Monitoring Analysis Of Surrounding Soil Displacement Caused By Deep Foundation Pit Construction

Tianfu square tunnel is taken as the engineering case, starting with factors and mechanism of soil deformation caused by excavation of deep foundation pit, analysis of soil deformation characteristics is made primarily according to pit pumping, excavation and support structure; the necessity and importance of monitoring is emphasized, research and analysis on settlement, tilt and horizontal displacement of slope is made, forecast and valuation is made by gray model, hyperbolic curve, exponential curve and pier curve, comparison with gray model, exponential smoothing method is suggested; summarize the rule of deformation by numerical modeling.According to a quantity of monitoring data, the result shows that settlement, tilt and horizontal displacement of slope has a larger value, but it is easy to stabilization after support, intense deformation will appear in rainstorm. Better linear relationship exists between tilt and depth; settlement increases in some place; because of deep foundation pit, construction procedure and time factors has effect on gray model prediction, the forecast accuracy turns lower with increasing of time, exponential smoothing method is suggested.Analysis of numerical modeling of K0+500 shows that the rim angle of deep foundation pit has stronger spatial effect, the middle of deep foundation pit is not; the middle of floor has larger lift, which does not appear centre of floor but appear circular arc in floor that shows obvious spatial effect; the deeper of depth, horizontal displacement of slope is larger, and exceed previous working condition, horizontal displacement of slope turns larger with increasing of excavation depth, the position of the largest displacement is downwards and stop to middle-up of deep foundation pit from excavation to the end of support; the distribution of settlement surrounding deep foundationpit takes on groove, the largest settlement is not side of deep foundation pit but appears in place that is three to five meters away from deep foundation pit, thirty meters away deep foundation pit, the settlement is smaller, and there is settlement in a certain distance, but it is smaller by comparison.