Geotechnical Engineering


by: aayush210789


Topics
1Introduction

IIntroduction
Soil mechanics is the branch of science that deals with the study of physical properties of soil and the behavior the study of physical properties of soil and the behavior of soil masses subjected to various types of forces.
According to Terzaghi (1948):
“Soil Mechanics is the application of laws of mechanics and hydraulics to engineering problems dealing with sediments and other unconsolidated accumulations of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixture of organic constituent.” 

Determination of Particle Size Distribution
Mechanical analysis is used in the determination of the size range of particles present in a soil expressed as a size range of particles present in a soil, expressed as a percentage of the total dry weight.
There are two methods that generally utilized to determine the particle size distribution of soil:
  • Sieve Analysis (for particle sizes > 0.075mm in diameter)
  • Hydrometer Analysis ( for particle sizes< 0.075mm in diameter )
  
IIParticle size distribution curve
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IIIDefinitions
Some commonly used measures are:

a) Effective size : 

It is the diameter in the particle size distribution curve (D10)
It is the diameter in the particle size distribution curve corresponding to 10% finer. (maximum size of the smallest 10% 
of the soil) 

b) Uniformity Coefficient:

It is the ratio of the maximum diameter of the smallest 60% to the effective size
Cu= D60/D10

A well graded soil will have
Cu > 4 for gravels
Cu > 6 for sands

c) Coefficient of Curvature:
 
 Cc = 
(D30)^2 / (D60 *D10) 
D30 : Diameter corresponding the 30% finer 

e) Well-Graded Material – Contains particles of a wide range of sizes. The smaller particles fill the spaces left between the larger The smaller particles fill the spaces left between the larger particles; therefore the soil has greater strength than a poorly 
graded soil, and lower permeability. 

f) Poorly – Graded Material – Contains a large portion of uniformly sized particles. This particular soil has larger voids in its structure 
and poor strength along with high permeability.

 
IVSoil gradation curve
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