Civil Engineering (CE)  >  Foundation Engineering  >  Shallow Foundations - 2

Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)

1 Crore+ students have signed up on EduRev. Have you?

Effect of Water Table on Bearing Capacity of Soil
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE) 
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
where Rq* and Ry* are water table correction factor.
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
when 0 ≤ zq ≤ Df when 0 ≤ zγ ≤ B.
If Zγ > B they Rγ= 1
If Zγ ≤ 0 they
If water table rise to G.L
Rq* = 1 / 2 and Rγ* = 1 / 2

Plate Load Test

  1. Significant only for cohesionless.
  2. Short duration test hence only results in immediate settlement.
    (i) quf / qup = Bf / Bp
    (ii) quf = qup
    ..for ∅ = soil … for C-soil
    If plate load test carried at foundation level then
    Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
    (iii) Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
    (iv) Sf / Sp = Bf / Bp
    … for dense sand.  … for clays
    (v) Sf / Sp = (Bf / Bp)n + 1 
    … for silts.
    where,
    quf =Ultimate bearing capacity of foundation
    qup = Ultimate bearing capacity of plate
    Sf = Settlement of foundations
    Sp = Settlement of plate
    Bf = Width of foundation in m
    Bp = Width of plate in m
    Housels Approach
    QP = mAP + nPP
    Qf = mA+ nPf
    where, Qp = Allowable load on plate m and n are constant
    P = Perimeter Ap = Area of plate
    Af = Area of foundation

Standard Penetration Test

Significant for Granular Soils

  1. Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE) and Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
    where, N1 = Overburden pressure correction
    N0 = Observed value of S.P.T. number.
    = Effective overburden pressure at the level of test in kM/m2.
  2. For Saturated Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)   fine sand and silt, when N1 > 15
    N2 = 1/2(N1 - 15) + 15
    where, N2 = Dilatancy correction or water table correction.
    Nq + Nγ related to N value using peck Henson curve or (code method)
    Teng's formula relate N value with reading capacity of granular soil.

Pecks Equation
qa net = 0.44NS = CwkN/m2
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
Dw = depth of water table below G.L
Df = Depth of foundation
B = Width of foundation
N = Avg. corrected S.P.T. no.
S = Permissible settlement of foundation
Cw = Water table correction factor
qa net = Net allowable bearing pressure.

Teng's Equations
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE) 
Cw =Water table correction factor
Dw = Depth of water table below foundation level
B = Width of foundation
Cd =Depth correction factor
S = Permissible settlement in 'mm'.

I.S Code Method
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE) 
qns =Net safe bearing pressure in kN/m2
B = Width in meter.
S = Settlement in 'mm'.

I.S. Code Formula for Raft

qns = 0.88NSCw

Cw: Same as of peck Henson.

Meyer-Hoffs Equation

qns = 0.88NSCwCd
where, qns = Net safe bearing capacity in kN/m2.
B < 1.2 m
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE) 
Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)
B ≥ 1.2 m (where qns is in kN/m2.

Cone Penetrations Test

  1.  Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)where, = Static cone resistance in kg/cm2c = Compressibility coefficientShallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)  = Initial effective over burden pressure in kg/cm2.
  2.  Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)where, 'S' = Settlement.
  3. qns = 3.6qsRw B > 1.2 m.where, qns = Net safe bearing pressure in kN/m2.
  4. qns = 2.7qc.Rw B < 1.2 m.where, Rw = Water table correction factor.  
The document Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE) is a part of the Civil Engineering (CE) Course Foundation Engineering.
All you need of Civil Engineering (CE) at this link: Civil Engineering (CE)
18 videos|27 docs|20 tests
Download as PDF

Download free EduRev App

Track your progress, build streaks, highlight & save important lessons and more!

Related Searches

Free

,

Extra Questions

,

Important questions

,

Previous Year Questions with Solutions

,

Semester Notes

,

Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)

,

Summary

,

Objective type Questions

,

Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)

,

MCQs

,

Viva Questions

,

shortcuts and tricks

,

Sample Paper

,

study material

,

ppt

,

past year papers

,

mock tests for examination

,

video lectures

,

Shallow Foundations - 2 - Notes | Study Foundation Engineering - Civil Engineering (CE)

,

practice quizzes

,

pdf

,

Exam

;