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深厚冲积层冻结压力取值大小是冻结法凿井外层井壁设计计算的重要依据。为此,基于符合深井冻土蠕变特性的改进西原模型,利用ABAQUS软件的用户子程序接口,实现该模型的UMAT开发。考虑土体冻结过程中的热-力耦合作用获得井筒开挖前土体冻胀应力分布规律,在此基础上,计算分析了深部冻结井的掘砌过程,获得了作用于外层井壁的冻结压力发展变化规律。计算结果表明:土体埋深、冻结壁温度、土体冻胀率等因素均影响冻结压力的大小。在其他条件不变的情况下,当埋深由400 m增加到500 m时,冻结压力增加21%;当冻结壁平均温度由-16℃降低至-18℃时,冻结压力减小10%;当土体冻胀率由2%增加到3%时,冻结压力增加3.8%。冻结压力随层位深度及土体冻胀率的增加而增加,而降低冻结壁温度则有利于冻结壁的稳定。数值计算结果与实测值的误差小于15%,比理论计算更有利于实际工程中深井冻结压力的计算预测。
The value of freezing pressure of deep alluvium is an important basis for the calculation of the design and calculation of the outer shaft wall of freezing shaft method. Therefore, based on the improved Nishihara model which accords with the creep characteristics of deep permafrost and the user subroutine interface of ABAQUS software, the UMAT of this model is developed. Based on the thermo-mechanical coupling effect of soil freezing process, the frost heave stress distribution of the soil before wellbore excavation is obtained. On the basis of this, the excavation process of the deep frozen well is calculated and analyzed, Freezing pressure development and changes. The calculation results show that the factors such as the depth of soil body, the temperature of frozen wall and the frost heave rate of soils all affect the size of freezing pressure. Under the same conditions, the freezing pressure increased by 21% when the depth was increased from 400 m to 500 m. When the average wall temperature decreased from -16 ℃ to -18 ℃, the freezing pressure decreased by 10% When the soil frost heaving rate increased from 2% to 3%, the freezing pressure increased 3.8%. The freezing pressure increases with the depth of the horizon and the frost heave rate of the soil, while decreasing the temperature of the frozen wall is beneficial to the stability of the frozen wall. The error between the numerical calculation and the measured value is less than 15%, which is more conducive to the calculation and prediction of the freezing pressure in deep wells than the theoretical calculation.