| With the rapid development of China’s transportation industry and national economy,many highways constructed in the early stage have insufficient operational capacity to meet the current economic and transportation demands.To address this issue,plans to widen or reconstruct multiple highways have gradually been put on the agenda.However,at present,the expressway reconstruction and expansion project in coastal cities of China started earlier,and there is relatively little research analysis on the expansion and deformation control technology of highways in special soil areas such as loess.In order to avoid engineering problems such as large differential deformation and roadbed instability caused by special soils in loess areas,and extend the service life of highways in loess areas,this paper employs finite element technology to create finite element numerical models based on the physical project of a certain highway reconstruction and expansion project under construction in Shaanxi Province.The study analyzes and explores deformation control technologies such as vehicle load and roadbed over-excavation section,assesses the effects and control effect of vertical and horizontal deformation of the widening area,and draws the following main conclusions:(1)During the operation of the expanded and reconstructed highway,the position of vehicle load action and the newly built shoulder are subjected to significant changes in shear stress.The deformation of the widening area in the X and Y directions increases with the increase of the width of the newly built roadbed.The inflection point of the deformation at the newly built shoulder in the Y direction becomes more and more apparent,and reinforcement measures should be taken for the road structure at these two positions.(2)Setting the over-excavation section of the roadbed has a significant control effect on the deformation of the widened area of the highway in loess areas.The maximum deformation reduction is 30.97%.The control effect of the over-excavation section of the roadbed on deformation is positively correlated with its length,and it is recommended to set the length according to the cross-sectional form of the road.If setting the over-excavation section alone does not meet the deformation requirements in the specifications,measures such as adding steps or replacing with cemented soil can be taken to reduce the maximum deformation by about 23.09%.(3)The soil foundation of the highway in loess areas has an impact on the deformation of the widening area.Measures such as replacing and filling with cement-soil can reduce differential settlement by 3.55%.However,as the depth and width of the replacement and filling area increase,the control ability of the soil foundation replacement and filling on the deformation of the widening area becomes weaker,with a maximum reduction of approximately 50%.It is recommended to use a replacement and filling depth of about 1 meter and a width equal to that of the new subgrade base when carrying out the replacement and filling.(4)Using cement-soil as the filling material for the newly built roadbed in highway reconstruction and expansion projects in loess areas can reduce differential settlement by a maximum of 9%,and the control effect on deformation of the widening area is significant.There is a negative correlation between the deformation of the widening area and the cement content of the improved soil.Taking into account environmental protection,economy,and other factors,it is recommended to use a 3% cement-soil filling material to control the deformation of the widening area.(5)When using a symmetrical widening scheme for the highway reconstruction and expansion project in loess areas,the deformation of the widening area is smaller than that of the non-symmetrical widening scheme.Therefore,when designing the reconstruction and expansion project,priority should be given to using a symmetrical widening scheme. |
