Modelling of desiccation crack development in clay soils
- Authors: Costa, Susanga , Kodikara, Jayantha , Thusyanthan, N.I
- Date: 2008
- Type: Text , Conference paper
- Relation: 12th Int. Conf. of the Int. Assoc. for Computer Methods and Advances in Geomechanics p. 1099-1107
- Full Text: false
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Numerical modelling of laboratory tests on desiccation cracking
- Authors: Amarasiri, Aruna , Kodikara, Jayantha , Costa, Susanga
- Date: 2009
- Type: Text , Conference paper
- Relation: 1st Int. Symp. on Computational Geomechanics (COMGEO I ) p. 302-310
- Full Text: false
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Investigating performance of stormwater filters under controlled and uncontrolled environments
- Authors: Meade, Ben , Heyne, Marcus , Li, Lianggang , Jackson, Daniel , Ooi, Ean Tat , Lee, Lisa , Costa, Susanga , Kandra, Harpreet
- Date: 2017
- Type: Text , Conference paper
- Relation: International Conference On Sustainable Civil Engineering Practices
- Full Text: false
- Reviewed:
- Description: Hydraulic performance and its evolution over time is a key design parameter for stormwater filter systems. The major impact affecting stormwater filters is the reduction in infiltration rate, or otherwise known as clogging. This paper focuses on the effect of biological clogging of non-vegetated high flow stormwater filters in Australian conditions. An experimental column study was undertaken. Five semi-synthetic stormwater dosing configurations were tested: (i) Typical stormwater (base), (ii) Stormwater with high nutrient load, (iii) Typical stormwater with chlorine tablets, (iv) sterilized stormwater, and (v) potable water. Each configuration had 6 replicate columns, 3 were placed inside under controlled laboratory conditions and 3 were placed outside under normal Australian spring weather conditions, except for the potable water case (v) where it only had 2 replicate columns and both were placed outside. The results found were inconclusive due to the insignificant reduction of the infiltration rate over time and the columns did not clog, which is due to the size of sediment used in this study. It is suggested that further work should be undertaken on investigating the effect of stormwater composition in stormwater filters in real world conditions.
Investigation of engineering performance of gravels mixed with additives for unsealed pavement stabilization
- Authors: Huxtable, David , Xue, Jianfeng , Costa, Susanga
- Date: 2012
- Type: Text , Conference paper
- Relation: 11th Australia - New Zealand Conference on Geomechanics: Ground Engineering in a Changing World p. 1244-1249
- Full Text: false
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- Description: A case study was undertaken to assist Central Goldfields Shire Council, Victoria, Australia, in assessing the success of its unsealed road stabilisation program. A section of road was treated in 2009, with different combination of additives (RT20 and Eko-Soil) and then post construction testing was carried out in 2010 to verify the success of the trial. A set of parameters, including California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), Maximum Dry Density (MDD), and Optimum moisture content was tested after the setting of the additives. The results indicated that Eko-Soil performed better than Reynolds RT-20 in treating the selected site.
Numerical modelling of desiccation cracking
- Authors: Amarasiri, Aruna , Kodikara, Jayantha , Costa, Susanga
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal for Numerical and Analytical Methods in Geomechanics Vol. 35, no. 1 (2011), p. 82-96
- Full Text: false
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- Description: The ability to model and predict the formation of desiccation cracks is potentially beneficial in many applications such as clay liner design, earth dam construction, and crop science, etc. However, most studies have focused on statistical analysis of crack patterns and qualitative study of contributing factors to crack development rather than prediction. Because it is exceedingly difficult to capture the nonlinear processes during desiccation in analytical modelling, most such models handle crack formation without considering variation of material properties with time, and are unattractive to use in realistic modelling. The data obtained from laboratory experiments on clay soil desiccating in moulds were used as a basis to develop a more refined model of desiccation cracking. In this study, the properties, such as matric suction, stiffness and tensile strength of soil, and base adhesion, could be expressed approximately as functions of moisture content. The initial conditions and the development of suction due to desiccation and the varying material properties were inputted to UDEC, a distinct element code, using its internal programming language FISH. The model was able to capture some essential physical aspects of crack evolution in soil contained in moulds with varying lengths, heights, and materials of construction. Extension of this methodology is potentially beneficial not only for modelling desiccation cracking in clay, but also in other systems with evolving material properties such as concrete structures and road pavements.
