REINFORCED EARTH WALL

             REINFORCED EARTH WALL
 

I am mentioning hereunder some merits of construction of precast panel instead of cast in situ Retaining Wall.

A)COST: To construct RE Wall is much more cost effective than cast in situ retaining wall. It was analyzed and found that 20 -25% cost we can save if we construct RE Wall instead of retaining wall.

B) TIME: Time has a great essence to any contract.  Lot of time can be saved if we construct facia panel, synchronies program also possible if we plan to construct RE Wall. Below we mention some practical aspect which shows how RE Wall construction is time effective in comparison to retaining wall.

Ø  In RE Wall construction we can perform 2 activity simultaneously in a particular time frame of time  casting and fixing the RE Panel and earth work but in retaining wall we can perform single work in a time frame ,either casting of wall or earth work.

Ø   In RE Wall construction there are no idle construction phases. In Retaining wall construction there  are 7 -14 days idle construction phase. Until or unless cast in situ wall do not achieve the required  strength we cannot able to perform the next phase of work i.e. compaction of earth layer upto the RE WALL level.

Ø   After deshuttering the retaining wall it shall generally take minimum 4 -5 days for reuse shuttering  and reinforcement for the next lift. In case of facia panel casting it generally takes 24 hrs to reuse  the shuttering.

Ø   Progress Retaining wall casting depends on availability of front at site, Facial panel casting-

    progress is totally independent of front at site.

Ø   In case of urgency steam curing procedure can be adopted in facia panel casting, but in RE Wall  casting curing can be perform only using the conventional method which takes minimum 14 days Over all it was observed 80% time can be saved if we construct RE WALL instead of retaining wall.

Ø   AESTHETIC LOOK: RE Wall have a good and variety of aesthetic look in comparison of retaining  wall.

Ø   QUALITY: Degree of quality control is much higher in Precast Panel over cast in situ retaining wall.

Ø   All and above Precast panel constructions are accepted as good and variant solution to cast in situ.

STANDARD OR FULL-HEIGHT ‘’AN’’ PANELS OF SIZE 1.6M X 2.0M (WHERE 1.4 IS THE NOMINAL HEIGHT AND OTHER 2.0M – IS THE C/C DISTANCE BETWEEN CENTER LINE AXIS OF THE AXIS OF THE PANEL SHOULDER) ARE USED FOR THE MAJORITY OF THE WALL EACH PANEL IS REFERRED BY A LETTER WHICH INDICATES THE  TYPE OF PANEL AND A NUMBERS, WHICH INDICATES THE NUMBER AND TYPE OF CONNECTOR AND ALSO THE TYPE OF POLYMERIC STRIP ATTACHEMENT WITH A PARTICULAR PANEL.

Ø  SETTING UP OF CASTING YARD

Ø   THE FOLLOWING FACILITIES SHALL BE SETUP IN ORDER TO IMPLIMENT THE CASTING OF THE

              

 PANELS IN MOST EFFICIENT WAY, AS WELL AS TO PROVIDE THE BEST POSSIBLE QUALITY OF  

 WORK:-

Ø  CASTING AREA

Ø  CASTING AREA SHOULD NOT BE LOCATED IN AREA WHICH WILL MAKE BASIN OR LOW LANDS OF A PLOT WHICH COULD GIVE RISE TO POUNDING OF WATER IN RAINY SEASON.

Ø  IN CASTING AREA PRECAUTION TO BE TAKEN UPTO PREVENT CASTED UNITS GETTING SPOLDING FROM AFFECTS OF RAIN, SUNLIGHT ETC.

Ø  A CONCRETE, BRICK OR SIMILAR HARD FLOOR ASSURES THAT THE BASE PLATES OF THE MOULDS ARE HORIZONTAL AND PROVIDES GOOD CONDITIONS OF WORK. SUPPORT PEDESTAL BEAM MINIMUM 35CM WIDE SHALL SUPPORT THE BASE PLATE OF THE MOULDS. THEIR PURPOSE IS TO PROVENT THE MOULDS FROM UNDESIRABLE DEFORMATION. AS WELL AS TO PROVIDE BETTER CONDITIONS OF WORK.

FIXING OF MOULDS

        

TO FIX THE SHUTTERS TO THE BASE PLATE. THE FOLLOWING PROCEDURE MUST BE FOLLOWED:-

Ø  PLACE THE TOP, BOTTOM AND SIDE SHUTTER ON THE TABLE. WITHOUT  FIXING THEM YET.

