# Experimental Study on Mechanical Properties of Highway
## 5 Conclusions  
In order to explore the influence of freeze-thaw cycles, freezing temperature, moisture content, and confining pressure on the mechanical properties of subgrade soil after thawing in cold regions, and to guide how to take corresponding measures to improve the bearing capacity and durability of the subgrade in practical engineering, indoor triaxial tests were conducted to measure the mechanical properties of subgrade soil in cold regions after melting under different conditions. The following conclusions were drawn:  
1. After seven freeze-thaw cycles, the destructive stress of the roadbed soil decreased from 321.7 kPa to 289.9 kPa, representing a decrease of 9.9%, and the elastic modulus decayed by 19.9%. As the number of freeze-thaw cycles increased, the initial tangent modulus and ultimate deviatoric stress gradually decreased, while the damage ratio slowly increased by 6.4%.
2. When the freezing temperature was lowered from \(-5\)\({}^{\circ}\)C to \(-15\)\({}^{\circ}\)C, the destructive stress of the roadbed soil decreased from 303.9 kPa to 290.1 kPa, a reduction of 13.8 kPa, or approximately 4.5%, and the elastic modulus decreased by around 1.6%. The initial tangent modulus exhibited a roughly linear increase with the ultimate deviatoric stress, while the damage ratio fluctuated slightly between 0.90 and 0.91.
3. Increasing the water content from 6% to 12% resulted in a decrease in the destructive stress from 405.43 kPa to 288.4 kPa, representing a reduction of 29.1%. The modulus of elasticity decreased approximately linearly, with a decay of 50.4%. The initial tangent modulus and ultimate deviatoric stress gradually decreased, while the damage ratio increased slowly by 9.0%.
4. By increasing the peripheral pressure from 50 kPa to 150 kPa, the destructive stress increased from 194.7 kPa to 367.7 kPa, an increase of 173 kPa, corresponding to an 88.8% increase in destructive stress. The modulus of elasticity increased with the rise in circumferential pressure, with an increase of approximately 154.1%. The initial tangent modulus exhibited a roughly linear increase with the ultimate deviatoric stress, while the damage ratio increased slowly by 6.9%.
5. The strength of thawed soil approaches its potential ultimate strength as the number of freeze-thaw cycles, water content, and confining pressure increase. The freezing temperature has a lesser impact on the strength of thawed soil.  
**Author Contributions:** Conceptualization, [PERSON] ([PERSON]) and D.L.; methodology, [PERSON] ([PERSON]) and [PERSON]; software, [PERSON] ([PERSON]); validation, [PERSON] ([PERSON]), D.L. and [PERSON]. ([PERSON]); formal analysis, Q.S.; investigation, [PERSON] ([PERSON]) and [PERSON]; resources, D.L. and [PERSON]. ([PERSON]); data curation, [PERSON] ([PERSON]); writing--original draft preparation, [PERSON] ([PERSON]) and [PERSON]; writing--review and editing, D.L. and Q.S.; visualization, D.L.; supervision, [PERSON] ([PERSON]); project administration, D.L.; funding acquisition, D.L. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The authors are very thankful to the financial support of the National Natural Science Foundation of China (No. 42061011 and 41977236), the Key Research and Development Programs of Jiangxi Province (No. 20232 BB50025 and 20223 BBG71W01), and Jiangxi Province Graduate Innovation Special Fund Project (No. YC2023-B209).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The datasets generated and analyzed during the current study are not publicly available, but are available from the corresponding author on reasonable request.  
**Conflicts of Interest:** The authors declare no conflict of interest.