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Single Drum Rollers with Polygonal Drum

Research results, application recommendations and constructionsite practice

1 Introduction

Increasing the compaction performance of soilcompaction equipment has always been aprimary aim in refining existing machinetechnology. The focus of this matter hastraditionally been more on the physical size ofamplitude or static linear load of the drum.BOMAG has completely re-evaluated andimplemented this construction industryrequirement with the development of thepolygonal drum. Due to the excellent

introduction of the compaction energygenerated by the drum this drum shape canopen totally new performance ranges whenused appropriately. The main advantage of thepolygonal drum is the excellent depth effectwhich enables these machines to be usedespecially for post-compaction of sub-soils orto increase the thickness of layers to becompacted by up to 100%.

2 Polygonal drum

The polygonal drum consists of three axiallyadjacent octagonal elements which arearranged in a staggered position to theneighbouring segment. Laterally welded ringsprevent the drum from tipping, if the middleelement is standing exactly on its edge, and

thereby enables quick transport travel on solidsub-soils (Fig. 1).

Unlike conventional drum forms the polygonaldrums have an excellent self-cleaning effect sothere is no need to use scrapers.

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Fig. 1: The form of the polygonal drum in detail Fig. 2: VARIOCONTROL ensures maximumcompaction energy

The directed vibrator developed by BOMAG(Fig. 2) is used with the single drum rollers withpolygonal drum. This new type of self-regulating system recognises the energyrequirement needed for the compactionprocess and regulates it automatically. TheVARIOCONTROL system works on the basisof the interaction between the drum and the

stiffness of the soil material to be compacted.Compaction energy is automatically optimisedby utilising acceleration signals measured onthe drum. This adaptation means that themaximum compaction energy possible can beintroduced into the soil at any time without thedrum skipping into disadvantageous jumpoperation.

3 Mode of operation

Unlike a round drum where the effective forcedirection remains constant during the rollingprocess, the special compaction effect of thepolygonal drum lies in the permanent changingof its direction of force from plate to wedgesegments and vice-versa. The plate segments

compact by introducing concentrated verticalpressure forces. The wedge segments create adeformation effect in the soil where pushingforces are introduced by the high linear loadand the rotational movement of the drum whichdisplace the soil locally (Fig. 3).

Fig. 3: Effective directions of force with round and polygonal drums

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The combination of peak pressure and pushingforces results in kneading and de-tensioning ofthe soil which promotes compaction. Thiseffectively prevents wedging of soil particleswhich can inhibit compaction. Since this doesnot result in the formation of compactedcovers, the polygonal drum creates theprerequisite for a great depth effect (Fig. 4).Because of localised de-tensioning in front ofand behind the polygonal drum wedge, the soilin the contact area gets “softer” and trapped aircan escape. Distinct plasticizing occurs,whereby the global contact force between thedrum and soil is so greatly reduced thatoperational conditions such as “jumping”,“tumbling” or “chaotic behaviour” do not occur.

Together with the absence of a bow waveoccurring in front of a round drum and with the

excellent positive forward drive, this effectenables a slower travel speed with highercompaction and depth effects in combinationwith a drastically reduced number of passes.

For the reasons already mentioned, this drumtype is in principle suitable for compaction of allsoil types, but because of the specialinteraction between plate and wedgesegments on coarse particle soils you shouldbe aware of the fact that there will be stronglyloosened surface zones. Accordingly, theadvantages of the single drum rollers withpolygonal drum really come into play on highlift heights or when post-compacting subsoils.The distinct formation of a surface pattern onfine particle soils causes better interlocking ofthe layers on dam fills or on sloping layers(landfill construction).

