Study On The Mechanical Characteristic Of The Rubber Asphalt Permeable Stress-absorbing Layer And The Combination Optimization Of Pavement Structure

Because of the dry shrinkage and temperature shrinkage of the semi-rigid base, it will have to crack in the construction and maintenance process. Under the wheel load and temperature load, the cracked pavement structure will have stress concentration phenomena at the cracks location. The stress at the bottom of asphalt surface layer is so large that it results in the reflective cracking. These cracks will extend to pavement surface and affect the integrity of the pavement structure. On the other hand, water will enter through cracks into base,sub-base, and even the internal of the sub-grade, reducing the strength of pavement structure and bringing in the earlier distress.In order to prevent the emergence of reflective cracking, it had been laying large-stone porous asphalt mixture base(LSPM)on the semi-rigid base in a number of highways of Shandong Province. Using of the large pore structure and good deformability, it makes the LSPM as stress-absorbing layer of the pavement structure to reduce the stress at the bottom of asphalt surface layer.Rubber asphalt has a good elastic recovery capability,adhesion and low temperature anti-cracking performance, so using the rubber asphalt as binder of the LSPM, it is to design Permeable Stress-absorbing Layer(PSAL) to further enhance the absorptive capacity of the LSPM. Relying on the topic of HaiYang-JiMo Highway, laying the rubber asphalt test pavement sections of the LSPM and planting fiber Bragg grate (FBG) sensor at the bottom of this base, it will further description the mechanism of stress-absorbing of LSPM. Through the Hamburg rutting test,low temperature split test,immersing Marshall test,fatigue test and the dynamic modulus test, it illustrates that the rubber asphalt LSPM has unique advantages performance at high temperature,low temperature cracking resistance, water stability and anti-fatigue performance compared to a large-stone asphalt mixture. Particularly its smaller modulus has better deformation capacity and plays the better role of stress absorption.Through the finite element software ANSYS to analyze the LSPM pavement structure and general semi-rigid pavement structure which are new and cracked under the wheel loads,temperature loads and coupled field when the semi-rigid is cracked, the calculation results show that the LSPM can significantly reduce the stress at the bottom of asphalt surface by its own deformation capacity. On the other hand, because the LSPM has a certain thickness, it can reduce the temperature load on the role of base and the stress of semi-rigid base.Analyzing the pavement structure by BISAR3.0, it will not weak the performance of pavement structure by appropriately reducing the thickness of the LSPM, so it can reduce the cost to some extent. In order to better decrease the reflective cracks of the asphalt surface and make full use of the respective advantages of LSPM and modified asphalt stress absorbing layer, a new type of pavement structure: 10cm LSPM +2 cm modified asphalt stress absorbing layer is proposed.Though detecting by FBG planted t at the bottom of the LSPM, it illustrate that there are different of the strains in different seasons and under different temperature conditions. The larger high-temperature, the larger strain numerical; the greater modulus, the greater the strain, which are consistent with theoretical results.Through the pavement performance tests,theoretical analysis,the detection of data analysis and structural optimization of the pavement of the rubber asphalt LSPM, it show that the rubber asphalt LSPM can play a very good role in absorbing stress and has unique advantages to prevent reflective cracking and it can be a good pavement structure layer to promote its use.