project class

Conducted by: Offered to :

Riyadh, Saudi Arabia, 2019-2020

Dr. Mohamed Ezzat Assistant professor of Civil Eng.

Department of Engineering Management

College of Engineering.

Prince Sultan University

Undergraduate Students –Senior Level.

Engineering Management Department.

College of Engineering.

Prince Sultan University

2nd semester- Year 2019-2020.

EM 306 : Soil Mechanics and Foundations

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TENTATIVE WEEKLY COURSE SCHEDULE WEEK UNIT/ TOPIC

Number of Contact

hours

1 Introduction 5

2 Soil Formation 5

3 Engineering Properties of Soil 5

4 Soil Exploration 5

5 Soil Compaction 5

6 Water in Soil 5

7 Stress in soils 5

8-9 Consolidation of soil 5

10-11 Shear Strength of soil 10

12-13 Bearing Capacity and Shallow Foundations 10

14 Deep Foundations 5

15 Lateral Earth Pressure & Retaining Structures As Scheduled

❑ Stresses in Soil Topic No. 7

EFFECTIVE, NEUTRAL AND TOTAL STRESSES IN SOIL

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❑ Stresses in Soil Topic No. 7

EFFECTIVE, NEUTRAL AND TOTAL STRESSES IN SOIL

A. Total stress (σ):

σ = σ eff + u

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❑ Stresses in Soil Topic No. 7

EFFECTIVE, NEUTRAL AND TOTAL STRESSES IN SOIL B. Effective stress (σ‘):

σeff = σ t - u

C. Neutral stress (pore pressure u):

u = γw . hw

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❑ Stresses in Soil Topic No. 7

CASES TO BE CONSIDERED

(A) Case of submerged soil

σ = γsat . h + γw . h1

u = γw . h1

σ' = γsub . h

Calculation of effective stress in submerged soil

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❑ Stresses in Soil Topic No. 7

(B) Case of soil with surcharge

σ = q + γb . h1 + γsat . h

Calculation of effective stress in loaded soil

u = γw . hw

σ' = q + γb . h1 + γsub . h

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❑ Stresses in Soil Topic No. 7

Example 1

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❑ Stresses in Soil Topic No. 7

Solution:

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❑ Stresses in Soil Topic No. 7

STRESSES IN SOIL DUE TO EXTERNAL LOADS

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❑ Stresses in Soil Topic No. 7

INTRODUCTION ❑

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❑ Stresses in Soil Topic No. 7

❑

INTRODUCTION

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❑ Stresses in Soil Topic No. 7

▪

▪

▪

▪

ELASTIC THEORY

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❑ Stresses in Soil Topic No. 7

o Boussinesq equation:

1. STRESSES DUE TO CONCENTRATED LOAD

Pz = 𝟑𝐐

𝟐𝛑 𝐳𝟐 𝟏

𝟏+ 𝐫

𝐳

𝟐

𝟓

𝟐

𝐩𝐳 = 𝐐 = 𝐳 = =

Zone of influence for concentrated Load

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❑ Stresses in Soil Topic No. 7

o Boussinesq equation:

1. STRESSES DUE TO CONCENTRATED LOAD

❑

𝒑𝒛 = 𝟑𝑷

𝟐𝝅𝒛𝟐 𝟏 + (𝒓/𝒛)𝟐 𝟓/𝟐 =

𝑷

𝒛𝟐 𝑰𝑩

𝐖𝐡𝐞𝐫𝐞, 𝐈𝐁

❑

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❑ Stresses in Soil Topic No. 7

𝒑𝒛 = 𝟑𝑷

𝟐𝝅𝒛𝟐 𝟏 + (𝒓/𝒛)𝟐 𝟓/𝟐 =

𝑷

𝒛𝟐 𝑰𝑩

Example 2

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❑ Stresses in Soil Topic No. 7

Given Data :

𝒛 = 6m, 𝒓 = 0, 𝑷 = 2500kN

From eqn,

𝒑 = (𝟑)(𝟐𝟓𝟎𝟎kN)

(𝟐)𝝅(𝟔𝐦)𝟐[𝟏 + (𝟎/𝟔𝐦)𝟐]𝟓/𝟐 = 𝟑𝟑.𝟐kN/m𝟐

𝒑 = 𝟑𝑷

𝟐𝝅𝒛𝟐 𝟏+(𝒓/𝒛)𝟐 𝟓/𝟐

Solution:

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❑ Stresses in Soil Topic No. 7

❑

(cont’d)

pz = 𝑷

𝒛𝟐 IB

pz = 𝟐𝟓𝟎𝟎

(𝟔 𝒎)𝟐 * 0.48 = 33.3 kN/m

Solution:

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❑ Stresses in Soil Topic No. 7

2. STRESSES DUE TO A LINE LOAD

Pz = 𝐪

𝐳 . NL

Where:

𝐱

𝐳

𝐲

𝐳

Figure 6.3: Stresses due to line load

Pz

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❑ Stresses in Soil Topic No. 7

❑

❑

❑

3. STRESSES DUE TO A LOADED SURFACE AREA

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❑ Stresses in Soil Topic No. 7

𝒑𝒛

𝑷/A

𝑳 + 𝒛

o

3.A Approximate method

o

𝒑𝒛 = 𝑷

(𝑩 + 𝒛)(𝑳 + 𝒛) eqn 6−6

𝐩𝐳 = 𝐏 = 𝐁 = 𝐋 = 𝐳 =

𝒑𝒛 𝒁

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❑ Stresses in Soil Topic No. 7

o  

3.A Approximate method

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❑ Stresses in Soil Topic No. 7

❑

Example 3

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❑ Stresses in Soil Topic No. 7

p = 𝑷

(𝑩+𝒛)(𝑳+𝒛)

P = 𝟑𝟔𝟎𝟎 𝒌𝑵

(𝟑 𝒎+𝟔 𝒎)(𝟓 𝒎+𝟔 𝒎) = 36.4 kN/m2

Solution:

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❑ Stresses in Soil Topic No. 7

1. Uniform load on a circular area ▪

▪

▪

▪

▪

3.B Method based on Elastic Theory

𝒑𝒛 = 𝑷 ∗ 𝑰

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❑ Stresses in Soil Topic No. 7

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❑ Stresses in Soil Topic No. 7

❑

Example 4

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❑ Stresses in Soil Topic No. 7

𝑟

𝑎

0 𝑚

2 𝑚 𝑧

𝑎

5 𝑚

2 𝑚

𝒑𝒛 = 𝑷 ∗ 𝑰

Solution:

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❑ Stresses in Soil Topic No. 7

(cont’d)

Total vertical pressure = overburden pressure (po)

+ vertical increment (p)

po = γz = 16.97 kN/m 3 (5 m) = 84.8 kN/m2

Total vertical pressure = 84.8 + 60.0 = 144.8 kN/m2

Solution:

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❑ Stresses in Soil Topic No. 7