Influence of Borehole Deviation on Pressure-type Anchor Cables: Characteristics of Stress Distribution and Transmission

In this study, a mathematical model was established for calculating the axial force and shear stress distribution and transmission of the linear and bending pressure-type anchorages, and analyzing the effect of tensile loading, anchorage length, borehole diameter and bending radius. Furthermore, an indoor test based on the Xuecheng 1# Tunnel slop was conducted to verify the effectiveness of the proposed model. The results showed that, the borehole deviation increased both the peak and residual values of axial force and shear stress on the pressure-type anchorages. The shear stress is about 1% ~ 2% larger on the outer surface than that on the inner surface. A larger residual value on the former anchorages led to a greater peak and residual value on the latter anchorages, called superimposed effect, was also enhanced by the borehole deviation. Borehole deviation has a small effect on the peak shear stress (1.8 ~ 5.9%), but a significant effect on the residual shear stress (19.1%-99.6%). The values calculated from the proposed model are in good agreement with the experimental data obtained from the indoor tests with an error of less than 3%. These results indicate that the borehole deviation obviously impacts the stress distribution and transmission of the pressure-type anchor cables, this influence can be analyzed by the proposed mathematical model.