GPR Investigation of Cobblestone Road Pavement Degradation

Transcription

1 GPR nvestigtion of Colestone Rod Pvement Degrdtion Colgrnde Diprtimento di rhitettur e Urnisti, Università di l quil, Monteluo di Roio 674, L quil tli sndro@du.ing.univq.it D. Rnlli; M. Sozzfv; M. Tllini Diprtimento di ngegneri delle Strutture, delle que e del Terreno, Università di L quil, Monteluo di Roio 674, L quil tli Synopsis Struturl degrdtion of rod pvements is thret to trffi sfety. Defets or dmges in the rod surfe mke driving unsmooth nd unomfortle nd inrese the likelihood of idents. Ground Penetrting Rdr (GPR) hs een suessfully used in non-destrutive investigtion of rod pvement degrdtion nd identifition of its uses. The pper desries the results of GPR study tht ws onduted on the olestone rod pvements of the historil enter of L quil (ruzzo, tly). The investigtion hd the purpose of finding orreltions etween the following vriles: type of stone surfe; trffi lod; rod surfe degrdtion; nd results from GPR sns. Both qulittive nlyses (nomlies on rdr setions) nd quntittive nlyses (urves of rdr signl ttenution with depth) were rried out. The investigtion ws onduted on 15 sites representing vrious omintions of the ove-mentioned vriles. h site hd surfe re of 3 x 3 m. The ntenn rrys hd nominl frequeny of 1,6 MHz (down to depth of 1 m) nd of 6 MHz (down to depth of 4 m). The sns were performed on grids with mesh of 1.5 nd.5 m, respetively. The investigted sites were grouped into lsses of pvement surfe degrdtion (PSD) nd of trffi lod (TL). The groups (no degrdtion, verge nd high) of the first index were estlished on the sis of diret oservtions of defets. Conversely, the groups of the seond index were sed on the numer of pssing vehiles per unit of time. lso in this se, three lsses were defined: hevy, verge nd low. The olestones used in the investigted sites were mde up of red porphyry from the Bolzno re, lol limestone nd leuititi lv from the Lzio Region. Comprisons etween rdr ttenution urves (nd relted PSD nd TL lsses) nd types of olestone eluidted some spets onerning GPR lirtion in the investigtion of the olestone rod pvements. n terms of types of rod pvement nd PSD nd TL lsses, the porphyry pvement hd more mrked eletromgneti wve refletion thn the limestone or leuititi lv ones. This is due to the ft tht porphyry hs high iron ontent, whih mplifies inident rdr signl refletion. n terms of trffi on sites elonging to the sme PSD lss nd with the sme pvement, hevy-lod rods hd more pronouned eletromgneti wve refletion thn verge- or low-lod rods. This finding is justified y the more signifint destruturing of the olestone rod pvement nd, ultimtely, y inresed porosity of the rod emnkment, whose internl voids indue the multiple refletions oserved in the ttenution urves. Sites with the sme type of rod pvement nd the sme TL lss were lso investigted under vrile surfe degrdtion onditions. The more degrded is the surfe degrdtion of these sites, the more rpidly dmpened re their ttenution urves with depth. This oservtion is due to the ft tht higher surfe degrdtion (high PSD lss) immeditely dmpens the refleted rdr signl efore it rehes the deeper lyers of the rod struture.

