Abstract: Longdong is a typical loess region,where local buildings are easily impacted by the collapsibility of loess.This study examines the section from K171+398.23 to K171+370.23 in Zhaike Township,Guyuan City,on the Yinkun Expressway.It investigates the temperature and humidity field changes and settlement deformation characteristics of the foundation and subgrade under atmospheric circulation during and after construction.The results indicate that during high temperature and freezing phases,the temperature and humidity changes inside the roadbed exhibit a linear distribution with depth.In contrast,the foundation experiences relatively minor changes,with the top layer showing significantly higher temperature and humidity variations than the bottom layer.The minimum recorded temperature is close to 2℃,with a freezing depth of less than 1.5m.Settlement deformation predominantly occurs during construction,severely affected by mechanical disturbances,with a maximum value of 24mm and a minimum of 0.88mm in the post-construction stage.The settlement of the deep soil layer is substantially higher than that of the upper layer,with differential settlement prominently observed at the interface between the roadbed and foundation,as well as at a depth of 1m within the foundation.