Dynamic Behavior of Gravity Retaining Walls with Coral Sand Backfill Under Earthquakes:Shaking Table Tests

The retaining walls in coral sand sites are inevitably threatened by earthquakes. A series of shaking table tests were carried out to study the seismic stability of gravity retaining walls with coral sand backfill. Parallel tests with quartz sand were performed to compare and discuss the special dynamic properties of coral sand sites. The results show that the acceleration difference between the retaining wall and the coral sand backfill is 76%-92% that of the quartz sand,which corresponds to the larger liquefaction resistance of coral sand compared with the quartz sand. However, the horizontal displacement of the retaining walls with coral sand backfill reaches 79% of its own width under 0.4g vibration intensity. The risk of instability and damage of the retaining walls with coral sand backfill under strong earthquakes needs attention.

Upper bound seismic rotational stability analysis of gravity retaining walls considering embedment depth

Stability analysis of gravity retaining wall was currently based on the assumption that the wall had no embedment depth. The effect of earth berm was usually neglected. The present work highlighted the importance of embedment depth when assessing the seismic stability of gravity retaining walls with the pattern of pure rotation. In the framework of upper bound theorem of limit analysis, pseudo-static method was applied into two groups of parallel rigid soil slices methods in order to account for the effect of embedment depth on evaluating the critical acceleration of wall-soil system. The present analytical solution is identical to the results obtained from using limit equilibrium method, and the two methods are based on different theory backgrounds. Parameter analysis indicates that the critical acceleration increases slowly when the ratio of the embedment depth to the total height of the wall is from 0 to 0.15 and increases drastically when the ratio exceeds 0.15.

Shaking table test of subgrade slope reinforced by gravity retaining wall with geogrids

Gravity retaining wall with geogrids has showed excellent seismic performance from Wenchuan great earthquake.However,seismic damage mechanism of this kind of wall is not sufficiently clear.In view of this,a large shaking table test of the gravity retaining wall with geogrids to reinforce the subgrade slope was carried out,and based on the HilbertHuang transform and the marginal spectrum theory,the energy identification method of the slope dynamic failure mode was studied.The results show that the geogrids can effectively reduce displacement and rotation of the retaining wall,and it can effectively absorb the energy of the ground movement when combined with the surrounding soil.In addition,it also reveals the failure development of the gravity retaining wall with geogrids to reinforce the subgrade slope.The damage started in the deep zone near the geogrids,and then gradually extended to the surface of the subgrade slope and other zones,finally formed a continuous failure surface along the geogrids.The analysis results of the failure mode identified by the Hilbert marginal spectrum are in good consistency with the experimental results,which prove that the Hilbert marginal spectrum can be applied to obtain the seismic damage mechanism of slope.

Time history of seismic earth pressure response from gravity retaining wall based on energy dissipation

The seismic design of gravity retaining walls is based mostly on the pseudo static method.The seismic earth pressure is assumed to be a constant without considering the wave traveling effect when the seismic wave propagates through the slope.However,under continuous ground motion,the actual earth pressure on the retaining wall varies with time.The present seismic earth pressure calculation method yields results that differ significantly from the actual scenario.Considering this,a slip surface curve was assumed in this study.It is more suitable for engineering practice.In addition,a theoretical calculation model based on energy dissipation was established.The time history of seismic earth pressure response under continuous ground motion was calculated using the equilibrium equation between the external power and the internal energy dissipation power of the sliding soil wedge.It can more effectively reflect the stress scenario of a retaining wall under seismic conditions.To verify the applicability of the proposed approach,a large-scale shaking table test was conducted,and the time history of the seismic earth pressure response obtained from the experiment was compared with the calculation results.The results show that the proposed approach is applicable to the calculation of the time history of seismic earth pressure response of gravity retaining walls.This lays the foundation for the seismic design of retaining structures by using dynamic time history.