2 GPR nvestigtion of Colestone Rod Pvement Degrdtion The onditions of the rod pvement, its roughness nd evenness nd its lk of lolized or diffuse fults hve ruil impt on driving omfort nd trffi sfety. Consequently, the degrdtion of rod pvements plys drmti role in rod sfety, diretly or indiretly. f dmges to rod pvements re not prevented with dequte mintenne, they my signifintly inrese the likelihood of idents nd the severity of dmges. Thus, orret pproh to rod mngement emphsizing sfety nd preventing idents requires omprehensive pln with the following key elements: identifition nd lssifition of rod pvement degrdtion; nlysis of the senrio of possile uses; definition of the methodology to e followed nd of the Best ville Tehnology for identifying the uses of the pvement degrdtion; predition of the evolution of degrdtion over time; nlysis of the severity of rod pvement dmges nd of their evolution over time in terms of rod sfety; identifition of the most effetive nd effiient rehilittion projets. The pper ddresses these prolems with referene to olestone rod pvements loted in the historil enter of L quil. n view of the reent rekthroughs of reserh in this setor (Benedetto & ngiò, 22; Benedetto & De Blsiis, 21; Chun-Lok & Sullion, 1992), the uses of degrdtion of these rod pvements were investigted with dvned GPR tehniques. PPLCTN F GPR TCHNQUS T RD PVMNTS Getting n in-depth understnding of rod pvement mens identifying its type, size, mterils, s well s the thikness of its lyers nd the mehnil properties of its onstituents. The study of rod pvement omposition my rely on onventionl methods, suh s oreholes, or on non-destrutive geophysil tehniques. Boring of holes into the rod surfe is time-onsuming nd destrutive pproh, whih interferes with rod trffi. n the pst few yers, Ground Penetrting Rdr (GPR) tehniques hve een extensively used thnks to their high effiieny, fst speed, non-destrutiveness nd limited interferene with pedestrin nd vehile irultion (Benedetto & ngiò, 22; Buhi et l., 22; Gtti & Liuzzi, 1998). The GPR n emit rdio frequeny signls in the typil rnge of 1-2 MHz nd reord the ehoes rdited y the ojets ontined in the medium or y the lyers of different type whih mke up rod surfes. trnsmitter genertes pulse signl with given pulse repetition frequeny. These suessive pulses produe signl with durtion in the rnge of nnoseonds. The signl is rdited y rod-nd ntenn. The energy pulse propgtes to the rod pvement t given veloity: when the pulse meets lyer whose dieletri properties re different from the ones of the overlying lyer, then prt of the energy is refleted y the lyer, while the remining energy rosses it. t the surfe, the ntenn reeives the refleted signls. The mplitudes of the refleted wves provide informtion on the dieletri properties of the investigted lyers. nterfe ehoes nd eho spings (time intervls tht the pulse tkes to ross the lyers) n e identified on the reeiver-reorded tre. From these time intervls, lyer thikness n e determined. The hoie of the ntenn in GPR tehniques is essentil. Suh hoie should e sed on the desirle depth of investigtion, on the types of mterils to e investigted nd on the expeted imging resolution. Low-frequeny ntenns hve high penetrtion (8 35 MHz). They re used for deep investigtion of strtigrphi horizons, groundwter, ves, et. Medium-frequeny ntenns (35 6 MHz) re suitle for shllow investigtion of rod pvements nd underlying utility grids. High-frequeny ntenns (6 2 MHz) offer high sptil resolution ut shllow penetrtion. n the study reported in this pper, use ws mde of 1,6 MHz monostti ntenn to get informtion on the olestone rod surfe, nd of 6 MHz istti ntenn to identify its underlying utility grids, if ny. Both ntenns nd their dt olletion nd proessing softwre were developed y ngegneri dei Sistemi Sp (Pis, tly).

