Cons t Manual

7/30/2019 Cons t Manual

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2011 Rev. 1.5

Construction Procedures


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IntroductionThis manual presents the methods and pro-

cedures necessary for the proper erection ofa LOCK+LOAD retaining wall.

Each LOCK+LOADmodule consists of twopieces, a panel and counterfort that are eas-ily assembled at the project site; as shown inthe picture above.

LOCK+LOAD alsohas several unique aspectsthat require procedures different and at timesin direct contravention of procedures com-monly used in the building of other masonryblock retaining walls.

First and most importantly, LOCK+LOAD allowsand requires full compaction all the way tothe face of the wall (back of the panel). Thisis required because the reinforced concretefascia is held in place by friction between thebackfill and the counterfort. Typical masonrywall procedures require only light compactionwithin three feet of the wall face to avoid mis-alignment due to compaction forces. This

zone of light compaction may cause

problems later during the service life of the

wall structure.

The LOCK+LOADwall system provides uniformcompaction from the face to the far end ofthe soil reinforcement creating a monolithicmass of reinforced soil faced with 5500 psisteel reinforced concrete.

Second, each LOCK+LOADmodule is independ-ently stable and does not stack upon thelower wall modules. This allows the wallstructure to consolidate as it is being erected

and therefore eliminates unwanted stress inthe wall face and soil reinforcement.

Third, LOCK+LOAD places the soil reinforcement(geo-grid etc.) at the mid-point of the panelwhere the grid is contact only with the backfill(just as it is everywhere else in the fill) andso cannot be damaged by being sandwichedbetween rigid masonry blocks.

The Vertical locking force on the LOCK+LOADcounterfort is always larger than the horizon-tal loads placed upon the wall panel allowinglarge compaction equipment to be used inclose proximity to the wall face.


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Layout Base RowConsult Engineer: Locate survey control

points and confirm with the engineer thatfoundation soils have adequate bearing ca-pacity for the wall height and then if neces-sary strengthen the foundation where re-quired. Once foundation condition, wall planand schedule is approved construction maybegin.

Excavate for the foundation pad: Removesurface vegetation and organic soils andthen excavate a minimum 36 wide founda-tion to 6 below base elevation. If there are

elevation steps in the foundation cut eachstep 16 higher than the next lower level. Op-tionally, cut steps at 8 intervals if half highpanels are to be used for transitional steps.

Access to a laser level this will greatly accel-erate this process allowing grade to bechecked all along the wall alignment. Otherleveling devices may be used, but must beaccurate. Foundation cut is a minimum of

36 wide to allow for a drainage pipe atthe foundation level behind the counterforts

or geo-grid. Drain system placement, is site,and soil specific and must be constructed inaccordance with the plan.

Compact foundation pad: Place Minusstone 6 deep or as required and compact to95% Modified Proctor density for building thewall foundation: maintain 16 steps as nec-essary. When the base pad is compactedlayout panels face down along the wall align-ment and attach counterforts.

Set Bottom Row:Except for special circumstances always be-gin the building a wall from the lowest pointof the alignment. Set one panel at each endof the wall section to be constructed. Checkpanel with survey markers for correct posi-tion from survey hub. Place carpenters levelon back of panel and plumb by adding or

subtracting grading material under counter-fort until panel is vertical. Place level on topof panel and level horizontally in the samemanner. Check top elevation of both panelson each end of wall segment being con-structed with laser level to ensure run will belevel.

Compaction: Compact in 8 lifts using a


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Base Row cont.Secure a metal stake at each, set and lev-

eled, panel ( 50 to 80 ft apart ) and run astring line the entire distance of wall segmentto be constructed. Additional stakes at maybe added to eliminate sag in the string line.Double check alignment, with laser or surveyinstrument. Now set the intervening panelsalong the string line.

Use wedges between the counterfort headand the panel back to remove play and makethe module rigid.

At this point, the top rear of panels will varyslightly off the string line. Adjust panel align-ment by adding or subtracting gravel fromunderneath each counterfort until all panelsalign with string. If adding material undercounterfort, make sure to tamp material tight.Height adjustment, if necessary, is con-

ducted in the same manner adding or sub-

tracting grading material. Slight variations ofpanels exceeding string line height, can beadjusted by tapping the top of the panel witha sledge hammer using a piece of scraplumber to prevent chipping of the concrete(similar to setting bricks in mortar). Low pan-els can be adjusted up by tipping them for-ward and adding gravel under base of panel

to raise its elevation.

Invest the necessary few minutes to perfectthe alignment of the bottom row as it willsave time later and helps assure a beautiful,strait, level, aligned wall.

After some practice this process becomesquick, efficient, and productive. Accuratealignment and quality compaction are the dif-ference between a good and excellent wallinstallation.


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Drainage & BackfillPlace drainpipe: and drainage stone

(aggregate) as specified on the plans, or asapproved by engineer. On short (4 ft & less)non-engineered walls the drainpipe will belocated at the rear of the counterfort and onthe leveling pad (lowest elevation). On wallsusing geo-grid it may be at the backend ofthe geo-grid. Check the plans!

