Numerical Simulation Of A Deep Foundation Pit Of The Underground Plaza In Hefei And Inverse Analysis Of Parameters

With the arrival of the peak of China’s city construction，and the developmentof underground space increases, as well multi-storey basements have developed，corresponding foundation pits are more and more deep. Excavations and technicalproblems of supports of foundation pits are more and more important, theconsideration of the safety and the inpact of the surrounding buildings need to beaddressed. Therefore, the deformation and stability issues of deep foundation pitshave become more prominent.The deep foundation pit of the underground commercial plaza in Hefei VictorySquare was the study project in this paper. Combined with on-site monitoring,numerical simulation and theoretical analysis to study the variation of the envelopesystem and the foundation soil, and the inverse analysis of model parameters based onthe analysis in Flac was studied. Through the data of on-site monitoring, variationswere analysised, including deep horizontal displacements, horizontal displacements atthe top of supports, displacements at the top of column, settlements of outside pittable and surrounding high-rise buildings, anchor foce of the deep foundation pit.Thenumerical simulation of section4-4of the foundation pit was done by Flac.Thenumerical simulation results, including horizontal displacements during theexcavation of deep foundation pit, vertical displacements of the bottom of the pit andnear the ground, and structural units. And results of deep horizontal displacements bynumerical simulation and on-site monitoring were compared, the result showed thatthe idea of numerical simulation is correct.Cohesions and angles of internal friction ofthree soils, within the foundation pit excavation, were disigned by unniform defignmethod. Then multiple sets of parameters obtained were substituted into the model inFlac.These simulation data were obtained by analysis in Flac. These data were inputvalues of the RBF neural network.Soil parameters values were output. The optimalparameters of the soil were obtained by the method for solving the optimal parameters.Finally, the inveres analysis was done by the measured data.The main conclusionswere: (1) During excavation, deep horizontal displacement was graduallyincreasing, and the curve of displacement changed as bow with depth, the largestdeformation of displacement closed to the pit central. the horizontal displacement ofpit column and anchor dynamometer little changed.(2) The numerical simulation of section4-4of the foundation pit was doneby Flac. The conditions of the simulation is divided into four kinds, the excavationand support of foundation pit were reproducted. The trend of anslog and measuredcurves of deep horizontal displacement was almost same, only a small part of thevalue is somewhat different. It indicated that the model and the selected parameterswas reasonable. By numerical simulation and reasonable soil parameters, the generallaw of the deformation of the foundation pit could be reflected.(3) In the paper, uniform design sampled by three ways: the mean point wasthe center, the range was the mean point plus or minus the mean square error. Thecoefficient of variation of the parameters were set to0.12,0.25and0.37. Under threeconditions, soil optimal parameters obtained by parameters inverse analysis werebasically the same, indicating that the correctness of the parameters inverse analysis.