温度应力对环形地连墙围护结构受力变形的影响分析

Effects of temperature stress on diaphragm wall of circular deep foundation pit

温度场对深基坑围护结构受力变形的影响不仅是温度场与应力场的热力耦合问题,同时也是水、土、围护结构共同作用问题。通过对日本东京新丰洲变电所深基坑工程实测结果的反分析,确定了温度场对环形深基坑围护结构受力变形影响的分析方法,获得了温度场变化引起的围护结构受力变形模式,并将研究成果应用于上海世博变深基坑围护结构受力变形分析。分析结果表明:基坑开挖后,围护结构的内侧面暴露在大气中,受大气温度变化的影响,地连墙内外侧存在温度差,且不同位置、不同施工阶段,地连墙的温度场不同;开挖面以上的地连墙没有坑内土体的约束作用,其环向应力的大小主要取决于坑外水、土压力的作用,温度下降时,地连墙向坑内收缩变形;开挖面以下及开挖面附近的墙体,墙体收缩变形受到坑内土体的约束,温度下降时,地连墙的环向应力减小。

The effects of temperature on retaining structure of deep foundation pits are related with the thermal-mechanical coupling problem of temperature and stress fields and the interaction of water, soils and retaining structures. Through the back analysis of the measured data of Shin-Toyosu substation deep foundation pit in Tokyo, an analysis method for the effects of temperature fields on retaining structures of circular deep foundation pit is determined, and the changing patterns of temperature fields in the retaining structures are acquired. The research results are applied to the analysis of Shanghai 2010 Expo underground substation. The results show that the inner surface of the retaining structures is exposed to the atmosphere, and that temperature difference occurs between the inner and the outside of the wall due to change of atmospheric temperature. The temperature fields vary in different positions and construction stages. There is no constraint effect of soils in the pit, so the hoop stress of diaphragm wall above the excavation face mainly depends on the water-earth pressure outside the pit, and if temperature decreases, the volume of diaphragm wall will shrink. The diaphragm wall under or near the excavation face is restricted by the soils in the pit, so the hoop stress of the diaphragm wall will decrease when the temperature decreases.