Deformation Analysis And Prediction Of Deep Foundation Pit

With the development of urban construction,underground space has entered a peak period and the fact that the scale of foundation pit engineering is getting bigger and bigger,it is very important to ensure the safety and stability of excavation and to reduce the impact on the surrounding around foundation pit.The excavation of foundation pit will cause deformation,how to control the deformation of foundation pit is essential.Construction monitoring is the key link of informative construction,it makes the changes of displacement and internal force be observed in real time,the safety of foundation pit and surrounding buildings be controlled.By simulating the process of construction,we can grasp the overall deformation pattern and its trend effectively during the construction of excavation,and it's very beneficial to construction.It is also of great importance for engineering practice to predict the subsequent deformation of excavation by using high precision model of excavation deformation.All three are important means to control the deformation of excavation.The subject will take a deep excavation construction project with top-down construction project as an example.Firstly,analyzing the actual monitoring data with Origin,including the deformation of diaphragm wall,the settlement of surrounding soil and buildings,to find the reasons on where the deformation is abnormal,and the deformations described above are calculated by empirical formula.Then tsimulating the excavation process of deep foundation pit by using MIDAS GTS NX software and taking time effect into account,so the displacement of characteristics and trends as above can be concluded.The deformation of diaphragm wall is assumed as a S-shaped curve.Surrounding soil settlement is assumed as an inverted bow and the maximum settlement is located at 6~10m distant from foundation pit.The pit bottom rebound gradually increased with the soil excavation.Then set an analysis on the influences of certain factors.Finally,based on grey theory,we will make an prediction on the excavation deformation during the followinig construction by making a reliable non-equidistance GM(1,1)model with MATLAB.Markov chain,BP neural network and grey Markov model of-BP neural network is more accurate but the prediction result is conservative,grey system model has “small sample,poor information”characteristics and the model is suitable for short-term prediction the prediction values are close to reality and can get a limit value during the construction.Based on the value,adequate security measures can be taken to control the deformation.Therefore,the non-equidistance GM(1,1)model can be used in practical engineering of foundation pit to predict the deformation of foundation pit,it is of great significance to guide the construction and ensure the safety and stability of foundation pit.