Dynamic Failure Mechanism Of Horizontalcomplex Layered Rock Slope In Highintensity Area

High-intensity areas such as Yunchuan and Tibet are in the period of rapid development of infrastructure construction such as roads,railways,and water conservancy.The collapse of rock slopes induced by earthquakes is one of the common technical difficulties in the process of engineering protection and management.Rocky seismic slopes are the main ones.Under the combined effect of weathering of soft rock caverns and earthquakes,this type of slope instability often causes huge economic and property losses.However,the dynamic failure mechanism of horizontally complex layered rock slopes under the combined action of earthquake and weathering involves many disciplines such as mathematics and mechanics.The calculation process is undoubtedly very complicated.Therefore,the dynamics of horizontally complex layered rock slopes under the combined action of the two is revealed The destruction mechanism has important scientific guiding significance and practical value.(1)Based on the limit equilibrium method,the calculation method of slope stability coefficient under different weathering and seismic longitudinal and longitudinal waves is established.It is found that the slope with a cavity depth of 1.5 ～ 4.5m and a fissure depth of 25% ～ 50% is greatly affected by the shear wave effect of the earthquake.The slope with a depth of 6m and a fracture penetration rate of 62.5% is greatly affected by the action of seismic longitudinal waves.Combining fracture mechanics,material mechanics and Newton ’s second law,the stability factor of a horizontally complex layered rock slope under seismic action is established,considering the interlayer load The calculation method reveals the stability decay process of each rock block of the slope,and the caving time is obtained.(2)The mesoscopic parameters of the rock in the PFC three-dimensional particle flow numerical model were obtained by conducting indoor sand and mudstone routine,dynamic triaxial test and PFC numerical triaxial servo test,and the macroscopic mechanical properties and the mechanical properties of the two types of rocks were discussed The effect of intensity attenuation.It was found that in the conventional triaxial test,the brittleness of sandstone gradually weakened with the increase of confining pressure,and the attenuation characteristics of mudstone brittleness showed a V-shaped change;in the PFC numerical triaxial servo test,the mudstone particles showed shear failure and the sandstone particles showed tension Failure;in the dynamic triaxial test,the peak stress of the compressive strength of the sandstone with cracks was reduced by 16.7% ～ 25% compared with that without cracks.(3)Taking the horizontal layered rock slope of Wendu Highway in Sichuan Province as the research object,the three-dimensional particle flow numerical model of the slope was established using the PFC three-dimensional discrete element particle flow method,and the failure of the rock slope under the combined action of weathering and earthquake was developed.Analysis of patterns,collapse sequences,stability changes and dynamic response laws.It was found that the basic failure modes of this kind of rock slope under earthquake action can be divided into tensile cracking-horizontal slip failure(cavity depth 1.5m,fissure depth 25%),tensile cracking-caving-dumping failure(cavity depth 3m,fissure Depth 37.5%),4 types:caving-dumping-rotation failure(cavity depth 4.5m,fissure depth 50%),caving-slip-rotation failure(cavity depth 6m,fissure depth 62.5%).It is found that with the increase of the depth of the cavity and the increase of cracks,the rock mass collapse time is accelerated from 8.7 to 11.4s to 2.3 to 9.0s,and the bottom and top rock blocks without base support are more likely to collapse under the action of earthquake.The PGA amplification factor and dynamic response of the rock block are positively correlated with the development of the cavity and fissure.The PGA amplification factor of the rock block of Model 1 is between 0.45 and 0.9,and it is distributed in a zigzag pattern with the increase of the vertical elevation of the rock layer;The PGA magnification factor of the block is between 1.1 and 2.1,and there is a clear elevation magnification effect;the PGA magnification factors of the rock blocks of Model 3 and Model 4 are between 2.1 and 3.7,and 2.9 and 5.2,respectively."U" shaped distribution.(4)Based on the HHT Hilbert-Huang transform method and the principle of energy dissipation,the frequency spectrum and energy analysis of complex layered rock slopes with different degrees of weathering in the cavity under earthquake action are developed,revealing their time-frequency characteristics under earthquake action,Energy change law and dissipation mechanism.It is found that the main frequencies of the four slope models under earthquake action are concentrated at low frequency 0 ～10Hz.The vibration signal energy,the overall frequency bandwidth of the slope,and the significance of high-frequency effects are positively correlated with the depth of the rock cavity and fissures,and the weathering degree of the rock cavity increases The time-frequency diagram shows multiple main peak distributions at the main frequency;the total energy dissipation of the slope can be divided into two stages of fracture collision and overall collapse,and the energy consumption curve shows the characteristics of first fast and then slow over time.The energy consumption accounts for 89% ～ 95% of the total energy,and the maximum instantaneous energy between the particles decreases from 155 MJ to 72 MJ as the weathering degree deepens.