gravity, while nearly isotropic shrinkage occurred after entering residual shrinkage. Our study revealed the irreversible deformation and deformation anisotropy of clay loam collected from farmland during drying–wetting cycles and analyzed the shrink–swell behavior during cycles from both macroscopic and microscopic points of view. The results are expected to improve the understanding of the shrink–swell behavior of clay loam and the development of soil desiccation cracks, which will be benefit research on water and solute migration in farmland.

Effects of fibre additions on the tensile strength and crack behaviour of unsaturated clay

Desiccation cracking in clay soils is a combined mechanical and hydraulic problem and such soils can be improved by various methods including reinforcement with fibres. The relationships between tensile strength, cracking resistance and water-retention properties of fibre-reinforced fine-grained soils lack coverage in the literature to date. In this study, these three properties are evaluated and connected by way of a series of tensile strength and desiccation cracking tests on fibre-reinforced London clay. The results confirm that increased fibre addition delays the occurrence of peak stress and changes failure behaviour from brittle to ductile. The tensile strength increment gets higher as water content decreases, and reaches a maximum value of 460 kPa when the water content is 12%. The crack intensity factor reduces from 7.20% to 0.89% when 12 mm long fibre is used at a ratio of 0.9%. Fibre reinforcement also changes the crack development pattern by reducing the size of large cracks and increasing the proportion of small individual cracks. However, the presence of fibres was not observed to change the water-retention properties of the soil, indicating that the tensile improvement comes from the pull-out resistance of the fibres rather than suction changes.

Desiccation cracking of soil subjected to different environmental relative humidity conditions

Relative humidity (RH) is among key environmental and climatic factors that affect the evolution of soil desiccation cracking. This study aims to investigate how RH variations influence soil desiccation cracking, addressing an overlooked aspect in prior studies. A set of laboratory tests were performed to examine a fat clay undergoing desiccation cracking at various controlled RH levels of 15.0%, 44.0%, 66.0%, 76.0%, 83.5% and 93.7%. During testing, all samples were weighed and photographed simultaneously to monitor evaporation and surface cracking. The evolution of the surface crack network was quantitatively analyzed by an image processing technique. Results highlight the strong dependence of soil desiccation cracking on RH conditions. Increasing RH is found to decrease the overall evaporation rate and increase the water content at which cracking starts. Under high RH levels, the formation of surface cracks exhibits an evident hierarchical process with wide primary cracks developing first followed by fine sub-cracks propagating from the primary ones. Different cracking developing rates between a primary crack and sub-crack give rise to the remarkable multi-stage growth of crack length. Besides, owing to an increase in RH, desiccation cracks at a given water content tend to be wider and the width distribution of the final crack network changes from a unimodal to a bimodal feature. Lowering RH causes a faster cracking rate and makes the hierarchical process invisible, resulting in the formation of a longer total crack length at the end of evaporation. This study is expected to help analyze the underlying formation mechanisms of desiccation cracking-inducing geohazards and assess the long-term performance of earth structures under future climate changes.

Modelling soil desiccation cracking by peridynamics

Understanding of desiccation-induced cracking in soil has improved over the last 20–30 years through experimental studies, but progress in predictive modelling of desiccation cracking has been limited. The heterogeneous structure of soils and the multi-physics nature of the phenomenon, involving emergence and propagation of discontinuities, make the mathematical description and analysis a challenging task. The authors present a non-local hydro-mechanical model for soil desiccation cracking capable of predicting crack initiation and growth. The model is based on peridynamics (PD) theory. Attempts to model soil desiccation cracking by PD are limited to a purely mechanical description of the process that involves calibration of the parameters. In contrast, the model presented in this paper describes soil desiccation cracking as a hydro-mechanical problem, where moisture flow and deformation are coupled. This allows for investigating and explaining the mechanisms controlling the initiation and propagation of discontinuities. The model is applied and tested against two sets of experimental data to explain the typical features of drying-induced cracking of clays. The validations use experimental parameters (Young's modulus, water retention characteristics) and avoid calibrations to test the accuracy of the model. The correlations between the shrinkage of soil clay, changes in displacement fields and crack growth are demonstrated. Crack initiation, propagation and ultimate crack patterns simulated by the model are found to be in very good agreement with experimental observations. The results show that the model can capture realistically key hydraulic, mechanical and geometry effects on clay desiccation cracking.

