6 Permeability - Flow of Water Through Soils A ball on a...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Flow of Water Through Soils A ball on a Hill Ball on top of hill will not move if surface flat (horizontal) Ball on slope will roll down hill Movement of ball due to gravity requires a change in slope or a gradient Mg Mg
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Water also flows downhill Soil • Soil can be considered to consist of discrete particles (solids) • The voids or pore space between the particles are all interconnected • If the voids are full of water (Sr=1 or 100%) water will flow from regions of 100%) water will flow from regions of higher to lower pressure
Background image of page 2
3 Partially Water Saturated Soils • Soils voids are filled with water and air Sr<1 or 100% Water Saturated Soils • Soils voids are 100 percent filled with water
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Positive Porewater Pressure + acts normal to soil particles and is equal in all directions • pushes soil grains apart resulting in a decrease in soil particle to particle contac + to particle contact + Negative Porewater Pressure + acts normal to soil particles and is equal in all directions • pulls soil grains together resulting in an increase in soil particle to particle contac - to particle contact -
Background image of page 4
5 Ground Water Table Definition: • Surface on which the fluid pressure in the pores of the porous media is exactly atmospheric • Location is revealed by the level at which water stands in a shallow open we water stands in a shallow open well Pore water Pressure (u) above and below GWT u ve 0 Standpipe open to the atmosphere wrt atmospheric pressure u -ve Suction Water pushing il ti l Water pulling soil particles together u +ve z Ground surface z soil particles apart In soil mechanics problems we assume no soil suction i.e. u=0 above ground water table
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Changes in Degree of Saturation Sr w 0 1 Sr 1 Capillary Fringe Sr w 0 1 Capillary fringe is zone of soil above GWT where soil is close to 100 percent saturated but has negative porewater pressure Fine grain soil can have large capillary fringes (m) Course grained soils small capillary fringes (mm)
Background image of page 6
7 Aquifers • In an unconfined aquifer the ground water table forms the upper boundary of the aquifer • A confined aquifer is an aquifer confined by two
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 02/09/2010.

Page1 / 26

6 Permeability - Flow of Water Through Soils A ball on a...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online