Backfill : Start by placing backfill materialover the tail of the counterfort first. Keep aminimum of 2.0 ft. of select 3/4 clearcrushed rock material behind wall face forthe foundation of the next row. Beyond thisuse the specified backfill material. Placementis approximate and need not be perfect.Panel rows should be back filled and com-pacted in two lifts of ~8 with the second liftrising to approximately 2 above panels topedge so that the compacted soil will consoli-date to top of panel. Make minor field adjust-ments as necessary.

For rows that will contain soil reinforcementthe grid is placed after the first lift of fill iscompacted so that geo grid is located atabout the mid-point of the wall panel.

Once select fill material is placed over thecounterforts the specified backfill can beplaced, leveled and compacted in ~8 liftswithin the reinforced soil zone using heavyequipment. Take care not to displace the wallalignment or damage soil reinforcement.


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Compactionplate compactor of 800 lbs. minimum, since

the ability to compact 18 of soil is required toerect a row of panels two lifts will be re-quired. If a smaller compactor is used liftsmust be reduced to 8 maximum and eachcoarse of panels compacted in three lifts.Compaction to 95% Modified Proctor is re-quired and should be checked and verifiedby the Geotech.Even better compaction equipment are large

reversible diesel plate compactors with oper-ating weights of 900 to 1100 lbs. [Examples:Wacker models (BPU-3345) or Multi Quip(MVH-200DA) or equivalent]. Roller com-pactors can safely be used to within 16 ofthe wall face. All compaction activity alwaysbegins with compacting over the tail of thecounterfort first locking it into place.Compact along the horizontal distance of thewall, and then proceed to back of the rein

forced fill zone. Finally finish with the plate

compactor up to and abutting the wall face.Note: This differs from typicalmodular block wall systemsthat specify Light Equip-ment compaction within 3 to5 behind the wall face.

LOCK+LOAD retaining walls require compactionto the wall face, because the counterfort is

the facings attachment to the soil mass.

Safety dictates keeping large ride on rollers aminimum of 16 behind the wall face and us-ing the large plate compactors to compactthis area. For taller walls local codes mayrequire that this no ride zone increase.

Leveling for Next Row: Using a flat pointshovel scrape along the first 5 of wall face


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Subsequent Rowsusing the top of the previous coarse as a

guide until level.

Note:PANELS DO NOT STACK!!!

Back needs to be level with the top of previ-ous panel and compacted. The 1 gap at thebase of the next panel is for isolation, move-ment during a seismic event, and to allow formass consolidation in taller walls. Repeatlayout & align step 4, backfill step 6 and,compact step 7, etc.


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Now carefully backfill over the grid, to the topof wall panel, keeping the geo-grid tight andfree of wrinkles., A minimum of 2 foot of se-lect material is to be maintained at the wallface. Compact as previously described be-ginning over the tail of the counterfort to thepanel back and then toward the back end ofthe geo-grid Insure that the geogrid remainsin contact with the panel back after compac-tion.

When the back fill is compacted to specifica-tion and leveled to the top of the panels thecompaction should be checked and ap-proved by the engineer, as required, beforeconstruction proceeds. Once approved thisconstruction sequence repeats for the nextand subsequent rows until the wall is com-pleted.

Geo-grid Placement: When installing geo-grid

in the reinforced soil mass, backfill only ap-proximately the way up panel back makingsure that the fill is evenly distributed andabout level over the whole grid area. Com-pact, this lift of fill being careful over thecounterforts. Roller compactors may not beused to compact on the first lift over the, bar-ley covered, counterforts since they may bedamaged.

Once compacted and ~leveled place geo-grids with grid directional strength, perpen-

dicular to the wall face. Check against theplans to insure that the geo-grid is the properstrength and length for its position in the re-taining wall structure. Place the geogrid sothat a minimum of 3 inches remains verticaland in contact with the panel back.

Subsequent Rows cont.


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The Steps In Pictures


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VariationsRadius Inside and Outside: Curve align-

ment can be accomplished in several waysan easy method for short radii is to use arope from a single radius point and swingingan arc. Set the first panel and the nextpanel will abut it and the opposite edge dis-tance is checked with the rope. Longer ra-dius curves generally will be set as off setsfrom survey stakes. Once several units areset a string line is run along the outside ofthe panels and slight a variations removed.For tight curves of 8 radius or less: use halfwide panels and construct in the same man-

ner as standard curves.

Corners: LOCK+LOAD does not need to bebuilt on bond but if it is required, for aes-thetic reasons, the panels will need to betrimmed for inside corners. The need to trimpanels is due to the wall batter. On insidecorners the length of subsequent rows growsby 40 mm or 1 9/16. Using a diamond bladecut off saw mark cuts on panel back accord-ing to the attached detail and trim to lengthsrequired to maintain the split bond.

Outside corners are made using theLOCK+LOAD corner panels. When possible be-gin walls at outside corners to minimizepanel trimming if on bond erection is re-quired.

Note: Corner counterfort mayneed to be chipped to round thehead so that it can be rotated to

avoid interference with adjacentpanel counterforts.


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Step by Step

Retaining Module Assembly

Prepare Foundation & Layout 1st Row

Compact Over Counterfort Tail First

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