Study On The Engineering Properties Of Aeolian Sand And Gravel Soil Low Embankment Under Vehicle Load

Low embankment is an important development direction of highway construction in our country because of its lower filling height, less quantities and land areas, especially it can merge with the natural landscape easily and has less effect on natural ecological environment. Because the engineering properties of low embankment under vehicle load have not been fully understood and some parameters were unreasonable in the design process, resulting in large settlement of subgrade, pavement cracking and road service level becoming low. So understanding the engineering properties of low embankment under vehicle load has important theoretical significance and engineering practical value for the design and construction.The paper depended on the project of reasonable highway subgrade height in Xinjiang Oasis-desert region of western traffic construction projects of science and technology. The engineering properties of low embankment under vehicle load were systematically studied through indoor test, model test, numerical simulation and theoretical analysis methods. The main research work and results can be summarized as follows.1. Using a quarter vehicle model, considering the influence of tire damping and road roughness, vehicle load cycle characteristic, additional dynamic load and dynamic load calculation formula of vehicle were gotten.2. Dynamic characteristics of Aeolian sand and gravel soil in Xinjiang were systematically studied through dynamic triaxial test, including dynamic stress-strain relation, the dynamic elastic modulus,damping ratio and the critical dynamic stress and dynamic strength. The influence of confining pressure, water content, compaction degree, load frequency and the initial static deviatoric stress on those was concluded, then hyperbolic model for dynamic stress-strain relation, power function model for dynamic elastic modulus-strain relation and index curve model for dynamic strength-number relation were put forward. The critical dynamic stress of Aeolian sand and gravel soil under different conditions were determined.3. Low embankment model tests with different subgrade material gravel soil or Aeolian sand under three different foundation conditions were done. Simulating different axle load and speed of vehicle load by changing the load size and frequency, engineering properties of low embankment were analyzed under static load, short and long time dynamic load. Dynamic stress of different depth, dynamic strain of different structural layer, transmission and attenuation properties of dynamic stress within the scope of subgrade and foundation were obtained. Meanwhile influence laws of static load value, peak value and frequency of dynamic load, the number of dynamic load, water content of foundation and subgrade filling on engineering properties of low embankment was gotten. Engineering properties differences of low embankment were analyzed under static load, short and long time dynamic vehicle load. Dynamic stress accumulation model of low embankment under long time dynamic load was put forward.4. Three-dimensional finite element model for dynamic analysis was established, then its correctness was verified by field measurement results and low embankment model test results. Based on the model, the influence of the embankment height and modulus, base layer thickness and modulus, surface layer thickness and modulus, vehicle speed, overload rate and road roughness on dynamic stress of different depth and subgrade workspace of low embankment was analyzed.5. Based on stress transfer and diffusion equation of layered structure under static load, according to low embankment model tests results and numerical simulation analysis results, considering the influence of vehicle load speed, the road roughness, overload, cumulative effect, road structure and dynamic stress attenuation property, calculation formula of dynamic stress for low embankment was deduced. Based on the formula, the parameter value of replacement reinforcement measure for low embankment foundation in Xinjiang was gotten.