| Along with the development of the large-scale engineering construction,there are more and more in the practical engineering problems of silty sand land area,deep foundation pit engineering has significant effect of time,the creep characteristics of silty sand soil deformation of the slope protection pile increase over time,stop time is too long to wait for supporting is not timely,construction causes overterm service are likely to result in foundation pit engineering accidents.Exampled by a certain area of yulin a silty sand deep foundation pit engineering as an example,the analysis of the extended under creep on the impact of the silty sand soil,at the same time of theoretical analysis,combined with numerical simulation,this paper studies the time effect of deformation under the scope and trends and laws,and establish the corresponding constitutive model,to make reasonable forecast on the stability of foundation pit in the future,Providing the basis for managing mine engineering for planning and later extension services,the following aspects of work are mainly carried out:(1)We have summarized the characteristics of current basic pit engineering and the problems that exist in basic pit engineering research.Through a detailed survey of the national and international research status,we will briefly summarize the national and international research status and results in terms of soil creep characteristics,foundation pit engineering deformation and time effects.Based on the survey and physical and mechanical test of fine sand soil in this area,the creep effect of fine sand soil in this area is analyzed and evaluated according to the triaxial creep test results of fine sand soil.(2)Taking the deep foundation pit of fine sand in this area as an example,the Sing-Mitchell,Mesri and Bailey Norton creep equations of stress,strain and time are introduced respectively on the basis of elasto-plastic deformation of soil and considering the influence of time.Three elastoviscoplastic models which can describe the creep characteristics of fine sand in this foundation pit are fitted respectively.The advantages and disadvantages of each creep model were analyzed and compared,and the creep model closest to the test results was selected to work out the corresponding creep equation,which provided a theoretical basis for the study of the dynamic change of foundation pit stability with time.(3)Numerical simulation analysis,the finite element software ABAQUS,against the background of the three projects set up silty sand soil deep excavation,the finite element calculation model and parameter sensitivity analysis,the creep model respectively to study the creep parameters,A,m,n,The effect of the presence of anchor cables on the deformation.Determine the correct calculation and simulation parameters used in the specific project and calculate and analyze the long-term loading of the excavation and the creeping effect of the silt layer.Soil and soil structure of the protective piles on the slopes of the excavation pit,and through the parameter inversion parameters with measured data,generated forecast model are used to calculate the foundation pit slope protection pile under lateral creep deformation range and trend,reasonable prediction on the stability of foundation pit in the future.(4)The monitoring data and numerical simulation results show that fine sand soil has creep characteristics,so the deep foundation pit will show time effect under extended service state,and the deformation of foundation pit under extended service state cannot be ignored.The creep model is established to reasonably simulate the deformation law of foundation pit excavation and support and extended service of fine sand soil in sanguan project of a city.Through parameter inversion with monitoring data,the modified creep parameters make the calculation result more close to the actual situation.The successful prediction of the future stability of the foundation pit provides a basis for the schedule arrangement and later management of the foundation pit in extended service. |
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