Prediction of the Effect of Using Stone Column in Clayey Soil on the Behavior of Circular Footing by ANN Model

2018 ◽  
Vol 24 (5) ◽  
pp. 86
Author(s):  
Omar Khaleel Ismael Al-Kubaisi
Keyword(s):  
Clayey Soil ◽  
Ground Improvement ◽  
Bending Moment ◽  
Horizontal Stress ◽  
Soil Strength ◽  
Stone Columns ◽  
Stone Column ◽  
Soil Consolidation ◽  
Ann Model ◽  
Circular Footing

Shallow foundations are usually used for structures with light to moderate loads where the soil underneath can carry them. In some cases, soil strength and/or other properties are not adequate and require improvement using one of the ground improvement techniques. Stone column is one of the common improvement techniques in which a column of stone is installed vertically in clayey soils. Stone columns are usually used to increase soil strength and to accelerate soil consolidation by acting as vertical drains. Many researches have been done to estimate the behavior of the improved soil. However, none of them considered the effect of stone column geometry on the behavior of the circular footing. In this research, finite element models have been conducted to evaluate the behavior of a circular footing with different stone column configurations. Moreover, an Artificial Neural Network (ANN) model has been generated for predicting these effects. The results showed a reduction in the bending moment, the settlement, and the vertical stresses with the increment of the stone column length, while both the horizontal stress and the shear force were increased. ANN model showed a good relationship between the predicted and the calculated results.  

scholarly journals Comparison between unit cell and plane strain models of stone column ground improvement

2018 ◽  
Vol 7 (2) ◽  
pp. 263
Author(s):  
Maryam Gaber ◽  
Anuar Kasa ◽  
Norinah Abdul Rahman ◽  
Jamal Alsharef
Keyword(s):  
Stress Concentration ◽  
Plane Strain ◽  
Clayey Soil ◽  
Cell Model ◽  
Ground Improvement ◽  
Soft Soil ◽  
Unit Cell ◽  
Stone Columns ◽  
Stone Column ◽  
The Impact

This article presents a comparative study of the behaviour of clayey soil reinforcements using stone column ground improvement by means of numerical analyses. Two-dimensional finite element analyses with commercially available software, PLAXIS, were performed on end-bearing stone columns using 15-noded triangular elements to investigate the impact of the modelling type on the stress concentration ratio and failure mechanism of an improved foundation system. Consolidation analyses were conducted throughout the study using Mohr-Coulomb’s criterion. The computed values of the stress concentration ratios were compared for different key parameters, including the diameters of stone columns, c/c spacing of columns, friction angle of stone column material, and undrained cohesion of soft soil. The major conclusions of this study were that the stone column in the unit cell model shared between 2.5 to 3.14 times more loads than the surrounding soil, whilst in the plane strain model it shared between 1.7 to 2.9 times more loads. The use of plane strain approach to model the stone column gave a more comprehensive representation of the stress distribution and load transfer between the soil and columns, in addition to being a better method than the unit cell concept to evaluate the failure mode in this system.

scholarly journals Investigation of the Effect of Dimensional Characteristics of Stone Column on Load-Bearing Capacity and Consolidation Time

2018 ◽  
Vol 4 (6) ◽  
pp. 1437 ◽  
Author(s):  
Mohammad Reza Mohtasham ◽  
Mahdi Khodaparast
Keyword(s):  
Bearing Capacity ◽  
Clayey Soil ◽  
Stone Columns ◽  
Stone Column ◽  
Rigid Foundation ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Soil Subsidence ◽  
Behavioural Model ◽  
Consolidation Time

