Research On The Influence Of Large Diameter Porous Parallel Pipe Jacking Construction On Surrounding Soil Deformation

Compared with the single hole pipe jacking,the construction of large-diameter multi hole pipe jacking has more serious disturbance to the soil mass,resulting in greater land subsidence.In this context,this paper mainly analyzes the construction process of large-diameter porous pipe jacking,in order to explore the disturbance mechanism of pipe jacking on the surrounding soil and the adverse effects of land subsidence.The specific research contents and conclusions are as follows:(1)This paper introduces the influence of soil warehouse pressure,stratum loss,grouting pressure and pipeline deviation correction on soil mass.The prediction methods of ground settlement caused by single hole pipe jacking construction are summarized,including peck settlement formula,random medium method,centrifugal experiment method and source sink method.This paper introduces the common calculation methods of ground settlement in parallel pipe jacking construction,including peck correction formula,equivalent large circle model,double circle superposition model and random medium theory model.(2)The three-dimensional model of porous pipe jacking construction is established by using ABAQUS finite element software.And the selection method of various material parameters and the application of various conditions in the model are introduced in detail.The ground settlement under different soil warehouse pressures is analyzed.The settlement curve obtained by numerical calculation is in accordance with the peck settlement curve.When the soil warehouse pressure is within ±20 k Pa of the static earth pressure at the pipeline axis,the ground settlement caused is the smallest.(3)For the first time,the problem of land subsidence caused by different longitudinal spacing is considered.In view of this problem,six kinds of construction conditions are discussed and verified by numerical simulation.When the parallel pipe jacking construction is carried out at the same time,the ground settlement caused by the parallel pipe jacking construction increases gradually with the increase of the longitudinal spacing.When the two pipe jacking construction is carried out at the same time without the longitudinal spacing(k = 0L),the soil is evenly stressed,the ground settlement caused by the construction is the smallest.And the rapid ground subsidence will be caused when the second pipeline starts construction.(4)Based on the four hole parallel pipe jacking project in the second phase expansion project of Meilan Airport in Haikou,the influence of the construction sequence of four hole pipe jacking on the final ground settlement is studied.Using the double circle superposition model to verify the land subsidence curve.In the construction process of four hole pipe jacking,the land subsidence caused by jacking from left to right is the largest,and the maximum value appears in the middle of the line of pipe jacking axis.The interval construction can reduce the disturbance caused by the adjacent pipe jacking construction and reduce the ground settlement,but the maximum value will shift.(5)The stress distribution of soil around large diameter four hole pipe jacking is discussed.The soil around the pipeline has obvious stress release phenomenon.The soil stress above and below the pipeline is less than the surrounding soil stress,and the soil stress between the pipelines is greater than the surrounding soil stress.