Anisotropic Strength Of Silty And Active Earth Pressure Of Retaining Wall In The Flooded Area Of The Yellow River

A large number of deep foundation ditch and general retaining wall works have been produced by development of infrastructure construction in the Yellow River Basin.Due to anisotropy of soil strength,it is necessary to calculate the magnitude and distribution of soil pressure accurately for ensure safety of foundation ditch and retaining wall works.The relationship between the shear strength parameters of silt and the angle of shear direction relative to the sedimentary direction were studied by consolidated quick shear test of undisturbed silt samples using a direct shear instrument in order to better understand anisotropy of silt strength in the northern plain new area of Zhengzhou.The influence of shear strength parameters on active soil pressure of retaining wall was analyzed by considering anisotropy of silt strength and modifying horizontal slices analysis method.The main conclusions as follows:(1)Although silt strength was obvious anisotropy and the degree of anisotropy is different in different positions,but the general pattern of change was similar in Henan section Yellow River Basin.The relationship between angle of internal friction and angle of shear direction relative to deposition direction was approximately parabola,the aggrandizement of cohesive forces non-linearly as increase of angle.(2)When the silt material sedimentation surface is parallel to the horizontal direction,regardless of the anisotropy of the internal friction angle of the silt,the resultant force of active earth pressure is lower and the point of action is higher,which will overestimate the anti-overturning stability of the retaining wall;Regardless of the anisotropy of silt cohesion,the resultant force of earth pressure is higher,and the position of application point is increased,which will eventually underestimate its anti-overturning stability;The dip angle of fracture surface and force of active earth pressure and height of action point were all reduced by considering anisotropy of strength parameters compared with isotropy,however,the stability against overturning was improved.(3)When angle between sediment surface and horizontal direction increases in the range of 0~o～45~o,if only considering anisotropic angle of internal friction of silt,the resultant force of the earth pressure increases first and then decreases,the position of the action point is improved,and the anti-overturning stability coefficient of the retaining wall decreases first and then increases slightly;The resultant force of earth pressure and the height of the action point increases,but the stability coefficient of anti-overturning decreases with increase of angle between surface and horizontal direction when only considering anisotropy of cohesive force;At the same time,considering the anisotropy of the two,the resultant force of earth pressure increased first and then decreased,and the height of action point increased.When the angle is large,the anti-overturning stability will be overestimated according to isotropic strength calculation.