One of the best methods for rehabilitating loos and soft soils is the application of stone columns. This method enhances the soil properties by increasing its load-bearing capacity, decreasing the soil subsidence, and accelerating the consolidation rate. In the present paper, numerical analysis of a stone column of 10 m in length into a clayey soil using ABAQUS software is presented. The stone column was modelled based on the concept of unit cell, i.e. a single stone column with the surrounding soil. In this respect, material of the stone column was modelled using the elastoplastic behavioural model of Mohr-Coulomb, while Cam Clay behavioural model was used for the surrounding clayey soil. Furthermore, throughout the analyses performed in this study, effects of different parameters (e.g. applied load on rigid foundation, and the stone column length and diameter) on the subsidence and consolidation time of the rigid foundation were examined. The results indicated that, construction of a stone column into clayey soil decreases the subsidence and consolidation time of the soil considerably. In additions, increases in length and diameter of the stone column were found to significantly contribute to reduced subsidence and consolidation time of soil.

scholarly journals Seismic Analysis of Floating Stone Columns in Soft Clayey Soil

2021 ◽  
Vol 318 ◽  
pp. 01008
Author(s):  
Mahdi O. Karkush ◽  
Amer G. Jihad ◽  
Karrar A. Jawad ◽  
Mustafa S. Ali ◽  
Bilal J. Noman
Keyword(s):  
Clayey Soil ◽  
Seismic Analysis ◽  
Lateral Displacement ◽  
Soft Soil ◽  
Soft Clay ◽  
Surface Displacement ◽  
Stone Columns ◽  
Stone Column ◽  
Plastic Behavior ◽  
Ground Acceleration

The response of floating stone columns of different lengths to diameter ratio (L/D = 0, 2, 4, 6, 8, and 10) ratios exposed to earthquake excitations is well modeled in this paper. Such stone column behavior is essential in the case of lateral displacement under an earthquake through the soft clay soil. ABAQUS software was used to simulate the behavior of stone columns in soft clayey soil using an axisymmetric finite element model. The behavior of stone column material has been modeled with a Drucker-Prager model. The soft soil material was modeled by the Mohr-Coulomb failure criterion assuming an elastic-perfectly plastic behavior. The floating stone columns were subjected to the El Centro earthquake, which had a magnitude of 7.1 and a peak ground acceleration of 3.50 m/s2. The surface displacement, velocity, and acceleration in soft clayey enhanced by floating stone columns are also smaller than in natural soft clay. The findings of this research revealed that under the influence of earthquake waves, lateral displacement varies with stone columns of various lengths.

scholarly journals LIGHTWEIGHT SLAG, PFA COLUMN A NEW SOFT GROUND IMPROVEMENT METHOD

2020 ◽  
Vol 4 (1) ◽  
pp. 04-07
Author(s):  
Hafez, M. A ◽  
Sidek, H.N ◽  
Moustafa Z. Ibrahim ◽  
Almkahal, Z
Keyword(s):  
Shear Failure ◽  
Ground Improvement ◽  
Performance Testing ◽  
Pozzolanic Reaction ◽  
Total Weight ◽  
Stone Columns ◽  
Stone Column ◽  
Power Station ◽  
Unconfined Compression Test ◽  
Curing Method

This study investigates how to reduce the demand on in non-renewable granite source, by replacing granite aggregate with boiler slag in the stone column. It is a fact that boiler slag is a power station waste material which causes too many environmental problems. By introducing it as a ground improvement technique, we can reduce the bulging and shear failure problems encountered on stone columns application by adding more improvement to the stone column mixture. For more enhancements to the mixture, pulverized fly ash (PFA) of Class F is added. By increasing the amount of PFA, the resistance of the stone column in term of shear and bearing capacity are increased as the PFA pozzolanic reaction begins to produce more strength during the increasing time of the curing period. Both samples of the boiler slag and PFA are taken from Sultan Salahuddin Abdul Aziz Power Station, Klang, Selangor. The materials mixed are sand, cement and water to make boiler slag aggregates -PFA (slag) mixture. This study aims to define the slag concrete performance according to the optimum configuration of the materials used in the mixture. Unconfined Compression Test (UCT) is applied to define the ideal ratio of boiler slag between 60% to 30% ratios from the total weight which applied with 2% ratio of cement from the total weight. The results of the study show that the number of boiler slags, the period of curing, and the method of curing are the most important factors in defining the slag stone column performance. Testing the samples in ordinary circumstances to entire areas can be accomplished by determining the soil properties and meeting them. The best result gained was the 40% ratio of boiler slag in a curing method that preserved the mixture moisture and temperature, which led to the optimum strength of the slag stone column.

