Study On The Influence Of Uneven Settlement Of G110 Old Road Reconstruction And Expansion Subgrade On The Mechanical Properties Of Pavement Structure

The outline of the 14 th five year plan for national economic and social development of the people’s Republic of China and the long-term goal for 2035 has been issued.The outline puts forward the goal of building a modern infrastructure system and speeding up the construction of a transportation power.Specifically,it is to build a modern comprehensive transportation system,improve the comprehensive transportation channels,and improve the quality of the national highway network.However,the operation life of the early built highway is close to the design service life,which can not guarantee its normal performance.In order to ensure the normal use of the original highway,the main measure is the reconstruction and expansion of the highway.At present,due to the geological and regional differences in highway reconstruction and expansion projects,there are many studies on the characteristics of uneven settlement of subgrade,but there are few studies on the uneven settlement of subgrade and its influence on the additional stress of pavement structure layer based on entity widening project.Therefore,based on the reconstruction and expansion project of national highway G110 from Hohhot to Bikeqi in the northern region of China,this thesis studies the uneven settlement parameters of subgrade and its influence on the mechanical properties of pavement structure layer,establishes the finite element subgrade and pavement model through ANSYS computer finite element software,and carries out numerical simulation analysis on the mechanical properties parameters,and obtains the following conclusions:(1)Based on the analysis of the influence of widening width and height of subgrade,engineering property parameters of subgrade and foundation,and design parameters of subgrade excavation steps on the settlement of new and old subgrade,it is concluded that the step excavation at the junction of new and old subgrade in subgrade expansion project can effectively reduce the uneven settlement of widened subgrade,and the size of excavation steps is suggested to be 80 ～ 150 cm in height,The width is 100 ～ 150cm;The maximum settlement of widened subgrade does not change with the width and height of widened subgrade,but is still at the junction of new and old subgrade;In the selection of new subgrade filler,it is suggested to use light materials with certain strength.(2)After simulating the uneven settlement of subgrade and the parameters(thickness and modulus)of pavement structure layer,it is concluded that the uneven settlement of subgrade will lead to the horizontal additional stress in the pavement structure layer;Under the condition of meeting the requirements of bearing capacity of pavement structure layer,the thickness of base and subbase should be controlled to avoid large additional stress in pavement structure layer.(3)Through the finite element simulation and field engineering sampling,it is concluded that the use of geosynthetics,impact compaction and widening pavement structure,and the use of double stranded steel wire mesh reinforcement material can significantly reduce the additional stress of pavement structure layer.