Research On Deformation Properties Of Subway Station Foundation Pit In Soft Soil With High Creep Strength

With the high-speed development of China’s coastal areas, theincreasing density of urban buildings makes the development and utilizationof underground space becoming more important. Naturally, the number ofdeep excavation engineering is also increasing. Deep excavationengineering is one of the most complex geotechnical problems, especiallyprominent in the coastal soft soil area with complex formation, highconstruction difficulty. Silty soft clay,with its high creep strength, highmoisture content, high void ratio, high compression and low permeability,brings a series of technical problems to the deep foundation construction,such as large and uncontrolled deformation. Therefore, it’s necessary tostudy of deformation properties of subway station foundation pit in soft soilarea, which has high creep strength. Research results can provide referencefor similar projects.Based on the deep foundation pit engineering of the South East OuterRing Road Station in Ningbo Rail Transit Line1, through experiments,theoretical analysis and numerical simulation with PLAXIS, deformationproperties of subway station foundation pit in soft soil of Ningbo area weresystematically studied in this paper.The main contents of this research are as follows:(1)Organize, summarize the results of previous studies; systemsanalysis of creep mechanism of soft soil and its influencing factors,deformation mechanism of pit and its influencing factors and controlmeasures.(2)Based on the whole course monitoring of pit engineering of the South East Outer Ring Road Station, detailed collation and analysis wasundertaken to the monitoring data. Focus on the disturbance displacement ofsoil, deformation of diaphragm wall and axial force in support, deformationlaw was carried out.(3)PLAXIS finite element method was taken to calculate the transientdisplacement of each condition in pit excavation. Combined with amendedempirical creep model for soft soil of Ningbo area, adding the displacementaging coefficient as a coefficient, long-term displacement can be calculated.The high fitting degree of deformation results derived by this method andthe on-site monitoring data proved that this method can be used as a generalmethod in deformation prediction of foundation pit construction in Ningbosoft soil area.