Dan Hancheng

Research on Predicting the Rutting of Asphalt Pavement Based on a Simplified Burgers Creep Model

Rutting is one of the most important distresses for asphalt pavement structures especially due to the heavy traffic loadings. In this paper, the solution of Burgers model is employed and simplified, which makes the residual strain only depend on the applied load. Then, the governing equation for dynamic response of pavement was established and a semianalytical solution related to the stress state of asphalt pavement was obtained. Further, an explicit expression was presented and validated to calculate rutting depth of asphalt pavement through incorporating the dynamic stress solution, simplified Burgers model solution, and time hardening model. Compared with the FEM method, the calculation error is less than 5%, which proved the method proposed to be feasible. Compared with the numerical simulation method, every derivation of the rutting formula in this paper has the clear physical meaning and is hence easy to be understood. Besides, the proposed method can save a significant amount of time consumed due to its fast and reliable calculation.

Experimental investigation on the resilient response of unbound graded aggregate materials by using large-scale dynamic triaxial tests

Resilient modulus is an important response index for unbound graded aggregate materials (UGAM) as a drainage layer in pavement structure. In this paper, a large-scale dynamic triaxial test (300 mm in diameter and 600 mm in height) is conducted with four gradations under conditions of repeated loading tests to investigate the resilient responses with various stress levels and water contents. Then, a model is introduced to quantify the moisture sensitivity of the resilient response of UGAM with the consideration of stress level, fine fraction porosity and gradation. Through comparison between experimental and predicted values, the proposed model is validated and shows that the resilient modulus at certain water content level can be predicted well when the resilient modulus at other water content level is known by experiment.

Three-Dimensional Ground Settlement Induced by Metro Tunnel Excavation Considering the Influence of Group Piles

Considering the influence of group piles, a prediction model for three-dimensional ground surface settlement induced by circular metro tunnels excavation in incompressible rock masses is proposed based on the stochastic medium theory and the shear displacement method. The surface settlement caused by the metro tunnel opening is divided into two parts. One part is soil mass settlement caused by the metro tunnel opening and calculated by the stochastic medium theory. The other part is the settlement induced by the friction force between the group piles and the soil mass around the metro tunnel cross section and calculated by the shear displacement method. The three-dimensional prediction of the ground surface settlement is obtained by the linear superposition of the two parts. The validation of the proposed prediction approach is proved by comparing with the measured data and the numerical model of the double tunnels under the Puyuan overpass where metro tunnels undercrossed group piles. The effects of buried depth, radial convergences, center distance of double tunnels, position and size of piles, and group piles are analyzed and discussed. The improved prediction approach can be applied to calculate the three-dimensional ground settlement, especially for the metro tunnels crossing through group piles.