考虑开挖反弹的桩锚结构土压力计算方法研究

桩锚支护结构中,土压力的计算未考虑支护结构位移及坑底土体的卸载反弹影响,可导致主动区土压力计算值偏小,被动区土压力计算值偏大,降低支护结构的安全度水平.以弹性长桩理论和经典土压力理论为基础,考虑施工过程坑底土体开挖反弹效应和土的短期应力历史,研究桩锚支护结构土压力的演化进程和计算方法,提出了土压力的"反零点分布"模式、"零分布"模式、"零点分布"模式、"梯形分布"模式以及"矩形分布"模式之间的相关关系及其影响因素和演化机制.指出桩锚支护结构土压力的计算应综合考虑开挖速度、各工况暴露时间以及土体反弹特性的影响.

Study on the Calculation Method of Earth Pressure for Pile-anchor Bracing Structure Considering the Excavation- rebounding Effect

In pile-anchor bracing structure, the deformation of bracing structure and the unload-rebounding effect of the bottom soil were not taken into consideration in the calculation of earth pressure in the past, which might cause a lower calculation value of earth pressure in the active zone and the larger calculation value of earth pressure in the passive zone, and the safety level of bracing structure will be undervalued. On the basis of elastic long pile and classical earth pressure, both the evolution process and computation method of earth pressure for pile-anchor bracing structure are studied in this paper, considering both the excavation-rebounding effect and short-term stress history for the death earth in the bottom of foundation pit during construction, and the "counter-zero point distribution pattern", "zero distribution pattern", "zero point distribution pattern","trapezoidal distribution pattern","rectangular distribution pattern", and the correlation relationship in between, influencing factors and evolution mechanism are also presented. In in this paper, it is also pointed out that the excavation speed, the exposure time for all cases and the influence of earth rebounding properties should be comprehensively taken into consideration in the computation of earth pressure for pile-anchor bracing structure.The computation method of earth pressure proposed in this paper provides a theoretical guide to some extent for the displacement calculation and deformation control during construction for pileanchor bracing structure.