scholarly journals Settlement Behaviour of Soft Clay Bed Reinforced with Stone Column under Sustained Loading

2019 ◽  
Vol 9 (2) ◽  
pp. 1744-1749
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Reinforced Soil ◽  
Sustained Load ◽  
Stone Column ◽  
Sustained Loading ◽  
Settlement Behavior ◽  
High Area ◽  
Area Replacement Ratio

This research paper investigates the behaviour of soft clay reinforced with stone column under sustained loading. Experiments were conducted in the laboratory on stone column reinforced prepared soft soil bed of kaolin having strength of 7.5 kPa with aggregate of size 2.5 to 10 mm as column material. The stone column with four diameters of 38.1, 50.8, 63.5 and 76.2mm were constructed which correspond to low to high area replacements ratios (i.e. 6.93% - 26.49%). The plain and reinforced soft clay beds were subjected to a sustained load of 150, 200, 250 and 300 kPa where each applied load has been maintained for 24 hours and the settlement behavior of composite ground was taken into account. The test results represent the settlement of reinforced soil bed decreases with increase of column diameters. The settlement reduction ratio is a measure of ground improvement which increases with area replacement ratio. The experimental and theoretical results values were compared as per IS15284 (Part 1): 2003 with reference of stress concentration ratio ‘n’(The ratio of stress in the column to the stress of surrounding ground area). The % variation in theoretical and experimental results is in the range of 50% and therefore the theoretical procedure needs to be revised.

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.

Uplift and Settlement Prediction Model of Marine Clay Soil e Integrated with Polyurethane Foam

2019 ◽  
Vol 9 (1) ◽  
pp. 481-489
Author(s):  
D.C. Lat ◽  
I.B.M. Jais ◽  
N. Ali ◽  
B. Baharom ◽  
N.Z. Mohd Yunus ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Clay Soil ◽  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Effective Thickness ◽  
Marine Clay ◽  
Uplift Pressure ◽  
Pu Foam ◽  
Improvement Method

AbstractPolyurethane (PU) foam is a lightweight material that can be used efficiently as a ground improvement method in solving excessive and differential settlement of soil foundation mainly for infrastructures such as road, highway and parking spaces. The ground improvement method is done by excavation and removal of soft soil at shallow depth and replacement with lightweight PU foam slab. This study is done to simulate the model of marine clay soil integrated with polyurethane foam using finite element method (FEM) PLAXIS 2D for prediction of settlement behavior and uplift effect due to polyurethane foam mitigation method. Model of soft clay foundation stabilized with PU foam slab with variation in thickness and overburden loads were analyzed. Results from FEM exhibited the same trend as the results of the analytical method whereby PU foam has successfully reduced the amount of settlement significantly. With the increase in PU foam thickness, the settlement is reduced, nonetheless the uplift pressure starts to increase beyond the line of effective thickness. PU foam design chart has been produced for practical application in order to adopt the effective thickness of PU foam within tolerable settlement value and uplift pressure with respect to different overburden loads for ground improvement works.

scholarly journals Performance of soft clay stabilized with sand columns treated by silica fume

2018 ◽  
Vol 162 ◽  
pp. 01007
Author(s):  
Zeena Samueel ◽  
Hussein Karim ◽  
Mohammed Mohammed
Keyword(s):  
Silica Fume ◽  
Carrying Capacity ◽  
Construction Projects ◽  
Ground Improvement ◽  
Soft Clay ◽  
Road Construction ◽  
Reduction Ratio ◽  
Area Replacement Ratio ◽  
Second Category ◽  
Improvement Ratio

In many road construction projects, if weak soil exists, then uncontrollable settlement and critical load carrying capacity are major difficult problems to the safety and serviceability of roads in these areas. Thus ground improvement is essential to achieve the required level of performance. The paper presents results of the tests of four categories. First category was performed on saturated soft bed of clay without any treatment, the second category shed light on the improvement achieved in loading carrying capacity and settlement as a result of reinforcing with conventional sand columns at area replacement ratio = 0.196. The third set investigates the bed reinforced by sand columns stabilized with dry silica fume at different percentages (3, 5 and 7%) and the fourth set investigates the behavior of sand columns treated with slurry silica fume at two percentages (10 and 12%). All sand columns models were constructed at (R.D= 60%). Model tests were performed on bed of saturated soil prepared at undrained shear strength between 16-20 kPa for all models. For all cases, the model test was loaded gradually by stress increments up to failure. Stress deformation measurements are recorded and analyzed in terms of bearing improvement ratio and settlement reduction ratio. Optimum results were indicated from soil treated with sand columns stabilized with 7% dry silica fume at medium state reflecting the highest bearing improvement ratio (3.04) and the settlement reduction ratio (0.09) after 7 days curing. While soil treated with sand columns stabilized with 10% slurry silica fume provided higher bearing improvement ratio 3.13 with lower settlement reduction ratio of 0.57 after 7-days curing.

