The 2nd Badong International Geohazards Symposium (BIGS2019)

79 / 2019-07-30 19:05:06

Study on Pile Foundation Deformation Induced by Excavation of Foundation Pit

foundation pit excavation; Buildings; Pile foundation; Numerical analysis

Prevention and Control of Reservoir Geohazards and Ecological Environmental Protection > Technologies of geohazards Prevention and Control

Foundation pit excavation often has an impact on adjacent buildings. At present, most scholars study the influence of foundation pit excavation on the surrounding environment, but few have been conducted on the pile foundation of neighboring buildings. Therefore, this paper takes a deep foundation pit in Guangdong province as an example, establishes a numerical model through flac-3d, and analyzes the deformation law and mechanism of the pile foundation of surrounding buildings induced by foundation pit excavation. The length and width of the foundation pit are 80 meters and 60 meters respectively, and the excavation depth is 20 meters. The surrounding structure of the foundation pit is pile row support with pile diameter of 1200mm. C30 concrete is adopted and pile spacing is 200mm.The excavated soil in the project site is divided into five layers, including miscellaneous fill, sludge, silt, thick silty clay, and bearing layer. The section diagram is shown in figure 2 below. Mohr-coulomb was adopted as the constitutive model for the foundation pit model. The side length of the model was taken as 180m x160m x60m, as shown in figure 1 below. The excavation is divided into four working conditions. In the first working condition, the excavation is 5 meters, and the internal support is set at 4 meters. In the second working condition, the inner support is set at 9 meters when the excavation reaches 10 meters. In the third working condition, the inner support is set at 13 meters when the excavation reaches 14 meters. In the fourth working condition, inner support is set at 17 meters at the bottom of excavation, and then the deformation of pile foundation under each working condition is analyzed. Results show that without during excavation, almost no deformation, building pile foundation after the excavation to the bottom of the foundation pit, the deformation of the pile foundation of the no. 1 presents the "first increase, then decrease the deformation trend of", in about 6 m pile of maximum deformation, and the deformation of the pile foundation of the no. 2 and no. 3 is at the top of the pile in maximum deformation, then gradually reduce , shown in the diagram below. Taking no. 1 pile foundation as the research object, under each working condition of foundation pit excavation, the deformation trend of "first increase, then decrease" is presented, as shown in figure 4 below, indicating that the foundation pit excavation has a great impact on the building pile foundation. The excavation not only changes the deformation value of the building pile foundation, but also changes the deformation law. For similar projects, this research can help to reduce the deformation of buildings and make the construction safer, which has certain theoretical guiding significance and practical significance.