Study On Seismic Responses And Anchoring Mechanism Of Anchored Rock Slope

Slope failure wherefrom heavy casualties and property loss can occur will be a greater calamity in the earthquakes, so that it is of great significance in engineering practice to study how to improve the seismic performance of the slope reinforcement technology. As we know, the anchorage technique has been successfully and widely used due to its convenience, economy, less disturbance, and efficiency. However, the current understanding of the slope anchor’s strengthening influence on the slope dynamic performance is still not thorough but deficient in research. The currently existing research still cannot abundantly account for the failure mechanism of rock slopes, and there is no method acknowledged to be a reasonable calculation of the seismic stability of rock slopes. Moreover, the anchoring mechanism researches of the bolts in the rock slope under earthquakes are lack of in-depth. Therefore, in engineering practice, it is urgent to study on the seismic performance of anchored rock slope, whereby the slope anchorage can be optimized.There are many factors affecting the stability of rock slope, and earthquake is one of the important external factors. Since the stability of rock slope is mainly controlled by rock mass structure, failure mechanism of rock slope varies with the structures. For the slopes of same structures but under different seismic waves, the seismic responses characteristics are different; And for rock slope of different structures, the effects of earthquake and the anchor effects of anchored rock slope also should be different. So the anchor effects should be improved by optimizing the structure characteristics of slope rock mass and the effects will be reflected on the dynamic responses characteristics of the slopes.Analysis of the slope seismic responses is an important means to research the slope failure mechanism, seismic stability and anchoring mechanism. In this paper, we established an anchored rock slope model and computed it using the finite difference software FLAC3D. The seismic responses, such as displacements, accelerations, axial forces of rock bolt, are analyzed so that the interaction between rock bolts and the surrounding rocks and the influences of the anchor on rock mass material properties are presented and discussed. The results show that the permanent displacement is excited by larger accelerations, and the increase of displacement is a cumulative process. Anchor can also improve the material properties of rock mass, but the effect is not obvious. We also give a failure criterion of rock slopes under the earthquakes based on the average tension strain and nominal shear strain suggested in this paper. Especially, the criterion only needs the data of displacements on the surface of slope which are easily obtained in engineering monitoring. Additional, a method to determine the failure surface is put forward base on the seismic simulation.In order to study the influences of different ground motion parameters, including amplitude, frequency and duration of earthquake, on the seismic responses of rock slopes, we applied different waves to the model, and then got the law of influences. The results showed that the structure characteristics are the dominating factor of the dynamic responses, and the main function of anchor is to improve the structure of slope in the aspect of anti-seismic. Hence, a complex analysis of the seismic stability of slope can be reduced to an analysis of the slope structure.To further explore the anchor role and mechanism of slope bolts under earthquakes, we adopted different damage models of rock mass structure components and discussed the influences of seismic force and anchor force on the rock mass stability. Then the transfer process of the force in the slope bolt system is analyzed, and a simplified dynamic model of single anchored rock system was presented. Based on the simplified model and the analytical solutions of the bolt axial force distribution, the distributions of bolt in the anchored rock model including single and double interfaces were calculated. Then the influences of different stress status in the process of earthquake, the rock mass and bolt material parameters on distribution of axial force were discussed. In addition, we also presented an anchoring mechanism of slope bolts from a perspective of force analysis, and put forward with an optimal anchoring design of rock slope which is controlled by multiple structural surfaces.The final part of this paper unfolds based on the analysis of Grottoes cliff. For such a special rock slope of the complex geometric features, the geometric characters cannot be ignored to simulate its seismic responses. We obtained the coordinates of points cloud on cliff surface using total station, and then built a relatively fine3D model with the CAE software. Based on the method of seismic responses of slope analysis, we simulated the seismic responses of grottoes cliff, obtained the dynamic responses characters of grottoes cliff, discussed the influences of digging grottoes on dynamic responses of cliff, and analyzed the possible failure modes and the causes, In addition, we simulated the seismic responses of anchored cliff by reinforcing the upper rock mass of the model with small bolts which was used in the grottoes reinforcement. Then the seismic performance of small bolts was discussed, and the suggestion of anchoring engineering was given.The results of this paper contribute to further understanding the seismic responses, seismic stability of anchored rock slope, and the anchor role and anchoring mechanism under the earthquakes. These also provide some theoretical basis for anchor design of rock slope.