Theoretical analysis of desiccation crack spacing of a thin, long soil layer
- Authors: Costa, Susanga , Kodikara, Jayantha , Barbour, S. Lee , Fredlund, Delwyn
- Date: 2018
- Type: Text , Journal article
- Relation: Acta Geotechnica Vol. 13, no. 1 (2018), p. 39-49
- Full Text: false
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- Description: Soil desiccation cracking is important for a range of engineering applications, but the theoretical advancement of this process is less than satisfactory. In particular, it is not well understood how the crack spacing-to-depth ratio depends on soil material behaviour. In the past, two approaches, namely stress relief and energy balance, have been used to predict the crack spacing-to-depth ratio. The current paper utilises these two approaches to predict the approximate spacing-to-depth ratio of parallel cracks that form in long desiccating soil layers subjected to uniform tensile stress (or suction profile) while resting on a hard base. The theoretical developments have examined the formation of simultaneous and sequential crack patterns and have identified an important relationship between the stress relief and energy approaches. In agreement with experimental observations, it was shown that the spacing-to-depth ratio decreases with layer depth, and crack spacing generally increases with layer depth. The influence of the stiffness at the base interface indicated that decreasing the basal interface stiffness makes the crack spacing to increase in sequential crack formation. The experimental observations also show a decrease in cracking water content with the decrease in layer thickness, and this behaviour was explained on the basis of a critical depth concept.
Shrinkage properties of fibre-enzyme reinforced clay
- Authors: Zhou, Limin , Xie, Yuekai , Costa, Susanga , Kandra, Harpreet
- Date: 2017
- Type: Text , Conference paper
- Relation: International Conference On Sustainable Civil Engineering Practices
- Full Text: false
- Reviewed:
- Description: Shrinkage of clay soils during drying can impose significant unfavourable effects on engineering applications. Researchers have attempted to amend drying shrinkage by mixing soil with various additives such as nanomaterials, fibre, geo-polymer etc. This paper discusses the shrinkage characteristics of an expansive clay mixed with nylon fibre and an organic enzyme. As clay is mostly used in compacted form in civil engineering applications, the study was focused on the shrinkage behaviour of compacted clay. Different percentages of nylon fibre, ranging from 0 to 1.2 percent by weight, were mixed with soil. The amount of enzyme added to each mixture was kept fixed at 0.35 g of enzyme per kg of dry soil. Compacted soil blocks were made using standard compaction procedures and cut in to rectangular specimens of size 80 x 60 x 40 mm.Compaction test results indicated that addition of fibre and enzyme can slightly improve the dry density of soil. Rectangular block specimens were allowed to dry without restraints under room temperature. Change in moisture content, linear and volumetric shrinkage and change in void ratio were investigated. Image analysis techniques were used to measure the changes in dimensions.
Controlling desiccation cracks in clay with fibre and enzyme
- Authors: Costa, Susanga , Kim, Sungho , Xue, Jianfeng , Xie, Yuekai , Zhou, Limin
- Date: 2017
- Type: Text , Conference paper
- Relation: 2nd Symposium on Coupled Phenomena in Environmental Geotechnics (CPEG2)
- Full Text: false
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- Description: Desiccation cracking is a common, undesirable phenomenon in many geotechnical engineering applications, particularly in compacted clay liners as it causes significant changes to the hydraulic and mechanical properties of soils. This is one of the major concerns in design and construction of landfill clay liners in arid regions. This paper reports the findings of laboratory tests conducted to investigate the effects of adding nylon fibre, guar gum and organic enzyme to the soil to control desiccation cracks. Merri-Creek clay, a highly expansive soil from Victoria, Australia, was used in the tests. The additives were mixed with soil in different combinations and in varying proportions. Desiccation tests were conducted in thin, long moulds as in the free shrinkage tests. It was observed that very small quantities of these additives were sufficient to alter the properties of overall mixture. The results indicated that fibre – enzyme is the most effective combination to reduce desiccation cracks. This additive combination contained 0.3% percent of fibres by dry weight of soil and 0.35 g of enzyme per kg of dry soil. There was a modest improvement in dry density in the fibre -enzyme mixture compared to pure Merri-Creek clay. Fibre-enzyme combination also showed the ability to reduce the hydraulic conductivity. It was discovered that guar gum is not desirable to mix with clays in terms of reducing desiccation cracking or decreasing hydraulic conductivity.
