Study On The Settlement Characteristics And Reinforcement Measures Of High Fill Foundation Of Mountain Airpor

With the rapid development of economy,airport construction is increasing in mountainous areas of our country.Airport construction in mountainous areas is confronted with complex geological conditions,high fill,high fill foundation deformation control difficulty and other problems.In the deformation control of high fill foundation,the reinforcement measures of dynamic compaction,ultra-high fill and pavement structure are commonly used,while the reinforcement measures such as geograe and geocell are gradually appearing in recent years.This paper selects Jiuzhai Huanglong Airport and Longdongpu Airport high fill foundation as engineering cases,summarizes and analyzes the settlement deformation characteristics of high fill foundation,and uses numerical simulation method to simulate and analyze the reinforcement mechanism and reinforcement effect of dynamic compaction and geocaille reinforcement of high fill foundation.The stress state and deformation characteristics of tunnel structure layer under the condition of uneven deformation are simulated and analyzed and the parameters are optimized.The main conclusions are as follows.(1)By summarizing and analyzing the monitoring data of layered settlement,slope displacement,deep displacement and tunnel settlement of high-fill foundation in Jiuhuang Airport design gully,it is considered that high-fill foundation is a complex system composed of upper fill body and soft foundation at the bottom,and the settlement of high-fill foundation is mainly composed of self-compressive compaction settlement of fill body and drainage consolidation settlement of soft foundation at the bottom.Because the consolidation settlement of soft foundation is relatively slow,the high fill foundation has the characteristics of large settlement,uneven deformation and long deformation duration.(2)The numerical simulation results of dynamic compaction of high trench fill foundation show that the compaction degree and bearing capacity of the foundation soil can be greatly improved by dynamic compaction.The settlement and horizontal displacement of the top of the fill body are reduced by 15.4%-31.1% and 14%-19.3%before and after the reinforcement.The results show that the compaction is effective in controlling the settlement and horizontal displacement of high fill foundation.(3)The numerical simulation results of geocell reinforcement for high fill foundation of Longdongpu Airport expansion project show that geocell can restrain the lateral deformation of soil well,so that the deformation process of soil in the geocell shows strong three-way stress state characteristics of soil under confining pressure.The horizontal displacement and vertical displacement at the top of the fill body decreased by 25.4% and 5% before and after the reinforcement of geotell.The results show that geocell reinforcement is effective in controlling the horizontal displacement of high fill foundation and improving the uneven settlement of foundation.(4)The numerical simulation results of dynamic consolidation and geocoll reinforcement show that the dynamic consolidation method is suitable for the deformation control of high fill foundation with large settlement and significant horizontal displacement,while geocoll reinforcement is suitable for the deformation control of high fill foundation with significant horizontal displacement and strict requirements of uneven settlement.(5)Aiming at the prominent uneven settlement of high fill foundation,the method combining numerical simulation and orthogonal test is adopted to optimize and analyze the main parameters of the pavement structural layer.Under the conditions of the pavement structure,the thickness of the pavement layer is 0.25 m,the modulus of the pavement layer is 3000 mpa,the thickness of the base layer is 0.4m,and the modulus of the base layer is 4000 MPa,The tensile stress of the surface layer is at a low level,which can greatly alleviate the adverse effect of uneven settlement of foundation soil on the structural layer of the tunnel surface.