3 CBBLSTN RD PVMNTS Undenily, olestone rod pvements hve high estheti nd historil vlue n tly, they re found in mny historil enters of mjor towns, ut lso in numer of smll villges. Due to their often nient origin, they represent heritge whose vlue is to e proteted, preserved nd enhned. These rod pvements ommonly onsist of ue- or prism-shped stones, whih re qurried y mens of utting mhine provided with lded hmmer. The upper prt of the olestone is left rough, while its lterl wlls (otined y frturing) re usully inlined towrds the ed surfe, so s to form n elongted pyrmid trunk. Common types of stone rrngement re: ontrsting rhes, redns, peok s til nd regulr ourses. The ontrsting-rh rrngement is the most widespred, espeilly for vehile trffi. ndeed, rhes hve unique pility of ering hevy lods nd thrusts; in the se of olestone pvement, the lods nd thrusts re horizontlly trnsmitted s result of the grip of tires on the rod surfe. Contrsting rhes re defined s suh euse their position ontrsts the one of their neighors nd of the rod edges. n the tlin re, the most frequent types of stone re: rystlline rok (gneiss, grnitoids), lv (porphyry, leuitite, slt, et.) nd sedimentry rok (limestone, sndstone, et.). The size of the ue stones generlly vries with the type of mteril nd is usully in the rnge of 5-15 m. Colestones re lid on n out 5 m-thik lyer of rendering snd, ording to the seleted lyout, leving nrrow (mx 5 mm) nd prllel joints etween them. Then, the joints re refully filled with wshed snd nd the olestones re rmmed with virting rmmers. The lst step in the proess is the seling of the shllow portion of the joints etween the stones with wterproof inders; the most ommonly used mterils re ement slurry, hot nd old itumen msti (Blno, 1995). The other lyers of the struture hve signifint impt on olestone pvement durility. These lyers re pled etween the suse nd the overlying snd ed surfe ommodting the stones. n the pst, use ws mde of grnulr mix of vrile thikness, depending on the lod-ering pity of the suse. n reent yers, onrete sl hs lso een used in order to mintin the evenness of the rod surfe nd llow it to etter withstnd the lod of trffi (in urn res, minly us trffi). The onrete sl is ppropritely sized, ording to the hrteristis of the underlying lyers nd of the trffi lods predited throughout the useful lifetime of the rod pvement. The upper prt of the sl is generlly reinfored with steel wire net, so s to minimize shrinkge nd rking proesses, whih re typil of this type of rod pvements. Figure 1 shows the typil ross-setions of olestone rod pvement of ordinry type nd of olestone rod pvement inorporting reinfored onrete sl. 1 PVMNT () 1 PVMNT (B) m 5 m m 5 m m m 15-2 m 6 Figure 1: Typil ross-setions of olestone rod pvement of ordinry type () nd of olestone rod pvement inorporting reinfored onrete sl (B). 1- seling itumen; 2- stone pver; 3- wshed snd; 4 edding snd; 5- grnulr suse; 6- sugrde; 7- reinforing steel mesh; 8- onrete sl t this stge, it is worth desriing the ftors whih my trigger degrdtion of olestone rod pvements. The min ftor is the rod surfe deformtion, whih my originte from prolems in oth onstrution nd opertion of the rod infrstruture. ommon prolem rising fter rod onstrution is the permnent deformtion of the suse nd of the grnulr mterils mking up the pvement. This prolem my e regrded s the omintion of different ftors, whih re outlined elow: unevenness of the suse ed surfe; poor workmnship in the pling of the lyers; poor omption; uneven omption; inorret finishing (wter puddles); uneven surfe; non-homogeneous thikness. Conversely, the repeted-stress deformtion due to trffi lods origintes in the grnulr lyers of the suse nd is used y the use of unsuitle mterils, suh s: grnulr mixes with rushle ggregte; grnulr mixes with exess fines; 6

