Deformation Analysis And Parameter Optimization Of A Deep Foundation Pit In Hangzhou

At present,the surrounding environment of the deep foundation pit project in the city is extremely complicated,it often closely adjacent to existing buildings,structures,underground pipe networks,river channels and so on,which has the characteristics of concealment and complexity of construction.The design and construction are difficult and the risks are high.Hangzhou is a silt-rich soft soil area,the formation is complex,changeable and poor soil conditions with frequent accidents.Therefore,it is of great theoretical and practical significance to study the deformation law of the retaining structure and the surrounding soil during the excavation of the foundation pit to further explore the relevant parameters of the foundation pit,so as to guide the design and construction of the deep foundation pit in the soft soil area.In this paper,the support system of the inner-pillared row of piles in soft soil area of Hangzhou City is further studied.The deformation of the enclosure structure is analyzed by the combination of measured data and finite element numerical simulation,the relevant parameters are optimized by the analysis results.Through the research and analysis,the main research contents and conclusions are as follows:1.Taking a deep foundation pit project in Hangzhou as an example,the design and calculation of the deep foundation pit project in Tongji,Shanghai is performed using FRWS software.It is found that the displacement of the pile body during the initial excavation had little change,the depth increases with the excavation depth of the foundation pit,and the surface subsidence shows a "parabola" distribution.2.The field survey data are analyzed,including the horizontal displacement of deep soil,the settlement of ground surface around the foundation pit,the axial force of support and the horizontal displacement of pile top,of which the settlement of ground surface and the horizontal displacement of pile top in soft soil strata are the highest,It is a small trend on both sides of the middle and large,the maximum horizontal displacement increases with the excavation depth.3.The 3D finite element numerical simulation of this project is carried out by using Midas GTS NX.The Mohr-Coulomb constitutive model is selected and the mixed grid is used to divide the soil.A total of 242229 nodes and 215589 units are obtained.After simulating the construction conditions The simulation results of surface settlement,supporting axial force and pile top horizontal and vertical displacements around the foundation pit are extracted.By comparing the design results,simulation results andmeasured results,it is found that the measured results tend to be larger than other results,and the causes of the differences are analyzed.4.The pile length and pile spacing are optimized by numerical simulation method.The pile length is optimized from 23 m to 22 m and the pile spacing is optimized from1.5m to 1.7m,which can reduce the construction cost under the condition of safety.