Soil properties Flashcards
What are the two properties of a soil section and what do they describe
Nature - characteristics of the soil itself such as plasticity and size
State - The conditions in which the soil exists such as the water in the section and the amount of void
What are the two main methods of sorting soil sizes and in what are they used for
Sieving and sedimentation. Sieving is for larger soils and sedimentation for smaller soils (below 425 microns)
What are the two methods of sieving
Dry and wet. Wet is used for coarse grain, while dry can be used for smaller grains but cannot contain significant amounts of silt and clay grade grains.
What is a PSD graph and give the two ways the graph describes the soil sample.
Particle size distribution. The line’s length in the x axis gives its range of sizes and the gradient shows the abundancy. The steeper the line, the more of that particle size is present in the sample.
What is poorly graded, well graded and gap graded and how can the PSD line show this along with the coefficient equations
poorly graded, very little variety in rock sizes, shown as a rather line that has a very low range in the x axis with a coefficient of conformity d60/d10 < 4
well graded, lots of variety in rock size, shown as line with a lot of range in the x axis and a coefficient of curvature 1<d30^2/(d60xd10)<3
gap graded, large range in rock sizes but lacking in certain sizes between, shown as a line that will occasionally become horizontal. coefficient of curvature outside of 1 to 3.
(dn ,where n is a number represents the particle size in which n% of the particles are smaller than)
What principle does sedimentation use
stokes law. Doesn’t work for particles smaller than 0.2 microns as Brownian motion becomes prevalent. Uses the equation in stokes law to calculate approximate radius, after the particle reaches terminal velocity in the liquid
What are the three phases in a section of soil
solid, water and air
Define water content, void ratio, saturation and porosity
mass of water/ mass of solid
volume of voids/ volume of solid
volume of water/ volume of voids
volume of voids/ total volume
Define specific gravity and specific volume
density of solid/ density of water
total volume/ volume of solid
Define bulk density and dry density
total mass/ total volume
mass of solid/ total volume
What are the 4 states of a soil section
undisturbed - completely untouched
intact- relatively undisturbed, some structure lost
remoulded - disturbed, most of its structure removed due to mechanical means
reconstituted - structure completely removed due to mechanical mixing
Define the liquidity index with an equation and explain the terms within it. Also state for what grade of soils is it used for
liquidity index = w-wp/wL-wp
w=water content
wp= water content at plastic limit, the smallest water content at which the concrete can deform without cracking/ crumbling
wL = liquid limit, the largest water content at which the soil can retain its shape
Used for clays
Define the relative density with an equation and explain the terms within it. Also state for what grade of soils is it used for
relative density = emax-e/emax-emin
emax = maximum void ratio
e= void ratio
emin = minimum void ratio
Define plastic index with an equation
wL-wP
wp= water content at plastic limit, the smallest water content at which the concrete can deform without cracking/ crumbling
wL = liquid limit, the largest water content at which the soil can retain its shape
what are the methods to determine liquid index and state which one is less subjective and give a brief explanation of it
cone penetrometer and casagrande cup
Cone penetrometer is less subjective and involves penetrating a soil sample contained within a cup with a cone shaped metal device for 5 seconds. Then the water content is measured so that a graph of cone penetration and water content can be plotted. The liquid limit is defined at a penetration depth of 20mm
