季冻区越冬基坑变形特性研究

Deformation Characteristics of Deep Excavation Supporting Structures in the Seasonal Frozen Region

随着经济的发展,高层建筑日益增多,建筑基坑的规模随之变大,施工周期也越来越长,尤其是季节性冻土地区的基坑不可避免的会遇到越冬的问题。为研究季冻区深基坑在冻融作用下的变形规律,对长春市某深基坑的支护体系进行数值模拟。研究发现,冻胀作用会使基坑顶部地面沉降位移减小,使坑底隆起位移增大,并会使支护桩水平位移及钢筋混凝土内支撑轴力增大;经过融化作用后地表沉降位移、坑底隆起位移、支护桩水平位移及钢筋混凝土内支撑轴力均大于冻结前。通过对比监测值发现,模拟值与监测值的大体趋势一致,并且冻融循环作用使基坑产生了不可恢复的变形。

With the development of economy and the increasing number of high-rise buildings,the dimensions of deep excavation projects become larger and larger,and the foundation construction duration becomes longer and longer.Especially,excavated areas in the deep excavation in seasonal frozen soil areas will inevitably encounter the geohazards induced by the cold weather.In order to study the deformation characteristics of supporting structures in the deep excavation in seasonal freezing areas under the effect of freezing and thawing cycles,numerical analyses are performed for the support system of a deep excavation project in Changchun.It is found that the freezing effect will reduce the ground subsident at the top of the excavation;increase the bottom heave at the excavated area and increase the horizontal displacement of the supporting structure and the axial force of the reinforced concrete internal support.After the thawing effect,the ground subsidence,the bottom heave at the excavated area,the horizontal displacement of the supporting structure and the axial force of the reinforced concrete internal support are all greater than those before the freezing.By comparing with the construction monitored data,it is found that the general trend of simulated values and monitored values are consistent,and the effect of freeze-thaw cycle has produced unrecoverable deformation in the deep excavation supporting structures.