干坞开挖状态下基底承载特性研究

天津滨海新区中央大道海河沉管隧道的沉管管段需要在干坞内预制完成,干坞内土体在卸荷状态下的承载与变形特性将发生变化,影响干坞基底承载力。根据干坞开挖的卸荷应力路径,通过室内试验,对卸荷状态下干坞基底土承载与变形特性进行试验研究。得出了不同深度土层卸荷后强度的变化情况,同时对卸荷影响深度进行了试验研究。由于开挖对不同土层不同深度土体强度影响不同,很难用传统的极限承载力公式计算基底承载力,根据试验得出的卸荷后土体强度指标,对干坞基底承载和变形特性进行了有限元计算,根据计算结果确定干坞基底在沉管管段荷载作用下的稳定性和安全系数,为以后的干坞设计提供依据。

Load-bearing Character of the Dry Dock Foundation under Excavation State

The caisson segments of the Bianhai Highway tunnel crossing Haihe River in Tianjin Binhai New Area need to be prefabricated in the dry dock;the load-bearing and deformation characters of the foundation soil in the dry dock will be changed under unloading state,which will affect the bearing capacity of the dry dock foundation base.According to the load path of the dry dock excavation,indoor tests were carried out to study the load-bearing and deformation characters of the foundation soil.The change of the bearing capacity was estimated from the test results.At the same time,the effected depth by excavation was found through the test results.It was found that the influence on the bearing capacity of the soil foundation induced by the dry dock excavation decreases along with depth and varies with different types of soils.Therefore,it is difficult to calculate the bearing capacity by using the classical formulae.The load-bearing and deformation characters were analyzed by the established FE method in accordant with the strength parameters obtained from the unloading tests.The stability and safety coefficient of the foundation under the segments self-weight load was established according to the FEMresult.This achievement has been taken as the reference for the dry dock design.