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结合南京地铁10号线过江隧道盾构始发工程,运用有限元软件建立三维数值模型,对大直径杯型冻土壁温度场的发展与分布规律进行研究,分析不同因素对该温度场的影响规律,比较研究不同土层下该温度场的降温规律。数值计算表明:在设计冻结方案下,杯型冻土帷幕厚度满足加固范围要求,开始交圈时间由早到迟依次为外圈管>中圈管>内圈管,形成闭合大直径杯型冻结帷幕的时间为12 d;冻结壁交圈时间随导热系数的增大而线性减小,随容积热容量和原始地温的增大而线性增大,原始地温每升高5℃,冻结壁交圈时间增加约1 d;相变潜热变化对冻结初期和后期土体降温过程几乎没有影响;不同土层降温速度由快到慢分别为砂土水泥土>黏土水泥土,砂土>黏土;砂土水泥土与砂土、黏土水泥土与黏土几乎同时达到相变阶段;无论水泥改良与否,砂土总比黏土的开始交圈时间早4 d。所得结果为今后类似工程设计提供了理论依据。
Combined with the project of shield tunneling in the cross-river tunnel of Nanjing Metro Line 10, a three-dimensional numerical model was established by using finite element software to study the development and distribution of temperature field in the large-diameter cup-shaped frozen soil wall. The effects of different factors on the temperature field Influence law, comparative study of the law of temperature drop in different soil layers. The numerical results show that under the design of freezing scheme, the thickness of cup-shaped frozen soil curtain meets the requirements of the reinforcement range, and the time of the initial lap crossing is from the outer ring tube to the middle ring tube to the inner ring tube, forming closed large-diameter cup-type freezing The time of the curtain is 12 d, the time of the intercourse of the frozen wall decreases linearly with the increase of the thermal conductivity, increases linearly with the increase of the volumetric heat capacity and the original ground temperature, when the original ground temperature increases by 5 ℃, Increase about 1 d; the change of latent heat of phase change has almost no effect on the cooling process of the soil in the initial stage and the late stage of freezing; the cooling rate of different soil layers is sand cement soil> clay cement soil, sand> clay; sand cement Soil and sand, clay soil and clay reached the phase transition stage almost at the same time. No matter whether the cement was improved or not, the sand always lasted 4 days earlier than the start of clay. The results provide a theoretical basis for similar projects in the future.