软土堤岸支护锚索预应力损失特征研究

Study on Prestress Loss Characteristic of Anchor Cable for Soft Soil Embankment

预应力锚索已广泛应用于岩土支护工程中,但对于其在锚固后的预应力损失问题研究较少,特别是对软土中锚索张拉锁定后及后续工况影响下的预应力损失研究更鲜有报道。通过现场试验对软土堤岸支护工程中锚索预应力变化进行全程监测,研究与对比分析了锚索在张拉锁定、土体开挖和土体堆载后的预应力损失特征。结果表明,土体蠕变与钢绞线松弛是引起软土中锚索预应力损失的主要原因;锚索在锁定后30天预应力损失趋于稳定,预应力损失为10.5%;后续工况中的土体开挖与土体堆载对预应力锚索的影响作用相当于对张拉锁定后的锚索预应力损失进行荷载补偿张拉,经荷载补偿张拉后,锚索预应力初始值越大,预应力损失量越小。

Prestressed anchor has been widely used in geotechnical supporting engineering.However,few researches on prestress loss issues after anchoring have been carried out,especially the study on prestress loss after anchor cable was locked and affected by subsequent construction conditions in soft soil area is rarely reported.In a field test,the changes of prestress of anchor cable in the whole process of supporting soft soil embankment has been monitored.Prestress loss characteristics have been separately analyzed and compared among three different construction conditions,such as after anchor cable was locked,after excavation and after backfilling of soil.The results show that creep deformation of soil mass and relaxation of steel strand are the main reasons for prestress loss in soft soil area.Prestress loss trends to stable at 10.5 % after anchor cable was locked for 30 d.In a sense,excavation and backfilling of soil in subsequent construction conditions are equivalent to the effect of compensating for the prestress loss of anchor cable after locked.After load compensation,the greater value of the initial prestress of anchor cable,the less amount of prestress will lose.