4 grnulr mixes with plsti fines; mixes of indequte grin size; plsti suses; ompressile suses. Furthermore, the sel of the joints etween the olestones plys n importnt role; inorret seling of the joints my initite degrdtion of the pvement, euse the ltter: i) does not ensure n even rod surfe; ii) does not prevent wter from infiltrting into the underlying lyers; iii) llows vehile tires, rin nd lening vehile rushes to esily remove the snd fill from the joints. Finlly, it should e pointed out tht, in most urn res, dmges to olestone rod pvements depend ove ll on the underlying utility grids, whih indue pvement instility upon their instlltion nd mintenne. TH NVSTGTD RD PVMNTS nlysis of Rod Pvement Types, Trffi nd Degrdtion ll the investigted rod pvements onsist of olestones nd re loted in the historil enter of L quil (ruzzo Region tly) (Figure 2) LGHR CLL D D 7 L V km V C 83 9 Colle S.nofrio NT RSC H N 77 9 L 7 7 U 89 G SRB T CQUDTT PR TUR D FUM TRN P C N VNT GULN SRBT CQUDTT 91 M DNN D LL CN C S C STLVCC H PTTN FRM DLL TT MN LL GCM N GUL MR T R NN 77 C PR D L C TT DR 85 R M -L'QUL-TR M 84 CS LN UTSTRD 86 N G. GNL L BNU TR SGN NZN L 72 V 7 69 V T LL LL N 8 85 L D MD D'T SSS U NVRS T' F CLT ' D SCNZ V 8 75 GRN DL C MP S PRTV V T CL D V D L V T DL L NCLL FR N DL D MDN FNT LL D GULN V T CSTRNL 76 C 73 P G N 85 D VCN L 8 4 MTR F UN DLL SCR 75 SSS 6 6 FGL MSCH D D LL V 8 79 SST 82 PSTR LL N C LL CSLL UT STRDL L 'QUL VST 81 DR D STR 74 UT SVLT 6 8 DLL VSCH DL VNT N. N 17 BS - TRM 24 RM - L'QUL R M D PGNC ST RD - L'Q 74 SL RNR M VN CS ZUCH V CNL UL - TR 85 D L STRD N SSS LL PRSCH GRZ LL D DLL CN D L D'TL T RN RM T VLL LPRD MR TT BRB R L R M-L' NUM GR SR BST CQUD TT CS RM 63.P FU M S QU 79 STRD 65 LM RUC NTN M DNN 79 CS D ND GUG L VSCH L D'T V TR D C C NTN L GRN 8 SSS SPD L CVL 7 GRN GGTT CS D M RCHS 82 CRF NUM 8 ML N CSLL UTSTRDL L'QUL VST VNT 7 DL VSCH MNT MR V FN VST 17 ZZS 76 CGN CLL BBRU 63 D D VTT NNN P RTR S ST VT PP C DUT P R T LL 63 FSS 17 DLL' N.17 PZZ SM N B LVR 72 L L M T S 74 MNT TR NLL 82 MN GVN N RSS L 68 CR C 76 L L DLL CRC 78 DLL RSS TRN ST V. NTN VC 68 C T N D R C CR C FUM CR RD DGL RSN ZN NDUSTRL 78 V STN BT 65 T LTL T CR V D LL MLN BT D 8 VNCN Z NDR 64 CMPLSS SPRTV CNT-C LLL 81 TRM 68 V B V PR T CRR D CLL NTN LD F RNC D'SSRG L 63 C. CN T CLLL NT V L D CH VS V S L PRD BN TR P RTTT 73 S.S XX N N. 17 TR BRT 75 VN G 72 TR NT L VSCH V D NN 73 P. Z S.D M N C PR TUR PL 71 V F NT P NS RN LT N P.Z N GN. D NN 17 D V V V TR 62 MRTR V CN D STR 7 3 LL'T LD SC V ST N G.P PLTN V FUM G. N 73 LF F. FLMUS V - TRN S.TRS GU SULMN R G SPR FRR 72 N UTSTRD 24 M RRUCCN 64 STZ RTTT L D DUC PRR V D L UZZ P RM. D DL MP CMP BS BR LS N. STLL 63 VST C NT SLR SSS DL 72 SPZ DG L V SCR D LL ' BR USN N GR STTM NPL TN RT 76 T S 63 MRLTT PRTT MR P LGN XX RM-L'QUL-TRM R D C RC D D MLN D PL V V SC BUCC NS TNCR N D P.Z FNT SCC V PL GN 71 TS 65 TL N FN R DGL 7 TRN 69 GR TT D NVRR P S.M.Z R D R 67 STRD 66 N. 615 VC N L T RN 74 V C. FC 75 V D LL TR FUM N C...M.. PR TL VN G STZ N F. F.S.S. RR XX V 64 TR PLV R T RN R NT TRR D CPPUCCN 615 XX.PNS N. DLL G BSS H P.L ST D LL ZN 63 CC - TRN VNN RC V SULMN D RCC CRBB ZN RT GNL D PL FRR RM L V G P. Z L D LL LUR TN L PR XXV SLR P G USP CCCH MUL N 63 D L CS BRNRD 7 V GNFL PPR DR D P Z Z CRDNL FUM Co ntrd quilio TM BR N ST TR P. N.615 G RR RT V L'CQU V NRD R Peshiolo L Plomr Pinet di Roio MR DGL NGL 79 L. STURZ MR N P N T S Colle Vernso DR L NP 65 CSCN CMUNL N.615 N.615 RN 64 S. T MUSN MRN BRUZZ 95 M. LUC 77 NN PPN PRT F UM N.6 15 DR Monte Luo DGL CRR N F Colle di Roio 8 Fonte Volpe DN 85 V 7 DR L. T N D DLL CRC RSS N VC FC LT' D NG G NR C R 67 C CR L P.Z DLL LURTN V G V NN D RC R M CR C D M RL TT DL L'S PZ L B R UZ Z TM BR PR TT T MRRUCCN D VSTN G V N N XX PR TT T B R T L P.Z DMNC T PRTUR L P.Z NGN D V MR TR. D NN 71 FNT L P RD T R S SBN D L D V M D U R C D. V G ST N MRS PLG XX PR T TT D D CC NN V XX XX BU G F NT S CC P.Z FNTSCC RTL N GL D 7 V P.Z MR D R GNFL R DR 68 PZZ CRDNL S TT M R BR PP D GR T R NRD T RN 67 F. CR 67 S. N.17 RD N L. STURZ 67 MR DGL NGL 65 P RT DGL FUM NP 5 m L Figure 2: nvestigted re nd lyout of the historil enter of L quil

