scholarly journals Pressure Settlement Behaviour and Bearing Capacity of Asymmetric Embedded Plus Shaped Footing on Layered Sand

2021 ◽  
Vol 31 (3) ◽  
pp. 152-176
Author(s):  
Priyanka Rawat ◽  
Rakesh Kumar Dutta
Keyword(s):  
Bearing Capacity ◽  
Numerical Study ◽  
Friction Angle ◽  
Thickness Ratio ◽  
Embedment Depth ◽  
Loose Sand ◽  
Dense Sand ◽  
Comparison Of The Results ◽  
Abaqus Software ◽  
Settlement Behaviour

Abstract The aim of the present numerical study was to analyse the pressure settlement behaviour and bearing capacity of asymmetric plus shaped footing resting on loose sand overlying dense sand at varying embedment depth. The numerical investigation was carried out using ABAQUS software. The effect of depth of embedment, friction angle of upper loose and lower dense sand layer and thickness of upper loose sand on the bearing capacity of the asymmetric plus shaped footing was studied in this investigation. Further, the comparison of the results of the bearing capacity was made between the asymmetric and symmetric plus shaped footing. The results reveal that with increase in depth of embedment, the dimensionless bearing capacity of the footings increased. The highest increase in the dimensionless bearing capacity was observed at embedment ratio of 1.5. The increase in the bearing capacity was 12.62 and 11.40 times with respect to the surface footings F1 and F2 corresponding to a thickness ratio of 1.5. The lowest increase in the dimensionless bearing capacity was observed at embedment ratio of 0.1 and the corresponding increase in the bearing capacity was 1.05 and 1.02 times with respect to the surface footing for footings F1 and F2 at a thickness ratio of 1.5.

Bearing capacity of rectangular footing on layered sand under inclined loading

2021 ◽  
Vol 108 (2) ◽  
pp. 49-62
Author(s):  
V. Panwar ◽  
R.K. Dutta
Keyword(s):  
Bearing Capacity ◽  
Numerical Study ◽  
Thickness Ratio ◽  
Failure Pattern ◽  
Width Ratio ◽  
Loose Sand ◽  
Sand Layer ◽  
Inclined Load ◽  
Dense Sand ◽  
Inclined Loading

Purpose: The study presents the numerical study to investigate the bearing capacity of the rectangular footing on layered sand (dense over loose) using ABAQUS software. Design/methodology/approach: Finite element analysis was used in this study to investigate the bearing capacity of the rectangular footing on layered sand and subjected to inclined load. The layered sand was having an upper layer of dense sand of varied thickness (0.25 W to 2.0 W) and lower layer was considered as loose sand of infinite thickness. The various parameters varied were friction angle of the upper dense (41° to 46°) and lower loose (31° to 36°) layer of sand and load inclination (0° to 45°), where W is the width of the rectangular footing. Findings: As the thickness ratio increased from 0.00 to 2.00, the bearing capacity increased with each load inclination. The highest and lowest bearing capacity was observed at a thickness ratio of 2.00 and 0.00 respectively. The bearing capacity decreased as the load inclination increased from 0° to 45°. The displacement contour shifted toward the centre of the footing and back toward the application of the load as the thickness ratio increased from 0.25 to 1.25 and 1.50 to 2.00, respectively. When the load inclination was increased from 0° to 30°, the bearing capacity was reduced by 54.12 % to 86.96%, and when the load inclination was 45°, the bearing capacity was reduced by 80.95 % to 95.39 %. The results of dimensionless bearing capacity compare favorably with literature with an average deviation of 13.84 %. As the load inclination was changed from 0° to 45°, the displacement contours and failure pattern shifted in the direction of load application, and the depth of influence of the displacement contours and failure pattern below the footing decreased, with the highest and lowest influence observed along the depth corresponding to 0° and 45°, respectively. The vertical settlement underneath the footing decreased as the load inclination increased, and at 45°, the vertical settlement was at its lowest. As the load inclination increased from 0° to 45°, the minimum and maximum extent of influence in the depth of the upper dense sand layer decreased, with the least and highest extent of influence in the range of 0.50 to 0.50 and 1.75 to 2.00 times the width of the rectangular footing, respectively, corresponding to a load inclination of 45° and 0° Research limitations/implications: The results presented in this paper were based on the numerical study conducted on rectangular footing having length to width ratio of 1.5 and subjected to inclined load. However, further validation of the results presented in this paper, is recommended using experimental study conducted on similar size of rectangular footing. engineers designing rectangular footings subjected to inclined load and resting on layered (dense over loose) sand. Originality/value: No numerical study of the bearing capacity of the rectangular footing under inclined loading, especially on layered soil (dense sand over loose sand) as well as the effect of the thickness ratio and depth of the upper sand layer on displacement contours and failure pattern, has been published. Hence, an attempt was made in this article to investigate the same.

