Factors influencing accuracy of free swelling ratio of expansive soil

Abstract

Many geotechnical structures, such as the subgrade of high-speed railway, are extremely sensitive to micro deformations. As one of the most commonly used indexes in China to evaluate the potential swelling level of expansive soils, the effectiveness and accuracy of free swelling ratio should be highly required. However, due to the deficiency of geotechnical test regulations for the free swelling ratio test, non-negligible variation difference is often observed among the test results of the same type of soil samples. Thus, a series of laboratory tests are conducted to figure out the influences of soil particle size, initial soil temperature, and wet-dry circulation on the free swelling ratio of expansive soils. The results show that the initial soil temperature exerts an obvious influence on free swelling ratio and a relative weak influence on soil mass of expansive soil with the micro soil particle size (d<0.075 mm), and the correlation becomes unclear when soil particle size is within the range of 0.075 mm≼d<0.500 mm. A larger particle size of expansive soils induces a larger free swelling ratio and soil mass in the soil measuring cup regardless of initial soil temperature. However, the enlarging amplitude decreases as the particle size of expansive soils increases. There is a progressive enlargement of free swelling ratio at the first two wet-dry cycles and then it attenuates gradually when the number of wet-dry cycles further increases.

Keywords

free swelling ratio / particle size / soil temperature / wet-dry circulation / expansive soil

References

[1] MawloodY I, HummadiR A. Reversible and irreversible deformations of expansive clays [J]. Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 2019, 172(5): 442-452

[2] MawloodY I, HummadiR A. Large-scale model swelling potential of expansive soils in comparison with oedometer swelling methods [J]. Iranian Journal of Science and Technology, Transactions of Civil Engineering, 2020, 44(4): 1283-1293

[3] VilarrasaV, RutqvistJ, BlancoM L, et al.. Use of a dual-structure constitutive model for predicting the long-term behavior of an expansive clay buffer in a nuclear waste repository [J]. International Journal of Geomechanics, 2016, 16(6): 1-13

[4] WangL, LeiX, LiuS. Investigation of immersion influence on dynamic properties of high-speed railway subgrade with semi-rigid waterproof functional layer through field-excitation testing [J]. Canadian Geotechnical Journal, 2018, 55(1): 19-33

[5] ZhangR, LongM, LanT, et al.. Stability analysis method of geogrid reinforced expansive soil slopes and its engineering application [J]. Journal of Central South University, 2020, 27(7): 1965-1980

[6] GuoA, KongL, ChenJ. Influential factors on free swell test [J]. Rock and Soil Mechanics, 2006, 27(11): 1949-1953(in Chinese)

[7] ZHU De-yu, LIU Ai-ye, TAN Yong-ping. Study on the effect of particle size on free swelling ratio of clayey soil [J]. Railway Investigation and Surveying, 2015(3): 41–44. DOI: https://doi.org/10.3969/j.issn.1672-7479.2015.03.014. (in Chinese)

[8] ZhangW, LiY, DangJ, et al.. Study on improving the accuracy of free swelling ratio test [J]. Journal of Northwest A&F University (Nat. Sci. Ed.), 2015, 43(9): 203-208(in Chinese)

[9] SunH, MašínD, NajserJ, et al.. Water retention of a bentonite for deep geological radioactive waste repositories: High-temperature experiments and thermodynamic modeling [J]. Engineering Geology, 2020, 269105549

[10] Molinero-GuerraA, DelageP, CuiY, et al.. Water-retention properties and microstructure changes of a bentonite pellet upon wetting/drying: Application to radioactive waste disposal [J]. Géotechnique, 2020, 70(3): 199-209

[11] YeW M, WanM, ChenB, et al.. Temperature effects on the swelling pressure and saturated hydraulic conductivity of the compacted GMZ01 bentonite [J]. Environmental Earth Sciences, 2013, 68(1): 281-288

[12] ZhuJ, ZhangW, ZhangY, et al.. Swelling characteristics of East-Africa black cotton soil based on computer molecular simulation [J]. Journal of Central South University, 2020, 27(7): 2054-2067

[13] WangH, GargA, ZhangX, et al.. Utilization of coconut shell residual in green roof: Hydraulic and thermal properties of expansive soil amended with biochar and fibre including theoretical model [J]. Acta Geophysica, 2020, 68(6): 1803-1819

[14] StewartR D, AbouN M R, RuppD E, et al.. Modeling multidomain hydraulic properties of shrink-swell soils [J]. Water Resources Research, 2016, 52(10): 7911-7930

[15] WellsR R, DicarloD A, SteenhuisT S, et al.. Infiltration and surface geometry features of a swelling soil following successive simulated rainstorms [J]. Soil Science Society of America Journal, 2003, 67(5): 1344-1351

[16] LloretA, VillarM V. Advances on the knowledge of the thermo-hydro-mechanical behaviour of heavily compacted “FEBEX” bentonite [J]. Physics and Chemistry of the Earth, Parts A/B/C, 2007, 32(8–14): 701-715

[17] RomeroE, SimmsP H. Microstructure investigation in unsaturated soils: A review with special attention to contribution of mercury intrusion porosimetry and environmental scanning electron microscopy [J]. Geotechnical and Geological Engineering, 2008, 26(6): 705-727

[18] MaT, WeiC, YaoC, et al.. Microstructural evolution of expansive clay during drying — wetting cycle [J]. Acta Geotechnica, 2020, 15(8): 2355-2366

[19] ZhaoN F, YeW M, ChenB, et al.. Modeling of the swelling — shrinkage behavior of expansive clays during wetting — drying cycles [J]. Acta Geotechnica, 2019, 14(5): 1325-1335

[20] JonesD E, HoltzW G. Expansive soils — The hidden disaster [J]. Journal of Materials in Civil Engineering, 1973, 43(8): 49-51

[21] StellE, GuevaraM, VargasR. Soil swelling potential across Colorado: A digital soil mapping assessment [J]. Landscape and Urban Planning, 2019, 190103599

[22] AmerO M, BulutR. Nonlinear determination of suction compression index in expansive soils for heave prediction [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2020, 146(10): 04020104

[23] WangX, ShaoH, WangW, et al.. Numerical modeling of heating and hydration experiments on bentonite pellets [J]. Engineering Geology, 2015, 19894-106