Numerical Analysis Of Deep Foundation Pit With Internal Braced System In Strata Of "Soil-rock" Dualistic Structure

With development of urban construction and the shortage of land resources, deepexcavations of subways, civil air defences and high-rise building basements are moreand more widespread in complex environment where buildings are thick andunderground pipelines interconnected. Due to the above the influence of many factors,underground engineering for the rational development and utilization of deepexcavation technology in our country in recent decades, get a degree of development.However, a considerable number of problems in the development and constructiondesign appeared in the various sectors，which may affect construction progress,inducing pit’s collapse, water gushing, sand gushing, threatening personal safetyeven directly made the excavation by halves. Therefore, many special and effectiveform of foundation pit supporting emerging in recent years and get a good applicationaccording to different situations, and how to select the reasonable foundation pitsupporting form also become the key research problems of foundation pitsupporting design.The computation methods and pertinent problems of the support works of deepexcavation are analyzed and summarized in detail in this paper,which are thereferences to the FEM analysis of the multi-staged excavation. The types thatsupporting structure of piles and internal support are rose and developed rapidly inrecent years. However, the engineering experience of their design and construction isnot sufficient, in the condition of dualistic structure of soil stratum and underlyingrock stratum. Therefore, analyses of their deformation and instability are veryimportant in practical engineering projects.Their deformation and instability were analyzed by using a combination bigFEM program Plaxis and combining with practical engineering cases. As for theinternal support, the distance and rigidity of internal support were the two main influencing factors to be analyzed, with the aim of proposing appropriate parametersof the two factors. As for the rock-sock eted pile, numerical simulation was carriedout on selection of the rocket length and bending rigidity of the piles. And byanalyzing the variation of rocked length and movement and bending moment of thepiles, the design parameters could be proposed appropriately.At the same time, a monitoring program for it excavation is developed inaccordance with the relevant specifications after analyzing the monitoring results andcomparing hose with the theoretical results. Get some useful conclusions which isuseful for design, construction and monitoring of similar engineering.