MODEL TEST STUDY ON FREEZE-THAW CHARACTERISTICS OF ARTI-FICIALLY FROZEN SOFT CLAY UNDER COMPOSITE STRATA SEEPAGE

Artificial ground freezing(AGF) is a construction method widely used in coastal tunnel engineering reinforcement. With more underground construction in coastal areas, clay-sand composite strata bring more challenges to AGF. Based on the actual engineering case of AGF, we designed a model tests to simulate the influence of soft clay-sand composite strata seepage on freezing process. We analyzed the frost heave displacement, temperature field distribution and water content change of upper clay layer under different seepage conditions of the underlying sand layer. We find that the existence of seepage in soft clay-sand composite strata not only influence the development of frozen wall, but also promotes the water migration of upper clay layer. Meantime paralleled fissures are well-developed surrounding frozen wall observed by image during freezing and subsequent image processing. All above increases thaw settlement and shorten the duration sharply. The research results above can provide important theoretical basis and significant reference for the application of AGF in soft clay-sand composite strata.