Mechanical Behavior of Nailed Soil Retaining Structures

• Main Authors: Hong, Yung-Shan, 洪勇善
• Other Authors: Chen, Rong-Her
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/66451369380893031377

博士 === 國立臺灣大學 === 土木工程學研究所 === 87 === Soil-nailing technique is a low cost, time saving, and flexible construction method. It has been used over twenty years mainly in excavation and slope stabilization. However, its mechanical behavior has not been well understood, and consequently there still exists confusion in selecting design parameters and the method for analysis. The purpose of this study is to investigate the mechanical behavior of soil-nailing wall through model tests in a sandbox. The sand that would be used in the model was tested by triaxial tests to develop its constitutive model of stress-strain-volume relationship, which provide the basis for numerical analysis. In order to verify the constitutive model, the result of numerical analysis was compared with that from a pullout test. The model proved that it could suitably simulate the pullout behavior of a nail. Thus it was used to study the influencing zone of a nail, the constrained boundary condition of the pullout box, and the failure mechanism around a nail. On the other hand, a model sandbox was developed through similarity analysis. The model nail was chosen based on the dimensionless factors, which relate to the tensile strength, the deformation property, the pullout resistance of the nail, etc. Six model tests of soil-nailing walls were carried out for different inclination and type of the nail and the bending stiffness of the facing. The result from the numerical analysis was in good agreement with that from the model study in excavation stages. To evaluate the stability of soil-nailing walls, a limit analysis method was developed based on the upper bound theorem of plasticity theory in which the stress-strain relationships of the soil and the nail were considered in an idealized manner. The prediction from this method compared well with the field experiment in terms of the factor of safety as well as the failure surface. Finally, the parametric study indicates that the tensile force in the nail contributes mainly the reinforcing effect. The shear force and the moment in the nail are small, hence may be neglected in the analysis for simplicity. Besides, the horizontal displacement of the facing increases with the inclination of the nail, especially at 30°inclination. The bearing capacity of the nailed soil wall also decreases with the inclination of the nail. Keywords: Soil Nailing, Model Test, Numerical Analysis, Limit Analysis