Influence of the coefficient of non-uniformity of expansion of clay soil specimen on mechanical characteristics

Introduction. Determination of strength and deformation characteristics of soils composing the soil mass is the key process of calculation and design of structures of all types. High accuracy in determining mechanical characteristics plays a huge role at every stage of project development. Triaxial compression units are one of the most popular and widely used devices for laboratory research, as this type of testing allows you to reproduce the stress-strain state of the soil mass and determine its mechanical characteristics most accurately.

Materials and methods. Experimental studies were performed on clay soil specimens (sandy loam, loam, clay) in a triaxial compression device in a consolidated-drained mode in order to study the effect of the coefficient of non-uniformity of expansion of the soil specimen on its mechanical properties.

Results. Analyzing the data of experimental studies, it was found that the coefficient of non-uniformity of expansion of specimen b has a significant effect on the obtained values of the mechanical characteristics of clay soil, namely: the values of the angle of internal friction in the medium increased by 5 %; the values of specific adhesion increased by 4.4 % on average. However, it should be noted that despite the increase in the strength characteristics of the tested soil specimens, the exclusion of the coefficient b from the treatment process led to a decrease in the values of the secant deformation modulus at 50 % strength E50 by an average of 4.5 %.

Conclusions. The obtained overestimated values of strength characteristics φ, c and underestimated values of deformation characteristics E50 are not critical, however, to increase the accuracy of calculations performed based on the results obtained as a result of in-house processing of laboratory test specimens, the coefficient of uneven expansion b of the specimen should be taken into account.

1. Mirny A.Yu., Ter-Martirosyan A.Z. Determination of the mechanical characteristics of coarse-clastic soils by direct tests in a three-axis device. Integration, partnership and innovation in construction science and education : collection of materials of international scientific conference. 2017; 937-941. EDN XSNIQV. (rus.).

2. Ishmaev O.A., Filimonova N.V. Results of three-axis tests of gravel sands in the complex “ASIS pro” with a sample diameter of 100 mm. News of the Ural State Mining University. 2022; 2(66):89-95. DOI: 10.21440/2307-2091-2022-2-89-95. EDN XNCBJY. (rus.).

3. Jiang C., Ding X., Chen X., Fang H., Zhang Y. Laboratory study on geotechnical characteristics of marine coral clay. Journal of Central South University. 2022; 29(2):572-581. DOI: 10.1007/s11771-022-4900-5

4. Koroleva I.V., Sagdatova M.R. Experimental studies of gray clay behavior under conditions of triaxial compression at different moisture. News of the Kazan State University of Architecture and Engineering. 2019; 4(50):228-235. EDN EUGJOR.

5. Hernández-Hernández V.A., Joya-Cárdenas D.R., Equihua-Anguiano L.N., Leal-Vaca J.C., Diosdado-De la Peña J.A., Pérez-Moreno L. et al. Experimental and numerical analysis of triaxial compression test for a clay soil. Chilean Journal of Agricultural Research. 2021; 81(3):357-367. DOI: 10.4067/S0718583920210003-00357

6. Lan L., Zhang Q., Zhu W., Ye G., Shi Y., Zhu H. Geotechnical characterization of deep Shanghai clays. Engineering Geology. 2022; 307:106794. DOI: 10.1016/j.enggeo.2022.106794

7. Wang G., Wang Z., Ye Q., Zha J. Particle breakage evolution of coral sand using triaxial compression tests. Journal of Rock Mechanics and Geotechnical Engineering. 2021; 13(2):321-334. DOI: 10.1016/j.jrmge.2020.06.010

8. Wils L., Van Impe P.O., Haegeman W. Triaxial compression tests on a crushable sand in dry and wet conditions. Proceedings of the XVI ECSMGE. Geotechnical Engineering for Infrastructure and Development. 2015; 3449-3454.

9. Hazout L., Cherif Taiba A., Mahmoudi Y., Belk-hatir M. Deformation characteristics of natural river sand under compression loading incorporating extreme particle diameters impacts. Marine Georesources and Geotechnology. 2022; 41(10):1156-1174. DOI: 10.1080/1064119X.2022.2122090

10. Nandanwar M.R., Chen Y. Simulations of triaxial compression test for sandy loam soil using PFC3D. Paper presented at the American Society of Agricultural and Biological Engineers Annual International Meeting 2014. 2014; 6:4097-4106.

11. Kozicki J., Tejchman J., Mühlhaus H. Discrete simulations of a triaxial compression test for sand by DEM. International Journal for Numerical and Analytical Methods in Geomechanics. 2014; 38(18):1923-1952. DOI: 10.1002/nag.2285

12. Benessalah I., Sadek M., Villard P., Arab A. Undrained triaxial compression tests on three-dimensional reinforced sand: Effect of the geocell height. European Journal of Environmental and Civil Engineering. 2022; 26(5):1694-1705. DOI: 10.1080/19648189.2020.1728581

13. Pinho-Lopes M. Sand reinforced with recycled cotton textiles from waste blue-jeans: Stress–Strain response. International Journal of Geosynthetics and Ground Engineering. 2022; 8(5). DOI: 10.1007/s40891-022-00404-z

14. Pantazopoulos I.A., Markou I.N., Atmatzidis D.K. Stress-strain-strength and hydraulic performance of microfine cement grouted sands. Journal of Materials in Civil Engineering. 2022; 34(10). DOI: 10.1061/(ASCE)MT.1943-5533.0004433

15. Yin Z., Zhang Q., Zhang X., Zhang J., Li X. Shear strength of grouted clay: Comparison of triaxial tests to direct shear tests. Bulletin of Engineering Geology and the Environment. 2022; 81(7). DOI: 10.1007/s10064-022-02739-3

16. Ekinci A., Vaz Ferreira P.M., Rezaeian M. The mechanical behaviour of compacted lambeth-group clays with and without fibre reinforcement. Geotextiles and Geomembranes. 2022; 50(1):1-19. DOI: 10.1016/j.geotexmem.2021.08.003

17. Sun A., Yang G., Yang Q., Qi M., Wang N., Ren Y. Experimental investigation of thermo-mechanical behaviors of deep-sea clay from the south China sea. Applied Ocean Research. 2022; 119:103015. DOI: 10.1016/j.apor.2021.103015

18. Yan R., Yan M., Yu H., Yang D. Influence of temperature and pore pressure on geomechanical behavior of methane hydrate-bearing sand. International Journal of Geomechanics. 2022; 22(11). DOI: 10.1061/(ASCE)GM.1943-5622.0002580

19. Zhang C., Pan Z., Yin H., Ma C., Ma L., Li X. Influence of clay mineral content on mechanical properties and microfabric of tailings. Scientific Reports. 2022; 12(1). DOI: 10.1038/s41598-022-15063-3

20. Ter-Martirosyan A.Z., Anzhelo G.O., Ermo-shina L.Yu., Bokov I.A., Manukyan A.V. Influence of the coefficient of non-uniform expansion of the soil sample on mechanical characteristics. Vestnik MGSU [Monthly Journal on Construction and Architecture]. 2023; 18(10):1574-1586. DOI: 10.22227/1997-0935.2023.10.1574-1586 (rus.).