Moso Bamboo Soil-Nailed Wall and Its 3D Nonlinear Numerical Analysis

This paper presents a new earth-retaining structure, the moso bamboo soil-nailed wall. Moso bamboo (including branches) is employed as soil nails and piles, and used to weave bamboo strip grids (replacing rebar grids) for sprayed-concrete surface courses. In this paper, the design and construction methods of this structure are elaborated using laboratory and field tests, and numerical simulations for two completed projects with respect to stability and deformation, respectively. In-situ tests show that the pulling capacity of bamboo nails (with branches) increased by approximate to 2.5-2.8 times in stiff soil or soft clay, respectively, compared with steel-pipe nails. For one wall in soft clay, numerical analysis was conducted, which verified the stability of the bamboo-reinforced system (compared with the soil-nailed wall constructed with steel-pipe nails, which failed). For another wall, the deformation and internal force of the structure were obtained using three-dimensional (3D) nonlinear numerical software. The prediction agrees well with the measured settlements, and has good accuracy against the measured horizontal displacements. The study indicates that the row of nails the lowest level receives the highest axial force (which requires the longest length). This trend is opposite to that in using conventional soil-nailed walls. The moso bamboo method renders an increase in the depth of sliding and thus the stability of excavation, which failed in the wall constructed with conventional steel-pipe soil nails.