Ø  PLACE THE CORNER SHUTTERS.

Ø  FIX THE SHUTTER TO THE BASE PLATE.

Ø  FIX THE SHUTTER BETWEEN THEM.

Ø  IF THE CUT SHUTTER IS USED. ASSURE THAT ITS POSSITION IS CORRECT.

Ø  CASTING

Ø  PREPARATION :-

Ø   PRIOR TO CASTING, THE BASE AND SIDES ARE CLEANED SO THAT THERE IS NO DUST, CONCRETE WASTE ON THE BASE, BUFFER TO BASE PLATES WILL BE DONE AS AND WHEN REQUIRED.

Ø  MOULDS ARE OILED WITH APPROVED QUALITY OF FORMWORK OIL AND EXCESS  OIL IS TO BE REMOVED.

PLACING OF THE PANEL ACCESSORIES

Ø  TO LIFTING ANCHORS WITH THEIR RUBBER RINGS ARE PLACED. THESE  RUBBER RING CAN BE USED SEVERAL TIMES AND THEREFORE SHALL BE COLLECTED BEFORE REMOVING THE PANEL FROM THE TABLE.

Ø  FIX THE OMEGA SELEEVE OF REQUIRED NUMBERS AS SHOWN IN THE  PANEL DRAWINGS.

Ø  REINFORCEMENT AS PER THE PANEL DRAWINGS IS PLACED. 

Ø  POURING THE CONCRETE

Ø  THE CONCRETE IS POURED IN EACH UNIT WITH A MINIMUM INTERRUPTION.

Ø  A NEEDLE VIBRATOR TO BE USED TO COMPACT THE CONCRETE.

Ø  IT MAY BE SUPPLEMENT THIS ACTION BY HAND TAMPING (MALLET) IN THE CORNERS.

Ø  IT IS IMPERATIVE TO MAINTAIN SLUMP OF THE CONCRETE BETWEEN 35 TO 45MM,  DEPENDING UPON PREVAILING TEMPERATURE, THE CONCRETE SUPPLYING AGENCY SHOULD TAKE CARE OF THE WEATHER AFFECTS TO ENSURE CONSISTENCY OF SLUMP AT THE AMBIENT TEMPERATURES.

Ø  THE CONCRETE POURED IN 2-3 STAGES, EACH STAGE SHALL BE SPREADED USING

   SPADE/FORK THEN VIBRATED BY NEEDLE VIBRATORS.

Ø  CURING :-

Ø  THE WATER CURING SHALL START AS SOON AS THE CONCRETE STARTS TO DRY.

Ø  A CURING COMPOUND IF NECESSACRY MAY BE SPRAYED OR COVERED WITH DARK TARPULIN JUST AFTER CASTING IN CASE OF VERY HOT TEMPERATURE.

Ø  PANEL MAY KEEP COVERED IN A HESIAN CLOTH PRIOR TO HANDLE THEM. 

Ø  PANELS STACKED IN CURING STACKS MAY BE CURED BY SPRINKLERS PLACED AT A

Ø   DISTANCE AND IN NUMBERS TO GIVE PROPER COVERAGE TO THE UNITS TO BE CURED.      

Ø  SPRINKLING CURING MAY BE FURTHER SUPPLEMENTARY BY MANUAL PIPE CURING WITH A    SPECIAL ATTENTION TO AREAS WHICH ARE BEYOND OF PRINKLERS SPRITZ.

Ø  THE PANELS SHALL STAY ON THE CURING AREA FOR 14 DAYS. PLACE NOT MORE THAN 5 (FIVE) PANELS IN A STACK AND WOODEN BLOCKS TO BE USED AS SEPARATOR BLOCKS BETWEEN STACKED.

Ø  HANDLING OF FACIA PANELS

Ø  DE-MOLDING

Ø  SIDE SHUTTER WILL BE REMOVED AFTER 6/7 HOURS (MAY BE EXTENDED DURING WINTER  CONDITIONS) AND THE PANELS WILL BE LIFTED FROM THE BASE PLATE AFTER 20 HOURS OR  ATTAINING OF CUBE STRENGTH OF MINIMUM 10 MPA.