Fig. 4: Tension measurements in the soil reveal the interaction of wedge (= pushing forces) and theplate (= pressure forces) directed into the depth

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4 Completed tests

4.1 Compaction of a 3 metre lift height

A trial area with 3 m layer of an extremely siltygravel (GU*) was laid to test the depth effect ofa 25t single drum roller with polygonal drum incomparison to a single drum roller of the sametype with a round drum. The layer was laid witha bucket excavator without pre-compaction.The following geo-technological measure-ments were carried out for each drum type atdifferent depths after 2, 4, and 8 passes:

• Settlement measurements with a levellingdevice

• Standard penetration test

• Density analyses with a double probe at 10cm intervals, down to 3 m

• Density analyses with a sand substituteprocedure at 50 cm intervals, down to 3 m

• Compressive stress measurements at 50cm intervals

All procedures seem to confirm the effectdescribed in section 3 for the drum typesexamined. The densities detected with thedouble probe are represented in Fig. 5 andFig. 6 as examples. The double probe is anisotope probe, type DS 100 LPC. Twomeasuring tubes inserted into the soil (senderand receiver) measure the density of the soilmaterial between the tubes, always at 10 cmintervals, using radiation absorption (caesium137 radiator).

Fig. 5, Fig. 6: Compaction degrees attained at different depths

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4.2 Improvement of subsoil by post-compaction

The depth effect of the polygonal drum wassystematically examined within the context ofthe pending road construction scheme B 95,south of Leipzig. At the forefront of the roadconstruction scheme there was initially a 5 mdeep subsoil improvement of the existing looseto fairly dense layered, extremely silty togravely sand. The significant depth effect ofthe 26t polygonal drum roller BW 225 D-3 BVCwas proven by a trial compaction of a test areawithin the area of the planned road, which ledto the development of an alternative to theplanned soil exchange. Tests were carried outby FUGRO Consult Leipzig (Fig. 7, Fig. 8).Five independent procedures were used toevaluate the bearing conditions of the subsoil

before compaction and to evaluate thecompaction depth and change in compactionafter 3 and after 8 passes:

• Analysis of the degree of compaction every0.50 m in depth

• Analysis of the dynamic E-modulus with thelight drop-weight device

• Analysis of the standard penetration testresistance

• Analysis of the static penetration testresistance

• Surface levelling for settlement measure-ments

Fig. 7: View of the test and the depression of the surfaceafter 8 passes with the BW 225 D-3 BVC withpolygonal drum

Fig. 8: Soil profile of the test field

All procedures show signs of a uniform result.In summary it can be established that a degreeof compaction of > 100 % can be proven atdepths of 0.7 m to approx. 2.5 below thecompaction level. At 2.0 – 4.0 there is still aclear increase (7-8 %) of compaction (Fig. 9,Fig. 10). From a depth of 4.0 m under thecompaction level, the compaction effectdecreases and comes close to the naturalmagnitudes without compaction in the areafrom 4.0 to 5 m under the compaction level.Loosening of the soil directly under the

compaction level down to a depth of 70 cm issignificant for the special depth effect of thepolygonal roller. On the one hand loosening iscaused by the movement of the drum and thehigh stress of the soil; on the other hand it iscaused by the typical loosening sensitivity ofsand. The decisive factor is the deep and clearincrease in compaction and load bearingcapacity which makes the polygonal druminteresting as an alternative to exchange ofsoil.

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Fig. 9, Fig. 10: The increase in degree of compaction acc. to the Proctor test of the number of impactsdown to 4 m below the working level is clearly recognisable

5 Completed construction measures

5.1 Runway extension at Hahn airport

Hahn airport is booming. Accordingly, in 2002,it became necessary to extend the runway.Extensive ground levelling was to be carriedout in the course of earthworks. In order to beable to choose the layer thicknesses as thickas possible and still achieve perfectcompaction a decision was made in favour of a26t single drum roller BW 225 D-3 BVC withpolygonal drum (Fig. 11). Layer thicknesses of

up to 1.50 m on non-cohesive and up to 1.0 mon cohesive soils were thus laid andcompacted. A single drum roller of the sameweight class was used with a smooth drum toeliminate surface loosening of the compactedlayer package which was caused by thepolygonal drum. In addition to this, smoothingthe surface assured problem-free drainage ofrain water.

