THE ACTIVE EARTH PRESSURE CALCULATION FOR RETAINING STRUCTURE OF DEEP FOUNDATION PIT ADJACENT TO RIVER BASED ON UPPER-BOUND ANALYSIS

In the deep foundation pit adjacent to river, the ground between bank slope and retaining structure is limited, as a result, the conventional models can not be used for the calculation of earth pressure. Based on the modified generation technology for multiple-segment slip surface, the active earth pressure of waterfront foundation pit in non-homogeneous ground was deduced through upper-bound analysis. On the homogeneous ground condition, the proposed method were validated throught a comparison with their counterparts of conventional linear or logarithmic fracture models. The proposed method was applied to an engineering instance (i.e. deep foundation pit of Agriculture and Forestry University Station in Fuzhou Metro Line 5), it is concluded that the active earth pressure of retaining structure increases approximately linearly with the rising of water level. On the other hand, the active earth pressure increases rapidly and then stabilize with the increase of width-height ratio of foundation pit. When the width-height ratio exceeds 0.7, the active earth pressure tends to stabilize, which implies that the slip surface transferred from mode Ⅰ (intersecting with slope) to mode ⅠI (intersecting with top). Furthermore, the numerical simulation results with bracing stiffness reduction show that the shape of sliding surface, the active earth pressure of retaining structure and the action point of resultant force are consistent with their counterparts of upper-bound analysis. These researches could provide some reference for the scientific design of retaining structures in the deep foundation pit adjacent to river.