Effect of Soil Moisture on the Deformation Characteristics of Forest Road Subgrade Soils Due to Climatic Change
Effect of Soil Moisture on the Deformation Characteristics of Forest Road Subgrade Soils Due to Climatic Change
PDFAuthors: Lenka Ševelová and Aleš Florian
Volume/Issue: Volume 28: Issue 2
Published online: 18 Nov 2025
Pages: 129 - 134
Abstract
The service life of road pavements, including forest roads, depends on many factors. When designing forest road pavements, it is essential to take into account the behaviour of the subgrade and the factors affecting its physical-mechanical properties, especially soil moisture, which significantly affect the deformation characteristics of the soil. This issue is becoming increasingly important with the increasing climate change. Poor design or intensive use can accelerate the road degradation, leading to environmental damage and reduced exploitation potential. A fundamental parameter for assessing the resistance of soil to repeated loading is the resilient modulus Mr, which is determined from a cyclic load test that simulates the effect of passing traffic. For low-volume roads, including forest roads, this modulus can be determined using a cyclic test with standard California Bearing Ratio testing equipment by applying repeated cyclic loading. One of these innovative cycling test machines was developed at the Mendel University in Brno. The paper presents the results of tests investigating the effect of soil moisture and compaction level on both the resilient modulus and the permanent and elastic deformations of two soil types. The obtained results confirm that the soil moisture content far from the optimum value should result in lower material stiffness and thus to smaller resilient modulus value. Also, they confirm that a larger resilient modulus should be obtained when the soil is compacted with higher compacting energy.
Keywords: resilient modulus, cyclic test, low volume road, pavement, soil, CBR, soil moisture, subgrade, subsoil
References
AASHTO. (2001). Guidelines for Geometric Design of Very Low-Volume Local Roads; American Association of State Highway and Transportation Officials, Washington DC, USA.
AASHTO. (2008). Mechanistic-Empirical Pavement Design Guide (MEPDG); American Association of State Highway and Transportation Officials: Washington DC, USA.
Abid, A. N., Salih, A. O., & Nawaf, E. A. (2017). The Influence of Fines Content on the Mechanical Properties of Aggregate Subbase Course Material for Highway Construction using Repeated Load CBR Test. Al-Nahrain J. Eng. Sci., 3, 615–624.
Bojacá Torres, D. C., & Campagnoli Martínez, S. X. (2022). CBR cíclico como método alternativo para la determinación del módulo resiliente en suelos blandos de subrasante. Cienc. E Ing. Neogranadina, 2, 85–98.
ČSN EN 13286-7. (2004). Unbound and hydraulically bound mixtures – Part 7: Cyclic load triaxial test for unbound mixtures; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
ČSN EN ISO 17892-1. (2015). Geotechnical investigation and testing – Laboratory testing of soil – Part 1: Determination of water content; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
ČSN EN ISO 17892-4. (2017). Geotechnical investigation and testing – Laboratory testing of soil – Part 4: Determination of particle size distribution; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
ČSN EN ISO 14688-2. (2005). Geotechnical investigation and testing – Identification and classification of soil – Part 2: Principles for a classification; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
ČSN EN ISO 14689-1. (2004). Geotechnical investigation and testing – Identification and classification of rock – Part 1: Identification and description; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
ČSN EN ISO 13286-2. (2015). Unbound and hydraulically bound mixtures – Part 2: Test methods for the determination of the laboratory reference density and water content – Proctor compaction; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
ČSN EN ISO 13286-47. (2015). Unbound and hydraulically bound mixtures – Part 47: Test method for the determination of California Bearing ratio, immediate bearing index and linear swelling; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
ČSN EN ISO 17892-12. (2018). Geotechnical investigation and testing – Laboratory testing of soil – Part 12: Determination of the liquid and plastic limits; Institute for Technology Standardization, Metrology and State Testing, Prague, Czech Republic.
Kuloglu, T. F., Lieffers, V. J., & Anderson, A. E. (2019). Impact of Shortened Winter Road Access on Costs of Forest Operations. Forests, 10, 1–20. DOI: 10.3390/f10050447
Mehrpazhouh, A., Tafreshi, S. N. M., & Mirzababaei, M. (2019). Impact of repeated loading on mechanical response of a reinforced sand. J. Rock Mech. Geotech. Eng., 11, 804–814. https://doi.org/10.1016/j.jrmge.2018.12.013
Nguyen, B. T., & Mohajerani, A. (2016). Resilient modulus of fine-grained soil and a simple testing and calculation method for determining an average resilient modulus value for pavement design. J. Transportation Geotechnics, 7, 59–70. https://doi.org/10.1016/j.trgeo.2016.05.001
Ortiz De Zarate, G., & Ševelová, L. (2015). The statistical analysis of the resilience module. In Public recreation and landscape protection – with man hand in hand (pp. 258–264).
Ševelová, L., Arias, P., & Šlezingr, M. (2020). Influence of Improving Materials of Forest Roads on the Surrounding Environment. Polish Journal of Environmental Studies, 29(5), 3821–3830. https://doi.org/10.15244/pjoes/115272
Ševelová, L., Florian, A., & Žák, J. (2021). Influence of Plunger Stress on Resilient Modulus of Forest Subgrade Soils Obtained from Cyclic CBR Test. Forests, 12, 1456. https://doi.org/10.3390/f12111456
Ševelová, L., Florian, A., Žáková K., & Žák, J. (2023). An Updated Cyclic CBR Test with Realistic Stress Values under the Plunger for Resilient Modulus Calculation. Forests, 14, 2425. https://doi.org/10.3390/f14122425
Ševelová, L., & Hauser J. (2013). 304642 – PV 2013-673. Automatic control geotechnical equipment for measuring soil bearing capacity and methods of work with this device. Mendel University.
Ševelová, L., Hauser, J., Zedník, P., Lažek, D., Matula, R., Kozumplíková, A., & Florian, A. (2015). The Methodical Guide to the Design and Implementation of Pavement of Low Volume Roads. Certified Methodology 23327/2015-MZE-16222/M108, (pp. 1–62).
TP 170. (2023). Design of pavement structures. Ministry of Transportation, Prague, Czech Republic.