Behavior of braced excavation in sand under a seismic condition: experimental and numerical studies

The behavior of braced excavation in dry sand under a seismic condition is investigated in this paper.A series of shake table tests on a reduced scale model of a retaining wall with one level of bracing were conducted to study the effect of different design parameters such as excavation depth,acceleration amplitude and wall stiffness.Numerical analyses using FLAC 2D were also performed considering one level of bracing.The strut forces,lateral displacements and bending moments in the wall at the end of earthquake motion were compared with experimental results.The study showed that in a post-seismic condition,when other factors were constant,lateral displacement,bending moment,strut forces and maximum ground surface displacement increased with excavation depth and the amplitude of base acceleration.The study also showed that as wall stiffness decreased,the lateral displacement of the wall and ground surface displacement increased,but the bending moment of the wall and strut forces decreased.The net earth pressure behind the walls was influenced by excavation depth and the peak acceleration amplitude,but did not change significantly with wall stiffness.Strut force was the least affected parameter when compared with others under a seismic condition.

Behavior of braced wall embedded in saturated liquefiable sand under seismic loading

It is well known that the generation of excess pore water pressure and/or liquefaction in foundation soils during an earthquake often cause structural failures.This paper describes the behavior of a small-scale braced wall embedded in saturated liquefiable sand under dynamic condition.Shake table tests are performed in the laboratory on embedded retaining walls with single bracing.The tests are conducted for different excavation depths and base motions.The influences of the peak magnitude of the ground motions and the excavation depth on the axial forces in the bracing,the lateral displacement and the bending moments in the braced walls are studied.The shake table tests are simulated numerically using FLAC 2D and the results are compared with the corresponding experimental results.The pore water pressures developed in the soil are found to influence the behavior of the braced wall structures during a dynamic event.It is found that the excess pore water pressure development in the soil below the excavation is higher compared to the soil beside the walls.Thus,the soil below the excavation level is more susceptible to the liquefaction compared to the soil beside the walls.

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.