软黏土三维水-热-力耦合冻融模型及应用

人工地层冻结法是沿海地区软黏土进行地层加固的一种常见绿色工法，地下空间开挖的大型及复杂化使目前冻结法面临更加复杂的渗流环境。为此，通过分凝冻胀理论刚性冰模型的三维化推广，建立能考虑水分迁移的热-水-力耦合作用冻胀融沉模型，以模拟复杂渗流环境下的人工冻结工程。基于模型使用COMSOL有限元进行模拟，与同尺寸室内模型试验数据进行对比，验证该模型在复杂渗流环境组合地层(软黏土、粉细砂)冻结中的适用性。模拟结果表明：在组合地层条件下，渗流会削减冻结稳定时冻结帷幕的厚度；当速度大于1.2 m/d时，冻结帷幕将不能达到设计厚度；冻结帷幕靠近渗流边界的一侧冻胀力增长缓慢、冻胀力的最大值较低；渗流致使地表产生不均匀沉降，下游区域的沉降量更大。利用已验证模型对组合地层渗流作用下的冻结法施工进行模拟预测，提出结合组合地层渗流因素的隧道安全冻结法分级标准，为冻结法在沿海更复杂渗流环境下的施工安全与预警提供依据。

Three-dimensional thermal-hydraulic-mechanical coupling frost thaw model of soft clay and its application

Artificial ground freezing is a common green construction method for strengthening the strata of soft clay in coastal areas. Due to the large-scale and complexity of underground excavation, the artificial ground freezing is faced with more complicated seepage situations. By extending the three-dimensional rigid ice model of the segregation frost heave theory, a thermal-hydraulic-mechanical coupling frost heave and thawing settlement model considering water migration was established to simulate artificial freezing under complex seepage environments. Based on the model, simulation was carried out by using COMSOL finite element, and results were compared with the experimental data of the indoor model of the same size, so as to verify the applicability of the model in the freezing of combined stratum (soft clay, silt fine sand) in complex seepage environment. Simulation results show that under combined formation conditions, seepage reduced the thickness of the freezing curtain when freezing was stable; when the speed was greater than 1.2 m/d, the freezing curtain could not reach the design thickness; the frost heave force on the side of the freezing curtain near the seepage boundary increased slowly and the maximum value was low; seepage caused uneven settlement on the ground, and the settlement in the downstream area was greater. Finally, the verified model was used to simulate and predict the construction of the freezing method under the action of combined stratum seepage, and the grading standard of the tunnel safety freezing method combining the combined stratum seepage factors was proposed to provide the basis for the construction safety and early warning of the freezing method in more complicated coastal seepage environments.