Numerical Analysis On Deformation Characteristics Of Subgrade Widening Of Lianzhu Highway

With the rapid increase in the number of vehicles and the expansion of the scale of transport,many highways have been unable to meet the existing capacity requirements.To solve this problem,it is bound to speed up the pace of construction of the highway.Due to the large investment and the excessive land resources of new expressway,many domestic highways have been widened to achieve the purpose of road expansion and improvement of service capacity.At present,we have accumulated some engineering experience in the widening of expressway subgrade,but relevant technical and theoretical results can not be applied to all circumstances.Especially the uneven settlement in the widening of the old road and the convergence problem of the old and new subgrade,often leading to instability on subgrade and structure damage of pavement.In this paper,the finite element model of subgrade widening is established to simulate the stress of the foundation under the existing subgrade and the deformation characteristics of the new subgrade.The characteristics of settlement of the new subgrade and the old subgrade with single or double subgrade widening are compared and analyzed.Different step sizes and geogrid embankment reinforcement under the subgrade have different settlement deformation.From the functional and structural aspects of pavement,the fatigue failure characteristics of pavement structure materials are mainly considered,and the uneven settlement control standard of subgrade after construction is determined.It is concluded that the embankments with single and double widening have different characteristics.Compared with the single widening,double widening is more conducive to control the uneven settlement of subgrade.The step can effectively restrain the uneven settlement of the subgrade,and the optimal height of the step is 100cm and the width is 150cm.The geogrid,which laying the bottom of the subgrade is the best,can improve the strength and deformation of the soil in a certain extent,and improve the overall stability of the subgrade.The uneven settlement causes the additional stress in the pavement structure,and the two values are basically linear.The greater the uneven settlement,the greater the additional stress.Finally,the uneven settlement control standard of the subgrade is determined to be 3cm,and the corresponding permissible slope rate is 0.25%.