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Theses Doctoral

Centrifuge Modeling and Numerical Analysis of Geosynthetic-Reinforced Soil Retaining Walls Having Different Facings

Xu, Lei

Centrifuge modeling technique is widely used in geotechnical research. Due to the complexity of geosynthetic-reinforced soil retaining walls (GRS-RWs), the centrifuge models of such walls are typically constructed in one stage, where the model is prepared to full height under 1-g and then spun in a centrifuge to the desired g-level or till failure. However, for a retaining wall built in the field, the placement of new soil layer and compaction induces deformations on the previously constructed soil layers, and the wall facing is aligned according to the design at each construction stage. The different construction sequences will lead to differences in the wall performance, including the stress mobilized in the geosynthetic layers.

In this study, a multi-stage constructed centrifuge modeling technique was proposed to simulate the construction sequence in the field. The wall facing deformation, tensile force in the geosynthetic layers, and lateral earth pressure behind the wall facing were measured and compared with the traditional one-staged centrifuge model. The results were verified with actual field measurements. The results obtained from multi-staged construction compared favorably to the field measurements. In addition to the construction sequence, the backfill close to the wall facing is usually not as well compacted in the field. The effects of such loose front backfill were also studied by a series of centrifuge models of reinforced soil retaining walls.

In addition to the centrifuge modeling of the reinforced soil retaining walls, two series of finite element models were conducted to further study the wall performance. The first series of numerical models included a unified sand model, which was implemented into Abaqus to simulate the backfill. The sand model was firstly calibrated based on the triaxial test results; then, it was used to simulate the wall performance under gravity and dynamic loading. An additional series of FE models were constructed in OptumG2, a 2D finite element geotechnical software to numerically study the influence of loose front and construction sequence of the concrete block reinforced soil retaining walls.

Based on the results of centrifuge modeling, simulation of the construction sequence is necessary to obtain a satisfactory assessment of GRS-RWs performance. In this study, the models prepared with multi-staged construction techniques showed better agreement with the field measurements than the models prepared with one-staged construction. In addition, the models with reinforcement simulating the stiffness of the prototype geogrid showed better agreement with field measurements than the models with reinforcement simulating the strength of the prototype geogrid. Besides, a loose front probably existed in the concrete block walls during the field construction based on the comparison of the test results and field measurements.

Conclusions from the centrifuge modeling studies were verified by FEM analysis. The dynamic simulation results showed that the studied gabion walls are stable when subjected to a horizontal acceleration up to 0.4 at the bottom of the wall.

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More About This Work

Academic Units
Civil Engineering and Engineering Mechanics
Thesis Advisors
Ling, Hoe I.
Yin, Huiming
Degree
Ph.D., Columbia University
Published Here
May 5, 2020