5 ll the olestone rod pvements of the historil enter of L quil my e grouped into the following three types: porphyry: this is the most widespred type of pvement. Porphyry is n effusive eruptive rok with high ontent of sili (over 7%) nd thus high resistne to stresses nd externl gents. Porphyries ome espeilly from the re of Bolzno (95% of the totl). The shpe of the stones used in L quil is pyrmid trunk with squre setion t the top nd side of 5-8 m; leuititi lv: this is poorly widespred type of pvement. Leuititi lv is n effusive mgmti rok with 5-6% sili. t is very ommon in the volni res of the Tyrrhenin mrgin of Lzio-Cmpni (espeilly in the ln hills). The stones used in L quil re prism-shped; they my hve squred or retngulr setion t the top nd side of 1-15 m; limestone: this is poorly widespred type of pvement. Limestone is sedimentry rok with lium ronte ontent exeeding 98%. t is very ommon in the ruzzo Region nd ours in mny vrieties.the min prolem of this stone is tht it my e esily smoothed nd worn y vehile trffi; therefore, it does not ensure n dequte tire grip on the rod surfe. ts use is due to estheti resons, i.e. the sme mteril (generlly, lol limestone) for oth rod pvements nd uildings of historil enters. The stones of L quil re ue-shped nd their sides hve size of 1-12 m. The trffi lod in the historil enter of L quil my e divided into three tegories, depending on the importne of the relted rods. n res of trffi restrint, the numer of pssing vehiles is smll; in dominntly residentil res, trffi lod inreses; on fst-trffi rods, trffi inreses signifintly nd inorportes hevy vehiles (espeilly uses) whih, however, never exeed 5% of the totl pssing vehiles. For eh rod, the referene prmeter, i.e. the verge Dily Trffi (DT), ws determined. fter diretly reording the Pek Hour Trffi (PHT), the DT ws lulted vi the well-known formul DT = (PHT /.1). The PHT vlues were otined y verging the vlues reorded in different pek hours of the dy nd on different dys of the week. To simplify the ssessment of the DT vrile, three trffi lod lsses were identified on the sis of omputed DT vlues: Low Trffi with < DT 8 verge Trffi with 8 < DT 2 Hevy Trffi with DT > 2. Bsed on diret oservtions of the rod surfe, the following three lsses of pvement surfe degrdtion were identified: no degrdtion = good pvement: olestones re unltered; joints re intt nd without gps; the rod surfe hs no dips; verge degrdtion = fir pvement: loss of joints; some olestones re missing; the rod surfe hs slight dips, ut no ruts or potholes; high degrdtion = poor pvement: loss of joints; the rod surfe hs ruts or potholes with exposed suse mteril, mrked dips nd sphlt pth repirs. With view to finding orreltions etween ll the investigted vriles (type of stone pvement, trffi lod nd pvement surfe degrdtion), 15 sites were tken into onsidertion, fter thorough nlysis of ll the rods in the historil enter of L quil. The 15 sites were seleted in suh wy s to represent of different omintions of the investigted vriles. Figure 3 shows the imges of the 15 sites, while Tle 1 displys the identifition dt of ll the sites, s well s the vlues ssigned to the vriles. Tle 1: Chrteristis of the investigted sites No. Rod Colestone Trffi Degrdtion Conrete sl Utility grids 1 Vi Snt gostino porphyry hevy no degr. YS YS (2) N 2 Vi Bfile porphyry hevy verge N YS (1) N 3 Vi Rom porphyry hevy high N YS (5) N 4 Vi delle Grzie 1 porphyry verge no degr. YS YS (3) N 5 Vi dell nnunzit porphyry verge verge N YS (2) N 6 Vi Sss porphyry verge high N YS (5) YS 7 Vi Borgo River porphyry low no degr. N YS (2) N 8 Vi Sllustio porphyry low verge N YS (3) N 9 Vi Sn Mihele limestone hevy no degr. YS YS (1) N 1 Vi degli lemnni limestone verge high N YS (4) YS 11 Vi delle Grzie 2 limestone low no degr. YS YS (3) N 12 Vi di Pisignol limestone low verge N YS (1) N 13 Pizz Sn Pietro leuititi lv low no degr. N YS (3) N 14 Vi Miniuio d Ugolino leuititi lv low verge N YS (3) N 15 Vi Snto Spirito leuititi lv low high N YS (5) YS Rdr disontinuities

