Characters Of Soil Nailing Work

The soil-nailed support system for deep excavation has got more application because of its advantages, such as easy to implement and less investment. With the help of centrifugal model experiment, finite element method and field test , This dissertation gives an all-around and systemic analysis on the mechanism of soil-nailed support system , strength , deflection and the effect of the support parameters , so as to put forward proposal on the application of the new technology.Firstly, a discrete two-dimensional (2-D) finite element model (FEM) has been developed. Several kinds of model are chosen to analogy the nonlinearity and inelasticity of soil , including E-B model and L-D model. The interaction between nails and soil is stimulated by the virtue of Goodman elements. The staged excavation and retaining can also be stimulated in this model. An engineering case is , as an example, analyzed and the validity and reliability of the model is proved by comparing the predicted deflection with those field measured. The behaviors of soil naing, the character of soil deflection and bar stress are applied to examine and parametric studies are also carried out to investigate the influnences of retaining parameters.Secondly, several centrifugal model experiments are obtained and comprehensive analysis of the measurement are given . combined with the element analysis , the mechanism of soil-nailed support system are futher investigated .Finally, A field test of soil-nailed project are obtained and comprehensive analysis of the measurement are carried out. the behaviors of the soil-nailed support system is studied at the stage of excavation.Some conclusions are proposed as follows:1. Because the stiffness of the nails is larger than the soil, the deformation of the soil is restricted. The soil that is restricted, acting as retaining wall, decrease the deformation of the soil that is not restrictedeffectively. The stress of the surface course and nails transfer diffusion, i.e. the surface course and nails transfer the excavating load to the soil that is restricted, so soil among more area take action, which slower the extend of the plastic area, and restrict the increase of the plastic deformation.2. When the angle between the nails and the cut slope is nearly right angle, the horizontal displacement of the soil behind the slope and the tension force of the nails are minimum. When the angle is smaller or larger than this angle, the values above increase.3. The vertical space has an optional range, and the value of the space should among this range. If the space is large than the optional range, the action of the nails is too small and the vertical displacement is too large. If the space is smaller than the optional range, it is too wasteful.4. Because the soil tension force distributes most equably and its horizontal displacement is minimum , it is proposed that the nails in the upper of the cut slope should be longer and shorter in the lower. But the nails in the lower should not too short.