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.