Study On Design And Construction Technology Of Gravel Soil Subgrade Seal Coat Material

The top seal layer of the subgrade plays an important role in the transition between the interlayer and the reinforcement,and on the other hand it can also play a role in preventing moisture migration.So,it can effectively regulate the water temperature condition and stress distribution of the subgrade and pavement structure.However,there are still a lack of systematic analysis and research on the material design and construction technique of the subgrade seal layer,especially the gravel soil subgrade seal layer.Therefore,based on the construction project of Bei’an to Fuyu Highway and from Bei’an to Gucheng section,the material design and construction technique of the gravel soil subgrade seal layer are studied systematically,and the technology reserve is provided for the design,construction and inspection of the gravel soil subgrade seal layer.First of all,according to the technical requirements of the seal structure and the characteristics of application environmental,the material composition of seal layer is designed and put forward two types of seal material.Based on it,the effects of different materials on the physical properties,strength properties,shrinkage properties and stiffness properties of the seal materials were analyzed.The results show that the strength,stiffness,temperature shrinkage coefficient and dry shrinkage coefficient of the two materials increase with the amount of binder.During the design,the cost and material comprehensive performance coordination should be taken into account.Secondly,based on the existing asphalt pavement design system in China,the variation law of the mechanical properties of the subgrade and the pavement structure under different thickness and modulus is analyzed by using the theoretical calculation method of the layered elastic mechanics system.The results show that the increase of the modulus and thickness of the seal structure can effectively reduce the deflection of the road surface and the tensile and compression stress of the layer bottom of the upper structure.Then,the influence of the setting of the seal structure on the deflection of the acceptance check is analyzed from the theoretical point of view.The results show that with the increase of the modulus and thickness of the gravel soil seal layer,the deflection value of the acceptance check of every structural layer presents basically reduced trend.At the same time,the long-term performance of the pavement structure with gravel soil subgrade seal is forecasted by adopting the new design specification.The results of the multi-index evaluation of new specification show that the setting of the seal layer significantly increases the life of the subgrade structure and reduces the acceptance value of the pavement deflection.Finally,built a gravel soil subgrade seal test road,and made large-scale applications in the Beigu highway.The construction quality control index of the gravel soil subgrade seal is put forward,and the technical indexes of the gravel soil seal material are tested after the construction,and the deflection of subgrade top whether setting gravel soil seal layer or not is compared and analyzed emphatically.The results show that the technical indexes of the seal structure meet the design requirements.