the evolution of reinforcement of the advance core using fibre

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LUNARDI AND BINDI: THE EVOLUTION OF REINFORCEMENT OF THE ADVANCE CORE USING FIBRE-GLASS ELEMENTS

FELSBAU 22 (2004) NO. 4

The Evolution of Reinforcementof the Advance CoreUsing Fibre-Glass ElementsBy Pietro Lunardi and Renzo Bindi

Die Entwicklung der Verstärkungdes Bereichs vor der Ortsbrust mittelsGlasfaserelementen

Die systematische Verstärkung des Bereichsvor der Ortsbrust eines Tunnels mittels Glas-faserelementen zur kurz- und langfristigenStabilisierung des Tunnels ist eine Bauweise,die in Italien entwickelt wurde und dort seitmehr als 18 Jahren angewandt wird. Wäh-rend dieser Zeit wurden bedeutende Weiter-entwicklungen in der Planung dieser Bauwei-se, bei den Bauverfahren und bei den Materi-alien gemacht. Der vorliegende Beitrag stelltdiese Entwicklungen vor.

Systematic reinforcement of the advance coreof a tunnel using fibre-glass elements as astructural component to stabilize it in thelong and short term is a practice developed inItaly that has been used for over eighteenyears. During this period significant develop-ments have occurred in the design techniquesused for this tunnelling technique, in the con-struction technologies and in the materials.This paper illustrates these developments.

Systematic reinforcement of the face of a tun-nel which is then demolished may seem a

strange contradiction and it is perhaps preciselybecause of this that eighteen years after it wasfirst tried, the technology of reinforcing the ad-vance core with fibre-glass structural elementsis viewed by some with suspicion and is oftenpoorly understood and badly performed even byexperienced underground design engineers de-spite the successes the technique has enjoyed.

A true and genuine construction system of thismethod was made which is a part of the tunneldesign and construction approach known asADECO-RS. As such it is one of the conservationtechniques and exerts a preconfinement actionon the cavity (9). It has shown considerable po-tential and has in fact been employed to industri-alize the construction of tunnels for the first timewith extraordinary results, even in groundswhich were impossible to tackle adequately be-fore now.

A short illustrationof the technology

The technology in question consists of dry drill-ing a series of holes into the face of a tunnel.They must be evenly distributed and at an anglejust off parallel to the centre line of the tunnel.Special fibre-glass reinforcement is then insert-ed into the holes (Figures 1 and 2) and then im-mediately injected with grout. When, after tun-nel advance, the remaining length of the rein-forcement in the face is insufficient to guaranteesufficient preconfinement of the cavity (a situa-

tion which is immediately identified by carefulmeasurement of extrusion), a new series of rein-forcements is placed.

Length, density, overlap, cross-section areaand geometrical distribution of the reinforcementconstitute the parameters that characterize thisreinforcement technique. The technology can beemployed in cohesive, semi-cohesive ground and,with a little extra intervention to ensure the sta-

Fig. 1 Reinforce-ment of the advancecore with fibre-glassreinforcement (FGR).Bild 1 Verstärkungdes Bereichs vorder Ortsbrust mitGlasfaserbewehrung.


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bility of the hole, even in ground with poor cohe-sion. If the technique is designed and performedwell, it improves the strength and deformationcharacteristics of the ground in the advance coreof a tunnel considerably and results in the devel-opment of effective preconfinement action. Clear-ly the idea of using fibre-glass for the reinforce-ment constituted the key to the success of thetechnology because this material combines highstrength properties with great fragility. Conse-quently it is easy to break reinforcement made ofthis material with the same bucket that is used forexcavating the ground (Figure 3).

The ADECO-RS approachcontext

In order to understand and use fibre-glass rein-forcement technology properly it is important tokeep in mind two concepts that lie at the base ofthe ADECO-RS approach of which it forms part:➮ The centrality of the deformation response of

the ground to the action of excavation (Fig-ure 4). The design engineer must give maxi-mum attention to this, firstly to analyse it andthen to control it (9).

