Abstract:

Grading macadam with good temperature and humidity stability is commonly laid under tunnel pavements to drain seepage from the bedrock. In this paper, some dynamic triaxial tests were performed to reveal the effect of bedrock seepage on the dynamic mechanical properties of the grading macadam layer, and a dynamic resilient model was established to describe the mechanical properties of grading macadam. Moreover, the stress state of the pave- ment was analyzed by means of the nonlinear finite element method. The results indicate that （ 1 ） dynamic triaxial tests well simulate the actual stress state of grading macadam under tunnel pavement; （2） the Uzan model conside- ring the shear performance of material better reflects the stress state of grading macadam ; （3） the regression coeffi- cient of the Uzan model presents obvious nonlinearity with the moisture variation, thus greatly affecting the dynamic resilient modulus; （4） the diminishing rate of the maximum tensile stress at the pavement bottom decreases with the increase in macadam modulus; and （5） in order to enhance its draining function and improve pavement stress states, the gradation of macadam should be rigidly controlled-specifically, the content of the macadam in the size of less than 0. 075 mm should be controlled in 5% -7% and the resilient modulus should be in 200 -300 MPa.

Key words: grading macadam, dynamic mechanical property, dynamic triaxial test, nonlinear finite element method, moisture, resilient modulus