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1 The conventional (non LRFD) calculation methodology generally adheres to the AASHTO Standard
Specifications for Highway Bridges (17th Edition, 2002). Additional methods and practices follow the FHWA
Mechinically Stabilized Earth Walls and Reinforced Slopes Design and Construction Guidelines, NHI-00-043.
Specific methods, procedures, equations, and nomenclature can be found in the Gravity Wall DesignMethodology and Example Gravity Calculations in the Engineering Manual and available on the Stone
Stron web site www.StoneStron .com.
2 The end user is res onsible for all hi hli hted in ut values and chan es to unhi hli hted ro ram default
USER NOTES
Stone Strong LLC is the owner of this computer file and retains all common law, statutory, and other reservedrights including the copyright. Limited license is granted to copy, print, or use this spreadsheet as an aid in
performing design calculations for Stone Strong retaining walls. Stone Strong LLC makes no warranties, either
expressed or implied, of merchantability or fitness for any particular purpose, and accept no responsibility for the
accuracy, suitability, or completeness of information contained herein.
Licensee acknowledges that this computer file is the proprietary property of Stone Strong LLC. Licensee certifies
that he/she will maintain this computer file as a confidential trade secret and will not copy or distribute the file to
any person or entity that is not acting under his/her direct supervision and control.
This calculation spreadsheet is provided for general information purposes only. Anyone making use of
this spreadsheet and related information does so at their own risk and assumes all liability for such use.
Site specific design should be performed by a licensed Professional Engineer based on actual site
conditions, materials, and local practices.
values. Properties for soil and other materials should be obtained through testing or from recommendations
by an experienced geotechnical engineer with knowledge of local materials and practices.
3 The backfill height defaults to the total wall height, assuming that the wall is backfilled to the top of any Capunits or Dual Face units. The backfill height may be overwritten where the Cap or Dual Face units are
allowed to project above grade. The total wall height and backfill height are measured from the top of the
base pad, neglecting embedment. The exposed height is the total backfill height less the embedment depth.
15 The base materials, configuration, and properties are entered to the right of the printable space. Sliding
resistance across the surface of the base is evaluated using a composit friction coefficient based on the
contributory area for each interface combination. The calculated coefficient can be overridden by entering a
composite coefficient in the OVERRIDE entry cell. If ANY value is entered in this cell, it will be used to
calculate the sliding resistence regardless of the other values entered. The sliding resistence routine also
includes evaluation of sliding failure throught the foundation soils below the base, and the lower result is
reported as the sliding resistance Rs.
16 The aggregate base thickness may be adjusted for site and other conditions. The base thickness is typically
set at 225 mm, but may be reduced to 150 mm for shorter walls (1.8 m or less) or for hard and stable
foundation soil conditions. In soft conditions with lower allowable bearing pressures, the contact pressure
may be reduced by increasing the thickness of the granular base. The horizontal dimension of the base
should be set to provide a minimum projection in front of the face equal to 1/2 of the base thickness plus 75to 150 mm inches for construction tolerance. The rear projection of the base behind the tail should provide
at least 75 to 150 mm for construction tolerance.
17 The thickness of a concrete base is typically set at 150 mm unless site conditions dictate a thicker base to
distribute the wall weight over soft soils. When an unreinforced concrete base is used, the front projection of
the footing should be at least equal to the concrete thickness. For calculating the equivalent bearing width
and the contact pressure, a 1:1 distribution is taken through the unreinforced concrete base instead of the
1:2 distribution traditionally used for an aggregate base. If a reinforced concrete footing is used, the front
projection dimension is used to calculate the equivalent bearing width regardless of the thickness.
18 An allowable bearing pressure may be entered if specified by the geotechnical report or other requirements.
This allowable bearing pressure will override the calculation of allowable bearing pressure based on the
entered properties of the foundation soil. If a net allowable bearing pressure is indicated, then the
overburden at the toe will be added to determine the gross allowable bearing pressure. If unsure as to
whether the specified bearing pressure is net allowable, select "gross" to indicate gross allowable
(conservative). If an allowable bearing pressure is not entered, bearing capacity is calculated using the
Vesic equation. The calculation includes the thickness of the aggregate base and the cover depth in theembedment factor D f .
19 Internal stability analysis can be performed at any unit interface within the wall. To switch to internal
analysis select "internal" in cell O10 At a minimum internal stability should be checked at each change in