➮ The use of the advance core of the tunnel (stiff-ened with of course fibre-glass reinforcementor protected with advance rings of improvedground or of fibre reinforced mortar) as the keyto interpretation (for analysis) and as a struc-tural stabilization element (for control) of thedeformation response mentioned above duringexcavation and construction (Figure 5).It has been demonstrated (7) that it is possible

to tackle full face excavation of tunnels even un-der the most difficult stress-strain conditions by

Fig. 4 The three components of the deformation response.Bild 4 Die drei Komponenten des Verformungsprozesses.

Fig. 3 View of a reinforced face.Bild 3 Ansicht einer verstärkten Ortsbrust.

Fig. 2 Sketch of a tubular fibre-glass element.Bild 2 Aufbau eines rohrartigen Glasfaserelements.

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FELSBAU 22 (2004) NO. 4

Fig. 7 Reinforce-ment of the advancecore with fibre-glasselements: examples

of use.Bild 7 Anwendungs-

beispiele für die Ver-stärkung des Bereichs

vor der Ortsbrust mitGlasfaserelementen.

applying these concepts. There is also the advan-tage of being able to plan tunnel advance in alltypes of ground by industrializing works (observ-ance of time schedules and costs) and applyingeven the most rigid quality assurance regulations.

In the ADECO-RS approach, the conservationtechniques for preconfining the cavity were de-signed to deal with all those situations wheretunnel advance is not possible or possible onlywith great difficulty using traditional methodsbecause of the huge deformation that would betriggered at the face and around the cavity. Themain advantages of the method are:➮ Full face advance always with obvious bene-

fits in terms of site organisation and the elim-ination of the delicate phase when bench hasto be excavated,

➮ Site cleanliness and safety even at the face,➮ Industrialized tunnel advance; excellent pro-

duction rates, constant and above all certain,➮ Certainty concerning costs, which are often

lower, when work is finished, than what theproject would have cost using traditional tech-nology,

➮ High flexibility; a wide range of different typesof grounds can be tackled with one set of equip-ment (Figure 6).

Reinforcement of the advancecore part of preconfinementof the cavity

Preconfinement of the cavity can be achieved us-ing different techniques depending on the type ofground (natural consistency), the stress states inquestion and the presence of water. Interventionthat takes place ahead of the face (designed toprevent relaxation and loosening of the groundand to conserve the principal minor stress σ3 atlevels above zero) is defined as “conservation” in-tervention as already mentioned. The types are asfollows:

Fig. 5 Definition ofthe advance core.Bild 5 Definition

des Bereichs vor derOrtsbrust .

Fig. 6 Types ofadvance core re-inforcement usingfibre-glass elements.Bild 6 Möglichkeitender Verstärkung desBereichs vor derOrtsbrust mittelsGlasfaserelementen.


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➮ Protective conservation, when the stressesaround the advance core are channelled toproduce a protective action that ensures thatthe natural strength and deformation charac-teristics of the core are conserved (e.g. shellsof ground improved by means of sub-horizon-tal jet-grouting, shells of fibre reinforced mor-tar of concrete created by means of mechani-cal pre-cutting);

➮ Reinforcement conservation, when the actionis applied directly to the consistency of the ad-vance core to improve its natural strength anddeformation characteristics by appropriatereinforcement techniques (e.g. reinforcementof the core using fibre-glass structural ele-ments).It is important to make it clear that this inter-

vention must be considered as complementary tothe traditional techniques of simple confinementof the face and cavity, since their effectivenessdepends on the continuity and regularity of thepassage from preconfinement of the cavity(ahead of the face) to confinement of the cavity(in the tunnel, back from the face).