scholarly journals Sustainable ground improvement method using encapsulated polypropylene (PP) column reinforcement

2021 ◽  
Vol 930 (1) ◽  
pp. 012016
Author(s):  
M Hasan ◽  
M S I Zaini ◽  
N A W Hong ◽  
A Wahab ◽  
K A Masri ◽  
...  
Keyword(s):  
Shear Strength ◽  
Soil Sample ◽  
Ground Improvement ◽  
Soft Soil ◽  
Control Sample ◽  
Replacement Ratio ◽  
Replacement Method ◽  
Penetration Ratio ◽  
Area Replacement Ratio ◽  
Strength Improvement

Abstract This study investigates the effectiveness of encapsulated polypropylene (PP) column in enhancing the undrained shear strength of kaolin (soft clay). The usage of PP in treating problematic soil is a more sustainable and cost-effective alternative compared to other materials. The installation of granular column can be done by using vibro-replacement method. Several geotechnical tests to determine the properties of materials were conducted. The shear strength of treated kaolin sample was examined by using Unconfined Compression Test (UCT). There are seven (7) batches of soil sample in total which included a control sample, three (3) batches of 14 mm and three (3) batches of 20 mm diameter PP column. Different diameters of PP column were examined with 60 mm, 80 mm and 100 mm height, respectively with soil sample of 50 mm in diameter and 100 mm in height. The shear strength improvement of kaolin is 33.82%, 46.51%, and 49.88% when implanted with a PP column with a 7.84 area replacement ratio and 0.6, 0.8 and 1.0 penetration ratio. The soft soil treated using 16.00 area replacement ratio with 0.6, 0.8 and 1.0 penetration ratio has a shear strength increment of 25.22%, 33.39% and 37.59% respectively. In short, the shear strength improvement of the kaolin clay depends on the parameter of the PP column used to reinforce the sample.

Field performance of the port of Sepetiba test fills

1995 ◽  
Vol 32 (1) ◽  
pp. 106-121 ◽  
Author(s):  
Vinod K. Garga ◽  
Luciano V. Medeiros
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Field Performance ◽  
Stone Columns ◽  
Field Investigations ◽  
Large Program ◽  
Soil Deposits ◽  
Load Tests ◽  
The Cost

The design of the industrial port of Sepetiba, 50 km south of Rio de Janeiro, Brazil, required a detailed evaluation of the underlying soft soil deposits. Initially, on the basis of laboratory tests, it was proposed to remove approximately 3.7 × 106 m3 of the very soft deposits in the stockpile area by dredging and substitute with hydraulic sand fill. Subsequently, in view of the cost of such a measure, a large program of field investigations was initiated to study the in situ characteristics of the soft clay to evaluate whether replacement of this material and (or) ground improvement was necessary. As part of this investigation, two large identically instrumented test fills (test fills B and D), each 65 m2 in plan and 5 m high, with 3:1 slopes were constructed. Test fill B was constructed over natural ground, whereas the subsoil beneath test fill D was treated with stone columns. The instrumentation for each test fill consisted of piezometers, deep settlement plates, surface settlement plates, and inclinometers. This paper provides a description of the field investigations, observations on installation of stone columns, analysis of instrumentation, a comparison of the behaviour of the two test fills, and a discussion on load tests on individual stone columns. Key words : case history, embankment, ground improvement, instrumentation, soft clay, stone columns.

