Fracture mechanics for crack propagation in drying soils

According to the unified soil classification system, the soil can be classified as low plasticity clay CL. The dry soil was sieved through a mechanical sieve of 1. Distilled water was added in required quantity to achieve the intended moisture content. Once a visibly homogeneous paste was obtained, its moisture content was determined before pouring it into the CT-moulds.

Moisture content was determined again when the experiment was completed. The CT-mould was filled with the prepared material in three layers in order to have a homogeneous density.

Loading pins were inserted to the specimens after removing from the moulds and a Methacrylate plate was inserted between the specimen and the nuts of the loading pin in order to ensure the correct load transmission to the right fracture zone just below the initial crack. The load was applied manually, with a constant frequency. The fracture load was de- termined counting all the weights in the loading pan after the specimen failed. The procedure was repeated for all the specimens.

For each size, moisture content and initial crack length, tests were repeated with a minimum of two specimens and in some cases with three. A total of 55 specimens were tested. Table 1 gives the details of the geometry of the test specimens, with length L , width B , and thickness W. The fracture energy G was calculated using Eq.

As a common and well known trend, here also the fracture load increases with decrease in initial crack length Lee et al.

Figure 2b shows the variation of the fracture energy, G, with the initial crack length. A similar experiment has been reported by Nahlawi et al. The equipment used in the present work is made up of 3 main parts see Figure 3a : two pieces of trape- zoidal shape, one fixed and another one freely movable on application of external force, and a central part that is removed just before the application of the load; this is the only part of the specimen which will be subjected to tension during the test.

Figure 3b shows a photograph of one specimen in the tensile apparatus. For each density and moisture content the tests were repeated with a minimum of two specimens and in some cases three. The soil used and the prepara- tion of the material was the same as explained earlier for the fracture toughness tests.

The depth of the soil placed in the equipment was fixed and the weight of the soil was varied to obtain different densities. Figure 4 shows the variation of tensile strength with moisture content for two dry densities. A clear difference in the tensile strength for different densities on the dry-side is observed, whereas on the wet-side the difference is smaller. Similar behaviour has been observed by other authors Favaretti ; Tamarakar et al.

Sequence showing crack development from appearance of first crack to the completion of drying and crack pattern formation corresponding to test A Soils are particulate media which inherently have fissures and crack-like imperfections; these flaws can trigger fracture or initiate a crack due to environmental action or when loaded.

Plastic or nonlinear strains unavoidably D prevail in the vicinity of these flaws or crack tip. Although LEFM holds good for linear-elastic materials only, it does provide an ideal and simple way of estimating the amount of energy required to create a new free surface in the material. As an example, the results of an experimental study Prat et al.

More details about the tests can be found in the previ- ous references since because space restrictions cannot be fully provided here. The experiments consist of five geometrically similar specimens sizes DIN A0 to A4 with two thicknesses for each size 10 and 20 mm , subjected to drying conditions in a laboratory controlled environment. Figure 5 shows the developing crack pattern for the largest specimen A0, 20 mm. Similar sequences are observed for the other sizes and thicknesses.

The main parameters that describe the evolving crack pattern crack density factor, crack length, intersection angles, etc. With these results it can be proved, in a qualitative manner, that cracking stress depends on the size of the specimen and therefore that fracture mechanics can be used to model these phenomena. Figure 6 shows the main results of the analysis.

Figure 6a represents the size effect law, where the cracking stress decreases as the size of the specimen in- creases. The algebraic system of equations that results from this formulation is highly nonlinear and non-symmetric, in D general. Ledesma , M. Lakshmikantha , H. Levatti , J. Keyphrases fracture parameter crack propagation crack initiation india fracture mechanic drying soil tensile strength soil mechanic laboratory moisture content increase new equipment tensile strength test fracture toughness decrease fracture toughness determination fracture toughness propagation criterion fracture mechanic experimental value soil mechanic numerical model direct method different moisture content published literature.

A fusion of science and policy. Glasgow, UK 17 - 21 May The role of education in civil engineering to face the climate change Levatti, H. The role of education in civil engineering to face the climate change.

Channel 7, Formosa, Argentina interview. El programa de Liliana Levatti Lopez, H. El programa de Liliana. Technical Education Day in Argentina. Formosa, Argentina 10 - 12 Nov A strategy to face the impact of Covid and technology disruption on higher education in the lustrum Lopez, H. Sih GC Strain energy density factor applied to mixed mode crack problems. Int J Fracture 10 3 — Geotechnique 19 2 — Int J Fracture 95 1—4 — Eng Geol 3—4 — Appl Clay Sci 52 1—2 — Geoderma 1 — Trabelsi H, Romero E, Jamei M Tensile strength during drying of remoulded and compacted clay: The role of fabric and water retention.

Appl Clay Sci — J Geotech Geoenviron 6 Vallejo LE Application of fracture mechanics to soils: An overview. ASCE, pp 1— Cement Concrete Res 10 1 — Can Geotech J 56 5 — Soil Sci Soc Am J 82 4 — Eng Fract Mech Geotech Test J 30 4 — Eng Geol 94 1—2 — Geotechnique 66 4 — Wells AA Unstable crack propagation in metals: cleavage and fast fracture.

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J Soils Sediments Download citation. Received : 10 August Accepted : 30 September Published : 09 November Anyone you share the following link with will be able to read this content:.

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Skip to main content. Search SpringerLink Search. Abstract Purpose Soil cracking is a common natural phenomenon. Materials and method We review the past research efforts devoted to the experimental investigations and applications of fracture mechanics in soil cracking, attempting to provide a better understanding of the formation mechanism of desiccation cracking with a perspective of fracture mechanics.

Results and discussion This review analyzes the influence of soil cracking on soil engineering properties and the significance of soil cracking phenomena. Conclusions Fracture mechanics is a significant method to explain soil crack initiation and propagation. References Abd El-Halim AA Image processing technique to assess the use of sugarcane pith to mitigate clayey soil cracks: Laboratory experiment.

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Geotechnique 63 1 —29 Google Scholar Costa S, Kodikara J, Xue J b J-integral as a useful fracture parameter for analysis of desiccation cracking in clayey soils.