Discrete element model for the failure analysis of partially saturated porous media with propagating cracks represented with embedded strong discontinuities

A novel, fully coupled hydro-mechanical model for the failure analysis of partially saturated porous media is presented. Failure mechanisms pertain to propagating discontinuities, i.e. tensile cracks and shear bands influenced by matric suction or capillary pressure, that arises in the partially water saturated conditions. In order to simulate propagating discontinuities, a discrete model based on lattice domain representation is used, where embedded strong discontinuities serve for mesh objective propagation of discontinuities. The full coupling is provided with Biot porous media theory, Bishop effective stress concept and nonlinear Richards’s equation for the unsaturated fluid flow. The relation between suction and saturation state is given through the van Genuchten constitutive model. The capabilities of the model are presented with the three representative simulations. The first one is related to unsaturated flow in one dimensional sand column. The second one deals with mechanically influenced propagation of dilatant and compactive shear bands with the goal of examining how these mechanisms influence the pore pressure field, suction development and saturation state of the porous media. The third one explores the important geo-environmental engineering application in which development of tensile cracks is triggered and propagated by drying mechanism of the porous media, also known as desiccation cracking of soils.

Investigating Soil Desiccation Cracking Using an Infrared Thermal Imaging Technique

AbstractSoil desiccation cracking is of great concern in many fields such as hydrology, geology and agriculture, whereas its multi‐physical governing mechanism remains unclear up to now. As evaporation is a key influencing factor to soil cracking, capturing the evaporation‐induced soil temperature will significantly contribute to the improved understanding of soil cracking behaviors. Infrared thermal imaging enables the surface temperature measurement through converting infrared radiation into visible images, and has not been applied for soil cracking characterizations in the past. In this study, the fundamental mechanisms of soil desiccation cracking are investigated through the combined usage of three noninvasive techniques including infrared thermal imaging, particle image velocimetry, and digital image processing. Experimental results reveal the correlation between the evaporation‐related temperature of soil and its hydro‐mechanical behaviors. The evaporation rate is proportional to the soil‐atmosphere temperature difference. The soil body with a higher water content corresponds to a larger temperature difference, with the more apparent correlation observed in the unsaturated state of soil. Furthermore, as indicated in a nonuniform soil temperature field, the pore water migrates from the soil body with high temperature into the body with low temperature, similar to the soil particle motion under drying. Hence, the soil body with low temperature attracts additional water to maintain a high water content, resulting in a fast evaporation rate and a low temperature field for a long time. The evolution of the desiccation crack network is also related to the temperature distribution. Soil desiccation cracks tend to form in a lower temperature area, whereas the soil body with a higher temperature presents a more remarkable volume shrinkage. Primary cracks (defined as those first to develop and cause the breaking up of the intact material into separate clods) propagate along the isotherm, while the propagation path of secondary cracks (defined as those sub‐cracks initiated from primary cracks and subdivide soil to smaller clods) is first orthogonal to the isotherm and then rotates to gradually overlap with the isotherm. This study highlights the potential application of the infrared thermal imaging technique to investigate the underlying mechanisms of soil‐atmosphere interaction and perform soil desiccation cracking prediction.

Automatic soil crack recognition under uneven illumination condition with the application of artificial intelligence

Drought-induced soil desiccation cracking has attracted great attention in various disciplines with the advent of global climate change. Accurately obtaining soil crack networks is essential to understand the cracking mechanism. Inspired by recent advances of artificial intelligence (AI) in computer vision, we propose a new automatic soil crack recognition method based a novel network architecture, named Attention Res-UNet. Deep Res-UNet inherits both the advantages from residual learning for training deeper networks and U-Net for semantic segmentation. Moreover, attention mechanism is utilized to alleviate the influences caused by the uneven illumination conditions. Firstly, the soil crack images under different uneven illumination conditions are collected to create a new soil cracking image dataset. Then, traditional method and multiple state-of-the-art deep learning based different semantic segmentation models are tested on our collected dataset. Finally, a professional evaluation standard, which considers both the overall metrics (precision, recall, dice, surface crack ratio) and details (crack total length, average crack width, number of crack segments) of the soil crack features is proposed to evaluate the recognition results of the different models. Extensive experimental results demonstrate the superiority of our proposed Attention Res-UNet approach compared with traditional methods and other deep learning models in recognizing soil cracks under complex environmental conditions. Our method is also suitable for crack recognition of other materials under complex environmental conditions.

