Experimental Study on Failure Modes of Composite Structures with Scattered Row Piles and Soil Nailing

A series of centrifuge tests of composite structure with scattered piles and soil nailing (PSN) were carried out by Tongji University. Based on the results of 13 group tests, the failure modes of PSN structure and the effecting law of parameters, including pile spacing and soil nailing, were explored. The results showed that the failure modes of PSN structure could be mainly expressed as three forms. When the soil nails were longer than 2H/3 (H was excavation depth of pit) or the pile space was larger than 8D (D was pile diameter), the pit supporting structure with PSN was dominated by soil nailing and the failure of PSN structure was similar to pit supporting structure with soil nailing. On the other hand, when the soil nails were shorter than H/3 or the pile space was smaller than 4D, the PSN structure was dominated by scattered row piles and the failure of PSN structure was similar to pit supporting structure with scattered row piles. The failure modes of other kinds of PSN structures were multiple failure modes controlled by both soil nailing and scattered row piles, which were presented as the failure of soil nail wall following by soil instability between piles.