Study On The Large Area Field Immersion Tests In Loess High Fill Ground

As the development of the western region economy and society,accelerating urbanization process,the development of the western region has entered a crucial period.The NW areas of our country is located in loess plateau,landforms complicated(vale,ridge and replat)and lack of available land.Therefore,Loess high fill project has been expanding urban space strategy choice.But it necessarily bring a lot of major geotechnical engineering and engineering geology problems.Among them,the settlement after construction is one of the core issues,and the rise and fall of groundwater influence the settlement,so study the influence is significance.This paper give priority to large area field immersion tests,combined with laboratory test and field monitoring and numerical simulation,analysis the variation of settlement after construction when the groundwater rising or surface water infiltration in high fill ground.for the high fill the late planning and construction of the site,That can provide guidance and reference for site planning and similar engineering.By collecting area and survey data,this paper expounds the engineering geological and hydrogeological conditions in the study area.The original physiognomy is loess hilly and gully region,strata are mainly Quaternary loess and Jurassic sandstone and mudstone.Groundwater is mainly of pore water and bedrock fissure water,supplied by atmosphere precipitation and discharged by runoff.The test pit diameter is 50 meters and deep 0.8 meters.And embedded instruments both inside and outside of the pit,such as settlement mark and monitoring devices.,The test was sustained for 107 days and flooding5000m~3.Study shows that water movement through combination surface of digging and filling or filling surface.When filling soil humidity even under the condition of saturation,will produce of wetting deformation,The settlement will increase sharply in the short term when filled soils be wetting or saturation.Besides,the interface of digging and filling is weakness surface,it will causes the differential settlement in the interface,and thus causes the ground cracks and collapse disaster.Finally,build the flow numerical model of unsaturated zone through the Modflow-Surfact program,and simulate water transport.Under the condition of the interface full of water,the undisturbed soil will give priority to reach saturation.At the interface make a drainage material can effective control groundwater level,and decrease the influence on settlement after construction.