关键词: 基坑开挖, 桩基础, 附加摩阻力, 中性点

Abstract: Unloading and rebound of soil induced by excavation can result in an adverse effect on existing piles with the action of the tensile force, meanwhile the tensile stress of pile reaches the maximum at the neutral point. The variation of neutral point of the additional skin friction is analyzed theoretically with a simplified distribution model. The variations of the neutral point location with pile length, excavation depth and the properties of surrounding soil are obtained by summarizing and analyzing the reported data of pile foundation during excavation. The results show that there is approximately linear positive correlation between the ratio of neutral point depth to pile length and the ratio of excavation depth to pile length. The location of neutral point descends with increasing the unit weight and the internal friction angle of the surrounding soil. Similar downward movement of the neutral point can also occur in the case of the absence of retaining structure for excavation or the presence of expanded pile tip. Based on this, a calculation model is put forward to predict the neutral point location. The predicted result is close to the numerical result.

Key words: deep excavation, pile foundation, additional skin friction, neutral point