scholarly journals Model Testing of Encased Stone Column Composite Foundations under Traffic Loads

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yongquan Yuan ◽  
Minghua Zhao ◽  
Yao Xiao ◽  
Chaowei Yang
Keyword(s):  
Stress State ◽  
Cyclic Load ◽  
Soft Soil ◽  
Composite Foundation ◽  
Stone Columns ◽  
Stone Column ◽  
Laboratory Model ◽  
Test Results ◽  
Efficient Treatment ◽  
Traffic Loads

In soft soil foundations, geogrid encased stone column composite foundation technology has been widely applied and developed in recent years due to its efficient treatment. In this study, eight groups of laboratory model tests were performed in a large-scale testing tank to investigate the bearing mechanism and stress characteristics of the composite foundation of geogrid encased stone columns under traffic loads with different cyclic load ratios. The stress at the bottom of the stone column and settlement of the composite foundation were measured and analysed. The test results show that cyclic shearing will cause the rearrangement of the soil particles at the column-soil interface, which will cause changes in the face pressure and effective stress state of the column-soil boundary. The cyclic load has a substantial influence on the accumulation settlement of the composite foundation and the development of the lateral stress state of the column. Based on the test results, the development law of the cumulative settlement is summarized, and the change mechanism of the column stress state is analysed and discussed.

scholarly journals Behavior of foundation soil improved by stone column under cyclic load

2018 ◽  
Vol 239 ◽  
pp. 05015 ◽  
Author(s):  
Kwa Sally Fahmi ◽  
Mohammed Fattah ◽  
Alena Shestakova
Keyword(s):  
Finite Element ◽  
Cyclic Load ◽  
Soft Soil ◽  
Current Method ◽  
Stone Columns ◽  
Elastic Response ◽  
Stone Column ◽  
Finite Element Analyses ◽  
Foundation Soil ◽  
Rate Of Loading

This paper deals with using the stone column as a technique for the enhancement of the soft ground. The key goal of utilizing stone column is to decrease settlement and to increment the soil bearing ability, as well as decreasing the consolidation period. Nowadays, the current method concerns with various kinds of soil granular and cohesive. It is clear that the delicate soils (cohesive) possess a good settlement because of the disability of the ground to control the sidelong development and protruding of the stone sections. Moreover, the ways of utilization of the geosynthetic materials for encasement of the stone sections are other perfect ways to enhance the implementation, the quality, and firmness of stone segments. The present work investigates the behavior of the soft soil reinforced with ordinary and encased stone columns with geogrid under cyclic load. Six model tests were carried out on a soil with shear strength of about 15 kPa for both ordinary stone columns (OSC) and geogrid encased stone columns (ESC). For validating the enhanced method of utilizing stone columns, finite element model using the software PLAXIS 3D and field load exams had been applied. It was concluded that the models subjected to cyclic loading under the rate of loading 10 mm/sec reached the failure level faster than models tested under the rate of loading 5 mm/sec. The results of the finite element analyses of settlement compared with the records of settlement after the laboratory load tests seem to yield reasonably comparable values up to 50% of the design load. Afterwards, the recorded settlements show up to 60% higher values in compare with the results of the finite element analyses. This observation can be attributed to the occurrence of plastic failures under increasing load after an initial elastic response.

Improvement of Soft Soil by Stone Column Treated with Bentonite

2020 ◽  
Vol 857 ◽  
pp. 283-291
Author(s):  
Safa Hussain Abid Awn ◽  
Jasim M. Abbas
Keyword(s):  
Clayey Soil ◽  
Slenderness Ratio ◽  
Soft Soil ◽  
Field Tests ◽  
Stone Column ◽  
Laboratory Model ◽  
Mix Proportion ◽  
Effective Depth ◽  
Concrete Footing ◽  
The Ideal