Numerical study of ultimate bearing capacity of rectangular footing on layered sand

2020 ◽  
Vol 1 (101) ◽  
pp. 15-26
Author(s):  
V. Panwar ◽  
R.K. Dutta
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bearing Capacity ◽  
Numerical Study ◽  
Friction Angle ◽  
Ultimate Bearing Capacity ◽  
Loose Sand ◽  
Sand Layer ◽  
Element Analysis ◽  
Dense Sand

Purpose: The purpose of this study is to investigate the ultimate bearing capacity of the rectangular footing resting over layered sand using finite element method. Design/methodology/approach: Finite element analysis was used to investigate the dimensionless ultimate bearing capacity of the rectangular footing resting on a limited thickness of upper dense sand layer overlying limitless thickness of lower loose sand layer. The friction angle of the upper dense sand layer was varied from 41° to 46° whereas for the lower loose sand layer it was varied from 31° to 36°. Findings: The results reveal that the dimensionless ultimate bearing capacity was found to increase up to an H/W ratio of about 1.75 beyond which the increase was marginal. The results further reveal that the dimensionless ultimate bearing capacity was the maximum for the upper dense and lower loose sand friction angles of 46° and 36°, while it was the lowest for the upper dense and lower loose sands corresponding to the friction angle of 41° and 31°. For H/W = 0.5 and 2, the dimensionless bearing capacity decreases with the increase in the L/W ratio from 0.5 to 6 beyond which the dimensionless ultimate bearing capacity remains constant for all combinations of parameters. The results were presented in nondimensional manner and compared with the previous studies available in literature. Research limitations/implications: The analysis is performed using a ABAQUS 2017 software. The limitation of this study is that only finite element analysis is performed without conducting any experiments in the laboratory. Further the study is conducted only for the vertical loading. Practical implications: This proposed numerical study can be used to predict the ultimate bearing capacity of the rectangular footing resting on layered sand. Originality/value: The present study gives idea about the ultimate bearing capacity of rectangular footing when placed on layered sand (dense sand over loose sand) as well as the effect of thickness of top dense sand layer on the ultimate bearing capacity. The findings could be used to calculate the ultimate bearing capacity of the rectangular footing on layered sand.

Bearing capacity of E-shaped footing on layered sand

2021 ◽  
Vol 2 (105) ◽  
pp. 49-60
Author(s):  
S. Nazeer ◽  
R.K. Dutta
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Shear Failure ◽  
Numerical Study ◽  
Lower Layer ◽  
Friction Angle ◽  
Ultimate Bearing Capacity ◽  
Loose Sand ◽  
Dense Sand ◽  
Square Footing

Purpose: The purpose of this study is to estimate the ultimate bearing capacity of the E-shaped footing resting on two layered sand using finite element method. The solution was implemented using ABACUS software. Design/methodology/approach: The numerical study of the ultimate bearing capacity of the E-shaped footing resting on layered sand and subjected to vertical load was carried out using finite element analysis. The layered sand was having an upper layer of loose sand of thickness H and lower layer was considered as dense sand of infinite depth. The various parameters varied were the friction angle of the upper (30° to 34°) and lower (42° to 46°) layer of sand as well as the thickness (0.5B, 2B and 4B) of the upper sand layer. Findings: The results reveal that the dimensionless ultimate bearing capacity was found to decrease with the increased in the H/B ratio for all combinations of parameters. The dimensionless ultimate bearing capacity was maximum for the upper loose sand friction angle of 34° and lower dense sand friction angle of 46°. The results further reveal that the dimensionless bearing capacity of the E-shaped footing was higher in comparison to the dimensionless bearing capacity of the square footing on layered sand (loose over dense). The improvement in the ultimate bearing capacity for the E-shaped footing was observed in the range of 109.35% to 152.24%, 0.44% to 7.63% and 0.63% to 18.97% corresponding to H/B ratio of 0.5, 2 and 4 respectively. The lowest percentage improvement in the dimensionless bearing capacity for the E-shaped footing on layered sand was 0.44 % at a H/B = 2 whereas the highest improvement was 152.24 % at a H/B = 0.5. Change of footing shape from square to E-shaped, the failure mechanism changes from general shear to local shear failure. Research limitations/implications: The results presented in this paper were based on the numerical study conducted on E-shaped footing made out of a square footing of size 1.5 m x 1.5 m. However, further validation of the results presented in this paper, is recommended using experimental study conducted on similar size E-shaped footing. Practical implications: The proposed numerical study can be useful for the architects designing similar types of super structures requiring similar shaped footings. Originality/value: No numerical study on E-shaped footing resting on layered sand (loose over dense) were conducted so far. Hence, an attempt was made in this article to estimate the bearing capacity of these footings.