Ø  REMOVAL OF THE PANEL FROM THE BASE PLATE:-

Ø   THE PANEL SHALL BE LIFTED BY MEAN OF A FOUR POINTS SLING USING AN PPROPRIATE    CAPACITY OVERHEAD GANTRY CRANE OR FORKLIFT.

Ø   IT IS TO BE NOTED THAT THE PANELS SHALL BE LIFTED HORIZANTALLY ONLY WITH OMEGA SLEEVE AT FOUR CORNER TO AVOID ANY POSSIBLE DAMAGE TO OMEGA SLEEVE DURING LIFTING AND RE-HANDLING PROCESS.          

Ø      JERKING AT THE TIME OF LIFTING AND SHIFTING AT THIS STAGE SHALL BE AVOIDED.

Ø  STACKING OF FACIA PANELS

Ø  STACKING IN THE CURING AREA :-

Ø  THE STACKS OF PANELS SHALL BE PLACED ON A HORIZONTAL CONCRETE SURFACE.

Ø   THE SURFACE SHALL HAVE BEEN PREVIOUSLY COMPACTED.

Ø  THE MAXIMUM HEIGHT ALOOWED IS 5 (FIVE) PANELS IN ONE STACK.

Ø  PANELS SHALL BE STORED IN A HORIZONTAL POSITION WITH 10CM SPACER CUBES BETWEEN THEM IN ORDER TO PREVENT THE CONNECTOR FROM BEING BENT OR DAMAGE.

Ø  IT IS DESIRABLE THAT SOME PLASTIC/RUBBER PADS SHALL BE FIXED ON THE TOP WOODEN  BLOCKS TO PREVENT THE SPOTS ON THE FACE OF THE PANELS (OPTIONAL).

STACKING IN THE YARDS :-

Ø  THE STACKS OF PANELS MUST BE PLACED ON A HORIZONTAL COMPACTED SURFACE.

Ø  THE USE OF RUBBER/PLASTIC PADS IS RECOMMENDED IF THERE IS ANY RISK OF RAIN DURING THE STORAGE PERIOD, WHICH IS THE MOST PROBABLE CASE (OPTIONAL IF VISIBLE MARKS ARE SEEN). THE PANELS CAN BE STORED IN STACKS UP TO 5 NOS. 

TRANSPORTAION OF FACIA PANELS

Ø   THE PANELS SHALL BE TRANSPORTED SO AS TO PREVENT THE TOPPLING, AS WELL AS TO PREVENT UNDESIRABLE CONSTRAINTS IN THE PANELS, STACKS OF PANELS SHALL NOT HAVE MORE THAN 5 (FIVE) UNITS DURING TRANSPORTAION.

Ø   SEPARATING EACH OTHER BY SUITABLE PADDING TO PREVENT THR BREAKAGE/TRANSIT  DAMAGES.

Ø  PRIOR TO THEIR ERECTION, THE PANELS SHALL BE STORED ON SITE IN THE SAME CONDITIONS AS ON THE PRE-CASTING YARD STACKING AREA.

Ø  REINFORCED EARTH WALL SYSTEM-CONSTRUCTION METHODOLOGY

Ø   THE WALL SYSTEM CONSIST OF ORIGINAL GROUND, CONCRETE LEVELLING PAD DRAINAGE  ARRANGEMENT CATERING TO CONSTRUCTION AND SEVICE CONDITIONS, TERRATEE DISCRETE WALL FACING PANELS. DRAINAGE SYSTEM, POLYMERIC STRIP, ACCESSORIES AND FITINGS, SELECTED BACKFIL AND TRAFFIC LOADS AND SURCHARGE. ALL OF THESE ITEMS HAVE AN EFFECT ON THE PERFORMANCE OF THE RE WALL AND ARE TAKEN INTO ACCOUNT IN THE DESIGN ANALYSIS. A CHANGE IN ANY OF THESE ITEMS WOULD HAVE A DETRIMENTAL EFFECT ON THE WALL.

Ø  SITE PREPARATION

Ø   FOR THE LENGTH OF THE RE WALL SECTION TO BE BUILT. EXCAVATE THE SIRE TO THE DEPTH, GRADE AND WIDTH SPECIFIED IN NECESSARY, AS PER SECTION 201 AND 305 OF MORHT SPECIFICATION.

Ø   LEVEL AND COMPACT THE FOUNDATION IN ACCORDANCE WITH THE PROJECT SPECIFICATIONS/CONSTRUCTION DRAWING.

