Structural Analysis of Tie Back Retaining WallTie-Back Retaining Wall
ByNick Crane Brett Morrow
ForCE 331, Spring 2007
Project 2
The Tie-Back Retaining Wall is 885 Feet Long and Varies in Height from 5 – 40 Feet
ContractorWyatt Construction, LLC
Structural EngineerSchnabel Foundation Company
Location
OwnerUniversity of Alabama
LocationRidgecrest South Residential Community, University of Alabama
Beginning Nowg g
The Tie-Back Retaining wall is C t t d f 114 12 53 H PilConstructed of 114 - 12x53 H-Piles
Driving PilesDriving Piles
The Wall is Constructed from Top to Bottom, Temporary Lagging is Placed Between the e po a y agg g s aced et ee t e
H-Piles in Order to Hold Back the Soil
Drainageg
Tie-Back DetailThe Tie-Backs Anchor the Piles Which Creates a Force That Pulls
A i t th L i O i th L t l S il P d K iAgainst the Lagging Overcoming the Lateral Soil Pressure and Keeping the Soil in Place
Soil Boring at H-Pile Number 37
15°
Ti B k
Brownish-Red Clayey Sand with Gravel
Loose to Firm, Moist 21ft.
Tie-Back
Brownish-Red Silty Sand with Gravel
Firm, Moist 10 ft.Light Gray Fat Clay
Firm to Very Stiff, Moist 4 ft.
H-Pile
Calculations of Lateral Soil Pressure
Drained Shear
Active Lateral Soil Pressure
Specific Weight of
Vertical Soil
Horizontal Soil
Type of SoilStrength
(Φ)Coefficient
(Ka)Depth
(ft.)
gSoil (γ) (lb/ft^3)
Pressure (Pv) (psf)
Pressure (Ph) (psf)
Clayey Sand, Loose to Firm 28° 0.361 21 115 2415 871.815
Silty Sand & Gravel, Medium 32° 0.307 10 115 3565 1094.455
Homogeneous Inorganic Clay, Sandy or SiltySandy or Silty Clay, Medium
Stiff to Stiff 28° 0.361 4 115 4025 1453.025
Typical Calculations
)sin(1)sin(1
Φ+Φ−
=Ka
)28sin(1361 −
DepthPv *γ= PvKaPh *=
2415=(115pcf)*(21’) 872=( 361)*(2415))28sin(1)(361.
+= 2415=(115pcf) (21 ) 872=(.361) (2415)
We Analyzed A Particular Beam (# 37) in th R t i i W llthe Retaining Wall
Free to Move
8.5 ft
#37
Roller Boundary Conditions Representing
35 ft#37Tiebacks16.5 ft
Fixed Boundary Condition
RISA Analysis and Unity Checks for H-Pile
Mu (kft) = (1.6)(Max Moment (kft))
29.345 kft = (1.6)(18.34 kft)
Unity Check
MnMuφ kft
kft5.277
35.29=
Unity Check
= .1058kft < 1, OK
Distributed Load (lb/ft) Moment Diagram (lb-ft)
Analysis of Shotcrete On Face of Wallf CLRFD Method Used for Concrete Design
Max Moment From the Worst Case Earth Pressure Load: 9.22 K-ft
))(')(85(.))((bfcf
fyAsa =)"12)(3)(85(.
)60)(6(."176.12
ksiksiin
=
)12/1)](2
()[)()(9.0( adfyAsMn −=φ
"1761
Mn < ΦMn 9 22<11 91 OK
)12/1)](2
"176.1("5)[60)(6)(.9.0( 2 −= ksiinMnφ
9.22<11.91, OK
a = depth of stress block (in.)As = area of steel (in^2)fy = yield strength of steel (ksi)f’ i t th f t (k i)f’c = compressive strength of concrete (ksi)Bf = effective flange width (in.)d = distance from extreme compression fiber to centroid of steel (in.)
Any Questions?