Seismic Characteristics Of High And Steep Slope With Jointed Rock Masses Using Shaking Table Tests

Regional geological situation, especially the major tectonic fracture system in boundary region of rock mass, and the distribution and combination of various joint set and weak plane is important to the rock slope stability. Nowadays, the problem of dynamic response and stability of rock slope under the effect of seismic load is one of hot issues in geotechnical earthquake engineering and earthquake engineering. The dynamic response of rock slope under intense earthquake is mainly determined by the geometric distribution and physical and mechanical properties of discontinuity surface. In particular, for the high steep rock slope containing bedding or toppling joint, collapse and other severer damage occurred during the earthquake have greatly influence on the safety of surrounding buildings. Due to geological structure, rock mass materials, discontinuous characteristics and complexity of ground motion, issues of the dynamic stability of rock slope are very complex. In this paper, based on the jointed rock masses and the dynamic performance of the seismic force, the finite element numerical simulation and large-scale shaking table test are carried out, the transmission characteristics of seismic force in jointed rock masses is discussed, the dynamic response rules of high steep rock slopeand the process and characteristics of failure is studied, the influence of discontinuous surface on the slope is revealed.Based on the rock slope containing forward and reverse joint, finite element numerical simulation is carried out. The influence of the joints on the propagation characteristics of seismic force and seismic stability are analyzed. Considering the multiple reflection refraction between the discontinuous surface and the surrounding rock masses interface, the finite element dynamic analysis is carried out in time domain. The distribution of wave field is analyzed at different instants of time. Due to the interaction of discontinuous joint and rock interface, seismic wave presents multiple reflected refraction phenomenon in slopes with discontinuous surface. High-frequency component becomes dominant and occurs with phase change, which is related to the layout and quantity of joints. Distribution of the wave field is obvious different between horizontal and vertical load. The ground motion shows magnifying trend along the slope, and the maximum value appears at the top of the slope, which decrease along the slope.Based on the rock slope with discontinuous surface, large-scale shaking table test research is designed and conducted. Through the shaking table test, the dynamic response rules of high steep slope with jointed rock masses are studied. And the dynamic response rules, the process and mechanism analysis of deformation and destruction of rock slope are discussed. Through the material test, the rock mass is simulated by the mixture of several materials, such as cement, sand, iron powder, clay and mixture. The Teflon tape, which has low skin-friction coefficient, is used to imitate the discontinuous joints. The high steep rock slope model is built. Through a series of shaking table test, the whole process of failure of the slope model is observed. In conclusion, the destruction process of the high steep slope model has three stages, thus development of cracks, spalling of the slope, collapse and sliding. The slide surface appears at the height of 2/3 of the slope.Seismic dynamic response data(acceleration, pressure, strain) are collected by sensors at different positions. Through data processing, analysis, the dynamic responseof the slope and its characteristicin different load case are obtained. Test results show that the slope has amplification effects on inputload. The amplification coefficient of PGA shows magnifying trend along the slope face upward, and the maximum value appeared at the top of the slope, while the value decrease along the surface into the slope inside. The amplification coefficient of PGA is enlarged slightly in the slope body in vertical direction.Acceleration amplification coefficient of PGA is affected by the joints and load direction. Acceleration amplification coefficient of PGA during horizontal load is greater than the vertical one, suggesting that the dynamic response is greater on the under horizontal direction. With the increasing load amplitude, dynamic response is amplified linearly in the slope, and regularly on the horizontal direction. Test result will help have a better understanding on the dynamic response of high and steep slope with jointed rock masses, and provide a basis of dynamic instability analysis and anti-earthquake design.