呼和浩特地铁深基坑支护冻胀影响数值分析

Analysis of the Influence of Frost Heaving on the Retaining and Protection of Deep Foundation Excavation of Subway Station in Hohhot Metro

研究目的:为研究低温作用下水土冻胀对地铁基坑支护结构的影响,依托呼和浩特市某车站地铁基坑,建立地铁深基坑数值计算模型,模拟季节温度变化对基坑体系的影响,探究越冬基坑在外界温度变化条件下,基坑周边土体、地下连续墙及坑底土体温度场变化规律,水土冻胀力主要影响范围,基坑支护体系内力及变形的变化规律。研究结论:(1)冻胀初期受表层温度影响较大的范围主要集中在5 m以内,随着外部温度的逐渐下降,土层冻结深度在逐渐增大,且在距离基坑0. 5 m范围内最大冻深达到15 m,在基坑外侧边缘的土体冻深相对较小,受气温影响较大;(2)基坑外侧土体受冻胀影响范围集中在7 m以上,随着基坑深度的增加,支护结构受冻胀的影响逐渐减少,且影响减少得较为迅速;(3)低温条件下考虑水土冻胀影响,基坑第一道横撑轴力增加约22%,地连墙最大水平位移增加约24%;(4)本研究成果可为严寒地区深基坑工程支护设计与施工提供参考。

Research purposes:In order to study the influence of soil frost heaving on the retaining and protection of subway foundation excavation under the action of low temperature,based on the foundation excavation of a subway station in Hohhot,a numerical calculation model of deep foundation excavation is established to simulate the influence of seasonal temperature change on the foundation excavation,and the model test is carried out to explore the law of temperature field dynamic change of the soil and underground diaphragm wall around the foundation excavation,the main influence scope of soil frost heaving,and the change law of the internal force and deformation of the foundation excavation support system under the condition of external temperature change.Research conclusions:(1)The influence of the surface temperature is mainly within 5 m in the initial stage of frost heave,and with the gradual decrease of the external temperature,the soil frozen depth increases gradually,and the maximum frozen depth reaches 15 m within 0.5 m from the foundation excavation,the soil frozen depth in the outer edge of the foundation excavation is relatively small,which is greatly affected by the external temperature.(2)The influence range of frost heaving on the soil outside the foundation excavation is within 7 m.With the increase of the depth of the foundation excavation,the influence of frost heaving on the retaining structure decreases gradually,and the influence decreases rapidly.(3)Considering the influence of frost heaving,the axial force of the top bracing of the foundation excavation increases by about 22%,and the maximum horizontal displacement of the diaphragm wall increases by about24%.(4)The research results can provide a reference for the design and construction of deep foundation excavation in severe cold area.