J -integral as a useful fracture parameter for analysis of desiccation cracking in clayey soils
- Authors: Costa, Susanga , Kodikara, Jayantha , Xue, Jianfeng
- Date: 2013
- Type: Text , Conference paper
- Relation: International Symposium on Coupled Phenomena in Environmental Geotechnics: From Theoretical and Experimental Research to Practical Applications p. 377-381
- Full Text: false
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- Description: Fracture behaviour of clay soils during desiccation is an important area in soil mechanics that needs further development. The current approach is to use Linear Elastic Fracture Mechanic parameters, such as fracture energy and fracture toughness, measured from load tests for analysis and modelling of crack propagation. However, the importance of taking plasticity of the material into consideration has been highlighted by several researchers. This is especially true for soft and/or slurry clay. The recently developed double ring test is the only test available up to date which enables determination of Elasto-Plastic Fracture Mechanic parameter, J-integral. This is an important parameter, which accounts for the change in potential energy with fracture propagation. Currently, there is no data for J-integral in literature as applicable to desiccation cracking. This paper fills the said gap by presenting a set of J-integral data for Churchill clay and Kaoline clay measured from the double ring test. Values have been calculated for both slurry and compacted clay with corresponding coefficients of linear shrinkage. The challenging task of calculating strains and stresses has been dealt with the use of an image analysis technique. In addition, the path independence for J-integral calculation and the behaviour of J-integral with the moisture content are also discussed.
Investigation of desiccation cracking using automated digital photography
- Authors: Costa, Susanga , Kodikara, Jayantha
- Date: 2007
- Type: Text , Conference paper
- Relation: 10th Australia New Zealand Conference on Geomechanics p. 338-343
- Full Text: false
- Reviewed:
- Description: Desiccation cracking can be heavily detrimental on the performance of clay soils in various engineering applications. Typical engineering applications include compacted clay barriers in waste containment, dam cores, canal liners and road pavements. The evolution of desiccation cracks has not been clearly understood and explained. A series of laboratory tests were conducted using Merri-Creek clay and potato starch. The evolution of cracks was captured by automated digital photography and presented in a time-lapse video format similar to the phenomenon of a blooming flower. To the authors’ knowledge, this is the first time such a video has been produced. Both simultaneous and sequential types of cracking are investigated. The relationship between desiccation rate, average cell area, thickness of the specimen and etc are examined and discussed.
Shrinkage development during soil desiccation
- Authors: Costa, Susanga , Kodikara, Jayantha
- Date: 2010
- Type: Text , Conference paper
- Relation: Unsaturated Soils: Theoretical and Numerical Advances in Unsaturated Soil Mechanics - Proceedings of the 4th Asia Pacific Conference on Unsaturated Soils p. 433-436
- Full Text: false
- Reviewed:
- Description: Clayey soils undergo shrinkage during desiccation. When shrinkage is restrained by the boundary conditions or by internal stresses, tensile stresses are generated within the soil body. These stresses eventually produce tension crackswhich create problematic situations in many engineering applications. Presence of shrinkage cracks is significant in many applications such as earth embankments, landfill clay liners, foundations, and road pavements. Desiccation or thermally induced induced shrinkage cracks cause problems in other disciplines as well, for example in mining engineering, agricultural engineering and materials engineering. It is important to understand the shrinking behavior of soil in order to study the desiccation crack development in clayey soils. Free shrinkage of slurry clay was observed in laboratory experiments. Image analysis, along with Particle Image Velocimetry (PIV) technique was used to analyze the data obtained. Relatively small specimens 100 mm longwere used so that strains could be measured to high accuracy.Werribee clay, an expansive clay found in West Melbourne, was used in the experiments. Basic clay properties include liquid limit of 127%, plasticity index of 101 and linear shrinkage of 22%. This paper discusses the relationship between strains (vertical, horizontal, and volumetric), displacements, water content, degree of saturation and void ratio. Shrinkage strain development prior to crack initiation was examined to identify crack failure condition.
