桩锚与土钉联合支护结构的优化选型

桩锚支护结构中预应力锚杆分为自由段和锚固段，通过施加锚杆预应力加强基坑边壁稳定性，锚杆预应力直接作用于排桩上，使基坑侧移受到限制；土钉支护结构中土钉全长锚固，通过基坑边壁侧移以部分释放土压力，并使土钉产生拉力，优势滑裂面前后土钉拉力平衡并直接作用于土体，限制土体边壁的继续变形，形成基坑边壁的支护结构。因此桩锚与土钉是两种受力机理不同的支护结构，将土钉与桩锚作为一个整体共同抵抗荷载和变形，关键是土钉和桩锚支护结构的选型设计，通过受力变形分析合理决策联合支护结构．使二者均能充分发挥其技术优势。本文根据桩锚和土钉支护结构的施工特点、受力变形特点，研究分析了土钉与桩锚联合支护结构协同工作的设计原理，根据工程实际环境条件建议了联合支护结构的优化选型方法。

Optimization in types choice of the combined retaining structure of pile-anchor and soil nailing

The soil anchor of pile-anchor retaining structure includes free section and anchored section. The prestress acts on the pile directly, and the stability of the foundation pit is strengthened. The displacement of the side of foundation pit can be limited by improving the prestress level of the anchor. In soil nailing, soil nails are wholly anchored. Soil stess is unloaded with the displacements of pit side, which compels soil nails to be pulled. After the force balance between the two sides of the possible sliding surface is achieved, the new deformation of the soil is limited, and then soil nailing is formed. So, the work mechanism of pile-anchor and soil nailing is different, and the key question for the combined retaining structure, which bears and deforms together, is the design of types choice. In this paper, the design principle of the combined retaining structure of pile-anchor and soil nailing is analyzed according to the load carrying and deformation characteristic and the behavior during construction, at the same time the method of optimization in types choice is put forward according to the construction conditions.