Behavior of reinforced foundations subjected to uniform and repeated loading

By Kianoosh Hatami, PhD, PEng

Current foundation response solutions using analytical approaches generally involve limiting assumptions on the problem geometry and material behavior. The experimental techniques on the other hand are bounded by such limitations as the test model dimensions and scaling effects. The numerical modeling approaches that are calibrated against analytical and experimental results provide a valuable tool to investigate the performance of footings of various sizes and configurations subjected to a variety of loading conditions. The focus of the current study is the load-settlement response of ballast foundations subjected to track loading, which is essential for design and maintenance of ballast-track systems. The measured settlement results of reduced-scale foundation models representing ballast foundation with different subgrade conditions subjected to monotonic and cyclic footing loads are compared with the corresponding predicted results using numerical simulation. The effect of geosynthetic reinforcement to improve the bearing capacity and serviceability of foundations subjected to static and cyclic loading is investigated.

Figure 1: Schematic Layout of the test apparatus:
Figure 2: Aggregates used in the reduced-scale model foundations:
Figure 3: Deviatoric stress response of foundation aggregate samples in triaxial tests:
Figure 4 & 5: Schematic of test cases with different tank base boundary conditions: a) rigid; b) stiff; c)soft and d) rigid covered with a geotextile layer (dimensions in mm). FLAC numerical grids of test cases with different foundation depth (dimensions in mm):
Figure 6: Measured and predicted load-settlement response of model foundation with round aggregates with different boundary conditions at the base: a) - d), 250 mm depth; e) and f), 100 mm depth. a) rigid base; b) and e) medium stiff base (E = 32 MPa); c) and f) very compressible base (E=1 MPa); d) rigid base + geotextile -
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