Measuring soil strain using fibre optic sensors
- Authors: Costa, Susanga , Kahandawa, Gayan , Chen, Jian , Xue, Jianfeng
- Date: 2019
- Type: Text , Conference proceedings , Conference paper
- Relation: 8th International Congress on Environmental Geotechnics, ICEG 2018; Hangzhou, China; 28th October-1st November 2018; part of the Environmental Science and Engineering book series p. 43-50
- Full Text:
- Reviewed:
- Description: Monitoring subsurface soil movement is important in many geotechnical engineering applications such as stability of slopes, road embankments and settlement in foundations. Soil displacement measurement is also helpful in understanding the formation of shrinkage cracks. Clay soils undergo shrinkage during drying and experience substantial stresses and strains, which results in shrinkage cracks. This paper presents a novel approach to measure soil strain using Fibre Bragg grating (FBG) sensors. In the experiments described, FBG sensors have been used to investigate the strain development in clay during drying. FBG sensors are fabricated in the core region of specially fabricated single mode low-loss germanium doped silicate optical fibres. The grating is the laser-inscribed region with a periodically varying refractive index, which reflects a specific light wavelength. Due to the applied strain, ε, there is a change in the wavelength which can be measured and is directly proposal to strain. Kaolin clay, mixed with water close to the liquid limit, was allowed to dry under room temperature. The specimens were prepared in thin, long linear shrinkage moulds. FBG sensors were placed inside soil at the centre of the specimen. The strain development during drying underwent four phases moving from compression to tension. An oscillating nature of strain was also observed throughout the drying process. Results obtained are useful to develop analytical solutions to describe stress-strain behavior of drying soil. © Springer Nature Singapore Pte Ltd. 2019.
Determination of cohesive properties for mode I fracture from compacted clay beams
- Authors: Amarasiri, Aruna , Costa, Susanga , Kodikara, Jayantha
- Date: 2011
- Type: Text , Journal article
- Relation: Canadian Geotechnical Journal Vol. 48, no. 8 (2011), p. 1163-1173
- Full Text: false
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- Description: Tensile fracture in mode I occurs in many geotechnical applications such as in slope stability, desiccation cracking, borehole pressuremeter testing, etc. The cohesive crack model is a powerful and versatile tool that can be used to numerically analyse mode I fracture, that has had very limited usage in geomechanics to date. This research reports findings from testing on single-edge notched beams manufactured from compacted clay fractured in three-point bending. Specimens were tested at a range of moisture contents to determine several fracture parameters including the parameters defining cohesive cracks. The properties for the cohesive crack were back-calculated by matching the numerically modelled load-load point displacement curve obtained using a hybrid continuum distinct element program with the ones obtained experimentally. It was found that the cohesive crack method could be successfully used in matching the load-load point displacement curves for a range of consistencies of the clay from soft to very hard. It is tentatively suggested that linear softening curves may be sufficient for modelling clay fracture, unlike for concrete, which typically displays distinctly bi-linear softening behaviour. Further research and testing along the discussion presented in this paper could be beneficial in numerically analysing geotechnical applications with mode I fracture.