6 Figure 3: The 15 investigted sites

7 P 5 To provide omprehensive piture of the pvements under review, Tle 1 lso indites: i) whether onrete sl is interposed etween the lyers of the superstruture; ii) whether utility grids re pled eneth the superstruture nd rrnged prllelly with the rod xis nd, if so, their numer; iii) whether the rod surfe hs 2-3 m-deep disontinuities. These detils were identified thnks to the use of the GPR. GPR Dt quisition Survey The GPR survey hd the purpose of identifying the types of lyers mking up the superstrutures of the pvements nd the presene of nomlies (e.g. utility grids) y proessing the rdr signls emitted y the trgets enountered t depth. h of the investigted sites hd surfe re of 3 x 3 m. The 1,6 MHz ntenn ws used for investigtions to depth of 1 m, while the 6 MHz ntenn ws used for investigtions to depth of 4 m; the sns were mde on grids with mesh of 1.5 nd.5 m, respetively. The gols of the 1,6 MHz ntenn survey were s follows: determining the influene of the hrteristis of the lyers mking up the rod superstrutures down to 1 m elow the rod surfe; sed on sttistil-desriptive nlysis of the rdrgrms, estlishing orreltions etween the inditors provided y the GPR tehnique (nlysis of sweep men nd sweep power reorded on the urves of signl ttenution with depth) nd the three investigted vriles: pvement surfe degrdtion, type of stone pvement nd trffi lod. s to the first point, the most signifint result ws the identifition of pvements where reinfored onrete sl hd een interposed etween the lyers of the superstruture (Tle 1). ll four pvements with uilt-in sl (Vi gostino, Vi delle Grzie 1, Vi Sn Mihele nd Vi delle Grzie 2) proved to hve no degrdtion; therefore, they re good. This finding onfirms the vlue of rigid lyer (reinfored onrete sl), whih prevents differentil settlements etween the pvement res exposed to trffi stress (trks left y tires) nd the remining pvement res. s to the seond point, three tegories of orreltions were estlished etween the investigted vriles. n the first tegory of orreltions, sites with the sme type of stone pvement nd the sme trffi lod were investigted on vrile ssumptions of pvement surfe degrdtion. Five omintions were identified mong the investigted rods (Tle 2). Tle 2: Rod pvements grouped y level of degrdtion No. Colestone Trffi Degrdtion Rod Code figs 4-5 no degrdtion Vi Snt gostino 1 porphyry hevy verge Vi Bfile high Vi Rom no degrdtion Vi delle Grzie 1 2 porphyry verge verge Vi dell nnunzit high Vi Sss 3 porphyry low no degrdtion Vi Borgo River verge Vi Sllustio 4 limestone low no degrdtion Vi delle Grzie 2 verge Vi di Pisignol no degrdtion Pizz Sn Pietro 5 leuititi lv low verge Vi Miniuio high Vi Snto Spirito Figures 4 nd 5 exhiit the sweep men nd sweep power digrms of the five omintions shown in Tle 2. n the tle, eh rod is ssoited with n lphnumeril ode, whih is found lso in the orresponding digrm. Compring the results of the sweep men digrms yields reurrent sequene etween the three levels of degrdtion (: no degrdtion; : verge degrdtion; : high degrdtion). n res where the rod is degrded, refleted signl is lmost lwys reorded. This signl, whih is piked up y the reeiver o ntenn, hs higher vlues thn the ones of less degrded rods. single exeption is omintion np (etween Vi Snto Spirito nd Pizz Sn Pietro), where signls re inverted. The nlysis of sweep power digrms shows tht they re firly onsistent with the onsidertions mde ove for the sweep men digrms.