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 Behavior of Stone Column improved Clay soil under static loading-A numerical exploration

2020 ◽  
Vol 9 (9) ◽  
pp. 440-445
Keyword(s):  
Bearing Capacity ◽  
Soil Stabilization ◽  
Clay Soil ◽  
Soft Soil ◽  
Soft Clay ◽  
Cost Effective ◽  
Element Model ◽  
Vital Role ◽  
Stone Column ◽  
Cost Effective Method

Problematic soil which cause extra problems from engineering point of views which result in its composition or environmental conditions change. The weak subsoil deposits like soft clay pose the low bearing capacity and more settlements over long periods of time. The stone column technique is better, economical and cost-effective method of soft soil stabilization. They are used to support embankments, large raft foundations and isolated footings. Numerous researchers have just completed various vertical stacking probes stone column balanced out clay bed and have discovered that expands bearing capacity of delicate clay, diminishes displacement and changes the conduct of burden settlement. In the current study, a 2D finite element model is completed to evalute how the delicate clay soil balanced out by stone column are affected by the vertical burdens. Stone column were intended for examinations with fluctuating in their angle proportions (change in estimations of length, L and breadth, D) of stone column. The effect of floating stone column and end bearing stone segment on delicate clay is in like manner controlled by using various L/D ratios. Besides, the present outcomes express how the heap conveying limit of stone column is differed by changing in the angle proportions of the stone column. Likewise ends were drawn that bulging impact of stone column plays a vital role in conveying vertical burden.

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 Design and construction of a deep excavation in soft soils adjacent to the Shanghai Metro tunnels

2003 ◽  
Vol 40 (5) ◽  
pp. 933-948 ◽  
Author(s):  
Z F Hu ◽  
Z Q Yue ◽  
J Zhou ◽  
L G Tham
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Theoretical Method ◽  
Horizontal Displacement ◽  
Deep Excavation ◽  
Construction Methods ◽  
Diaphragm Walls ◽  
Shanghai Metro ◽  
Design And Construction

This paper presents the design and construction of a deep excavation for building foundations in saturated soil. This deep excavation was of particular interest because it was located above and beside the Shanghai Metro tunnels. The twin Shanghai Metro tunnels had to be in full operation during the deep excavation. Potential large deformation of the twin tunnels was one of the main concerns during the design and construction for the deep excavation. The paper discusses in detail the criteria and measures for controlling the soil and tunnel deformation. The measures included cast-in-place concrete diaphragm walls with bracing structural members, pumping consolidation, cement–soil mix pile systems, and rational excavation procedures. A simplified theoretical method was proposed to estimate the increment in undrained shear strength in a soft clay layer due to pumping consolidation. Furthermore, conventional finite element methods were used to predict the soil vertical and horizontal displacements induced by the excavation. Using the design and construction methods discussed in the paper, the settlement and horizontal displacement of the tunnels were successfully controlled within 5.0 mm and 9.0 mm, respectively. The curvature of longitudinal deformation curve of the tunnels was less than 1/15 000. The horizontal displacement of the braced diaphragm walls was less than 0.12% of the total excavation depth. Key words: Metro tunnels, saturated soft soil, deep excavation, design, construction, ground improvement, case studies.

Analytical solution for radial consolidation considering soil structure characteristics

2015 ◽  
Vol 52 (7) ◽  
pp. 947-960 ◽  
Author(s):  
Cholachat Rujikiatkamjorn ◽  
Buddhima Indraratna
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Vertical Drains ◽  
South Wales ◽  
Surcharge Load ◽  
Speed Up ◽  
Soil Compressibility ◽  
Conventional Models

A system of surcharge load combined with vertical drains to speed up consolidation of soft soil by reducing the drainage path is one of the most efficient and economical ground improvement techniques. In the field, conventional theories including smear zone have been commonly employed to predict the radial consolidation behaviour induced by vertical drains in soft clay. One of the key parameters in conventional analysis is the use of mean coefficient of volume compressibility and soil permeability, which are often assumed to be constant. The effect of drain installation on the soil compressibility of the in situ clay structure is often ignored. Laboratory testing has shown that the soil compressibility and permeability can vary nonlinearly over a considerable range of applied surcharge pressure, and both these properties can be affected during the drain installation. This study presents a mathematical model of radial consolidation via vertical drains incorporating the variations of soil compressibility and permeability as well as highlighting the effects of drain installation on those parameters. The main differences between the proposed and conventional models are elucidated, in terms of stress history and preloading (surcharge) pressure. The effects of preconsolidation pressure and the magnitude of applied preloading are examined through the dissipation of average excess pore pressure and associated settlement. Supported by experimental observations, the proposed theory is validated with field data of a selected case study in the town of Ballina, New South Wales, Australia.

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