CALCULATION OF BASE HEAVE OF FOUNDATION PIT INDUCED BY UNSTEADY SEEPAGE

Based on one-dimensional unsteady seepage theory,the variation rule of water head inside and outside a foundation pit is investigated under the condition of large-scale excavation and retaining walls with large rigidity;and the corresponding analytical formulas for calculating water head are deduced.The variations of water head,pore water pressure,effective stress and heave of pit base with time are further analyzed.It is shown that excessive pore water pressure induced by unloading and seepage induced by water head difference between the inside and outside of the foundation pit cause the increase of pore water pressure beneath pit base with time,and thus the decrease of soil effective stress and the increase of pit base heave are induced.