8 Cse N 1 Cse N 2 Cse N 3 Cse N 4 Cse N 5 Figure 4: Sweep men of pvements grouped y level of degrdtion Cse N 1 Cse N 2 Cse N 3 Cse N 4 Cse N 5 Figure 5: Sweep power of pvements grouped y level of degrdtion

9 n the seond tegory of orreltions, sites with the sme level of degrdtion nd the sme trffi lod were investigted on vrile ssumptions in terms of type of stone pvement. Three omintions were identified mong the investigted rods (Tle 3). Tle 3: Pvements grouped y type of stone pvement No. Degrdtion Trffi Colestone Rod Code figs 6-7 porphyry Vi Borgo River 1 no degrdtion low limestone Vi delle Grzie 2 leuititi lv Pizz Sn Pietro porphyry Vi Sllustio 2 verge low limestone Vi di Pisignol leuititi lv Vi Miniuio 3 no degrdtion hevy porphyry Vi Snt gostino limestone Vi Sn Mihele Figures 6 nd 7 disply the sweep men nd sweep power digrms, respetively, of the three omintions shown in Tle 3. n the Tle, eh rod is ssoited with n lphnumeril ode, whih is used lso in the orresponding digrm. Cse N 1 Cse N 2 Cse N 3 Figure 6: Sweep men of pvements grouped y type of stone Cse N 1 Cse N 2 Cse N 3 Figure 7: Sweep power of pvements grouped y type of stone

10 P 2 P 2, P 2, P 2 Compring the results of the sweep men digrms gives reurrent sequene etween the three types of stone pvement (: porphyry; : limestone; : leuititi lv). Porphyry pvements hve more mrked refletion of eletromgneti wves thn limestone nd leuititi lv ones. This finding is less evident in o omintion np nmely on Vi Sllustio (porphyry pvement). The nlysis of sweep power digrms shows tht they in firly good greement with the onsidertions mde ove for the sweep men digrms, o nd the nomly deteted in omintion np is enhned. n the third tegory of orreltions, sites with the sme level of degrdtion nd the sme type of stone pvement were investigted on vrile ssumptions of trffi lod. mong the investigted rods, three omintions were identified, s speified in Tle 4. Tle 4: Pvements grouped y trffi lod N Degrdtion Colestone Trffi Rod Code figs 8-9 hevy Vi Snt gostino 1 no degrdtion porphyry verge Vi delle Grzie 1 low Vi Borgo River hevy Vi Bfile 2 verge porphyry verge Vi dell nnunzit low Vi Sllustio 3 no degrdtion limestone hevy Vi Sn Mihele low Vi delle Grzie 2 Figures 8 nd 9 exhiit the sweep men nd sweep power digrms, respetively, of the three omintions stted in Tle 4. n the tle, eh rod is ssoited with n lphnumeril ode, whih is found lso in the orresponding digrm. Compring the results of the sweep men digrms gives reurrent sequene etween the three trffi lods (: hevy; : verge; : low). n lmost ll ses, pvements exposed to hevy trffi lod hve more pronouned refletion of eletromgneti wves thn those where the trffi lod is lower. This finding o is less evident in omintion np nmely on Vi Bfile (hevy trffi). The sweep power digrms re firly onsistent with the onsidertions mde ove for the sweep men digrms, nd the nomly reorded in o omintion np is highly enhned. The gols of the 6 MHz ntenn survey were s follows: identifying utility grids, if ny, underlying the rod superstruture (i.e. in the suse t depth of over 1 m from the rod surfe); identifying extensive nd very deep disontinuities (i.e. t depth of over 2 m from the rod surfe). With regrd to the first point, the investigtion identified the numer of utility grids loted eneth the pvements (Tle 1). This finding infers tht ll pvements with high numer of utility grids (Vi Rom, Vi Sss, Vi degli lemnni nd Vi Snto Spirito) hve high level of degrdtion. This degrdtion depends on opening of trenhes for instlling or mintining utility grids nd onsequent reworking of the shllow lyers of the rod superstruture. The settlement of the trenh fills indues differentil filures nd ensuing deformtion of the rod surfe nd loosening of the joints etween the stones (loss of interloking effet). This proess filittes removl of some pvement stones y the tires of pssing vehiles. Cse N 1 Cse N 2 Cse N 3 Figure 8: Sweep men of pvements grouped y trffi lod

11 TB 11 TB 12 TB 13 TB 14 TB Cse N 1 Cse N 2 Cse N 3 Figure 9: Sweep power of pvements grouped y trffi lod With regrd to the seond point, the investigtion identified very deep disontinuities in the following three rods: Vi Sss, Vi degli lemnni nd Vi Snto Spirito. These rods re the sme s those hving high numer of underlying utility grids nd high level of degrdtion. Figures 1, 11 nd 12 disply the rdrgrms otined from the ove-mentioned three rods, whose disontinuities lie t depth of 2-3 m from the rod surfe. lso in this instne, the high degrdtion of the rod pvements depends on the lk of homogeneous suse nd on indequte omption of the deep lyers. L LRR 16 LRR 15 LRR 14 LRR 13 LRR 12 LRR 11 (,) LRR 1 Figure 1: Deep rdr disontinuity on Vi Sss 3. T L TB 1 TB Figure 11: Deep rdr disontinuity on Vi degli lemnni T

