预应力锚杆柔性支护体系中锚杆的变形

Anchor Deformation of Flexible Supporting System with Prestressed Anchors

锚杆的总变形主要由锚杆自由段的弹性变形、锚固体的弹性变形、锚固体与土体间的切向位移、锚杆钢筋与锚固体之间的切向位移组成。引入锚杆预应力损失剩余系数的概念,推导出锚杆变形的计算公式;进一步依据基坑或边坡坡面水平位移与锚杆变形协调的原则,给出锚杆预应力的确定方法。工程算例分析表明：在锚杆变形中,锚杆自由段的弹性变形量最大;从上至下锚杆的预应力逐渐变大,锚杆允许变形越小所需的预应力越大;锚杆变形随着锚杆预应力、锚杆锚固段长度、土体界面摩阻力的增加而减小,随着锚杆自由段长度的增加而增加,但不受锚固体直径的影响。建议在实际工程中：根据不同的土质情况,通过调整预应力的大小控制锚杆变形;综合考虑承载力、稳定性和变形控制的要求,合理确定锚杆自由段和锚固段的长度;锚杆锚固体的直径取130~150mm。

The total deformation of anchor mainly consists of four parts： the elastic deformation of the free segment of anchor, the elastic deformation of anchorage body, the tangential displacement between an- chorage body and soil mass as well as the tangential displacement between anchor bar and anchorage body. The formula for calculating anchor deformation is derived by introducing the concept of residual coefficient of anchor prestress loss. The method for determining anchor prestress is further proposed according to the principle of deformation compatibility between the horizontal displacement of foundation pit or slope and anchor deformation. The analysis of engineering example indicates that in the anchor deformation, the elastic deformation of the free segment of anchor is the largest. The anchor prestress values become larger from the top down gradually, and if the allowable deformation is smaller, then the required anchor pre- stress is larger. The anchor deformation decreases with the increase of anchor prestress, the anchorage segment length of anchor and the interface friction resistance of soil mass, and increases with the increase of the free segment length of anchor, but is not affected by the diameter of anchorage body. It is recommended that, the anchor deformation should be controlled by adjusting anchor prestress according to different soil status in practical engineering. Both the length of free segment and anchorage segment of anchor should be reasonably determined by comprehensively considering the requirements for bearing capacity, stability and deformation control. The diameter of anchorage body is in the range from 130 mm to 150 mm.