复杂地层差异温度人工冻结试验与数值分析

SCALE MODEL TESTS AND NUMERICAL ANALYSIS OF ARTIFICIAL FREEZING AT DIFFERENT TEMPERATURES IN COMPLICATED STRATA

针对立井冻结工程中存在的导热性能差异较大复杂地层,为加快局部地层冻结并对冷能进行优化,提出一种冻结管差异温度优化冻结方案,并研发单管双循环系统冻结器。为验证该方案的强化冻结效果和冻结器对冷能的调控能力,采用2套盐水循环系统对冻结器上、下管段提供不同温度的低温盐水,在模型试验箱体内进行砂土和粉质黏土的单管冻结试验,研究冻结管不同管段在不同盐水温度作用下形成的冻结壁温度场分布特征,并采用FLAC3D对冻结管进行冻结数值模拟。结果表明:该冻结器实现界面附近9.1℃的管段差异温度冻结,优化方案能有效调整冻结壁的厚度和平均温度,使导热性能稍差的粉质黏土较砂土得到一定程度强化冻结。

There is a great difference of thermal conductivity between strata in some shaft construction projects by artificial freezing method. An optimization freezing suggestion of flowing two types of negative temperature solutions in a freezing pipe is proposed to accelerate the freezing rate of local strata and to optimize cold energy adjustment. And a single freezing pipe of dual circulation system is developed for this purpose. To verify the effect of intensified freezing and the adjustment ability of the freezing pipe,a single freezing pipe test for sand and silty clay is conducted in a model test box using two sets of circulatory systems to provide calcium chloride solution of different negative temperatures for two sections of a single freezing pipe. Temperature field distribution characteristics of frozen wall in different levels of freezing pipe are analyzed. Meanwhile,the numerical simulation is adopted to calculate temperature field of the case using FLAC3D software. The results show that the difference of temperature can reach 9.1℃ between adjacent outer walls of the two different temperature sections, and the thickness and average temperature of freezing wall can be adjusted effectively. The silty clay has been intensified frozen more than sand certainly.