Seismic behavior of cantilever wall embedded in dry and saturated sand

The embedded cantilever retaining walls are often required for excavation to construct the undergroundfacilities. Significant numbers of numerical and experimental studies have been performed to understand the behavior ofembedded cantilever retaining walls under static condition. However, very limited studies have been conducted on thebehavior of embedded retaining walls under seismic condition. In this paper, the behavior of a small scale modelembedded cantilever retaining wall in dry and saturated sand under seismic loading condition is investigated by shaketable tests in the laboratory and numerically using software FLAC2D. The embedded cantilever walls are subjected tosinusoidal dynamic motions. The behaviors of the cantilever walls in terms of lateral displacement and bending momentare studied with the variation of the two important design parameters, peak amplitude of the base motions and excavationdepth. The variation of the pore water pressures within the sand is also observed in the cases of saturated sand. Themaximum lateral displacement of a cantilever wall due to seismic loading is below 1% of the total height of the wall in drysand, but in case of saturated sand, it can go up to 12.75% of the total height of the wall.

Seismic earth pressures on flexible cantilever retaining walls with deformable inclusions

In this study, the results of 1-g shaking table tests performed on small-scale flexible cantilever wallmodels retaining composite backfill made of a deformable geofoam inclusion and granular cohesionlessmaterial were presented. Two different polystyrene materials were utilized as deformable inclusions.Lateral dynamic earth pressures and wall displacements at different elevations of the retaining wallmodel were monitored during the tests. The earth pressures and displacements of the retaining wallswith deformable inclusions were compared with those of the models without geofoam inclusions.Comparisons indicated that geofoam panels of low stiffness installed against the retaining wall modelaffect displacement and dynamic lateral pressure profile along the wall height. Depending on the inclusioncharacteristics and the wall flexibility, up to 50% reduction in dynamic earth pressures wasobserved. The efficiency of load and displacement reduction decreased as the flexibility ratio of the wallmodel increased. On the other hand, dynamic load reduction efficiency of the deformable inclusionincreased as the amplitude and frequency ratio of the seismic excitation increased. Relative flexibility ofthe deformable layer （the thickness and the elastic stiffness of the polystyrene material） played animportant role in the amount of load reduction. Dynamic earth pressure coefficients were compared withthose calculated with an analytical approach. Pressure coefficients calculated with this method werefound to be in good agreement with the results of the tests performed on the wall model having lowflexibility ratio. It was observed that deformable inclusions reduce residual wall stresses observed at theend of seismic excitation thus contributing to the post-earthquake stability of the retaining wall. Thegraphs presented within this paper regarding the dynamic earth pressure coefficients versus the wallflexibility and inclusion characteristics may serve for the seismic design of full-scale retaining walls withdeformable polystyrene inclusions. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Shaking table tests on a cantilever retaining wall with reinforced and unreinforced backfill

Physical modelling of cantilever retaining walls with and without backfill reinforcement was conducted on a 1g shaking table to evaluate the mitigation effect of reinforcement on system dynamics(g denotes the acceleration of gravity).The model wall has a height of 1.5 m with a scale ratio of 1/4 and retains dry sand throughout.The input motions are amplified to three levels of input peak base acceleration,0.11g,0.24g,and 0.39g,corresponding to minor,moderate,and major earthquakes,respectively.Investigation of the seismic response of the retaining walls focuses on acceleration and lateral displacement of the wall and backfill,dynamic earth pressures,and tensile load in the reinforcements(modeled by phosphor-bronze strips welded into a mesh).The inclusion of reinforcement has been observed to improve the integrity of the wall-soil system,mitigate vibration-related damage,and reduce the fundamental frequency of a reinforced system.Propagation of acceleration from the base to the upper portion is accompanied by time delay and nonlinear amplification.A reinforced system with a lower acceleration amplification factor than the unreinforced one indicates that reinforcement can reduce the amplification effect of input motion.Under minor and moderate earthquake loadings,reinforcement allows the inertia force and seismic earth pressure to be asynchronous and decreases the seismic earth pressure when inertia forces peak.During major earthquake loading,the wall is displaced horizontally less than the backfill,with soil pushing the wall substantially;the effect of backfill reinforcement has not been fully mobilized.The dynamic earth pressure is large at the top and diminishes toward the bottom.

A hierarchical system to predict behavior of soil and cantilever sheet wall by data-driven models

The study proposes a framework combining machine learning(ML)models into a logical hierarchical system which evaluates the stability of the sheet wall before other predictions.The study uses the hardening soil(HS)model to develop a 200-sample finite element analysis(FEA)database,to develop the ML models.Consequently,a system containing three trained ML models is proposed to first predict the stability status(random forest classification,RFC)followed by 1)the cantilever top horizontal displacement of sheet wall(artificial neural network regression models,RANN1)and 2)vertical settlement of soil(RANN2).The uncertainty of this data-driven system is partially investigated by developing 1000 RFC models,based on the application of random sampling technique in the data splitting process.Investigation on the distribution of the evaluation metrics reveals negative skewed data toward the 1.0000 value.This implies a high performance of RFC on the database with medians of accuracy,precision,and recall,on test set are 1.0000,1.0000,and 0.92857,respectively.The regression ANN models have coefficient of determinations on test set,as high as 0.9521 for RANN1,and 0.9988 for RANN2,respectively.The parametric study for these regressions is also provided to evaluate the relative insight influence of inputs to output.