Concentrating on those preconfinement tech-niques based on improving the advance corewith fibre-glass reinforcement (FGR), it is inter-esting to observe that this technique comes infour different types, depending on the type ofground and the stress-strain situation to be tack-led (see Figure 4):➮ Fibre-glass reinforcement (FGR): simple rein-

forcement of the core by means of fibre-glassreinforcement (indirect conservation tech-nique),

➮ Pre-cutting plus fibre-glass reinforcement (PT+ FGR): strengthening of the advance core bymeans of fibre-glass reinforcement and simul-taneous protection of the core by means of ad-vance shells of shotcrete around it by meansof mechanical pre-cutting (mixed conserva-tion technique),

Fig. 8 Florence-Arezzo High SpeedRail Line, TerranovaLe Ville Tunnel: viewof the face reinforcedwith fibre-glassstructural elements.Bild 8 Hochge-schwindigkeitsstreckeFlorenz-Arezzo, TunnelTerranova Le Ville,Ansicht der mit Glas-faserelementen ver-stärkten Ortsbrust.

➮ Horizontal jet-grouting plus fibre-glass rein-forcement (HJG + FGR): strengthening of theadvance core by means of fibre-glass rein-forcement and simultaneous protection of thecore by means of advance arches of improvedground around it by means of horizontal jet-grouting (mixed conservation technique),

➮ Fibre-glass reinforcement plus fibre-glass re-inforcement (FGR + FGR): reinforcement ofthe core by means of fibre-glass reinforce-ment and simultaneous protection of the coreby means of advance shells of improvedground around it using fibre-glass elements,fitted with valves, inserted ahead of the tunneland injected with grout (mixed conservationtechnique).For each of these types an example of its use

can be found in the table in Figure 7 where it wastried out for the first time or some change wasmade to it. It is perhaps worthwhile at this pointlooking at the history of the technology.

Fig. 9 Mathematicalmodel for calculatingdimensions for ad-vance core reinforce-ment technique.Bild 9 Mathema-tisches Modell fürdie Dimensionierungder Verstärkung desBereichs vor derOrtsbrust.

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FELSBAU 22 (2004) NO. 4

History

If strengthening of the face using fibre-glass re-inforcement is considered on the same level asany other roof bolting intervention used occa-sionally for brief stretches of tunnel as a counter-measure to prevent fall-in from the face, then itis difficult to put a date on the first use of thepractice.

If, however, in the light of what has been said,strengthening of the advance core by means offibre-glass reinforcement is seen more correctlyas a true and genuine construction technology tobe applied systematically in average to extremestress-strain conditions to obtain complete con-trol over deformation phenomena (and of the

Fig. 10 Samplesof fibre-glass tubes.Bild 10 Bauarten

von Glasfaserröhren.

Fig. 11 Strengthtests of smooth and

corrugated fibre-glass tubes.

Bild 11 Festigkeits-untersuchungen an

glatten und profiliertenGlasfaserröhren.

subsequent surface subsidence when neces-sary), then its introduction to tunnelling practic-es can be dated with certainty as occurring in1985 when it was tried out for the first time inthe world by the authors during the constructionof some tunnels on the Florence-Arezzo sectionof the new high speed railway line betweenRome and Florence (the Talleto, Caprenne, Tas-so, Terranova Le Ville (Figure 8), Crepacuoreand Poggio Orlandi tunnels).

The idea began to make headway in the au-thors´ minds as part of the effort to develop theADECO-RS approach (which, as has been said, isbased on an analysis and on the control of thedeformation response of the ground to excava-tion, and is practised by adjusting the rigidity ofthe advance core) after resort was made withsuccess to placing roof bolts in the face to coun-ter fall-in phenomena which occurred withoutfail after work halted each weekend, during theconstruction of tunnels through clay on Sibari-Cosenza rail line (1984).

On that occasion the intervention consisted ofsimply pushing a certain number of steel roofbolts, Ø 24 mm and 4 m in length, into the faceusing the excavator bucket and a small crosspiece was attached to the end of them. The workwhich was then completed with the placing of asmall mantle of shotcrete turned out to be veryeffective since when work recommenced onMonday, it was sufficient to pull out the boltsgripping them by the cross piece and resumetunnel advance with no problems.