Bearing capacity mechanisms for pipes buried in sand

2020 ◽  
Author(s):  
Jinbiao Wu ◽  
George P. Kouretzis ◽  
Laxmi Prasad Suwal
Keyword(s):  
Bearing Capacity ◽  
Friction Angle ◽  
Flow Rule ◽  
Loose Sand ◽  
Buried Pipelines ◽  
Buried Pipes ◽  
Dense Sand ◽  
Physical Model Tests ◽  
Vertical Bearing ◽  
Sand Material

This paper presents results of scaled physical model tests performed to measure the reaction developing on a rigid pipe buried in dry sand, when the pipe is subjected to vertical downwards movement relative to its surrounding soil. The aim of this experimental study is to evaluate the efficacy of methods used to determine the properties of vertical bearing springs, an integral part of beam-on-nonlinear Winkler spring models used for the analysis of buried pipelines subjected to permanent ground displacements. We show that bearing capacity formulas used in practice to estimate the ultimate reaction developing on buried pipes may provide reasonably accurate estimates, provided that they are used together with sand friction angle values that account for the fact that granular materials do not obey an associative flow rule, and with bearing capacity factors compatible with the mode of sand failure observed in the tests. We also provide evidence suggesting that laying pipes in loose sand backfills does not have a beneficial effect on the reaction developing on the pipe, compared to medium dense sand, and we recommend against using loose sand material properties for the estimation of the properties of vertical bearing springs.

Bearing Capacity of Foundations with Inclusion of Dense Sand Layer over Loose Sand Strata

2017 ◽  
Vol 17 (10) ◽  
pp. 06017018 ◽  
Author(s):  
Vishwas N. Khatri ◽  
Jyant Kumar ◽  
Shamim Akhtar
Keyword(s):  
Bearing Capacity ◽  
Loose Sand ◽  
Sand Layer ◽  
Dense Sand

The Effect of Shallow-Water Waves on the Stability and Bearing Capacity of Sea Beds

1974 ◽  
Vol 14 (04) ◽  
pp. 330-336
Author(s):  
R. Fernandez Luque ◽  
R. van Beek
Keyword(s):  
Bearing Capacity ◽  
Water Waves ◽  
Pressure Fluctuations ◽  
Wave Action ◽  
Shallow Foundations ◽  
Loose Sand ◽  
Dense Sand ◽  
Model Experiments ◽  
Sea Bottom ◽  
Clay Deposits

