| The thesis aims to investigate the interaction mechanism between soil and soil nail in several aspects, including the theoretical pullout response of a soil nail, effects of several critical parameters on pullout resistance of soil nails, and the behavior of cement grouted soil nails in slopes and laboratory pullout test.;A simple analytical model has been developed for estimating the maximum shear stress of nail-soil interface. Theoretical comparisons and parametric studies show that the shear stress of nail-soil interface depends on the nail radius, grouting pressure and the location of failure surface. An analytical method has also been proposed to investigate the transitional interaction behavior between soil and soil nail in the passive zone of a slope. An extensive parametric study suggests that the pullout resistance of soil nails depends on several key factors including nail length and diameter, length of plastic zone, and elastic modulus of the soil nail.;A series of field pullout experiments were carried out on ten soil nails to investigate effects of soil nail depth and grouting pressure on the pullout resistance of soil nails. Test results indicate the overburden soil pressure seems to have no apparent correlation with pullout resistance when no grouting pressure was involved, but as the grouting pressure increased, the pullout resistance of soil nails increased substantially. To study the soil nail behavior in field, a monitoring program has been conducted to measure the strain/stress of soil nails in cut slopes. Test results show that axial forces of soil nails mostly increase after grouting work due to the established bonding stress at the nail-soil interface. As the cement grout has hardened, axial forces of soil nails appear to be time dependent, indicating that soil nails work passively in these cut slopes.;Two optical fiber sensor technologies including the Low Coherence Interferometry (LCI) and fiber Bragg grating (FBG) technologies have been used to measure the pullout strain/stress distributions of a soil nail in laboratory pullout test. Comparative studies indicate that soil nail pullout behavior can be well evaluated using the two techniques. |
