青藏铁路多年冻土区桩基础施工中的混凝土温度控制问题

简要介绍了青藏铁路沿线多年冻土的工程特性和分布情况及其与桩基础工程间的相互影响,论述了在青藏铁路高原多年冻土区施工环境下, 被广泛应用的钻孔灌注桩在施工过程中的混凝土温度控制问题. 讨论了影响桩基回冻时间的各种因素以及混凝土入模温度控制在其中所占的地位, 提出了对青藏铁路相关施工规范中桩基混凝土部份温度指标进行适当调整的建议.

Temperature Control Problem of Concrete of Pile Foundation under Construction in the Permafrost Regions of the Qinghai-Tibet Railway

For constructing the Qinghai-Tibet railway in the permafrost regions, temperature control problem needs to be solved in the construction of driven cast-in-place pile, the strength and durability of concrete must be ensured and the disturbance to the foundation soil should be avoided possibly. Additionally, the disturbed permafrost around the piles must refreeze in an allowable time. The temperature of concrete put into mold in the pile foundation is controlled in order to reduce the thermal disturbance to some extent and shorten the refreezing time of the permafrost around the pile. As compared with the heat of hydration of concrete, the sensible heat due to the increasing temperature of concrete put into the mold in a pile foundation is very small. The thermal disturbance due to the increasing temperature of concrete put into the mold in a pile foundation is secondary by comparison with such factors as the means of boring hole of pile and so on. Under special conditions, a proper temperature rising when the concrete put into the mold in a pile foundation is adoptable and necessary.