Investigating the effect of geotextile as reinforcement on the bearing capacity of granular soil

Considering that soils in parts of the Philippines, particularly Manila, is characterized as weak and soft, bearing capacity failure becomes a major concern. While many studies dealt with reinforced soil foundation, there are some crucial research gaps in observing ground deformation and explaining the role of geotextile in bearing capacity improvement. This paper addressed these questions through using a concentric static loading test for shallow foundations on granular soils with single layer of geotextile reinforcement placed at different depths relative to the footing base wherein [1] ultimate bearing capacity (qult) improvement was quantified and verified using Terzaghis and Vesics equations using frictional angle () from laboratory direct shear tests, [2] optimal depth of geotextile embedment (u) was identified using bearing capacity ratio (BCR) which is the ratio between the bearing capacity of the reinforced sample to that of the unreinforced sample, and [3] images of internal deformation of the model ground were obtained using a unique visualization technique. Results indicate that qult-values were improved for reinforced samples whose u-value lies within the maximum depth of failure zone at 1.00B where B is the footing width. The increase in bearing capacity was validated using direct shear test which highlights that increased by 2.50o between unreinforced and reinforced samples (from 40.70o to 43.20o), leading to good agreement with theoretical qult using Vesics formula. This qult improvement, however, varies with u; the optimal depth is tallied at 0.25B at BCR of 1.52. Meanwhile, the ground deformations were effectively observed wherein it was concluded that the unreinforced sample fails under local shear whereas the reinforced sample with maximum BCR undergoes punching shear