Calculation Method of Soil-Column Area Replacement Ratio in the Composite Foundation

2013 ◽  
Vol 405-408 ◽  
pp. 216-220
Author(s):  
Jing Qin ◽  
Wei Lu ◽  
Yun Zhao
Keyword(s):  
Soil Column ◽  
Engineering Application ◽  
Composite Foundation ◽  
Replacement Ratio ◽  
Pile Diameter ◽  
Error Ratio ◽  
Spacing Ratio ◽  
Pile Arrangement ◽  
Area Replacement Ratio ◽  
Two Parameters

The calculation equations of soil-column area replacement ratio (m) recommended by Chinese code Technical Code for Ground Treatment of Buildings (JGJ79-2012) have many limits in the practice. In this document, general equations of m value are derived by subdividing the composite soil element under the different pile arrangements. The results show that m value is determined by the two parameters: interval number among piles (n) and pile diameter-spacing ratio (d/s). m value greatly decreases with the increase of d/s at the constant n, whereas m slightly decreases with the increase of n at the constant d/s, and the larger n, the smaller drop of m value. Under triangular pile arrangement, the Chinese code recommended equations can be used with less than 10 percent of error ratio of m value when the width of composite foundation is above 10 m, but the general equations should be applied when the width is below 10 m. Under square pile arrangement, the recommended equations can be used when the width of composite subgrade is above 15 m, but the general equations should be applied when the width is below 15 m. The general calculation equations of m value derived in this paper can provide certain reference for theoretical calculation and engineering application.

Influence of gravel density in the behaviour of soft soils improved with stone columns

2015 ◽  
Vol 52 (12) ◽  
pp. 1968-1980 ◽  
Author(s):  
Marina Miranda ◽  
Almudena Da Costa ◽  
Jorge Castro ◽  
César Sagaseta
Keyword(s):  
Relative Density ◽  
Soil Column ◽  
Experimental Results ◽  
Stone Columns ◽  
Small Scale ◽  
Replacement Ratio ◽  
Soft Soils ◽  
Stress Concentration Ratio ◽  
Area Replacement Ratio ◽  
Horizontal Slice

Stone columns are frequently employed to improve the bearing capacity of soft soils, to reduce settlements, and to increase the speed of consolidation. Their behaviour depends on several factors, such as the density of the aggregate that forms the column and the area replacement ratio. This paper presents a study of the influence of the density of the gravel forming the columns on the deformation and stresses around end-bearing stone columns installed in soft soils. For this purpose, the behaviour of a horizontal slice of a unit cell has been analyzed by small-scale laboratory tests performed in a Rowe–Barden cell. Tests have been performed with a gravel relative density of Dr = 30% and with two area replacement ratios. Their results have been analyzed along with those from similar tests performed with a gravel density of Dr = 100%. The study is focused on the soil–column stress concentration ratio and the reduction of settlements. Finally, the experimental results are compared with numerical simulations. The results show that a reduction of settlements around 10% occurs when the relative density of the gravel increases from Dr = 30% to 100%. Numerical analyses reproduce well the behaviour of stone columns and are in good agreement with the experimental results.

Optimum Design Study on Leveling Variable Stiffness of Composite Foundation with Rammed Soil-Cement Pile

2010 ◽  
Vol 168-170 ◽  
pp. 2631-2635
Author(s):  
Zhen Shuan Zhang ◽  
Yu Deng ◽  
Wei Zhang ◽  
De Sheng Ju
Keyword(s):  
Optimum Design ◽  
Bending Moment ◽  
Variable Stiffness ◽  
Composite Foundation ◽  
Design Study ◽  
Replacement Ratio ◽  
Practical Project ◽  
Soil Cement ◽  
Area Replacement Ratio ◽  
Pile Length

According to the practical project, settlement, reaction and bending moment of composite foundation with rammed soil-cement pile are recalculated, which based on the change of the original area replacement ratio, pile length and foundation thickness. The method of optimum design study on leveling variable Stiffness is investigated.

