Study On Deformation And Mechanical Characteristics Of Foundation Pit Supported By Row Of Piles In Seasonal Frozen Area

Seasonal frozen soil is widely distributed in our country.Deep foundation pit projects in these areas often suffer from the problem of overwintering due to the large amount of work and long construction time.Therefore,in seasonal frozen soil areas,the influence of soil excavation and frost heave and thaw settlement with temperature changes on foundation pit engineering is worthy of in-depth study.In this paper,the analysis method combined with field monitoring and Midas GTS software numerical simulation is used to study the deformation laws and stress characteristics of the pile-anchor supporting system and the inner supporting system of piles in the excavation stage and the wintering stage.The main research contents and conclusions are as follows:First,on the basis of the existing research results at home and abroad,the theoretical analysis and summary of the deformation and stress of the foundation pit engineering,the frost heave process and mechanism of the seasonal frozen soil,and the influence of frost heave on the foundation pit engineering are carried out.Secend,the comparison between the numerical simulation results and the actual monitoring data shows that the analysis results of the two have the same trend as a whole,which verifies the reliability of the numerical simulation analysis method to a certain extent.Third,the research results show that the foundation pit supported by row of piles in the seasonal freezing area,during the normal temperature excavation stage,the surrounding ground settlement,pit bottom uplift,horizontal displacement of the supporting pile,and the axial force value of the anchor cable and the internal support are as a whole Both show a trend of increasing with the increase of foundation pit excavation;in the overwintering stage,the distribution of foundation pit deformation and stress curve is basically similar to that of normal temperature stage;foundation pit undergoes frost heave of negative temperature soil at the bottom of the pit The uplift displacement,the horizontal displacement of the supporting pile,the axial force of the anchor cable and the internal support all increase with the decrease of temperature,and the above-mentioned deformation and internal force gradually decrease with the temperature rise,and the deformation and internal force caused by frost heave increase.The amount of ground subsidence around the foundation pit rebounds under the action of negative temperature,and the subsidence continues to increase after the frozen soil gradually melts as the temperature rises,and the subsidence value of the surrounding ground after melting is more than Under normal temperature,the excavation of foundation pits is greater at the end;in summary,it can be seen that the frost heave and thaw settlement of the soil in the seasonal frozen soil area have a great influence on the internal force and deformation of the foundation pit overwintering and cannot be ignored.