Characterization of resilient behavior of a fine-grained subgrade filler under graded variable confining pressure

The prestressed subgrade is a novel subgrade reinforcement technique wherein horizontal prestress is applied to the subgrade soil through prestressed reinforcement devices. The applied prestress propagates from the slope to the interior of the subgrade, thereby enhancing the confining pressure ( σ 3 ) of the subgrade filler/soil. A series of dynamic triaxial tests with graded variable confining pressure were performed to assess the impact of horizontal prestress on the resilient behavior of a typical fine-grained subgrade filler. The resilient modulus ( M R ) characteristics and their variation patterns were meticulously analyzed and discussed. The results demonstrate that graded increasing σ 3 could enhance the subgrade filler’s resistance to dynamic elastic deformation, thereby significantly improving its M R , with final increments around 10 MPa. The dynamic loading cycle interval ( N c ) between two adjacent graded confining pressures markedly influences the developmental trend of M R , and earlier increasing σ 3 and smaller N c lead to a higher stable M R of the filler. Each graded increment in the σ 3 initially results in causes an immediate increase in the specimen’s M R , which is subsequently followed by a decline and eventual stabilization with increasing the dynamic loading cycles. Additionally, the advantages of graded increasing σ 3 may not counterbalance the detrimental effects of increased moisture content on the M R . Subsequently, a prediction model for the M R was developed accounting for the conditions of graded variable confining pressure. The model was validated by a high degree of concordance between the predicted and measured M R values of a stable specimen.