scholarly journals Settlement Behaviour of Soft Soil Reinforced with Geogrid Encased Stone Column under Sustained Loading

2019 ◽  
Vol 9 (2) ◽  
pp. 1307-1311
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Stone Columns ◽  
Stone Column ◽  
Replacement Ratio ◽  
Sustained Loading ◽  
Settlement Behavior ◽  
Column Material ◽  
Area Replacement Ratio ◽  
Different Diameters

The use of stone columns in improving the bearing capacity of soft soil is well researched, but the understanding of settlement requires further studies. This paper presents the results of a series of laboratory tests carried out to study the settlement behavior of soft soil bed reinforced with ordinary stone column (OSC) and Geogrid encased stone columns (GESC). Kaolin was used as the soft soil and stones of size from 2.5 to 10 mm were used as column material. The stone columns of four different diameters were installed, by the method of replacement, into the soil having undrained shear strength of 22.5 kPa. The OSC and GESC test beds were subjected to pressure of 250 and 300 kPa. Each pressure was sustained for 24 hours and the settlement of the composite soil with time was noted. It is found that Geogrid encased stone columns have small settlement than the corresponding ordinary stone columns. The SRR (settlement reduction ratio) being a measure of ground improvement, is found increasing with the area replacement ratio. Further, at a particular sustained pressure SRR is found more for GESC than the corresponding value for OSC.

scholarly journals Evaluation Of Use of Stone Column in Unengineered Closed Landfill Soil

2021 ◽  
Vol 23 (08) ◽  
pp. 538-548
Author(s):  
Mandeep Singh ◽  
◽  
Dr Prashant Garg ◽  
Keyword(s):  
Bearing Capacity ◽  
Load Capacity ◽  
Ground Improvement ◽  
Soft Soil ◽  
Confining Pressure ◽  
Lateral Spreading ◽  
Silty Sand ◽  
Stone Columns ◽  
Stone Column ◽  
Closed Landfill

In the building industry, ground improvement techniques based on stone column are widely employed. It is a very successful approach for enhancing the engineering characteristics of soil in all aspects, as well as reducing the settling issue in poor-grounded soils including silt, clay, silty sand, and organic soil. The performance of stone columns, is determined by the confining pressure provided by the surrounding soils. Engineering constructions built on thick layers of soft soil strata face issues such as limited bearing capacity, excessive total and differential settlement, lateral spreading, and so on. To address such issues, many ground improvement techniques are available. In exceptionally soft soils, the lateral confining pressure may be inadequate, resulting in column bulging failure. Individual stone column encasement improves lateral resistance to bulging by adding restricting pressure. This research focuses on the geotechnical aspects of building on closed landfill sites. A total of 33 models were tested in a geotechnical engineering laboratory on virgin former landfill soil and stone column with and without encasement in this current study. The increased diameter, length and L/D ratio of the column has demonstrated that the load capacity has increased and soil settling has decreased. When an unreinforced stone column has been installed, the ultimate bearing capacity of landfill soil is increased by 75-112.50 per cent and 87.50-176 per cent respectively, for 10mm and 20mm diameter stone column. Furthermore, when a fully reinforced stone column has been installed, it had increased by 156.25-212.50 per cent and 200-298 per cent for 10mm and 20mm diameters respectively. The stiffness of soil is increased by the stone column, which contributes to increase in the load capacity. The geogrid layer confines an aggregate, which contribute to enhance shear stiffness and bearing capacity.

