Abstract:The composite soil nailing is a new technique developed from soil nailing for retaining excavation or improving stability of existing slope. A modeling test of the composite soil nailing is carried out in laboratory to study its behaviors and working mechanism and hence facilitate its development. The retaining structures are modeled according to the similarity rule in which the geometric length of the structure is in inverse proportion to the duration of the structure deformation and the adopted similarity ratio was one to ten. The sequential excavation and retaining are conducted during the experiment to simulate the actual construction procedures in situ. Three cases,including composite soil nailing,soil nailing and excavation without any retaining,are executed in the modeling test to compare and analyze their behaviors. Ground subsidence,rebound deformation and horizontal deflection are measured by means of displacement transducers,and the displacements inside the excavated slope are monitored by a network of surface movement markers installed inside the transparent glass side of the modeling device. The measured results show that (1) the distribution of deformations of composite soil nailing is different from those of general soil nailing and excavation without any retaining because of the cooperation of the nails and the soil-cement piles,and among the deformations,those of composite soil nailing are the smallest and those of excavation without any retaining are the largest,(2) the cooperation of the nail and the soil-cement piles in the composite soil nailing causes more subsoil participating in retaining action than in the soil nailing due to the uniform stress distribution near the slope. The deformation induced by excavation is controlled effectively and the stability of the excavated slope is improved.