关键词: 锚杆, 扩大头, 摩尔强度理论, 力学机制, 计算方法

Abstract:

Based on the measured data of several projects, the mechanical mechanism of the bit expanded anchor rod has been studied. It is pointed out that the mechanical process can be divided into three stages. The first stage is of earth pressure at rest. The second stage is of the transition phase, which is characterized by the displacement curve that has an inflection point. The third stage is of plastic zone compaction - expansion stage, which is characterized by the soil compaction body to strengthen and expand the head improved anchorage force. In this paper, several instances consistent with the above-mentioned mechanical process are given. According to Mohr-Coulomb strength theory, the calculation formula of anti-pullforce of the bit expanded anchor rod are deduced; and the expansion the first burial depth, soil cohesion, internal friction angle and other factors against the pulling force are analysed; and it is pointed out the shortcomings of the calculation method in current industry standard. Finally, an engineering example is given, and compared with the method of the text and the existing norms. It is shown that the results of the proposed method is more reasonable compared with experimental results. For engineering practice, it has achieved good technical and economic effects.

Key words: anchor, bit expanded anchor rod, Mohr-Coulomb strength theory, mechanical mechanism, calculation method