| The dynamic stability of rock slopes under strong earthquakes is the subject of great concern in the geological field.The soft and hard interbedded rock slopes are widely distributed in meizoseismal area of western China,and the discontinuities with different joint wall material(DDJM)between soft and hard rocks is the weak link in this kind slope.The mechanical properties of DDJM deteriorate significantly under seismic loads and the slope body is prone to slide along DDJM,leading to large-scale geological disasters.Therefore,it is of great theoretical significance and engineering application value for the slope engineering safety and disaster prevention and reduction to study the dynamic stability of soft and hard interbedded rock slopes considering the vibration deterioration of DDJM in meizoseismal area.In this study,a typical soft and hard interbedded rock slope in Ludian County of Yunnan Province was taken as the research object.A mathematical model of vibration deterioration of DDJM under seismic load was established by field investigation and laboratory experiment and the application of the mathematical model was implemented in numerical analysis.The dynamic stability law and factors of rock slope considering the vibration deterioration of DDJM were studied.The dynamic stability of soft and hard interbedded rock slope and the support effect in the Shaba parking area of Duxiang Highway were evaluated.The main research achievements of this paper are as follows:(1)A mathematical model of vibration deterioration of DDJM under earthquake was established.Taking the typical interface between mudstone and siltstone in Ludian County of Yunnan Province as the prototype of DDJM,the samples of DDJM with natural surface topographies were manufactured based on the surface topography data collected in the field.Considering different cyclic loading and normal stress conditions,the cyclic shear tests of DDJM were carried out to analyze the strength deterioration of the samples under cyclic loads.The results show that during the seismic duration,the vibration deterioration of DDJM is affected by the amplitude of cyclic shear displacement,the number of cyclic shear and relative velocity.The mathematical model of vibration deterioration of DDJM was established based on the result of the test.(2)The application of vibration deterioration model of DDJM in numerical analysis was implemented.By using the Fish language programme in 3DEC and combining with the discontinuous deformation analysis and the dynamic contact force method,the dynamic deterioration process of DDJM under earthquake was implemented.The vibration deterioration model was applied to the numerical analysis of the slope.The results show that the dynamic stability of rock slope considering the vibration deterioration of DDJM are more consistent with the general law of nature.The application of the vibration deterioration model lays the foundation for the scientific evaluation of the dynamic stability of soft and hard interbedded rock slopes.(3)The dynamic stability law and factors of the rock slope considering the vibration deterioration of DDJM were studied.The dynamic stability of soft and hard interbedded rock slope considering the vibration deterioration of DDJM was analyzed by carrying out numerical experiments.Five parameters including soft rock strength,thickness ratio,seismic frequency,amplitude and duration were selected to study the influence of internal and external factors on the slope dynamic stability.The results show that:(1)bedding planes between soft and hard rocks play a main control role in the deformation and failure of the slope.Soft rocks have a significant amplification effect on the propagation of seismic wave.The surface displacement,PGA and Fourier spectrum values are greater than those without considering the vibration deterioration effect.(2)surface displacement and vertical PGA decrease with the increase of soft rock strength,and increase with the increase of thickness ratio.The strength of soft rock and the thickness ratio play a important role in the position of obviously amplified frequency bands.When they increase,the number of amplified bands remains same and the frequencies decreases.(3)The maximum permanent displacements of slope decrease with the increase of frequency,increases with the increase of amplitude and duration.Among the three ground motion parameters,the amplitude has the greatest influence on the vibration deterioration effect of DDJM,followed by duration and frequency.(4)The dynamic stability of soft and hard interbedded rock slope and the support effect in the Shaba parking area of Duxiang Highway were evaluated.Taking the soft and hard interbedded rock slope in the Shaba parking area of Duxiang Highway as an engineering application case,the dynamic stability of the slope and the support effects considering the vibration deterioration of DDJM were analyzed under the seismic load with intensities of Ⅵ,Ⅶ,and Ⅷ degrees.The results show that:(1)the permanent displacement of the soft stratum on the slope surface is greater than that of the hard stratum and the deformation degree of the slope considering the vibration deterioration effect is bigger than that without considering the vibration deterioration effect.(2)the maximum permanent displacement and dynamic stability coefficient of the slope increase and decrease respectively with the increase of seismic intensity,indicating that the dynamic stability of soft and hard interbedded rock slope is more susceptible to the vibration deterioration of DDJM under strong earthquake.(3)The existing supporting measures of the Shaba slope have a good supporting effect under the seismic load with intensity of Ⅵ degree,but will be destroyed when the seismic intensities are Ⅶdegree and Ⅷ degree.Optimal suggestions is needed to prevent the failure of the Shaba slope under future strong earthquake. |
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