Determination of J-integral for clay during desiccation
- Authors: Costa, Susanga , Htike, Wut Yee , Kodikara, Jayantha , Xue, Jianfeng
- Date: 2016
- Type: Text , Journal article
- Relation: Environmental Geotechnics Vol. 3, no. 6 (2016), p. 372-378
- Full Text: false
- Reviewed:
- Description: Fracture behaviour of clay during desiccation is an important area in soil mechanics that needs further development. The current approach is to use linear elastic fracture mechanics involving parameters such as fracture toughness, measured from load tests for analysis and modelling of crack propagation. However, the importance of taking crack tip plasticity of the material into consideration has been highlighted by several researchers. This may be especially true for soft and/or slurry clay. The recently developed double ring test is the only desiccation test available today that enables determination of the elastoplastic fracture mechanic parameter J-integral. This parameter accounts for the change in potential energy with fracture propagation. Currently, there are no data for J-integral in the literature as applicable to desiccation cracking. This paper fills this gap by presenting a set of J-integral data for Churchill clay and kaolin clay measured from the double ring test. J-integral values have been calculated for both slurry and compacted clay using corresponding coefficients of linear shrinkage. The challenging task of calculating strains and stresses has been dealt with by using image analysis. In addition, the path independence for J-integral calculation and the behaviour of J-integral with the moisture content are also discussed.
Desiccation cracking in clayey soils : Mechanisms and modelling
- Authors: Kodikara, Jayantha , Costa, Susanga
- Date: 2013
- Type: Text , Book chapter
- Relation: Multiphysical Testing of Soils and Shales p. 21-32
- Full Text: false
- Reviewed:
- Description: This paper presents a summary of the work undertaken on desiccation cracking in soils with special reference to the work undertaken by the authors and co-workers at Monash University. All areas of historical field observations, laboratory modelling and identified mechanisms are discussed briefly. Analytical and numerical approaches for modelling of the desiccation cracking and process are discussed. Cohesive crack approach is presented as a viable approach for modelling of desiccation cracking and fracture evolution catering for consistency change of soil during desiccation. It is highlighted that both tensile strength and crack opening displacement increases, thereby increasing the fracture energy of the soil as the moisture content reduces. This modelling approach can be extended to model wetting/drying cycles and to model crack dynamics. Associated moisture transfer modelling also needs to be advanced for a complete solution.
Mitigation of desiccation cracks in clay using fibre and enzyme
- Authors: Xie, Yuekai , Costa, Susanga , Zhou, Limin , Kandra, Harpreet
- Date: 2020
- Type: Text , Journal article
- Relation: Bulletin of Engineering Geology and the Environment Vol. 79, no. 8 (2020), p. 4429-4440
- Full Text: false
- Reviewed:
- Description: Formation of cracks during desiccation is a natural phenomenon in expansive clay. Mitigation of desiccation-induced cracks is highly beneficial for increasing the life span of geo-infrastructures particularly in hydraulic barriers. Improvement of soil properties using additives is a key method in controlling desiccation crack formation and their influence. This paper presents experimental results for an expansive clay modified with nylon fibre and an enzyme-based product. A series of desiccation cracking tests were carried out with varying fibre contents and a constant enzyme dosage. Three-point bending beam tests were performed to evaluate tensile strength of the modified clay. The additives, fibre and the enzyme were able to alter the crack patterns significantly thereby alleviating the effects of cracks. Furthermore, the addition of enzyme alone increased the tensile strength by about 50% while the combined effect of both fibre and enzyme increased the tensile strength by approximately 100% compared with untreated soil. Based on measurement of crack patterns and other properties of the modified clay, the investigation suggests the potential for the fibre-enzyme addition to mitigate desiccation cracks. Further work needs to be carried out to determine optimal dosing requirements for each additive and investigate the effects of potential interactions between the fibre and enzyme. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Salient factors controlling desiccation cracking of clay in laboratory experiments
- Authors: Costa, Susanga , Kodikara, Jayantha , Shannon, Benjamin
- Date: 2013
- Type: Text , Journal article
- Relation: Geotechnique Vol. 63, no. 1 (2013), p. 18-29
- Full Text: false
- Reviewed:
- Description: This paper elucidates some of the controlling factors governing soil desiccation. The desiccation tests were conducted on three materials-clay, potato starch and milled quartz sand-all three featuring similar fracture energy. Two controlling factors were identified in desiccation cracking, regardless of the material. The first is the tensile stress and strain energy development within the material when the material is restrained against shrinkage. The distribution of the tensile stress will depend on the boundary conditions and material stiffness, and will dictate where cracks are likely to originate. The second factor is that the exact positions of crack initiations will be controlled by the flaws and/or pores within the material. For materials such as clay, with very fine particles, the cracking mechanism is governed by flaws, since the desaturation of fine pores would require very high suction stress, and this requirement leads to sequential cracking and orthogonal crack patterns. If the material has particles giving relatively large and uniform pore sizes with high moisture diffusivity leading to high shrinkage energy prior to cracking, then the fracture energy balance indicates that cracking can occur in near hexagonal patterns with 120° crack initiations, which occur predominantly simultaneously. However, even for materials with lower moisture diffusivity, such as for clay, high desiccation rates can give rise to an 'effective layer' over which high suctions and strain energy develop, leading to almost simultaneous dense cracking.
