基于等效变温法的基坑钢支撑预应力损失研究

针对钢支撑预应力损失和复加对基坑稳定性及邻近桥桩的影响,基于等效变温法,将预应力损失(复加)量换算为温度变化量,通过改变钢支撑活络端温度模拟预应力加卸载;讨论了预应力损失量、桩顶荷载、桩端支撑屈服强度等因素对围护结构及邻近桩侧移、内支撑轴力、桩顶沉降及桩身内力等影响。结果表明:预应力损失将引起邻近支撑轴力增大,但随着与之距离的增大,远端支撑轴力的增量逐渐减小;相比于损失阶段,预应力复加过程中邻近支撑轴力及围护结构侧移的恢复达不到损失前状态;第二、三道钢支撑预应力先后损失引起的邻近桩响应(沉降和轴力)均大于2道支撑同步损失;增加桩顶荷载或降低桩端支撑屈服强度将加剧预应力损失引起的桩身沉降。

Study on Prestress Loss of Steel Supports of Foundation Pit Based on Equivalent Temperature-Changing Method

The study investigates the stability of the foundation pit and adjacent bridge piles experiencing prestress loss and subsequent loading compensation of the steel supports. Based on the equivalent temperature-changing method, the prestress loss and compensation are converted into the amounts of temperature change and then applied to the active end of the steel support. The influences of the prestress loss, superstructure loading, yield strength of the support at the pile tip on the displacements, internal forces of the retaining structure and adjacent piles, and the axial support force are analyzed. The results show that the prestress loss will increase the axial forces of the adjacent support while the increments gradually decrease with its distance from the support of loss. The axial force of inner supports and the horizontal displacement of the retaining structure after the loading compensation cannot restore or decrease to the original pre-loss state. The settlement and axial force of adjacent piles caused by successively prestressing loss of the second or third steel supports is larger than that by the synchronous loss. Increasing the pile head loading or reducing the pile tip's support strength will aggravate the pile settlement caused by prestress loss.