The authors were convinced of the impor-tance of the rigidity of the advance core for con-trolling deformation in the tunnel. It was a con-viction that had developed with positive confir-mation from experimental observation of thestress-strain behaviour of a few difficult tunnelsdriven full face with core protection only (hori-zontal jet-grouting, mechanical pre-cutting) be-forehand. The authors started to study the possi-bility of artificially increasing the rigidity of thecore until the desired level of strength wasreached. Reinforcing the advance core with spe-cial systematic bolting capable of ensuring sig-nificant increases in the strength and deforma-tion of cores treated, but not hindering demoli-tion during excavation, seemed a project worthstudying.

Once fibre-glass was identified as the mostsuitable material for all the purposes consid-ered, operational methods were studied to im-plement the technology checking its effective-ness against a store of original mathematicalmodelling methods on computers (Figure 9). Atthis point the new technology needed to be triedout in the field.

Tunnels on the new high speedRome-Florence rail line (1985)

The chance presented itself soon when the poorquality of the geological formations through


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Fig. 12 Work cycle adopted for the Caprenne and Talleto tunnels.Bild 12 Arbeitsablauf in den Tunneln Caprenne und Talleto.

which tunnels on the new high speed Rome toFlorence rail line were to pass caused seriousproblems resulting in the halt of works and theredesign of the works.

Thanks to the courage and farsightedness ofFerrovie dello Stato (Italian state railway) offi-cials and of the contractors (Ferrocemento S.p.A.and Fondedile S.p.A.) and to the trust they obvi-ously placed in Professor Lunardi, it was decidedto try out the new technology that had been pro-posed to them and so the whole line under con-struction between Florence and Arezzo becamea huge experimental tunnelling site.

It is interesting to look briefly at the principalcharacteristics of these first works, not to men-tion the tests, the monitoring and the most signif-icant measurements that were carried out orthat started to be developed in that pioneeringconstruction site.

Fibre-glass structural elementsThere was no choice but to select the fibre-glassstructural elements from among those on themarket, taking account also of transport consid-erations. A tube shape was chosen with 60 mmouter diameter, 10 mm thick and a length of15 m. Both smooth tubes and corrugated tubeswere tried for better adherence to the mortarcement (Figure 10).

Figure 11 gives a summary of the results ofthe strength tests performed at the time. Theywere indispensable for deciding the dimensions

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FELSBAU 22 (2004) NO. 4

Fig. 14 The use oftechnology involving

advance core re-inforcement in Italy.

Bild 14 Anwendungder Verstärkung des

Bereichs vor der Orts-brust in Italien.

Fig. 13 PoggioOrlandi tunnel: results

of strain measure-ments in instrumented

fibre-glass tubes.Bild 13 Ergebnisse

von Dehnungsmes-sungen an instrumen-

tierten Glasfaserröhrenim Tunnel Poggio

Orlandi.

of the intervention (shear and tensile strength)and for establishing the operating parametersto use for the mortar injections (burstingstrength).

Geometry and parameters for characterizingreinforcement of the advance core

The first reinforcement was performed with thefollowing parameters (see Figure 1):


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Fig. 16 San Vitaletunnel: longitudinaland cross section.Bild 16 TunnelSan Vitale: Längs- undQuerschnitt.

Fig. 15 Casertato Foggia rail line,San Vitale tunnel: re-inforcing the advancecore using tubularfibre-glass elements.Bild 15 Tunnel SanVitale auf der Eisen-bahnlinie Caserta-Foggia: Verstärkungdes Bereichs der Orts-brust mit röhrenartigenGlasfaserelementen.

➮ Length of each reinforcement advance step:L = 15 m,

➮ Resistant cross section of fibre-glass ele-ments: Ø = 60/40 mm,

➮ Density of the reinforcement: I = 0.35 to0.51 elements/m2,

➮ Overlap between advance steps: S = 5 m.Tunnel advance was full face with the tunnel

invert and the kickers placed at a maximum dis-tance from the face of 1.5 times the diameter ofthe tunnel. The face was concave in shape to fa-vour the natural mobilization of a longitudinalarch effect.

