Study on composite soil nailing in soft subsoil by model test

Composite soil nailing, which has been developed on the basis of soil nailing and gotten wide application, is a new retaining technique for excavation. The working principles of composite soil nailing were studied by model tests so as to provide reference to design and construction of the retaining system. The excavation models were designed by a similitude law, that is, the model length is inverse proportion to deformation duration, and the adopted model similitude ratio is one over ten. The tests simulated the actual procedure in situ with staged excavation and retaining construction. The measurements included soil displacements, land subsidence, bottom rebound deformations, surface cracks and failure configurations. The results show that surrounding soil will be acted on together with the composite system to a high degree to control the deformations during excavation effectively; the inserted depth and the strength of the cement-soil waterproof wall will play a great role in controlling the deformation and failure of the composite system; and the behaviors of composite soil nailing will be superior to that of soil nailing.