Study On Tension-shear Failure Of Soil Slope Under Earthquake Events

Earthquake induced landslides are among the most severe secondary disasters in the earthquake events.Road traffic jams which caused by the earthquake induced landslides will seriously delay and hinder the life-saving and earthquake relief work in the early stage of the earthquake,and it will result irreparable losses.Therefore,it is of great significance to study the earthquake induced slope failures.Essentially,the failure of soil slope under earthquake events is a near field nonlinear problem.The vibration of near filed,topography,geomorphology and geological conditions also have impact on this engineering problem,such as material nonlinearity effect,spatially non-uniform effect.Currently,the failure characteristics and failure form of soil slope under earthquake events is confused,and the slope configuration during the calculation of seismically induced slope failures is still not clear,so,it is unfavorable to the evaluation of slope safety and the analysis of anti-seismic.Consequently,the mechanism of slope failures and seismic responses are investigated in this paper.The slope configuration is suggested during the calculation of earthquake induced slope failures.The forms and characteristics of seismically induced slope tension-shear failures are elaborated in this paper.The calculation process of nonlinear seismically induced slope failures is given together with the tension-shear failure form of slope based on the nonlinear foundation.The main efforts are summarized as follows.1.Within the theoretical framework of the nonlinear near-field wave motion theory,the mechanical constitutive model of soil mass and the input method of seismic waves are developed.(1)Tension-shear strength criterion which established in the ?-? stress space is converted into the numerical form.The edges and singularities of the tension-shear strength criterion are rounded by the proposed method.The integral expression of tension-shear strength yield surface is established by the implicit back Euler method.Several numerical examples are used to verify the deviatoric plane and meridian plane of tension-shear strength criterion.(2)Together with viscous-spring artificial boundary,the oblique plane wave input methods of 2-D half space homogeneous field and layered field are established.The complex implement processes of equivalent nodal forces on the boundary during the oblique incident waves are simplified.So,the input earthquake wave in thehomogeneous field and layered field are automatically added.2.Based on the time-domain wave method coupling finite element method,the site effects of slope topography is analyzed,the slope configuration during the calculation of earthquake induced slope failures are discussed,the tension-shear failure form of seismically induced slope failures are determined,besides,the calculation process of nonlinear seismically induced slope failures are established,the tension-shear failures and seismic responses of soil slope under earthquake events based on nonlinear foundation are given.The detailed efforts are illustrated as follows:(1)The site effects of slope topography are investigated.The factors,included wave patterns,stratigraphic distribution,and the slope sizes,are discussed in the site effects.The influences of slope sizes to site effects with oblique incidence of seismic waves are mainly analyzed.The results of this section are the basis of the analyses of seismically induced slope failures in the following section.(2)The slope configuration during seismic calculation is determined.Based on the site effects and the response spectra,the single-faced slope configuration(usually adopted in the static analyses)and the proposed double-faced slope configuration are quantitatively analyzed.Based on the results,single-faced slope configuration lead to the amplification effects decrease owing to the lack of slope side,and the period of seismic response is missing.(3)The characteristics of earthquake induced slope failures are analyzed.The failure form near the slope crest is tension-shear failure during the earthquake events.It is important to describe the tension-shear region of material strength criterion in the analysis of earthquake induced slope failures.Besides,the tension-shear failure characteristics of slope under oblique incident seismic waves are also discussed.(4)The calculation process of seismically induced slope failures based on nonlinear foundation is established.The slope body is regarded as the “structure”,so the foundation and slope can be treated respectively.The tension-shear failure characteristics of seismically induced slope with nonlinear foundation are investigated.