Influence of positions of the geotextile on the load-settlement behaviour of circular footing resting on single stone column by 2D Plaxis software

Purpose: This study aims to study the load – settlement behaviour of circular footing rested on encased single stone column. Design/methodology/approach: The effect of vertical, horizontal and combined verticalhorizontal encasement of stone column on the load carrying capacity were examined numerically. The effect of stone column dimension (80 mm and 100 mm), length (400 mm and 500 mm), and spacing of reinforcement on the load carrying capacity and reinforcement ratio were assessed. Findings: The obtained results revealed that the load carrying capacity of geotextile encased stone columns are more than ordinary stone columns. For vertically encased stone columns as the diameter increases, the advantage of encasement decreases. Whereas, for horizontally encased stone column and combined vertical- horizontal encased stone column, the performance of encasement intensifies as the diameter of stone column increases. The improvement in the load carrying capacity of clay bed reinforced with combined verticalhorizontal encased stone columns are higher than vertical encased stone columns or horizontal encased stone column. The maximum performance of encasement was observed for VHESC1 of D = 80 mm. Research limitations/implications: For this study, the diameter of footing and stone column was kept same. The interface strength factor between stone column and clay bed was not considered. Practical implications: The encased stone column could be use improve the laod bearing capacity of weak soils. Originality/value: Many studies are available in literature regarding use of geosynthetic as vertical encasement and horizontal encasement of stone column. The study on combined effect of vertical and horizontal encasement of stone column on load carrying capacity of weak soil is very minimal. Keeping this in view, the present work was carried out.

Bearing Capacity Factor of Circular Footings on Two-layered Clay Soils

Geotechnical engineers often deal with layered foundation soils. In this case, the soil bearing capacity assessment using the conventional bearing capacity theory based on the upper layer properties introduces significant inaccuracies if the top layer thickness is comparable to the rigid footing width placed on the soil surface. Under undrained conditions the cohesion increases almost linearly with depth. A few theoretical studies have been proposed in the literature in order to incorporate the cohesion variation with depth in the computation of the ultimate bearing capacity of the strip and circular footings. Rigorous solutions to the problem of circular footings resting on layered clays with linear increase of cohesion do not appear to exist. In this paper, numerical computations using FLAC code are carried out to assess the vertical bearing capacity beneath rough rigid circular footing resting on two-layered clays of both homogeneous and linearly increasing shear strength profiles. The bearing capacity calculation results which depend on the top layer thickness, the two-layered clays strength ratio and the cohesion increase rates with depth are presented in both tables and graphs, and compared with previously published results available in the literature. The critical depth for circular footing is found significantly less than for strip footing. Doi: 10.28991/cej-2021-03091689 Full Text: PDF

Numerical Study of the Behaviour of a Circular Footing on a Layered Granular Soil Under Vertical and Inclined Loading

This paper aims to study the behaviour of a circular footing resting on two granular layers, i.e., a dense sand layer resting on loose sand strata, subjected to a vertical and an inclined loading (α=0°, 10°, 20°, 30°) using the finite element (FE) software PLAXIS-3D. The Mohr-Coulomb criterion is employed for the analysis of the model, in which two parameters are considered to vary significantly; (1) thickness of the top layer (dense layer) and (2) friction angle (ф) of both the layers. In the circular footing, the bearing capacity on the layered soil profile is assessed using the mechanism of punching shear failure following the desired area approach. The punching shear failure mechanism formed in dense sand has a parabolic shape at the ultimate load when the maximum mobilization of shear force through the failure surface is taken into account, otherwise, the punching failure is the actual failure while punching in the lower layer continues to a greater extent, depending on the interface load. Bearing pressure decreases as the inclination increases with respect to the vertical, along with bearing pressure increasing as the thickness of the dense sand layer increases. The software results compare well with data available from the literature.

Reliability Analysis of Circular Footing by Using GP and MPMR

Circular footings are designed to bear a load of super structures. Studies have been done on the influence of soil properties on bearing capacity of shallow foundations. The use of circular foundation is practical in geotechnical engineering. During the design of circular footing, bearing capacity of soil is taken into consideration, and cohesion (c), unit weight (γ), and angle of internal friction (ϕ) are the most variable parameters. Reliability analysis is used frequently for the design of circular footing. Most of the authors have used first order second moment methods (FOSM). However, FOSM is a time-consuming method. Drawbacks of FOSM have been overcome by genetic programming (GP), minimax probability machine regression (MPMR). This article gives a distinct analysis between the developed MPMR based FOSM and GP-based FOSM.