Desiccation cracking of heterogeneous clayey soil: Experiments, modeling and simulations

Experimental results for the cracking of heterogeneous clay samples during desiccation are reported, and an associated numerical model is developed for comparison. The clay samples contain embedded rigid inclusions to induce heterogeneous strain fields during drying. The crack paths and local strain fields are monitored during the desiccation process using digital image correlation. A numerical phase field model for crack initiation and propagation is introduced and compared with the experimental results. A qualitative agreement is found for the obtained crack paths, whereas discrepancies remain for the local strain fields. A discussion regarding the comparison between the experimental results and model is provided.

A FDEM 3D moisture migration-fracture model for simulation of soil shrinkage and desiccation cracking

This paper proposes a three-dimensional moisture migration model, which can simulate the moisture migration process in soil. A simple moisture transport example with analytic solutions is given to verify the correctness of the 3D moisture migration model. Combining the moisture migration model with the combined finite discrete element method (FDEM), a moisture migration-fracture model that simulates soil shrinkage and cracking is constructed and implemented in an in-house GPU parallel multiphysics finite element-discrete element software, namely MultiFracs. The calculation process of the three-dimensional moisture migration-fracture model is: first obtain the moisture field distribution of the solution domain through the moisture migration model; then obtain the shrinkage stress in all tetrahedral elements according to the change of the moisture field; finally, apply the shrinkage stress as a load to perform the deformation and fracture calculations of FDEM. The 3D moisture migration-fracture model is used to simulate an experiment of clayey soil shrinkage cracking. Image recognition technology is used to carry out quantitative statistics and analysis of desiccation crack patterns. The simulation results show high consistency with the laboratory experiment. Moreover, the influences of shrinkage parameter, water evaporation rate, and layer thickness on clayey soil desiccation cracking are studied comprehensively.

A 2D FDEM-based moisture diffusion–fracture coupling model for simulating soil desiccation cracking

A 2D FDEM-based moisture diffusion–fracture coupling model for simulating soil desiccation cracking

Use of X-ray computed tomography for studying the desiccation cracking and self-healing of fine soil during drying–wetting paths

Managed aquifer recharge is an efficient approach using surface water for groundwater recharge. However, soil clogging in the infiltration systems represents a critical problem that reduces the efficiency of recharge systems. In recent years, much research has been conducted to investigate clogging in subsurface and surface soil (cake). Cake prevents infiltration into the water table and can drastically reduce the recharge rate. In arid and semi-arid areas, alternation of humid and dry seasons has an effect on cake cracking. In the present research, the propagation of desiccation cracking and self-healing of unconsolidated soil (cake), placed in Plexiglas columns, was investigated using X-ray computed tomography (CT) during drying–wetting (DW) paths. The results showed that during the drying path, cracks initiated at the base of the soil by friction with the bottom of the column and then propagated to the top surface of the cake. As the drying time increased, evaporation at the top surface led to more cracks growing from the surface than from the bottom of the cake. However, the cracks at the bottom tended to stabilize because the water content was greater than at the top surface. The initiation, propagation, and expansion of the cracks developed in the saturated condition of the cake. During the wetting path, some cracks were closed while others appeared. The cracks tended to close progressively with wetting time, highlighting the self-healing phenomenon, probably due to the high plasticity index of cake soil. The results showed that cake swelling is mainly related to an increase of the void ratio due to a decrease in suction between particles. The results demonstrate the capacity of the X-ray CT technique to investigate the evolution of cracks during DW paths.

Measuring desiccation-induced tensile stress during cracking process

The desiccation cracking of soil occurs when shrinkage is restricted during the drying process and the induced tensile stress equals the tensile strength. Thus far, experimental estimations of the tensile stress of soil have not been realized, although such estimates are important for predicting crack initiation. This study presents the development of a laboratory-based desiccation stress test to measure the tensile stress generated during the drying process until crack initiation. In this proposed desiccation stress test, the tensile stress is induced during the drying process in the longitudinal direction of bar-shaped specimens with fixed ends. Desiccation stress tests were performed on sandy soil with a rich fine fraction, and the results were verified through photographic observations of crack initiation and comparisons with the results of direct tension tests. The results show that the desiccation stress test yields reliable tensile stress until cracking. The application of the desiccation test results is illustrated via the verification of an existing model of crack initiation by desiccation. The results of the desiccation stress tests are useful for determining the model parameters that significantly influence the development of tensile stress and enable its accurate prediction until crack initiation.