Research On Resilient Modulus And Shear Strength Of Unbound Granular Materials

For a long time, China’s high-grade asphalt flexible pavement typical structure is the semi-rigid base + asphalt surface layer(which is also called "Strong subgrade with Thin layer" road design theory) In order to meet the requirements of the roads function and the best economy benefit at the same time. This is also decided by the status quo situation of insufficient asphalt production. However, the reflective cracks and shrinkage cracks in the asphalt pavement caused by semi-rigid materials throughout the entire cycle of the road life and it is inevitable. In recent years, flexible particulate materials represented by graded crashed stone have good deform ability used between the asphalt surface and semi-rigid, as "stress dissipate Layer"(flip-chip structure). Practice has proved that this initiative can solve the crack problem of semi-rigid base. So the traditional flexible particulate materials as graded crashed stone come into the view of the road workers once again.For graded crashed stone material, barely used as high-grade base material independently in our country(mainly because of the fear that their strength is insufficient, deformation is too large), which to some extent, restricted the graded gravel material application. Due to limitations laboratory conditions and other factors, the traditional mechanical index mainly such as: CBR, shear strength, static resilience modulus. These indicators, either primarily as a property evaluation of soil(grading as gravel material, the mechanical properties of the soil were significantly different specific performance: stress-dependent characteristic); or infected by the static force measured means and confining restrictions, which cause the result tested in laboratory are not uniform with the actual construction and they can be very different.With the improvement and progress of laboratory test equipment, new types of mechanical indexes: Resilient modulus, shear strength of Octahedron τoct is attracting the attention of experts and scholars at home and abroad. Resilient Modulus Characterize the strength and deformation characteristics of road material, which is a relatively comprehensive laboratory test evaluation. Unlike traditional static resilient modulus, dynamic resilient modulus considers the stress dependence characteristics of graded crashed stone: dynamic load mode, in order to simulate loads acting under actual vehicle base material at the maximum extent,. Octahedral shear strength τoct characterization graded gravel plastic deformation characteristics, different from traditional shear model. According to the different types of grass, we can select the appropriate loading mode and data processing using computer technology to make mechanical analysis; it can be more convenient and fast.Based on the review of mechanical properties of graded crashed stone, and demonstrating the shortcomings of traditional mechanical evaluation index. In this paper analyze the Test Method for presentation graded crashed stone’s dynamic resilient modulus and octahedral shear strength τoct and to explore the influence of the temperature, gradation type, freeze-thaw cycles, and add the old asphalt material graded gravel on the dynamic modulus of resilience and Octahedral shear strength τoct.