Figure 12 shows the operating cycle adoptedfor the excavation of the Caprenne and Talletotunnels in the sections where face reinforcementwas combined with mechanical pre-cutting (PT +FGR).

In situ tests and measurementsNumerous in situ tests and measurements wereperformed during tunnel advance for in-depthstudy of both the nature of the interaction be-tween the fibre-glass elements and the sur-rounding ground (deformation and extractiontests, Figure 13), and the effect of the reinforce-

Fig. 17 Analysis ofan extrusion test.Bild 17 Analyse einesExtrusionsveruchs.

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FELSBAU 22 (2004) NO. 4

ment of the advance core on the stress-strainbehaviour of the cavity as it advanced under dif-ferent degrees of reinforcement. Methods ofmeasuring extrusion were developed preciselyfor this last purpose and were later to becomewidely used in tunnelling along with the moretraditional convergence measurements. Thesemeasurements were performed by inserting in-cremental extensometers, 15 m in length, intothe face, with measuring bases placed at inter-vals of 1 m.

Fig. 18 San Vitaletunnel: combinedmeasurements of ex-trusion and conver-gence.Bild 18 Tunnel SanVitale: KombinierteMessungen vonLängsverformungenund Konvergenz.

Fig. 19 San Vitaletunnel: calculation

of pre-convergence.Bild 19 Tunnel San

Vitale: Berechnung derVorkonvergenz.

The results of the extrusion, preconvergenceand convergence measurements taken allowedto increase the theoretical knowledge of thestress-strain behaviour of a tunnel at the faceconsiderably and they confirmed the effective-ness of the new technology in controlling defor-mation.

Spread of the technologyThe successes achieved on the Florence-Arezzoline in driving more than 11 km of tunnel under


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Fig. 22 Types offibre-glass structuralelements.Bild 22 Bauartenvon Ausbauelementenaus Glasfasern.

Fig. 20 Anconato Bari rail line, Vastotunnel: excavationstage.Bild 20 Tunnel Vastoauf der Eisenbahn-linie Ancona-Bari,Vortriebsarbeiten.

Fig. 21 Rome Metro:Baldo degli Ubaldistation: view of theface during the ex-cavation stage.Bild 21 U-BahnRom, Bahnhof Baldodegli Ubaldi: Ansichtder Ortsbrust währendder Ausbruchsphase.

objectively difficult conditions confirmed thecomplete reliability of the principles of full faceadvance in the presence of a rigid core throughsoft ground. This decreed the rapid spread ofconservation methods for preconfinement of thecavity and, above all, of strengthening of the ad-vance core with fibre-glass reinforcement as oneof these (Figure 14).

Evolution of the technologySince this technology of strengthening the ad-vance core using fibre-glass reinforcement wasfirst tried out it has evolved significantly in termsof design instruments, materials, different typesand operating techniques. The main stages ofthis evolution are given below with reference todesign examples (see Figure 7).

The San Vitale tunnelThe San Vitale tunnel (Caserta to Foggia StateRailway line) (5) was driven in 1991 through theArgille Scagliose (scaly clays) in which tradition-al tunnelling methods had failed completely (Fig-ure 15). The application of tunnel advance prin-ciples using a rigid core (ADECO-RS) made itpossible to save the tunnel, which had beenabandoned for over two years, and complete itwith average advance rates of 50 m/month. Fig-ure 16 gives a summary of the reinforcementand ground improvement parameters.

The difficulty of the task not only constituted asevere test for in-depth exploration of all the pos-sibilities of the new technology, but also an oppor-tunity for the development of new operating meth-ods, new types of laboratory and in situ measure-ments and new three dimensional mathematicalmodels capable of correctly simulating the effectof operations in the face-core zone on the stress-strain behaviour of the tunnel and on the entity ofthe long and short term loads on the linings:➮ As regards operating methods, the type FGR +

FGR (grouted fibre-glass in the face plusvalved and injected fibre-glass in advancearound the core) was introduced as opposedto PT + FGR which was little suited to theground due to the difficulty in guaranteeing acontinuous pre-cut shell,