Ø   ESTABLISH FORMWORK FOR LEVELLING PAD FORMWORK SHALL CONSIST OF TWO NUMBER OF  ISMC 150 CHANNELS, IN-PLACE ARRANGEMENT TO MARCH THE SECTION AND ALIGNMENT OF LEVELLING PAD.

Ø   MARK THE PAD ALIGNMENT ON THE COMPACTED FOUNDATION LAYER CONSIDERING THE ADDITIONAL WIDTH(C/C DISTANCE BETWEEN TWO PADS) WILL VARYDEPENDING ON HEIGHT OF WALL AT THAT LOCATION.

Ø   POUR THE CONCRETE LEVELLING PAD, THE PAD SHOULD BE CURED FOR 3 DAYS PRIOR TO USE, OR LONGER IF REQUIRED THE CONCRETE FINISH MUST BE SMOOTH AND FLAT AND MUST NOT  VARY FROM THE DESIGN ELEVATION MORE THAN 3mm.

Ø  INSERT 16MM DIAMETER PEGS IN THE CONCRETE, CARE TO BE TAKEN WHILE DRIVING THE PEGS THAT FINISHED CONCRETE SURFACE SHOULD NOT GET AFFECTED, IF PLANS CALL FOR THE  WALL TO HAVE A STEP UP IN ELECATION, POUR THE HIGHER LEVELLING PAD SO THAT ITS  SURFACE IS 0.800M ABOVE THAT OF LOWER PAD. LEAVE A 350mm GAP BETWEEN THE NEW PAD. 

Ø  ERECTION OF PANELS

Ø  SNAP A CONTROL LINE ON THE SURFACE OF THE LEVELLING PAD USING LIME OR MARINE BULE. ANCILLARY REFERENCE POINT SHOULD BE MARKED ALONG WITH CONTROL LINE. INDICATING THE POSITION OF CURVES, CORNERS, SLIP JOINTS ETC. IT IS DESIRABLE TO MARK CONTROL POINTS ON THE CURVE AT CLOSER INTERVAL

Ø  PLACE THE FIRST B(n) (HALF) PANEL 1 ON THE LEVELLING PAD. ALIGN THE FACE OF THE PANEL  ALONG THE CONTROL LINE ON LEVELLING PAD, AND USING HARDWOOD WEDGES, SET BATTER OF THE PANEL,

Ø  PLACE THE SECOND B(N) PANEL 2 ON LEVELLING PAD. ALIGN IT WITH THE CONTROL LINE, AND  SET IT THE CORRECT DISTANCE FROM THE PANEL 1.

Ø  PALCE A(N) (FULL) PANEL 3 BETWEEN THE TWO HALF PANEL 1 AND 2, CENTER THE PANEL TO ENSURE EQUAL VERTICAL JOINTS. WHEN PLACING PANELS, MATCH THE CENTER OF INDENT ON SHOULDER OF ONE PANEL TO THE CORRESPONDING MARK IN THE ADJACENT PANEL, SET THE PANEL’S BATTER AS BEFORE, CLAMPS THE PANEL TO PANELS 1 AND 2 TIGHTEN CLAMPS  SUFFICENTLY TO HOLD THE PANEL IN POSITION WITHOUT MOVEMENT. 

Ø  WHEN THE PANELS HAVE BEEN SET RE-CHECK WALL ALIGNMENT BY SIGHTING ALONG THE  WALL FACE. IF NECESSARY, ADJUST PANELS TO OBTAIN A TRUE LINE. CHECK THE SET VATTER  AND BEGIN BRACING THE INITIAL COURSE OF PANELS. USE TIMBER BRACE FOR EACH FULL PANEL. COMPACTION SHALL NOT BE LESS THAN 95% OF THE MDD BEYOND 1.5M FROM THE REAR FACE OF THE PANELS. HOWEVER, IN THE ZONE WITHIN 1.5M FROM REAR FACE OF THE PANEL, COMPACTION SHOULD NOT BE LESSER THAN 90% OF THE MDD.

Ø  DURING CONSTRUCTION CHECK THE OVERALL SLOPE OF THE STRUCTURE AT EACH COURSE USING A TEMPLATE.

