Toshinori Sakai

Evaluation of Shape Effects for Rectangular Anchors in Dense Sand: Model Tests and 3D Finite-Element Analysis

AbstractIn this study, three-dimensional finite element models, incorporating an elastoplastic material model coupled with isotropic simple softening law, nonassociated flow rule, and shear-band effect, are validated for the evaluation of the shape effect of the square and rectangular vertically uploaded anchor foundations embedded in dense Toyoura sand with embedment ratio of 2 and width of 50  mm. The proposed numerical model has closely predicted experimental uplift load-displacement relationships. The shape effects on the results are also discussed in relation to the progressive failure around the foundations and the shape of the failure boundaries on the ground surface.

Evaluation of sand–geosynthetic interface behavior for earth reinforcement

Abstract For the effective use of a geosynthetic material in earth reinforcement, along with mechanical properties the interaction behavior of geosynthetic with backfill material has significant importance regarding safety analysis. This paper investigated the interface behavior of a new type of geosynthetic, made of Basalt fiber, with sand through a series of direct shear tests. In the tests, the applied normal stresses were varied from 40 to 160 kPa. The test results reveal that the shear strength of all sand-geosynthetic interfaces increased with the increasing normal stresses. The geogrid having small apertures and thin ribs shows the maximum interface shear resistance whereas the sand-geotextile interface shows significantly lower shear resistance comparing to that of sand-sand interface. Strain hardening–softening behavior is clearly observed for the sand-geogrid interfaces, but the geotextile interface shows no softening behavior after the peak. It is also observed that the presence of sand in the apertures of geogrids dominates the dilatancy behavior of the sand-geogrid interfaces. The average interface efficiency of the sand-geogrid interfaces tested in this study is found ranging from 0·61 to 0·87.

Model Tests and 3D Finite Element Simulations of Uplift Resistance of Shallow Rectangular Anchor Foundations

AbstractAnchor foundations of various embedment ratios, shapes, and sizes are frequently used in civil engineering structures to provide uplift resistance. Therefore, to achieve economic and safe design of such foundations, engineers should understand the failure mechanism associated with them. In the present study, a three-dimensional (3D) finite element model incorporating an elastoplastic material model coupled with the isotropic strain-softening law, the nonassociated flow rule, and the shear-band effect, is used to investigate the failure mechanisms of vertically uploaded shallow rectangular anchor foundations buried in dense Toyoura sand. Satisfactory agreement was found between the experimental and numerical uplift resistance-displacement factor relationships. In particular, the peak uplift resistance, response stiffness, and passive plastic zone development are found to be functions of the embedment ratio, shape, and size. However, previous design approaches cannot capture the size effect on the p...

Experimental validation of a numerical model for the interaction of dip-slip normal fault ruptures, sand deposits, and raft foundations

Abstract An incomplete understanding of the failure mechanisms in fault rupture propagation has led to inconsistent and insufficient regulations in building codes. In the present study, a sophisticated numerical model is calibrated and validated in order to clarify a complex problem involving the interaction of fault ruptures, medium dense Fontainebleau sand deposits, and existing structures across the fault plane. Calibration is performed using direct shear test data. Repeatable centrifuge models of dip-slip normal faults with a dip angle of 60° in the free field condition and light and heavy rigid strong raft foundations are used for the validation. The present numerical model satisfactorily simulates the centrifuge models. Rigid rafts divert the shear bands so as to bypass the rafts, rather than rip them apart. The rafts tilt on the foundation soil during fault rupture. The raft-tilting increases as the raft bearing pressure on the soil decreases.