Bearing Behavior Of Strip Footing Reinforced With Horizontal-Vertical Geogrids

Geosynthetics have been successfully applied in foundations for three decades.The beneficial effects of using planar reinforcement to increase the bearing capacity of sand have been clearly demonstrated by several investigators.Besides planar reinforcements,considerable attention has been given to the development of advanced three-dimensional reinforcement.Recently,a three-dimensional inclusion was proposed.These three-dimensional inclusions were composed of several vertical elements and an ordinary horizontal plexiglas's strips.Some researchers have shown that these three-dimensional inclusions were superior to the traditional strip reinforcement.However,thefailuremodeandmechanismofthese three-dimensional inclusions is not well understood.There is still a lack of analytical models for estimating the ultimate bearing capacity of such three-dimensional inclusion reinforced footing.Meanwhile,it is really hard to use the plexiglas's three-dimensional inclusion into the engineering.Geogrids are the most popular type of geosynthetics used in the soil foundation for mechanical stabilisation and reinforcement purposes.In the paper,a new kind of horizontal-vertical geogrid was proposed.The bearing capacity and mechanism of a sand bed reinforced with traditional and horizontal-vertical(H-V)geogrid were investigated using laboratory model tests.Comparisons between sand beds reinforced with H-V geogrid and traditional geogrid reveal that the H-V reinforcement system behaves more uniformly,carries greater surcharge,and settles less than the equivalent traditional geogrid.Then particle flow code(PFC),based on the discrete element method(DEM)was used to investigate the soil properties from the micro point of view.The interface between particles and geogrid,and the reinforcement mechanism of the H-V geogrid reinforced foundations are studied through stress distribution graphs,displacement vector graphs and contact force graphs.The simulation results demonstrate that the vertical elements of the H-V reinforcement keep the particles from being displaced under the applied load.Furthermore,geogrid is in the form of grid structure with aperture geometry allows for soil particles penetrating from one side of the geogrid to the other.Meanwhile,the interlocking can be developed by the interaction of soil and geogrid.Consequently,lateral deformation or potential tensile strain of the reinforced soil is restrained.Finally,based on the failure mode and the mechanism of the sand beds reinforced with horizontal-vertical geogrid,the formula for calculate the ultimate bearing capacity of traditional and horizontal-vertical geogrid reinforced soil is investigated.An analytical solution is presented using the traditional N_?factors,unit weight of soil,footing width,geometry of the geogrid,soil shear strength angle.The accuracy of the analytical bearing capacity models for geogrid reinforced foundation was investigated using experimental results and analytical solutions by.The mean bias of the theoretical model was found to be about 10%.