Seismic displacement analysis of slope reinforced by frame prestressed anchor rod structure

Instability of slope induced by earthquake seriously affects casualties and property losses and hinders earthquake rescue, so the study of slope displacement under earthquake is of great significance. For the slope reinforced by frame prestressed anchor rod structure under earthquake, the calculation method of slope displacement and axial force of anchor rod under seismic action were derived by combing Newmark method and limit analysis method. This method proposed in this paper comprehensively considers the amplification effect of earthquake acceleration on the slope surface, the inertial force of reinforce structure and the dynamic change of axial force of anchor rod. The solution program of this method was compiled in MATLAB and its rationality was proved by a numerical model in FLAC3D software. The results show the slope displacement calculated by the method proposed is consistent with the variation law of slope displacement obtained by traditional methods. Regardless of whether the anchoring force is considered or not, the slope yield acceleration obtained by this method is very close to the slope yield acceleration obtained by the Bishop method. The critical sliding surfaces obtained by the two methods are very close, and the sliding points are located at the foot of the slope. Compared with the Bishop method, this method can consider the amplification effect of seismic force on the free surface of the slope and the gravity of the supporting structure. Ignoring the change of the axial force of anchor rod will make the slope displacement larger, while not considering the amplification effect of the seismic acceleration on the slope surface and the gravity of the reinforce structure will make the slope displacement smaller. This method proposed in this paper comprehensively considers the above factors and is more accurate. In the process of landslide mass sliding, the axial force of the anchor rods increase gradually, and the growth rate of the axial force of the lower anchor rods are larger than that of the upper anchor rods. The increase of anchor rod prestress and elastic modulus will reduce the seismic displacement of the slope, and the increase of the dip angle of the anchor rod will increase the seismic displacement of the slope. The dip angle of the anchor rod should be minimized without affecting the grouting effect of the anchor rod.