Abstract:
Based on a large number of measured data of surface settlement of open cut foundation pit engineering in different areas of Beijing in recent years, the typical curve "Four Point Broken Line Method" and its model parameters (slope
K and intercept
b) for predicting surface settlement are inversely analyzed by using theoretical calculation and regression analysis methods, and the empirical parameters for predicting surface settlement of open cut foundation pit under different regional geological conditions are obtained. Based on the statistical analyses of data and empirical parameters, the regional variation law of surface subsidence is summarized, and the range of parameters is defined. The prediction accuracy of empirical parameters is verified by using the measured data. The results show that the horizontal distance between the maximum settlement point and the retaining structure in the west of Beijing is larger than those in the middle and east of Beijing, which is about 30% of the depth of the foundation pit, while those in the middle and east of Beijing is relatively small, which are about 26% of the depth of the foundation pit. The surface settlement curve shape varies with the regional geological conditions, and the absolute value of the slope
K of the first line
AB of the four point broken line graph increases from west to east, showing the settlement slope of the east silty fine sand is more obvious than that of the west sandy cobble, and the absolute value of the slope
K of the second straight line
BC in the east is smaller than that in the west, indicating that the settlement influence range of the east is larger, the absolute value of the parameter
bAB increases from west to east, indicating that the settlement value of the pile side soil of the silty clay and fine sand in the east is larger than that of the sandy pebble in the west. It is about 31% of the maximum settlement, 21% in the central region and only 16% in the western region. The research results will provide an important reference for surface deformation prediction and safety risk control of open cut foundation pit engineering in this region.