Study On Design Theory And Methods Of Semi-flexible Compound Pavement Structure

Semi-flexible compound pavement is generally described as a composition pavement, which is filled with Portland cement grout in open-graded matrix asphalt mixture. A great deal of research had been done and taken into the application in domestic and overseas. But the research about semi-flexible pavement and its material is still in the start stage in our country, the application of the pavement in road hasn't got well researched and generalized. Semi-flexible compound pavement behaves with more rigidity than asphalt pavement and more flexibility than cement pavement. It has both virtues of normal asphalt and cement pavement but avoids the defects of them. So, it has great practical meaning and broad development prospects to study its application technology.Through theoretical analysis and laboratory test, the results showed that semi-flexible compound materials in the appropriate mixture grade and ratio of additive, process, conservation methods and other conditions, as compared with ordinary asphalt concrete, showing good road performance (such as rutting resistance at high temperature, water stability, crack resistance at low temperature, and so on), particularly the representation of rutting resistance at high temperature and water stability have been improved greatly. In addition, the experiment research on the linear contractive coefficient of semi-flexible compound materials showed that cooling brought smaller contraction, and then result in a smaller temperature stress, therefore, temperature cracks produced unlikely.In the paper, the design theory and design methods of semi-flexible compound pavement have been studied mainly. According to the materials which had higher static modulus and larger splitting strength, the relationship between stress and strain and its cracking characteristics and so on, the elastic layered system theory which is the design theory of asphalt concrete pavement would be selected as the new pavement structure's design theory. In addition, the paper analyzed load stress of semi-flexible compound pavement using ANSYS software, according to variation of each direction of the stress, and gave the response characteristics of load and the locations of the points which were used in pavement design.The paper analyzed the damage state of semi-flexible compound pavement and indicated that crack was its main failure mode, and then focus on discussing its cracking mechanism, in combination with conventional pavement design method in domestic and overseas, and then put forward design method of the new type of pavement structure, which is that tensile stress as design indicator, the vertical compressive strain of subgrade as checking indicator, and still using double circular vertical uniform load under the theory of multiple layered elastic system to calculate thickness, and then given specific design steps. In addition, the paper discussed its structure combination. Lay the foundation of application of technology of semi-flexible compound pavement in future.The paper got supported by the key project "rigid-flexible composite pavement structure and its application" in Chongqing Municipality.