Laboratorio de columnas. resistencia de materiales.
Column Piping.
distillation
Chromatography Technique, Column,
Full description
Descripción completa
BASIC DESIGN PARAMETERS (1) Stone Column Diameter (D) Due to lateral displacement of the stones during vibrator/ramming, the completed diameter of the stone column is always greater than initial diameter of the hole. (in field diameter increase10-20% more)(Normally diameter range from 0.6 to 1 m)
G.L.
D
De D De
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(2) Pattern Stones columns should be installed preferably in an equilateral triangular which is the most dense packing, although a square pattern may also be used. A typical triangular and square pattern is shown in figure.
(b) Square arrangement of stone columns
(a) Triangular arrangement of stone columns
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(3) Spacing (S)
Mitchell (1985)
(for stone column in a square pattern)
ei=initial void ratio e = required void ratio
Mitchell (1985)
(for stone column in a triangular pattern) normally spacing range from 1 to 2 m
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(4) Equivalent diameter (De) The tributory area of the soil surrounding each stone column forms regular hexagon around the column. It may be approximated by an equivalent circular area having the same total area.
D
De
De=1.05 × S (for an equivalent triangular pattern) De=1.13 × S (for a square pattern)
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(5) Replacement Ratio ( as) To quantify the amount of soil replaced by stone column, the term replacement ratio, as ,is used. Replacement ratio (as) is given by:
as
AS A As A 9
(6) Stress concentration ratio (n)
σ
n
s
σs
σg
g
The value of n generally (IS 15284 (Part 1), 2003) lie between 2.5 to 5 at the ground surface. 11
DESIGN APPROACHES Table : Various design approaches for bearing capacity Sr Approach No. 1 Passive pressure approach 2 General shear failure approach 3 Lateral limit state or Pressuremeter theory approach
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Empirical approaches
Author Greenwood (1970) Madhav and Vitkar (1978) Gibson and Anderson (1961) Amar and Jezequel (1972) Peteur (1973) Hughes & Withers (1974) Hughes et al.(1975) Mori (1979), Aboshi et al (1979) Thorburn & McVicar (1968) Greenwood (1970) Thorburn (1975) Smoltzyk (1979) 12
Tank
Sand pad
D Hard strata
De
Figure : Illustration of stone column parameter 13
Load
Stone column
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Load
Stone column 15
Load
σrL
Stone column
σrL Q1 = resistance against bulging
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Design example as per IS 15284 (Part 1) (2003) Data: A stone column is to be designed for the foundation of oil storage tank considering the following given data: Depth of soft clay: H = 7 m, undrainmed shear strength of clay: Cu = 18 kN/m2, Bulk density of clay: γb = 17.65 kN/m3, Submerged density of surrounding soil: γsub = 7.85 kN/m3, ground Water Table (G.W.T.) at 1 m below Ground Level (G.L.), Tank diameter: d =79 m, Load intensity from tank σ = 147 kN/m2, Tank Diameter of the stone column: D = 0.9 m, Sand pad Angle of internal friction of surrounding soil: Øc = 42°.
