34 0 432KB
Bearing Capacity PROJECT: Trinity River Corridor Project 352010 PROJECT #: CREATED BY: Mark Kacmarcik/CVO REVIEWED BY: ________________________
Given: Find: Assumptions: References:
DATE: 03/23/2009__ DATE: ___________
MODIFIED: ___________
Soil strength data from geotechnical investigation and laboratory analyses. Allowable Bearing Capacity for design of shallow footings. Noted below in calculation. Bowles, J. Foundation Analysis and Design. 5th ed. McGraw Hill. San Francisco, 1996. pp. 263-266. Cernica, J. Geotechnical Engineering: Soil Mechanics. Wiley. New York, 1995. pp. 418-420.
Material Properties: Assume that foundations are constructed in the Upper Clay Unit or Flaggy Zone. ϕ := 24deg
Effective stress friction angle from results of ICU triaxial tests..
c := 0psf
Effective stress cohesion. Conservatively assumed to be 0 psf..
γm := 120pcf
Moist unit weight..
γsat := 125pcf
Saturated unit weight.
γwater := 62.4pcf
Unit weight of water.
γbuoy := γsat − γwater
Trinity Bearing Capacity_mdk.xmcd
γbuoy = 62.6⋅ pcf
1/5
Buoyant unit weight.
Print Date: 7/9/2009
Footing Geometry: Dftg := 12ft
Footing depth.
σzD := Dftg⋅ γbuoy
Effective stress at footing depth, assumed GWT at ground surface.σzD = 751.2⋅ psf
Bftg := 10ft
Footing width
Lftg := 100000ft
Footing length, (extremely large for strip footings, set equal to B.ftg for square footings).
β := 0deg
β = 0 ⋅ deg
Assume horizontal ground surface.
Vesic's Bearing Capacity Formula: qult = c⋅ Nc⋅ sc⋅ dc⋅ ic⋅ b c⋅ gc + σzD⋅ Nq⋅ sq⋅ d q ⋅ iq ⋅ bq ⋅ gq + 0.5⋅ γ⋅ B ⋅ Nγ⋅ sγ⋅ d γ⋅ iγ⋅ b γ⋅ gγ where:
sc, sq , sγ = shape factors dc, dq , dγ = depth factors ic, iq , iγ
= load inclination factors
bc, bq , bγ = base inclination factors gc, gq , gγ = ground inclination factors Bearing Capacity Factors:
Nq := e
π tan ( ϕ)
tan 45⋅ deg +
Trinity Bearing Capacity_mdk.xmcd
ϕ
2
Nq = 9.603
2
2/5
Print Date: 7/9/2009
5.14 if ϕ = 0
Nc :=
Nq − 1
otherwise
tan( ϕ)
(
Nc = 19.324
)
Nγ := 2 Nq + 1 tan( ϕ)
Nγ = 9.442
Footing Shape Factors sc := 1.0 +
Nq Bftg Nc Lftg
sc = 1
sq := 1.0 +
Bftg ⋅ tan( ϕ) Lftg
sq = 1
Bftg sγ := 1.0 − 0.4⋅ Lftg
sγ = 1
Depth Factors: Dftg Bftg
k :=
= 1.2
Dftg Bftg
if
Dftg Bftg
≤ 1.0
k = 0.876
Dftg otherwise Bftg
atan
dc := 1 + 0.4⋅ k
dc = 1.35 2
dq := 1 + 2⋅ tan( ϕ) ⋅ ( 1 − sin( ϕ) ) ⋅ k dγ := 1.00
dq = 1.275
for all φ
dγ = 1
Inclination Factors: P := 0kip
Component of load that acts perpendicular to bottom of footing.
V := 0kip
Component of load that acts parallel to bottom of footing.
A := Bftg⋅ Lftg
Base area of footing
Trinity Bearing Capacity_mdk.xmcd
3/5
Print Date: 7/9/2009
Indicate direction of load Inclination by enabling appropriate scenario: Loads inclined in B direction. Bftg
2+
2+
Lftg
m :=
m :=
Bftg
1+
ic := 1 −
Loads inclined in L direction
1+
Lftg
m⋅ V
Lftg Bftg Lftg Bftg
ic = 1
A⋅ c⋅ Nc
V iq := 1 − A⋅ c P+ tan( ϕ)
m
iq = 1
m+ 1 V iγ := 1 − A⋅ c P+ tan( ϕ)
iγ = 1
Ground Factors: β gc := 1 − 147deg
gc = 1
gq := ( 1 − tan( β) )
2
gq = 1
gγ := gq
gγ = 1
Base Factors: Angle of inclination of base of footing.
α := 0deg
bc := 1 −
α
bq := 1 −
bc := 1
147deg α⋅ tan( ϕ) 57deg
2
bq := 1
bγ := b q
Trinity Bearing Capacity_mdk.xmcd
bγ := 1
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Print Date: 7/9/2009
qult := c⋅ Nc⋅ sc⋅ dc⋅ ic⋅ b c⋅ gc + σzD⋅ Nq⋅ sq⋅ d q ⋅ iq ⋅ bq ⋅ gq + 0.5⋅ γbuoy⋅ Bftg⋅ Nγ⋅ sγ⋅ d γ⋅ iγ⋅ b γ⋅ gγ qult = 12.15⋅ ksf
qallow :=
q ult 3
qallow = 4.05⋅ ksf
Trinity Bearing Capacity_mdk.xmcd
5/5
Print Date: 7/9/2009