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

2021 ◽  
Vol 2 (107) ◽  
pp. 59-74
Author(s):  
J.S. Yadav ◽  
K. Kumar ◽  
R.K. Dutta ◽  
A. Garg
Keyword(s):  
Carrying Capacity ◽  
Stone Columns ◽  
Stone Column ◽  
Load Carrying Capacity ◽  
Weak Soil ◽  
Load Carrying ◽  
Column Design ◽  
Practical Implications ◽  
Settlement Behaviour ◽  
Circular Footing

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.

scholarly journals ANALYSIS OF COMBINED FOOTINGS ON EXTENSIBLE GEOSYNTHETIC-STONE COLUMN IMPROVED GROUND

2017 ◽  
Vol 8 (2) ◽  
pp. 57-71
Author(s):  
Priti Maheshwari
Keyword(s):  
Flexural Rigidity ◽  
Nonlinear Behavior ◽  
Bending Moment ◽  
Stone Columns ◽  
Stone Column ◽  
Model Parameters ◽  
Geosynthetic Reinforcement ◽  
Foundation Soil ◽  
Lumped Parameter ◽  
Soil Foundation

Analysis of combined footings resting on an extensible geosynthetic reinforced granular bed on stone column improved ground has been carried out in the present work. Various components of soil-foundation system have been idealized using lumped parameter modeling approach as: combined footing as finite length beam, granular layer as nonlinear Pasternak shear layer, geosynthetic reinforcement as elastic extensible membrane, stone columns as nonlinear Winkler springs and foundation soil as nonlinear Kelvin body. Hyperbolic constitutive relationships have been adopted to represent the nonlinear behavior of various elements of a soil-foundation system. Finite difference method has been employed to solve developed governing differential equations with the help of appropriate boundary and continuity conditions. A detailed parametric study has been conducted to study the effect of model parameters like applied load, flexural rigidity of footing, configuration of stone columns, ultimate bearing resistance of foundation soil and stone columns, tensile stiffness of geosynthetics and degree of consolidation on response of soil-foundation system by means of deflection and bending moment in the footing and mobilized tension in geosynthetic layer. These parameters have been found to have significant influence on the response of footing and the geosynthetic reinforcement layer. To quantify this, results have been nondimensionalized to produce design charts for ready use for the analysis of combined footings resting on such a soilfoundation system.

Distribution of Stress on Stone Column-Reinforced Soft Soil under Cylindrical Storage Tank

2014 ◽  
Vol 567 ◽  
pp. 699-704 ◽  
Author(s):  
Kousik Deb ◽  
Amit Kumar Das
Keyword(s):  
Contact Stress ◽  
Storage Tank ◽  
Ground Improvement ◽  
Soft Soil ◽  
Ground Level ◽  
Stone Columns ◽  
Stone Column ◽  
Foundation Soil ◽  
Granular Fill ◽  
Mechanical Elements

Structures with circular foundation (chimney, silo, oil tank) constructed on compressible soft soil, often have to opt for ground improvement like stone columns before construction. In this paper, the stress distribution on stone column-reinforced ground under cylindrical storage tank has been presented. Actual foundation soil reinforced with stone column is assumed as composite ground of soil and hollow cylindrical stone rings keeping the area ratio constant to carry the analysis in axi-symmetric condition. The soft soil, stone columns and granular fill are idealized using mechanical elements. The floor slab of the storage tank is assumed to be flexible enough to satisfy the theory of thin plate. Governing differential equations are derived to determine the vertical settlement and solved with finite difference technique. Contact stress at ground level is calculated from vertical settlement. It is observed that soft soil experiences heavy settlement and contact stress when the tank is full despite of low spacing to diameter ratio (S/dc = 3) and reasonable modular ratio (Ec/Es = 20). It is also observed that stress acting on edge stone column is lower as compared to the stress acting on center stone column even under uniformly loaded condition.

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