➮ As regard measurements, new apparatus forperforming triaxial extrusion tests was studiedas well as for systematic measurement of ex-trusion which are extremely useful: the formerin the diagnosis phase for predicting the be-haviour category and in the therapy phase fordeciding the intensity of the reinforcementneeded to counter extrusion effectively (Figure17), the latter in the operational phase to opti-mize the length of the reinforcement advancesteps and their overlap (Figure 18),

➮ As regards mathematical models, in additionto refining 2D and 3D FEM models, special ta-bles were calculated to furnish values and dis-tributions of preconvergence ahead of theface for the first time (Figure 19).

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FELSBAU 22 (2004) NO. 4

Fig. 23 TGV Medi-terranée, Tartaiguilletunnel: View of theface reinforced withfibre-glass structuralelements.Bild 23 TunnelTartaiguille, Linie TGVMediterranée: Ansichtder mit Glasfaser-elementen verstärktenOrtsbrust.

Fig. 24 Bologna toFlorence High Speed

Rail Line, RaticosaTunnel: reinforcement

of the advance core byusing fibre-glass struc-tural elements (ground:scaly clays of Chaotic

Complex Formation,overburden: 500 m).

Bild 24 TunnelRaticosa auf der

Hochgeschwindigkeits-eisenbahnstrecke

Bologna-Florenz: Ver-stärkung des Bereichs

vor der Ortsbrustmittels Glasfaser-

elementen.

The Baldo degli Ubaldi tunnelThe Baldo degli Ubaldi tunnel on the Rome Met-ro (a span of approximately 22 m and a crosssection of 271 m2) (6) was driven, in 1997, under-ground in the centre of the city through clays andsandy silts (Figure 21). Tunnel advance afterfirst reinforcing the advance core was adoptedboth for the side wall drifts and for the subse-quent top heading in the crown. Civil engineer-ing works (excavation and lining of the stationtunnel) required only 18 months of work at a costof 568 EUR/m3. Surface subsidence was practi-cally negligible. A new innovative type of fibre-glass reinforcement was adopted for this project,flat elements, which can not only be assembledin a wide variety of types (Figure 22), but arealso very easy to inject and to transport, allowingreinforcement advance steps of 25 m as opposedto only 15 to 18 m with the tubular reinforce-ment. Table in Figure 7 gives the parametersthat characterize this type of reinforcement.

The Tartaiguille tunnelThe Tartaiguille tunnel (TGV Mediterranée,Marseilles to Lyons “G.V.” Line) was driven in1998 through the argile du Stampien, a verystrongly swelling formation (75 % of the contentis montmorillonite) (Figure 23). Given the in-creasing difficulty in advancing using traditionalsystems, the French railways asked leading Eu-ropean tunnel designers to put forward alterna-tive proposals for completion of the remaining900 m of tunnel (15 m outer diameter) in safetyand within the deadline for the commissioning ofthe railway line. The almost unanimous opinionwas that the tunnel could not be completed bythe required deadline. The only exception wasthe proposal put forward by Professor Lunardi touse full face advance after first reinforcing theadvance core according to the principles of theADECO-RS approach. This proposal guaranteedcompletion of the tunnel on schedule and withinthe budget with minimum advance rates of1.4 m/d. The tunnel was actually finished with-out any problems ahead of schedule with aver-age advance rates of approximately 1.5 m/d(during the last five months with production atfull speed, advanced rates actually reached1.7 m/d). Important studies were performed dur-ing construction of the Tartaiguille tunnel on dif-ferent types of extrusion and on the importanceof the distance at which the tunnel invert isplaced from the face when advancing with a stiff-ened advance core to minimise extrusion sur-face.

More recently advance core reinforcementand the ADECO-RS design approach of which itforms part have been and are being used withexcellent results in the construction of over100 km of tunnels in extremely varied types ofground and stress-strain conditions on the newhigh speed Bologna-Florence railway line (Fig-ure 24 and 25).