Evaluation of J integral for clay soils using a new ring test
- Authors: Costa, Susanga , Kodikara, Jayantha
- Date: 2012
- Type: Text , Journal article
- Relation: Geotechnical Testing Journal Vol. 35, no. 6 (2012), p. 981-989
- Full Text: false
- Reviewed:
- Description: Fracture behaviour of clay soils is an important area in soil mechanics that needs further development. Currently, there is no test method to determine fracture properties of clay soils during desiccation. The past work has been mostly on the use of fracture toughness as applicable to linear elastic fracture mechanics using external loading of specimens. However, importance of considering likely plasticity in fracture propagation, especially with soft soils, has been highlighted. J integral is an important parameter in elasto-plastic fracture mechanics, which accounts for the change in potential energy with fracture propagation. This paper presents an innovative test method to evaluate the fracture behaviour, in particular to determine J integral, as applicable to desiccating soils. The challenging task of calculating strains and stresses of slurry clays has been dealt with using an image-analysis technique. Starting from the fundamentals of fracture mechanics, J integral is expressed as a summation of several line integrals. The major advantage of the new method is its suitability for wet or slurry soils for which load tests are impossible. Copyright © 2012 by ASTM International.
Study of desiccation cracks evolution using image analysis
- Authors: Costa, Susanga , Kodikara, Jayantha , Thusyanthan, N.I
- Date: 2008
- Type: Text , Conference paper
- Relation: First European Conference on Unsaturated Soils (E-UNSAT 2008) p. 159-164
- Full Text: false
- Reviewed:
- Description: Desiccation cracking can be heavily detrimental on the performance of clay soils in various engineering applications. Typical engineering applications include compacted clay barriers in waste containment, dam cores, canal liners and road pavements. The evolution of desiccation cracks has not been clearly understood and explained. A series of laboratory tests were conducted using Merri-Creek clay. The evolution of cracks was captured by automated digital photography. It was revealed that under the conditions tested, the cracks occurred sequentially subdividing the overall surface area into cells. The relationship between desiccation rate, average cell area, thickness of the specimen and crack initiation are examined and discussed.
Prediction of parallel clay cracks using neural networks – a feasibility study
- Authors: Choudhury, Tanveer , Costa, Susanga
- Date: 2019
- Type: Text , Conference paper
- Relation: 2nd GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2018 - The official international congress of the Soil-Structure Interaction Group in Egypt, SSIGE 2018, 24 November 2018 through 28 November 2018 p. 214-224
- Full Text: false
- Reviewed:
- Description: Cracking in drying clay soil is a common phenomenon especially in arid and semi-arid regions. Proper understanding and reliable prediction of the extent and nature of cracks in clay is vital for the design and construction of geo-infrastructures. While many models have been developed over the years to predict cracking, they are focused on a single crack rather than the whole network. This paper presents a feasibility study on a novel intelligent approach based on artificial neural network to predict the number of cracks in soil for a given combination of input parameters. Initial moisture content, specimen layer thickness and size of the specimen are used as inputs to the model. The output is the number of cracks. The collected database is used to train, validate and optimise the neural network models. The optimisation steps are discussed and analysed as the predicted number of cracks are compared to the experimental ones. A reasonable agreement was found between the experimental and predicted data. The results indicate that the model can be further improved to make more reliable predictions. © 2019, Springer Nature Switzerland AG.