Ø  PLACE REINFORCING POLYMERIC STRUP ON THE COMPACTED BACKFILL POSITION IT PERPENDICULARLY TO PANELS. FOLD THE POLYMERIC STRIP AT THE PANEL FACE AND PASS THE  FOLDED PORTION THROUGH THE OMEGA SLEEVE. PULL THE POLYMERIC STRIP IN POSITION, THE  POLYMERIC STRUP MUST BE PLACE AT 5%DOWN SLOPE.

Ø  FOR ALL HORIZONTAL JOINTS OF PANELS 200MM WIDE FEOREXTILE SHALL BE USED AND ALL VERTICAL JOINTS OF PANELS 400MM WIDE GEOTEXTILE SHALL BE USED. 

Ø  BACKFILLING

Ø   THE CONTRACTIBILTY AND PERFORMANCE OF A REINFORCED EARTH STRUCTURE ARE DIRECTLY RELATED TO THE BACKFILL QUALITY AND IN THE MANNER IN WHICH IT IS  PLACED.

Ø   SPREAD THE BACKFILL BY PUSHING THE PILE PARALLEL TO THE PANELS AND WIDROWING IT TOWARD THE PANELS AND TOWARDS FREE ENDS OF THE POLYMERIC STRIPS.

Ø   IF POLYMERIC STRIP LENGTHS IS LONG, A SECOND LOAD MAY BE REQUIRED TO BACKFILL TO THE END OF THE STRIPS, IF SO, DUMP AND SPREAD THIS LOAD ONLY AFTER SPREADING THE FIRST.

Ø   THE SELECTED BACKFILL SHALL BE PLACED AND COMPACTED TO THE FIRST ROW OF CONNECTIONS TO THE DENSITY AS SPECIFIED THE COMPACTED FILL LEVEL SHOULD BE AT OR SLIGHTLY HIFHER THAN THE PANEL CONNECTIONS LEVERL. ON THE INTIAL ROW OF PANELS (AND ONLY THE INTIAL ROW OF PANELS) THE BACK FILL IS NOT PLACED AGAINST  THE PANEL UNTIL THE FIRST ROW OF PLYMERIC STRIP HAVE BEEN CONNECTED & THEN FILL IS PLACED ON THE POLYMERIC STRIP, THIS TO KEEP THE BOTTOM OF THE PANELS FROM ‘’KICKING OUT’’, FROM THAT POINT, THE BACKFILL IS BROUGHT UP UNIFOTMLY  FROM THE BACK OF THE PANELS TO THE END OF POLYMERIC STRIP.

Ø  COMPACTION

Ø  BEFORE COMPACTION IS STARTED PLACE PROPS SO AS NOT TO ALLOW ANY OUTWARD MOVEMENT OF PANELS FOR 2 LAYER, WEDGES MUST ALSO BE USED TO PREVENT SUCH MOVEMENTS.

Ø  COMPACTION EQUIPMENT USED WITHIN 1.5M OF THE WALL SHOULD BE A WORK BEHING ROLLER OR PLATE ROLLER WEIGHING NOT LESS THAT 1 MT CAPACITY ENSURING DENSIT OF MIN. 90% OF MIXIMUM PROCTOR DRY DENSITY.

Ø  BEYOND 1.5M FROM THE WALL FACING PANELS A ROLLER UPTO 8 TONNES VIBRAORY ROLLER WITH 8 TO 10 PASSES MAY BE USED SUBJECT TO SARISFACTORY PERFORMANCE.

Ø  BACKFILL COMPACTION SHALL BE PERFORMED IN SUCH A WAY THAT THE COMPACTOR  SHALL MOVE IN A DIRECTION PARALLEL TO THE WALL FACING PANELS AND WORK TOWARD THE END OF THE SOIL REINFORCEMENT AWAY FROM THE WALL FACING. TO ACHIEVE MIN. 95%  OF MAXIMUM MODIFIED, PROCTOR DRY DENSITY.

Ø  THE COMPACTION EQUIPMENT ROLLS PARALLEL TO THE WALL FACING, COMPACTION STARTS AT LEAST 1.5M FROM THE WALL AND WORKS TOWARDS THE END OF THE REINFORCEMENT.

Ø  REPEAT ABOVE STEP UNTIL THE TOP OF THE WALL IS REACHED. AS SOON A PRACTICAL THE FRONT OF THE WALL SHOULD BE BACKFILLED . THIS SHOULD OCCUR PRIOR TO REACHING THE TOP OF THE WALL.