| Abstract [eng] |
All road pavement structures according to national regulations are designed on the same strength of subgrade (45 MPa (roads), 30 MPa (pathways)), with the provision that the strength of subgrade does not decrease lower than the design limit value. Usually happens that subgrade strength during the spring thaw period decreases dramatically thus leading to insufficient (not supplying design criteria) pavement structure deflection and faster deterioration. The purpose of this master’s thesis is to investigate how bearing capacity changes during spring thaw dependent on pavement structures subgrade improvement type including natural subgrade case. Researchers note that pavement structure is being highly deteriorated during mild winter when the densest quantity of ice lenses forms in upper pavement structure layers and during the rapid spring thaw due to excess moisture content in the drainage. The author experimental research in 7 different roads sections and 2 seasons presented that the bearing capacity of the whole pavement structure is mainly dependent on asphalt layer thickness and thickness of the whole pavement structure. Results revealed that the subgrade area, compared to pavement structure layers, expresses the lowest E600,sub modulus values independently from road structure composition. The bearing capacity of the measured subgrade expressed with E600,sub modulus, varied from 159 MPa to 219 MPa in the dry autumn period and from 131 MPa to 189 MPa in the spring thaw period. Subgrade soil improvement or stabilization reduces the seasonal impact on the pavement structure performance by reducing the difference of the stiffness at the surface of the pavement structure during spring thaw and dry autumn periods since the difference of stiffness on unimproved roads is 32% and 8% on improved roads. The analysis presented that the deformation modulus of the subgrade still often decreases below 45 MPa during the spring thaw period even if the subgrade was improved. Master's thesis consists of 100 pages that include 55 figures, 13 tables and 53 references. |