Abstract This paper reports a theoretical and experimental investigation of the influence of shallow water waves on the bearing capacity of foundations in sea beds. The propagation of pressure waves through a porous sea bed is calculated, assuming plane elastic-plastic soil deformation under undrained loading conditions, and including the effect of dilatancy. The effective stresses thus generated are compared with the soil-stability limits. The consequences for both sand and clay deposits are considered individually. Model experiments in a flume demonstrate how prolonged wave action increases the density of an initially very loose sand, whereas it expands an initially dense sand. Because small changes in void ratio have a significant effect on the bearing capacity of a sediment, the bearing capacity of a loose sand bed increases with prolonged wave action, but that of a dense sand decreases. It was found, however, that under all circumstances the ultimate bearing capacity of a sandy sea bottom is largely sufficient for pile-foundation purposes. In fact, stormy weather tends to stabilize the bearing capacity of a sandy sea bottom. In contrast, calculations for clay deposits show that the excess pore pressure caused by wave action on a normally consolidated clay cannot be dissipated within a practical time limit. Waves are thus unable to compact a clay deposit. The shearing forces generated by shallow waves in an underconsolidated clay may therefore cause soil instability during a severe storm. Our calculations and model experiments seem to indicate that shallow foundations subject to strong wave action will settle gradually within a plastic region of the sea bottom as a result of cyclic wave loading. This paper describes a practical method for calculating a safe depth of burial and bearing capacity for shallow foundations subject to wave action. INTRODUCTION Ocean waves are able to generate significant shearing forces in sea-floor sediments up to total (water + soil) depths of approximately half the length of the waves. Waves could thus affect the end bearing capacity of shallow foundations or the lateral resistance at shallow depths of deep foundation piles. We shall first calculate the pressure fluctuations at the sea bottom due to plane irregular waves using the small-amplitude wave theory. We shall then calculate the stresses and pore pressures generated in the sea bottom by such irregular pressure fluctuations at the bed surface, assuming plane elastic - plastic soil deformation and introducing a pore - pressure parameter for the saturated soil under undrained, biaxial loading condition s. We shall compare those stresses with the soil stability limits and consider soil consolidation due to wave action. Then we shall present the results of model experiments performed in a laboratory flume, showing that prolonged wave action increases the density of an initially very loose sand, whereas it expands an initially dense sand. We shall compare theory and experiment. Finally, we shall discuss a method for calculating a safe depth of burial and bearing capacity for shallow foundations subject to wave action.

scholarly journals Numerical Study of Strip Footings Behavior on Compacted Sand

2019 ◽  
pp. 1-10
Author(s):  
Nasser A. A. Radwan ◽  
Khaled M. M. Bahloul
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Layer Thickness ◽  
Numerical Study ◽  
Computer Software ◽  
Strip Footing ◽  
Loose Sand ◽  
Strip Footings

The aim of this research is to investigate numerically the effect of using compacted sand as soil replacement layer beneath a strip footing on its bearing capacity. Finite element computer software Plaxis 2D version 8.6 was used to predict the behavior of strip footing resting on loose sand and on compacted sand. Study was conducted for footing widths of 1 up to 2 meters and various depths ranging from 1m up to 2m, also the effect of replacement layer thickness was investigated. It was found that using replacement layer beneath strip footing increases its bearing capacity for different widths and depths of footing. This improvement is observed up to thickness of replacement layer equal to 3 times the footing width (H/B=3), where further increase in replacement layer thickness does not affect significantly bearing capacity of footings.

Experimental and numerical studies of geosynthetic-reinforced sand slopes loaded with a footing

2000 ◽  
Vol 37 (4) ◽  
pp. 828-842 ◽  
Author(s):  
K M Lee ◽  
V R Manjunath
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Numerical Study ◽  
Slope Angle ◽  
Model Tests ◽  
Axial Stiffness ◽  
Edge Distance ◽  
Optimum Geometry ◽  
Fill Slope ◽  
Settlement Behaviour

This paper presents the results of a series of plane strain model tests carried out on both reinforced and unreinforced sand slopes loaded with a rigid strip footing. The objectives of this study are to (i) determine the influence of geosynthetic reinforcement on the bearing-capacity characteristics of the footing on slope, (ii) understand the failure mechanism of reinforced slopes, and (iii) suggest an optimum geometry of reinforcement placement. The investigations were carried out by varying the edge distance of the footing for three different slope angles and three different types of geosynthetic. It is shown that the load-settlement behaviour and ultimate bearing capacity of the footing can be considerably improved by the inclusion of a reinforcing layer at the appropriate location in the fill slope. The optimum depth of the reinforcement layer, which resulted in maximum bearing capacity ratio (BCR), is found to be 0.5 times the width of the footing. It is also shown that for both reinforced and unreinforced slopes, the bearing capacity decreases with an increase in slope angle and a decrease in edge distance. At an edge distance of five times the width of the footing, bearing capacity becomes independent of the slope angle. The effectiveness of the geosynthetic in improving the bearing capacity of the footing is attributed to its primary properties such as aperture size and axial stiffness. A numerical study using finite element analyses was carried out to verify the model test results. The agreement between observed and computed results is found to be reasonably good in terms of load-settlement behaviour and optimum geometry of georeinforcement placement.Key words: model tests, footing, bearing capacity, fill slope, finite element method, geosynthetic.

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