1 Phase Diagram

SOIL MECHANICSSOIL MECHANICSSOIL MECHANICSSOIL MECHANICS

PBW N302Credit HoursCredit Hours

CEM/WEE/STE

Dr. Asmaa ModdatherSoil Mechanics and Foundations

Faculty of Engineering – Cairo University

Dr. Asmaa Moddather – PBW N302 – Fall 2011

FALL 2011

D fi S ilD fi S ilDefine: SoilDefine: Soil

Naturally occuring particulate materialFormed directly or indirectly from solid rocksFormed, directly or indirectly, from solid rocks(i.e. weathering)C i i f il i l d dComposition of soil particles depends oncomposition of parent rockThe void space between the particles containwater and/or airwater and/or air


A li iA li iApplicationsApplications

Engineer uses the SOIL to build:◦ On it: e.g. buildingsOn it: e.g. buildings◦ In it: e.g. tunnels◦ With it; e g earth dams◦ With it; e.g. earth dams


E l B id F d iE l B id F d iExample: Bridge FoundationsExample: Bridge Foundations


E l T lE l T lExample: TunnelExample: Tunnel


E l E h DE l E h DExample: Earth DamExample: Earth Dam


E l F ilE l F ilExample: FailureExample: Failure


I d iI d iIntroductionIntroduction


C O liC O liCourse OutlineCourse Outline

Introduction

Ph diPhase diagram

Soil ClassificationSoil Classification

Compaction

Permeability

Stresses

ConsolidationConsolidation

Shear Strength


g

PBW N302 - Soil MechanicsFall 2011

Instructor: Dr. Asmaa Moddather(Teaching Assistant: Eng. Amr Morsy)

Lectures: Monday 12:00 pm – 02:00 pm, Classroom: 20510

Tutorials: Monday 02:00 pm 05:00 pm Classroom: 20510Tutorials: Monday 02:00 pm – 05:00 pm, Classroom: 20510

Textbook: Das, B.M. (2008), “Introduction to Geotechnical Engineering,”Thomson Learning Toronto Ontario CanadaThomson Learning,Toronto, Ontario, Canada.

Objectives: The purpose of this course is to familiarize students with thebasics of Soil Mechanics Lectures will focus on describingbasics of Soil Mechanics. Lectures will focus on describingthe nature and behavior of soils.



Grading: Attendance and Class Participation 10%

Assignments 10%

Quizzes 20%

Midterm Exam 20%Midterm Exam 20%

Final Exam 40%



Assignments:◦ There will be approximately seven (7) assignments.There will be approximately seven (7) assignments.

◦ Assignments shall be handed out in the tutorial sessions.

◦ Assignments must be submitted in person the week following end of classd f hdiscussion of the topic.

◦ Grades for late assignments shall be reduced by 25%.

◦ No excuses shall be given for late submittals without a written request andNo excuses shall be given for late submittals without a written request andapproval.

Q i Th ll b l (7) Quizzes: There will be approximately seven (7) quizzes.

Exams: One midterm will be given during the semester. A final exam Exams: One midterm will be given during the semester. A final exam will be given in the scheduled final exam period.



Web Site:

www.egypteducation.org

Enrol Key: PBWN302GB



Web Site:

www egypteducation orgwww.egypteducation.org

◦ Enrol Key: PBWN302GB◦ Enrol Key: PBWN302GB


D fi i iD fi i iDefinitionsDefinitions

Soil: is any accumulation of mineral particles formed by the

weathering of rocks, the void space between the particles

containing water and/or air.

Soil Mechanics: is the branch of science dealing with the study

of the physical properties of soil and the behavior of soil massesof the physical properties of soil and the behavior of soil masses

subjected to various types of forces


S il f iS il f iSoil formationSoil formation

Residual soil: the products of rock weathering remain at their

original location.

Transported soil: the products are transported and deposited

in a different location. (gravity, wind, water)



Weathering by mechanical or chemical processes

Mechanical by contraction and expansion of rock erosion by windMechanical by contraction and expansion of rock, erosion by wind

or water: resultant soil is bulky, angular, rounded, elongated, flat.



Chemical: results in changes in the mineral form of the parent

rock due to the action of water, oxygen, and carbon dioxide.