Field Study of Improvement Mechanism of Geogrid-Reinforced and Pile-Supported Embankment

2014 ◽  
Vol 587-589 ◽  
pp. 928-933 ◽  
Author(s):  
Feng Lian ◽  
Zhi Liu ◽  
Jie Xu ◽  
Qiang Wang ◽  
Xian Hu Hu ◽  
...  
Keyword(s):  
Load Transfer ◽  
Soft Soil ◽  
Composite Foundation ◽  
Replacement Ratio ◽  
Floating Pile ◽  
Pile Cap ◽  
Soil Arch ◽  
Better Than ◽  
End Bearing Pile ◽  
Pile Supported Embankment

Two experimental areas in a highway soft soil ground treatment project in Guangdong Province were designed to investigate the improvement mechanism of geogrid-reinforced and pile-supported embankment(GRPS).The experimental results showed: In End-bearing Pile Area,the differential settlement between pile and soil was bigger than that of Floating Pile Area,so the bearing capacity of soil was exerted to a certain extent in Floating Pile Area. The bearing efficacy of soil below the pile cap was little, so the replacement ratio of composite foundation could be calculated according to the pile cap dimension. The load transfer efficacy of the geogrid was better than that of the soil arch. Five kinds of methods were used to evaluate the soil arch in the fill and it was indicated that the results calculated by the BS8006 method and Carlsson method was close to the experimental data which was smaller than results calculated by Hewlett method and Terzaghi method, bigger than Guido method. Through the analysis of the pile-soil stress ratio, the improvement mechanism of the two types of GRPS were revealed.

Embankment Supported by Low Area Replacement Ratio Stone Columns, Monitoring and Numerical Studies

2021 ◽  
Author(s):  
Mario V. Riccio F ◽  
Marcio S. S. Almeida ◽  
Silvana M. Vasconcelos ◽  
Liliana G. S. Pires ◽  
Luiz F. Nicodemos R
Keyword(s):  
Stone Columns ◽  
Replacement Ratio ◽  
Low Area ◽  
Numerical Studies ◽  
Area Replacement Ratio

Piled Raft Structure Finite Element Analysis of Composite Foundation Settlement in Da XI Passenger Dedicated Line

2014 ◽  
Vol 937 ◽  
pp. 438-443
Author(s):  
Xiao Tong Ma ◽  
Guang Long Liu
Keyword(s):  
Finite Element ◽  
Composite Foundation ◽  
Foundation Settlement ◽  
Pile Spacing ◽  
Finite Element Software ◽  
Piled Raft ◽  
Pile Diameter ◽  
Foundation Treatment ◽  
Pile Length ◽  
Passenger Dedicated Line

Composite foundation settlement of piled raft structure in Da Xi passenger dedicated line is analyzed by the large finite element software MIDAS/GTS and established calculation model of foundation treatment. The problem of pile-soil contact is highlighted in the trail and analyzes the settlement nephogram and pile-soil stress nephogram. On this basis the foundation settlement factors was analyzed systematically that focus on the elastic modulus of pile, pile spacing, pile diameter and pile length in foundation treatment, especially for the characteristics parameters of contact element. Result shows that increasing the pile modulus, pile diameter, pile length and decreasing the pile spacing is all conducive to reducing settlement. The best advice is got that the pile diameter should be not more than 0.5m, pile length not more than 27m and the pile spacing be around 2m.

