Abstract: When the horizontal reinforced concrete struts are used in retained foundation pit of large area，the cost of horizontal reinforced concrete struts will be very high and need long construction period. Moreover, large amount of solid waste will be produced after the struts been demolished. Therefore, the multi-bench retaining method is developed and was used in large area foundation pit projects. The failure mechanism of multi-bench retained foundation pit is investigated and design method is studied. The multi-bench retaining structure can fail as overall stability failure or overall overturning failure like a gravity retaining wall when the width of the bench is small. The slip surface can extend into the soil between retaining pile of different benches with the increase of the width of the bench, this leads to the mutual-effect between the multi-bench retaining piles. Separate failure can occur to the multi-bench retaining pile when the width of the bench is big enough. The application of multi-bench retaining method shows that multi-bench retained foundation pit with the use of horizontal reinforced concrete struts can be highly cost-effective and construction period of underground structure can be significantly reduced.

Key words: foundation pit, stability, deformation, multi-bench retained excavation, application in engineering