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Fig. 11: Compaction of filled layers rangingfrom 1 m to 1.5 m at Hahn airport

Fig. 12: De-tensioning of the concrete superstructureon the A9 motorway at the Schkeuditzer Kreuz

5.2 Breaking up a concrete carriage-way

In the course of renewing the A9 at theSchkeuditzer Kreuz near Leipzig during thesummer of 2002 the old concrete carriagewayneeded to be broken up and removed. Thecontractor made a decision in favour of a 26tsingle drum roller BW 225 D-3 BVC withpolygonal drum (operating weight 26t) forcrushing the carriageway. The surface coverconsisted of 28 cm thick non-reinforcedconcrete. Thanks to the power of the singledrum roller with polygonal drum de-tensioningof the concrete surface was completed after 3passes. This resulted partially in the completedestruction of individual concrete slabs asshown in the illustration or to the formation of acrack structure through the entire slabthickness (Fig. 12). The de-tensioned routesection was in the meantime used as ahaulage road for the construction, until removalof the concrete. In spite of considerablesettlements and skewing, the stability of thesubstructure under the concrete slab was

sufficient to provide sufficient resistance for de-tensioning the concrete carriageway.

5.3 Coarse covering for municipalwaste disposal site

At the municipal waste disposal site in Leipzig-Möckern, a surface cover is currently beingapplied with a 50 cm equalising layer ofcohesive soil and a 1.50 m thick revegetationlayer. Different BOMAG single drum rollerswith smooth drum, padfoot drum and polygonaldrum are being used to compact the layerswith a single layer thickness of up to amaximum of 50 cm (Fig. 13, Fig. 14). Thesurface covering on the waste disposal sitehas a maximum inclination of 35 % or 1:3 onthe steepest construction sections. Due to thepolygonal shape of its drum the BW 213 DH-3BVC (operating weight 15t) is particularlycharacterised by its excellent gradeability onthe soil material to be laid, even on damp soilsurfaces. Furthermore, excellent interlockingwith the next layer is achieved by the wash-board pattern on the surface of the compacted

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soil layer, which ensures very good bonding between the individual soil packages.

Fig. 13: Two single drum rollers with polygonaldrum during compaction of the equalisinglayer

Fig. 14: The wash-board pattern ensures goodbonding between the individual layers

6 Application recommendations

The range of applications for single drum rollers with polygonal drum is explicitly represented in thefollowing table:

ApplicationBW 213 DI BVC

(15t operating weight)BW 226 DI BVC

(26t operating weight)Comment

Divided according to construction task

Post-compaction ofsubsoil layers ++ +++ Loosening of the surface

Compaction of high liftheights ++ +++ Only limited suitable for thin lift

height

Crushing of carriagewayswith concrete surface - +++ Good support is necessary

Differentiation according to soil type

Compaction of non-cohesive soil ++ ++ Strong surface loosening

Compaction of mixedparticle soils +++ +++ Moderate surface loosening

Compaction of cohesivesoils +++ +++ Minimal or no surface

loosening

Notes:

+++ very well suited ++ suitable - not suitable

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7 Summary

Single drum rollers with polygonal drumexpand the range of applications forconventional single drum rollers quiteconsiderably. The great depth effect of up toapprox. 4m and the versatility of this drum formare particularly outstanding, which means itcan be used for compaction of nearly everyexisting soil type, whether it is cohesive, non-cohesive or mixed particle soil. In addition tothis, the 26t design can be used to de-tensioncarriageways with concrete surface. As a resultof the effect of the polygonal drum, the fullperformance capacity of this drum shape onlycomes into play with larger layer thicknesses,because of the detected surface loosening ofthe layer to be compacted during compactionof mixed particle and non-cohesive soils. Ifnecessary, a single drum roller with smoothdrum should be used to achieve the definedcompaction goals, also in the areas near thesurface of the laid soil layers.

8 Bibliography

Fugro Consult GmbH: Technischer Bericht,Ermittlung der Einwirktiefe einer Polygon-bandagenwalze zur Bodenverbesserung Bau-vorhaben (Technical report, Construction planfor detecting the depth of effect of a polygonaldrum roller to improve the soil); B95 – areaaround Borna, Lot 2 – earthworks,Markleeberg, 2003

BOMAG GmbH: Research report, Wirkungs-weise der Polygonbandage (Effect of thepolygonal drum), Boppard 2004