Bearing capacity of spread footings on aggregate pier–reinforced clay: updates and stress concentration

2020 ◽  
Vol 57 (5) ◽  
pp. 717-727 ◽  
Author(s):  
Taeho Bong ◽  
Armin W. Stuedlein ◽  
John Martin ◽  
Byoung-Il Kim
Keyword(s):  
Stress Concentration ◽  
Bearing Capacity ◽  
Cross Validation ◽  
Slenderness Ratio ◽  
Ground Improvement ◽  
Analytical Models ◽  
Loading Test ◽  
Replacement Ratio ◽  
Area Replacement Ratio ◽  
Reinforced Clay

Aggregate piers represent an economical ground improvement technique used to increase bearing capacity and reduce settlements of weak soils. Several approaches have been developed to estimate the bearing capacity of aggregate pier–reinforced clay, but these models exhibit large prediction bias and uncertainty. This study uses newly developed footing loading test data to investigate the relationship between the bearing capacity and the area replacement and slenderness ratios. The bearing capacity of a single aggregate pier, whether isolated or in groups, below a loaded footing increases as the area replacement ratio decreases due to increase in extent of confined soil surrounding the pier. The length and diameter of an aggregate pier is also shown to result in significantly increased bearing capacity, an effect that diminishes with increasing slenderness. New modifications are proposed to existing simplified and cavity expansion models to account for the effect of confinement, area replacement ratio, and slenderness ratio using a leave-one-out cross-validation technique. The cross-validation analysis resulted in robust bearing capacity models that are more accurate than existing analytical models. Additionally, the stress concentration ratio for shallow foundations supported by aggregate pier–reinforced plastic soils at failure was estimated and compared with the available data, indicating its sensitivity to design variables and showing that this critical design parameter may be predicted using the updated models.

Experimental Study on Mechanical Properties of Recycled Concrete Specimens of Marine Engineering

2011 ◽  
Vol 71-78 ◽  
pp. 331-337
Author(s):  
Wen Bai Liu ◽  
Xia Li
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Engineering Application ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Replacement Rate ◽  
Replacement Ratio ◽  
Ordinary Concrete ◽  
Seawater Corrosion ◽  
Marine Engineering

Mechanical properties of recycled concrete under different conditions were studied in this paper. Based on three kinds of replacement percentage of recycled aggregate and four kinds of seawater corrosion conditions, the experimental study of mechanical properties of recycled concrete specimens corroded by seawater and produced under vacuum conditions were conducted, and compared with that of ordinary concrete specimens. Testing results show that compressive strength of recycled concrete decreases with the increase of both the replacement rate of recycled aggregate and the corrosion time by seawater, with the maximum reduce value is 17.96% and 24.52%; Vacuum conditions effectively improve the strength of recycled concrete, improved value is 1.03-1.19 times of the same replacement ratio of recycled aggregate, and 1.00-1.16 times of the ordinary concrete. It provides the reference for marine engineering application of recycled concrete.

Consolidation theory for a composite foundation considering radial and vertical flows within the column and the variation of soil permeability within the disturbed soil zone

2010 ◽  
Vol 47 (2) ◽  
pp. 207-217 ◽  
Author(s):  
Meng-Meng Lu ◽  
Kang-He Xie ◽  
Biao Guo
Keyword(s):  
Soil Column ◽  
Composite Foundation ◽  
Stone Column ◽  
Governing Equations ◽  
Soil Zone ◽  
Disturbed Soil ◽  
Variation Patterns ◽  
Present Solution ◽  
Actual Design ◽  
Continuity Assumption

To remedy the contradiction between the equal strain assumption and the flow continuity assumption at a soil–column interface, the traditional flow continuity assumption was abandoned and the radial and vertical flows within a stone column were incorporated to consider the column consolidation and deformation in a coupled fashion. Moreover, two possible variation patterns of the horizontal permeability coefficient of soil within the disturbed soil zone were included, to reflect the detrimental influence on the surrounding soil due to column construction. In addition, a linearly changed total vertical stress along the column depth was assumed, to achieve a more realistic stress distribution in practice. By considering the above mentioned characteristics, the governing equations for this type of consolidation problem were developed. The solutions for the governing equations were subsequently derived by using a new initial condition obtained from the equilibrium condition and equal strain assumption. On the basis of this, the average degree of consolidation of the composite foundation was obtained and discussed. Finally, a parametric study was performed and an application example was introduced to help engineers better utilize the present solution when applied to an actual design.

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