12 THH L 2. THH18 T THH19 Figure 12: Deep rdr disontinuity on Vi Snto Spirito CNCLUSNS The pper disusses the findings from GPR investigtion on olestone rod pvements loted in the historil enter of L quil (ruzzo Region). The investigtion ws imed t ssessing the degrdtion of the pvements nd their possile usl ftors. The GPR investigtion used 1,6 MHz (down to depth of 1 m) nd 6 MHz (down to depth of 4 m) ntenns. The gols of the investigtion on the upper lyers of the pvements (1,6 MHz ntenn) were s follows: determining the influene of the hrteristis of the rod superstruture lyers; finding orreltions etween the following vriles: type of stone pvement, trffi lod, pvement surfe degrdtion nd GPR sns. s to the first point, the investigtion showed no degrdtion in the pvements whose superstruture lyers hd n interposed reinfored onrete sl; thus, ll these pvements re good. s to the seond point, the investigtion estlished three orreltions etween the investigted vriles. n the first tegory of orreltions, sites with the sme type of stone pvement nd the sme trffi lod were investigted on vrious ssumptions of pvement surfe degrdtion. Results show tht in res where the rod is degrded, the refleted rdr signl hs higher vlues thn the ones of less degrded rods. n the seond tegory of orreltions, sites with the sme level of degrdtion nd the sme trffi lod were investigted on vrious ssumptions of type of stone pvement. Results show tht porphyry pvements hve more mrked refletion of eletromgneti wves thn limestone nd leuititi lv pvements. n the third tegory of orreltions, sites with the sme level of degrdtion nd the sme type of stone pvement were investigted on vrious ssumptions of trffi lod. Results shows tht pvements exposed to hevy trffi lod hve more mrked rdr signl refletion thn those where trffi lod is lower. The gols of the investigtion on the deep lyers of the pvements (6 MHz ntenn) were s follows: identifying utility grids, if ny, eneth the rod superstruture (i.e. in the suse t depth of over 1 m from the rod surfe); deteting extensive nd very deep disontinuities (t depth of over 2 m from the rod surfe). s to the first point, the investigtion identified the numer of utility grids underlying the pvements, inditing tht ll pvements with high numer of utility grids re ffeted y high degrdtion. s to the seond point, the investigtion identified rods with very deep disontinuities; lso in this instne, degrdtion is high. The study reported in this pper estlished good sttistil orreltions etween GPR signls nd the hrteristis of the investigted olestone rod pvements. n the future, these orreltions will hopefully mke it possile to develop ll-gpr tehniques for investigting rod pvement degrdtion. ndeed, these tehniques hve the dvntges of eing nondestrutive, esy nd fst to use nd ost-effetive. The results desried in this pper sustntite the expeted good performne of GPR tehniques in the investigtion of olestone rod pvement degrdtion.

13 RFRNCS BNDTT,.; NGÒ, C. (22), Rod sfety nd pvement mngement: new perspetives nd dvned tehnologies, Proeedings of nterntionl Symposium on Sfety Siene nd Tehnology (SSST), Ti n, Chin. BNDTT,.; NGÒ, C. (22), Dignosi del degrdo delle pvimentzioni on Geordr e siurezz strdle, in Riqulifizione funzionle e siurezz del sistem virio: Proeedings of the seond nterntionl Conferene, SV, Prm, tly, 3-31 otoer, volume 2, pp BNDTT,.; D BLSS, M.R., (21), Dignosti delle sovrstrutture strdli, Rivist tlin - Qurry & Constrution, giugno, s editrie: P, Prm, pp BLNC, G. (1995), Pvimentzioni in pietr, s editrie: L Nuov tli Sientifi, Rom. BUCCH,.; BSUZZ, K.; SNGRG, C. (22), ndgini strutturli integrte sulle pvimentzioni strdli, Rivist tlin - Qurry & Constrution, novemre, s editrie: P, Prm, pp CHUN-LK, L.; SCULLN, T.; CHN, P. (1992), Using ground penetrtion rdr tehnology for pvement evlutions in Texs US, fourth nterntionl Conferene on Ground Penetrting Rdr, June 8-13, Rovniemi, Finlnd, edited y Puli Hnninen nd Sini utio, Geologil Survey of Finlnd, Speil Pper 16, pp GTT, G.; LUZZ, R. (1998), L impiego del geordr per il rilevmento in sito delle pvimentzioni strdli, Rivist tlin - Qurry & Constrution, gennio, s editrie: P, Prm, pp