Study On Properties Of Gravel Soil And Airport Settlement In Jinzhou Bay Reclamation Area

With the continuous increase of population and the decrease of available land resources,how to solve the problem of insufficient land resources in the process of development has become a huge problem.In coastal areas,reclamation has become an important measure to solve the shortage of land resources.A large number of soft soil layers are distributed in the reclamation area,with high water content,high compressibility and low shear strength.The construction engineering in this area will produce great surface deformation,which will do great harm to the construction facilities.According to the design requirements,Kansai International Airport,the world's first artificial island airport for land reclamation,will be 4m above sea level to prevent the invasion of waves.However,by December 2012,the average settlement of phase I and phase II projects reached 12.9m and 14.2m respectively,far exceeding the expected settlement.Several typical reclamation areas,such as Incheon International Airport in Japan and Pudong International Airport in Shanghai,have experienced very large land subsidence.It can be seen that land subsidence has become one of the biggest problems affecting the safety and performance of construction facilities in reclamation area.Dalian is an important economic city in northern China.Due to the scarcity of urban construction land,the lack of land resources has become an important factor restricting the economic development of Dalian.It has been more than 40 years since Dalian began reclamation in the 1980 s.The existing airports in Dalian area can not meet the increasing demand of air transportation,so it is imperative to build airports by reclamation.Therefore,the study on the engineering properties of the reclaimed gravel soil and the airport land subsidence in Dalian reclamation area is of great significance for the follow-up engineering construction and rational utilization of the reclamation area.In this paper,aiming at the reclamation area in the west of Dalian,the engineering properties of the reclaimed gravel soil and the stability of the beach in the reclamation area are analyzed,and the ground settlement of the reclamation airport and the post construction settlement of the airport under different foundation treatment schemes are studied and predicted.The research results can provide reference for airport construction and operation planning.The main research results are as follows:(1)The main components of backfill gravelly soil are primary minerals,mainly dolomite and calcite,with little secondary minerals.The grain composition is mainly coarse,mainly gravel soil or gravel gravel soil,with poor and uneven gradation.The cohesive force of gravel soil is 12.5-24.2k Pa,and the internal friction angle is32.4-45.2 °.When the stone content of gravel soil is 45%-70%,the shear strength and internal friction angle of gravel soil are positively correlated with the stone content.When the stone content increases,the increase of internal friction angle first decreases and then increases,while the cohesion of gravel soil is inversely correlated with the stone content.When the stone content increases,the decrease of cohesion first decreases and then increases.(2)The standard method is used to calculate the ground settlement of the airport in the reclamation area.After preloading,the settlement of the site after dynamic compaction is mainly between 20 mm and 70 mm under the effect of design load,and the maximum settlement will reach 90 mm,which appears in the terminal area and runway apron area.The settlement of the site under the action of design load meets the control standard of post construction settlement.(3)FLAC3D is used to simulate the ground settlement of the airport under the design load,including natural preloading and dynamic compaction after natural preloading.Under natural preloading,the maximum settlement of the site is close to100 mm under the design load,which appears in the terminal area.The settlement speed of the airport is the fastest in the first five years,and the soil layer is basically consolidated and stable in the 15 th year.The site settlement mainly occurs in the middle silty clay layer and silt layer.These two layers should also be considered in the subsequent site foundation treatment or foundation selection.After natural preloading and dynamic compaction treatment,the ground settlement of the site is significantly reduced,and the reduction range of the ground settlement is about 15%.The maximum settlement rate of the airport is 11.14mm/a,and the soil layer is basically consolidated and stable in about 40 A.The research and prediction of the ground settlement of the airport under the design load has important reference significance for the subsequent airport engineering construction.(4)The beach stability of Jinzhou Bay is studied.All the sediments are shallow sea sediments,which are distributed from the top of the bay to the inside of the Bay in a NE-SW direction,with a gradual change law of coarse fine coarse.Based on the remote sensing data,the coastline change is studied,and the factors affecting the stability of the beach are analyzed.