Analysis Of The Lateral Pressure And Slip Zone Of In-fill Particles Under Asymmetric Displacement Of The Support Structure

In recent years,urban space above and below ground has become more and more crowded,and in practical engineering,we often encounter soil pressure problems in limited width soil bodies,such as retaining walls on both sides of a foundation pit or the inner fill of retaining walls on both sides of a road under limited width,which is a typical soil pressure problem in limited soil bodies.And in the engineering of both sides of the retaining wall by the asymmetric load situation occurs from time to time,both sides of the retaining wall will be displaced and thus interact with each other to affect the soil pressure of the inner fill,the soil pressure at this time is different from the conventional single side of the retaining wall moving behind the wall soil pressure,its internal is how the stress transfer law is worth studying.In view of this,based on photoelastic tests and discrete element PFC^2D software,this paper visualises and analyses the in-fill particles when a single side retaining wall is displaced and when both sides of the retaining wall are displaced,based on photoelastic tests and discrete element PFC^2D software,to investigate the internal stress state,deformation damage characteristics and the horizontal pressure law on the retaining wall under consideration of the rotation mode of the rigid retaining wall around the base of the wall,mainly as follows:（1）The model test was carried out by means of self-developed photoelastic test equipment to analyse the distribution law of the force chain of the in-filled particles when the unilateral retaining wall rotates around the bottom of the wall,and found that the force chain at the bottom of the wall forms a"stress arch",which causes a"stress shield"phenomenon at the bottom of the wall,resulting in a reduction of the pressure of the particles on the wall at the bottom.The stress arch causes a"stress shield"at the bottom of the wall,resulting in a reduction in the pressure of the particles on the wall at the bottom.The lateral pressure<F_x>of the particles at the retaining wall was obtained from the particle contact angle obtained by image recognition and the particle contact force obtained by the coloured gradient<G²>method,which showed a non-linear distribution along the wall height.At the same time,the displacement field of the in-filled particles was obtained by arranging measurement points,and the distribution and development law of the slip zone of the finite width in-filled particles was analysed.It was found that the slip zone showed dynamic changes with the displacement of the retaining wall,and eventually evolved into a stable slip surface,which had different characteristics under different width-to-height ratios.（2）By means of photoelastic model tests,the force chain arching characteristics of the in-filled particles and the lateral pressure<F_x>of the particles were analysed for two engineering situations:the two sides of the retaining wall rotating in the same direction and the opposite direction.The test found that the force chain at the bottom of the left-hand retaining wall formed a"stress arch"when the two walls were rotating in the same direction,with<F_x>increasing and then decreasing in the depth direction;the force chain at the bottom of the right-hand retaining wall showed a"stress concentration"phenomenon,with<F_x>increasing and then decreasing in the depth direction due to the compression of the left-hand retaining wall.The non-linear increase in<F_x>at the base of the wall is due to the compression of the left-hand retaining wall.The displacement field of the in-fill particles was also analysed and it was found that the particle displacements on both sides of the retaining wall,whether in the same direction or in the opposite direction,interacted with each other at finite widths and that the slip zones of the in-fill particles in the retaining wall intersected,forming distinct slip and stability zones.（3）The lateral stresses at different depths of the inner fill with the displacement of the retaining wall when both sides of the wall rotate around the bottom of the wall are analysed by discrete element PFC^2D software simulation,as well as the distribution characteristics of the lateral stresses along the depth of the soil,and compared with Coulomb earth pressure.The results show that the lateral stresses of the in-fill particles are between the Coulomb active earth pressure and passive earth pressure when the two retaining walls are displaced in the same direction;the lateral stresses of the in-fill particles at the left and right retaining walls show a non-linear distribution along the depth when the two walls are displaced in the opposite direction.The analysis of the principal stresses in the in-fill also shows that the magnitude distribution and deflection of the principal stresses is similar to that of the force chain,and the principal stresses near the retaining wall will deflect to form a"stress arch",which is one of the main reasons for the non-linear distribution of the lateral stresses.