Effects of seasonal temperature change on a large excavation project

The effects of seasonal temperature change on loads of circle beam strut, displacements of retaining structure and variation of the surroundings are investigated based on 16 months' monitoring data of a stagnant braced excavation in soft clay area. The excavation, 148 m wide and 178 m long, is supported by soldier piles and lagging with circle beam reinforced concrete struts. The monitoring results indicate that the loads of the circle beam with the arrival of the summer continue to increase, and decrease gradually after the winter comes. The supporting load is consistent well with the change of the seasonal temperature. At the same time, the soldier piles show apparent movement to the pit and there is approximately a linear relationship between the horizontal displacement of pile top increment and the temperature change. The temperature decrease induces the inverted triangle deformation pattern in enclosure structure with multi-level support system. The increase of horizontal displacement of the retaining structure further aggravates the soil settlement outside the foundation pit, causing adverse effects on the whole deformation of the foundation pit and the surrounding environment. In addition, three-dimensional finite element (FE) analysis is performed. The results suggest that the stiffness of retaining structure plays an important role in strut stress. The harder the soil conditions, the greater the temperature effects on the axial force.