Chemical weathering results in the formation of groups ofcrystalline particles of size (<0:002 mm) known as clay minerals.y p ( ) y



Most clay mineral particles are of ‘plate-like’

Dispersed Flocculated


P AS AG APHASE DIAGRAM


S il V l d W i ht R l ti hiS il V l d W i ht R l ti hiSoil Volumes and Weights RelationshipSoil Volumes and Weights Relationship

Particles (solids)

Air

Water

Solid

Phase diagram

Soil sample Voids Air (dry soil)

g

water (saturated soil)


Air/water (wet soil)

Ph diPh diPhase diagramPhase diagram

Air

Water

Solid

WeightsVolumes



Vs = Volume of solids

V = volume of voidsVv = volume of voids

Vw = volume of water

V = l f iVa = volume of air

VT = total volume = Vs + Vw +Va = Vs + Vv

Ws = weight of solids Air

Ww = weight of water

Wa = weight of air = 0Water

WT = total weight = W + W

Solid


WT total weight Ws Ww WeightsVolumes


γw = Density of water = 1.0 t/m3 = 1.0 gm/cm3 = 10.0 kN/m3

γ = W /Vγw = Ww/Vw

Ww = γw Vw

γs = Density of solids = Ws/Vs = 2.5 – 2.8 t/m3

G = specific gravity = γ /γGs = specific gravity = γs /γw

W V G V

Air

Ws = γs Vs = Gs γwVs

2 70 t/ 3

Water

S l dex., γs = 2.70 t/m3

Gs = 2.70/1.0 = 2.70

Solid

WeightsVolumes


ex., γs = 26.5 kN/m3

Gs = 26.5/10.0 = 2.65

WeightsVolumes


oRatios:Air

e = void ratio = Water

Could e be equal to zero? No

Could e be equal to 1.0? YesSolid

Could e be greater than 1.0? Yes WeightsVolumes

S = degree of saturation =

Could S be equal to zero? Yes

Could S be equal to 1 0? Yes


Could S be equal to 1.0? Yes

Could S be greater than 1.0? No


oRatios:Air

n = porosity = Water

Could n be equal to zero? NoSolid

Could n be equal to 1.0? No

Could n be greater than 1.0? NoWeightsVolumes

g

w = water content = w water content

Could w be equal to zero? Yes

Could w be equal to 1 0? Yes


Could w be equal to 1.0? Yes

Could w be greater than 1.0? Yes

Ph diPh diPhase diagramPhase diagramAir

oDensities:Water

γd = dry unit weight = Solid

W i htV lγwet = wet (bulk) unit weight = =

WeightsVolumes

ws

VWW +

γsat = saturated unit weight =

TV

γsat saturated unit weight

T

vws

VVW γ+

γsub = submerged unit weight = γsat - γw


E l (E l (11))Example (Example (11))

The following observations are taken in the laboratory for determining

th t t t f l lthe water content of a clay sample:

Weight of container + wet soil = 85.0 gm

Weight of container + dry soil = 75.4 gm

Weight of empty container = 40.2 gmg p y g

Assuming the sample to be fully saturated before oven-drying, determine

th t l t t t it d id ti Wh t ill b th the natural water content, porosity, and void ratio. What will be the

submerged density (Gs = 2.65)?

weight of wet soil = 85.0 – 40.2 = 44.8 gm = wt


weight of dry soil = 75.4 – 40.2 = 35.2 gm = ws


wt = ww + ws 44.8 = ww + 35.2 ww = 9.6 gm

ww = γw vw 9.6 = 1x vw vw = 9.6 cm3

γw = 1.0 gm/cm3

ws = Gs γw vs 35.2 = 2.65 x 1 x vs

vs = 35.2/2.65 = 13.3 cm3

AirAir

Water

??

9.6??

9.6

Solid13.3 35.244.8



The following observations are taken in the laboratory for determining

th t t t f l lthe water content of a clay sample:

Weight of container + wet soil = 85.0 gm

Weight of container + dry soil = 75.4 gm

Weight of empty container = 40.2 gmg p y g

Assuming the sample to be fully saturated before oven-drying, determine

th t l t t t it d id ti Wh t ill b th the natural water content, porosity, and void ratio. What will be the

submerged density (Gs = 2.65)?



S = 1.0 vv = vw

vt = vv + vs vt = 9.6 + 13.3 = 22.9 cm3t v s t

e = vv/vs = 9.6/13.3 = 0.72

w = ww/ws = 9.6/35.2 = 0.273 = 27.3%

n = vv/vt = 9.6/22.9 = 0.42

γsat = (ws + γw vv)/vt

Air

Water9.622 9

9.6

= (35.2+1x9.6)/22.9 = 1.96 gm/cm3Water

Solid13.3 35.2

22.9

44.8


γsub = γsat - γw = 1.96 – 1.00 = 0.96 gm/cm3Solid

1 Phase Diagram

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