Seismic Responses Of Wake Interlayer And Initiation Mechanisms Of Large Landslide During Strong Earthquake

China is one of the contries with most earthquakes all over the world.Eaarthquake-induced landslide was one of the most serious problems,especially the Wenchuan Earthquake which triggered the most landslides in a single earthquake occurred in Longmenshan tectonic fault in 2008.It triggered more than 100 landslides with area larger than 0.5 km~2,bringing catastrophic losses.However,compared with the movement and the accumulation,the research on the large-scale earthquake landslide is very difficult because there is less evidence left in the starting process,which is of great significance to the stability evaluation of seismic slopes,the prediction of earthquake and geological disasters and the active disaster prevention decision-making.In the active alpine gorge area,extensive primary or secondary large weak zones are widely developed in the slopes.More and more examples reveal that they are the key control stabilities in strong earthquakes such as the Daguangbao landslide Belt background is the pre-deep buried layer structure belt.Although a great deal of achievements have been made in the response to slope earthquake,the existing researches have not fully understood the dynamic response of the key weak zone of the slope and paid little attention to the slip control mechanism.China is one of the contries with most earthquakes all over the world.Eaarthquake-induced landslide was one of the most serious problems,especially the Wenchuan Earthquake which triggered the most landslides in a single earthquake occurred in Longmenshan tectonic fault in 2008.It triggered more than 100 landslides with area larger than 0.5 km~2.Some of them were involved in weak interlayer.The Daguangbao(DGB)landslide was paied much attentions,which has preexisting weak fault in deep part had failed along the weak layer during the strong earthquake and formed the largest landslide.Based on the investigation of the DGB landslide during 9years after Wenchuan earthquake,a series of shaking table tests were conducted.The results show that(1)dynamic non-compatible deformation btween upper and lower lyaers was trigged by weak interlayer,in which earth pressure was ten times larger than the upper and lower layers,resulting damage and dialation of potential sliding zone.(2)Four dynamic non-compatible deformation models and six engineering geological effects were summarized.Two big types,incduing 8 small types were analyzed.(3)The geologic significance of landslide engineering is discussed in this paper.In practice,the effect of vibration and shearing-tensioning on the weak layer can cause the landslide to slide,Hard layer peak acceleration amplification effect,can enlarge the extent of surface damage,the impact of the lower hard layer vibration can lead to bed rock fragmentation,double weak layer effect can lead to hard layer crack slope,soft layer effect can lead to landslide lock Segment damage.The frequency-intensity coupling of the influencing factors shows that a strong earthquake may not produce large damage if the frequency conditions are not met;on the contrary,if a sensitive frequency is included,even a small earthquake may cause great damage;the exciting time of the influencing factors The effect shows that medium and long-lasting small earthquakes may cause greater damage.Based on the DGB landslide,the mathematical model of dynamic response of weak layer is established by the theory of elastic wave dynamics and ray theory,which can be used to reasonably describe the partially dynamic incompatible deformation modes revealed by shaking table tests.The laboratory dynamic test and PFC numerical model test reveals that local stress concentration?residual stress?differential unloading rebound caused by dynamic incompatible deformation is the main mechanism of dynamic damage and crack expansion.It is suggested that the rapid entry of groundwater into the weak layer may cause the water hammer effect.Based on the Joukowsky equation of hydrodynamics and the theory of water hammer,a model for calculating the water hammer force of the weak layer is established,The calculation of water hammer in the Dagaungbao landslide zone shows that the shear strength of the slip zone can be reduced to 0,and the maximum water hammer pressure is close to 20MPa.The process mechanism model is proposed which is weak interlayer dynamic response?damage,cataclasite,dilatation?excess pore water pressure?landslide initiation.