Experimental Study On Seismic Bearing Capacity Adjustment Factor Of Q₃ Loess Foundation

With the rapid development of China's economy,the scale of engineering construction in the loess area is expanding.The loess generally has characteristics such as collapsibility,and thefactors affecting the bearing capacity of the loess are more complicated.Therefore,it is of great significance to carry out in-depth study on the bearing capacity of the foundation in the loess area.In addition,China is a country with frequent earthquakes.In recent years,several major earthquakes in China?such as Wenchuan Earthquake,Yushu Earthquake,Ya'an Earthquake,etc.?have caused serious disasters,which have caused people's attention to the dynamic bearing capacity of buildings under earthquake loads.In view of this,this paper takes Q₃ undisturbed loess in Shaanxi as the research object,and carries out dynamic and static triaxial tests on Q₃ undisturbed loess with different grain size composition?Jingbian sand loess,Luochuan powder loess,Fuyang sticky loess?and different water content.The dynamic and static strength characteristics of Q₃ undisturbed loess and the adjustment coefficient of seismic capacity of foundation are analyzed and the following main conclusions are drawn:?1?The loess stress-strain curve is characterized by strain softening and strain hardening.Under the same confining pressure,the shear strength of loess gradually decreases with the increase of water content.Under the same water content,the shear strength of loess gradually increases with the increase of confining pressure.Compared with the water content,the confining pressure has a greater influence on the shear strength.With the increase of water content,the cohesive force of loess gradually decreases,and the internal friction angle also decreases.Compared with the internal friction angle,the water content has a greater influence on the cohesive force of the loess and less on the internal friction angle.?2?Under the same water content and confining pressure,the dynamic shear stress of loess gradually decreases with the increase of the failure vibration.When the water content is the same,the dynamic shear stress corresponding to the same vibration times increases as the confining pressure increases.When the confining pressure is the same,the dynamic shear stress corresponding to the same vibration times decreases as the water content increases.With the increase of water content,the dynamic cohesion of Jingbian sand loess gradually decreases,and the internal friction angle does not change much.Compared with the internal friction angle,the water content has a great influence on the dynamic cohesion of Jingbian sand loess.With the increase of water content,the dynamic cohesion of Luochuan powder loess changed little,and the internal friction angle decreased gradually.Compared with dynamic cohesion,the water content has a great influence on the internal friction angle of Luochuan powdered loess.With the increase of water content,the cohesive force of the viscous loess gradually decreases,and the internal friction angle also decreases.Compared with the internal friction angle,the water content has a great influence on the dynamic cohesion of the viscous yellow soil.The dynamic shear stress of Jingbian sand loess is greater than that of Luochuan powder loess and Xiangyang sticky loess.?3?With the increase of normal stress,the adjustment coefficient of seismic capacity of loess gradually increases.With the increase of the failure vibration times,the adjustment coefficient of seismic capacity of loess gradually decreases.With the increase of water content,the seismic load capacity adjustment coefficient of sand loess and the seismic load capacity coefficient of clay loess did not change much,and the adjustment coefficient of seismic capacity of silt loess gradually decreased.From sand loess to silt to sticky loess,the seismic bearing capacity adjustment coefficient is gradually increasing.From sand loess to silt to sticky loess,the average value of the seismic capacity adjustment coefficient gradually increases.