Soft clayey soils cover wide Iraqi areas specially the regions close to rivers and the southern part of this country Heavy weight structures like: highways, dams, multiple story buildings are suffering unacceptable settlement, when constructing on soft soils. The high contamination of water in such soils decrease the effective stress and reduce bearing capacity. The need was appeared to improve such problematic soil by the use of new technique of stone column treated with different percentages of natural bentonite by a series of field tests using full scale concrete footing constructed on soft soil in addition to a laboratory model to investigate settlement with time at constant stress. The soil that used in this study is natural clayey soil, brought from a location south of Diyala governorate, from a farm area. The study includes also: The effect of stone column diameter treated with bentonite on the behavior of footing constructing on soft clayey soil, The effect of stone column length on the behavior of footing on such soils. Results of field and laboratory model tests reviled that the treated model by stone column mixed with 40% bentonite is the ideal one, which reduces the settlement by 55%. In other hand problems of uneven settlements appear when using 60% bentonite as a mix proportion. The Ideal slenderness ratio (Ds/Ls<25%). The effective depth of stone column treated with bentonite is (1/3H).

scholarly journals Stability analysis of roadway embankments supported by stone columns with the presence of water table under short-term and long-term conditions

2018 ◽  
Vol 162 ◽  
pp. 01013 ◽  
Author(s):  
Shaymaa Tareq Kadhim ◽  
Ziad Bashar Fouad
Keyword(s):  
Water Table ◽  
Factor Of Safety ◽  
Soft Soil ◽  
Stone Columns ◽  
Stone Column ◽  
Stability Factor ◽  
Short Term ◽  
Long Term Conditions ◽  
The Stability

Use of stone column technique to improve soft foundation soils under roadway embankments has proven to increase the bearing capacity and reduce the potential settlement. The potential contribution of stone columns to the stability of roadway embankments against general (i.e. deep-seated) failure needs to be thoroughly investigated. Therefore, a two-dimensional finite difference model implemented by FLAC/SLOPE 7.0 software, was employed in this study to assess the stability of a roadway embankment fill built on a soft soil deposit improved by stone column technique. The stability factor of safety was obtained numerically under both short-term and long-term conditions with the presence of water table. Two methods were adopted to convert the three-dimensional model into plane strain condition: column wall and equivalent improved ground methods. The effect of various parameters was studied to evaluate their influence on the factor of safety against embankment instability. For instance, the column diameter, columns’ spacing, soft soil properties for short-term and long-term conditions, and the height and friction angle of the embankment fill. The results of this study are developed in several design charts.

scholarly journals Laboratory Model Tests on Stone Column and Pervious Concrete Columns: A Comparative Study

2021 ◽  
Vol 12 (1) ◽  
pp. 75-89
Author(s):  
Jignesh Patel ◽  
Chandresh Solanki ◽  
Yogendra Tandel ◽  
Bhavin Patel
Keyword(s):  
Carrying Capacity ◽  
Deformation Behavior ◽  
Concrete Columns ◽  
Model Tests ◽  
Pervious Concrete ◽  
Stone Columns ◽  
Stone Column ◽  
Laboratory Model ◽  
Load Carrying Capacity ◽  
Load Carrying

This study aims to perform laboratory model tests to investigate the load-deformation behavior of stone columns (SCs), pervious concrete columns (PCCs), and composite columns (CCs). Here, CC refers to the column which has the upper portion made of PCC and the lower portion made of SC. The parameters investigated in this study include column diameters, column lengths, and installation methods (pre-cast and cast-in-situ methods). The results of the model tests reveal that the axial load-carrying capacity of PCC is nearly 8 times more than that of SC with the same diameter. Moreover, it is also observed that at the top portion of SC, with the PCC length which is about 3.75 to 5 times the column diameter, the load-carrying capacity can significantly increase. It is concluded that the installation methods have marginal influence on the load-deformation behavior of PCC.

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 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 The Impact of Using Different Types of Soft Soils Treated by Stone Columns on Creep Behavior

2022 ◽  
Vol 961 (1) ◽  
pp. 012052
Author(s):  
Sura Tawfeeq Al-Auqbi ◽  
Nahla M. Salim ◽  
Mahmood R. Mahmood
Keyword(s):  
Soft Soil ◽  
Horizontal Displacement ◽  
Cohesive Soil ◽  
Stone Columns ◽  
Stone Column ◽  
Geometric Conditions ◽  
Improvement Factor ◽  
Soil Deposits ◽  
Different Types ◽  
The Impact

