Field Monitoring of the Behavior of Pile-Net Composite Foundation in Oversize-Deep-Soft Soil

For the observation of the behavior of the pile-net composite foundation in oversize-deep-soft soil, some cross sections in the Chaoshan railway station were selected for field monitoring. According to the recorded data, an analysis on the behavior of this structure was conducted with the following conclusions reached: (1) At the beginning of filling, the values of the earth pressure on pile tops and in the soil between piles both increased abruptly. And the growth rate of the earth pressure on pile tops is higher than that of soil between piles. When the depth of fill hits a certain value, the pile-soil stress ratio will reach its maximum value with an arching effect appeared. (2) As the increase of filling depth, pore water pressure increased with excess pore water pressure generated. After the filling, the distribution of excess pore water pressure disappeared gradually. (3) The axial force and the skin resistance of tube pile present a close relationship with the properties of each stratum. (4) The settlement value of each layer is also relevant to its depth and properties with its settlement ratio directly proportional to the increase of filling depth. (5) As the increase of filling depth, the tensile displacement of geogrid presents an increasing trend. The increase of the tensile displacement of geogrid in soil between piles presents a lag effect with its lag time about 50 days. (6) The generation of lateral displacement is accompanied with the filling of embankment. Nearer the surface, the value of lateral displacement was higher. And as the increase of depth, it decreased gradually. For different layers, the value of lateral displacement also varies.