The Vasto tunnelThe Vasto tunnel (Ancona to Bari State Railwayline) (4) was driven in 1993 through a heteroge-neous formation of silty clays containing sizeablesandy, water bearing, lentils. There was a pas-sage with a shallow overburden (8 m) close to thesouthern portal under residential buildings.Here too, the use of traditional tunnelling meth-ods (partial face advance and preliminary stabi-lization using steel ribs, radial roof bolts andshotcrete) had failed completely. Use of theADECO-RS approach made it possible to com-plete the tunnel at an average speed of around50 m/month. The combination of fibre-glass re-inforcement in the face + horizontal jet-groutingin advance around the future tunnel was em-ployed during construction for the first time (Fig-ure 20). The Table in Figure 7 gives the rein-forcement parameters.


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Fig. 25 Bologna to Florence High Speed Rail Line, Raticosa Tunnel: view beforecasting the invert near the face.Bild 25 Tunnel Raticosa auf der Hochgeschwindigkeitseisenbahnstrecke Bologna-Florenz: Blick in den Vortrieb vor dem Betonieren der Sohle nahe der Ortsbrust.

References1. Lunardi, P. ; Bindi, R. ; Focaracci, A.: Nouvelles orienta-tions pour le projet et la construction des tunnels dans desterrains meubles. Etudes et experiences sur le preconfine-ment de la cavité et la préconsolidation du noyau au front.Colloquio Internazionale su “Tunnels et micro-tunnels en ter-rain meuble” – Parigi, 7-10 Febbraio, 1989.2. Lunardi, P. et al.: Tunnel face reinforcement in soft ground:design and controls during excavation. Convegno Internazi-onale su “Towards New Worlds in Tunnelling”, Acapulco,16-20 Maggio, 1992.3. Lunardi, P.: La stabilité du front de taille dans les ouvragessouterraines en terrain meuble: études et experiences sur lerenforcement du noyau d’avancement. Symposio Internazi-onale su “Renforcement des sols: experimentations en vraiegrandeur des années 80”, Parigi, 18 novembre 1993.4. Lunardi, P. ; Focaracci, A.: Aspetti progettuali e costruttividella galleria “Vasto”. In: Quarry and construction, agosto 1997.5. Lunardi, P.: Convergence-confinement ou extrusion-pré-confinement ? Colloque ”Mécanique et Géotechnique”, Lab-oratoire de Mécanique des Solides – École Polytechnique,Paris, 19 mai 1998.6. Lunardi, P. ; Focaracci, A.: Design and construction of astation on the Rome metro. In: T&T International, March 1998.7. Lunardi, P.: The influence of the rigidity of the advancecore on the stability of tunnel excavations. Gallerie e grandiopere sotterranee, 1999.8. Andre, D. ; Dardard, B. ; Bouvard, A. ; Carmes J.: Latraversée des argiles du tunnel de Tartaiguille. In: Tunnels etouvrages en souterrains, No. 153, 1999.9. Lunardi, P.: Design & constructing tunnels – ADECO-RSapproach. In: T&T International special supplement, May2000.10. Lunardi, P.: The ADECO-RS approach in the design andconstruction of the underground works of Rome to NaplesHigh Speed Railway Line: a comparison between final designspecifications, construction design and ”as built”. AITES-ITA World Tunnel Congress on “Progress in tunnelling after2000”, Milan, 10th-13th June 2001, Vol. 3, pp. 329-340.

11. Bindi, R.: Il recupero di gallerie in situazioni difficili. Ruoloe valorizzazione dei consolidamenti. In: Quarry and Con-struction, October 2002.12. Bindi, R. ; Cassani, G.: New prospects for tunnelling withthe ADECO-RS approach. Schubert (ed.) “EUROCK 2004 &53rd Geomechanics Colloquium“. Essen: Verlag Glückauf,2004 (in print).

AuthorsProfessor Ing. Pietro Lunardi, Consulting engineer, and Dott.Ing. Renzo Bindi, Rocksoil S.p.A., Piazza San Marco 1, I-20121 Milano, Italy, E-Mail [email protected]

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