Abstract: Targeted research is performed on several problems about the application of the soil nailing wall combined with row piles in tunnel deep foundation pit support. Based on the theoretical and numerical analysis of engineering examples, the selection principle are proposed for the slope ratio i of soil nailing wall, the diameter-separation distance of the row pile as well as the relative stiffness between row pile and inner support while the inner support is applied. It is shown that 1) the smaller the value of i , the more stable the soil nailing wall, but the larger the moment and the displacement on the row pile are. The value of i should take a small value when the sliding stability of the soil nailing wall is fulfilled. 2) The larger the diameter and space between the piles, the smaller the horizontal displacement of the row pile, so that less concrete and steel rebar is required, resulting in a more cost-effective design, though the protection for the soil between piles will be more difficult. Hence, the diameter and the space between the pile should assume larger values when the engineering geological conditions is good and the water level is low, and vice versa. 3) Supporting effect of weak pile with strong support is better, but the construction interference for the surroundings is larger, while the cost of the strong pile (non-cantilever) with weak support is less. To achieve the purpose of safety and reliability and economical efficiency, it is necessary to consider engineering geological conditions, surrounding environment requirements, construction period, cost, and so on, in selecting the relative stiffness of the pile need.

Key words: open cut tunnel, deep foundation pit, soil nailing wall, row piles, inner support