Abstract The stone column technique is an effective method to increase the strength of soft cohesive soil, which results in a reduction in foundation settlement and an increase in bearing capacity. The topic of restraining creep settlement through the use of stone columns techniques has gained increasing attention and consideration; because stone columns are widely used to treat soft soil deposits, caution should be applied in estimating creep settlement. We discovered a reversible relation between shear parameters and the creep settlement in floating stone columns; while, in case of end-bearing stone columns shows a direct positive relation between shear parameters and the creep settlement, and the creep settlement began at the primary settlement. The shear parameters affected the improvement factor (n) of creep settlement in both floating and end-bearing stone columns. The standard creep coefficient’s n values in floating and end-bearing conditions were more significant than the low creep coefficient’s n values in forwarded geometric conditions. The stress in both floating and end-bearing stone columns was increasing and uniformly distributed along the length of the floating stone column and in the case of end-bearing stone column was limited to the stiffness layer; the maximum vertical stress was in the central point of the embankment. The embankment’s maximum horizontal displacement occurred on the edge.

scholarly journals Laboratory Experimental Analysis on Encapsulated Stone Column

2013 ◽  
Vol 59 (3) ◽  
pp. 359-379 ◽  
Author(s):  
Y.K. Tandel ◽  
C.H. Solanki ◽  
A.K. Desai
Keyword(s):  
Carrying Capacity ◽  
Soft Soil ◽  
Stone Columns ◽  
Stone Column ◽  
Radial Deformation ◽  
Load Carrying Capacity ◽  
Column Length ◽  
Confinement Pressure ◽  
Load Carrying ◽  
Lower Load

Abstract The application of stone column technique for improvement of soft soils has attracted a considerable attention during the last decade. However, in a very soft soil, the stone columns undergo excessive bulging, because of very low lateral confinement pressure provided by the surrounding soil. The performance of stone column can be improved by the encapsulation of stone column by geosynthetic, which acts to provide additional confinement to columns, preventing excessive bulging and column failure. In the present study, a detailed experimental study on behavior of single column is carried out by varying parameters like diameter of the stone column, length of stone column, length of geosynthetic encapsulation and stiffness of encapsulation material. In addition, finite-element analyses have been performed to access the radial deformation of stone column. The results indicate a remarkable increase in load carrying capacity due to encapsulation. The load carrying capacity of column depends very much upon the diameter of the stone column and stiffness of encapsulation material. The results show that partial encapsulation over top half of the column and fully encapsulated floating column of half the length of clay bed thickness give lower load carrying capacity than fully encapsulated end bearing column. In addition, radial deformation of stone column decreases with increasing stiffness of encapsulation material.

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.

Numerical Modeling of Horizontally Layered Geosynthetic Reinforced Encased Stone Columns Supporting Embankment on Sabkha Soil

2021 ◽  
Vol 52 ◽  
pp. 164-178
Author(s):  
Imad Eddine Debbabi ◽  
Mohamed Saddek Remadna ◽  
Ahmad Safuan A Rashid
Keyword(s):  
Lateral Pressure ◽  
Soft Soil ◽  
Research Work ◽  
Stone Columns ◽  
Stone Column ◽  
Weak Zone ◽  
Small Areas ◽  
The Stability ◽  
Weak Zones ◽  
Very High

The present research work is concerned with the construction of road embankments on a Sabkha soil in Algeria. This soil is not only soft and very humid during the flooding seasons but also has frequent small areas of very soft soil which are called locally weak zones (LWZ) in the context of this study. LWZ are characterized by low strength and high compressibility. Two-dimensional axisymmetric analyses were carried out using PLAXIS 2D 2017. The study demonstrated that ordinary stone columns (OSC) are ineffective given the nature of these soils due to the excessive bulging caused by the lack of lateral pressure. On the other hand, the reinforced stone columns with external and internal reinforcements called as vertical encasement and horizontal strips (VESC+HRSC) are one of the best improvement methods of locally weak zones (LWZ), especially to increase the stability of embankment on the highway, namely, a much reduced bulging and a reasonable settlement, so that it is possible to build safe and very high embankments (indeed, numerical results showed for a (VESC+HRSC) combination, a vertical settlement of 0.74 m and a lateral deformation of 20.02 mm vs. 1.56 m and 221.16 mm for an OSC). Besides, an extensive parametric study was conducted to investigate the effect of the spacing of the horizontal reinforcing strips and of the column reinforced length. The influence of stone column diameter, depth of locally weak zone, and the effective stiffness of the geosynthetic, on the performance of the (RSC) - embankment composite were also investigated. The computational results are presented in the form of tables and graphs, and compared with previous published results available in the literature.

Sign in / Sign up

Export Citation Format

Share Document