TIRE DAMAGE DURING TAXI-IN.

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AFTER LNDG AT NARITA INTL. WE WERE INSTRUCTED TO TAXI VIA ALPHA TO PAPA 6. FO CONTACTED RAMP CTL AND WAS INSTRUCTED 'CLRED TO GATE VIA PAPA 6. UPON ENTERING RAMP AREA; WE STRUCK A LARGE BUMP. I HAD NOT OBSERVED ANYTHING WHICH WOULD HAVE CAUSED A BUMP. I CONTINUED TO GATE (APPROX 75 YARDS). AFTER PARKING THE ACFT; THE OTHER CAPT AND I WENT TO CHK THE ACFT. 2 TIRES HAD DEEP GASHES AND ONE HAD A CHUNK OF CONCRETE APPROX 4 INCHES IN DIAMETER EMBEDDED IN IT. THE WX WAS FOGGY WITH MIST. IT WAS DUSK AND VISIBILITY WAS POOR. I HAD CROSSED OVER AN AREA OF RAMP CONSTRUCTION WHICH WAS NOT NOTAMED; BUT IS SHOWN ON COMMERCIAL ARPT PAGE PAGE 20-8H NEW TOKYO INTL. THE FOLLOWING DAY I OBSERVED THE AREA FROM THE TERMINAL BUILDING. IT APPEARED TO HAVE A BARRIER APPROX 18 INCHES HIGH OF SOME TYPE BLOCK; SPACED APPROX 10 FT APART. THERE WAS NO LIGHTING ON IT. IN CONVERSATIONS WITH OTHER CREWS; THEY HAD BEEN COMPLAINING FOR 2 DAYS ABOUT THE LOW VISIBILITY OF THE BARRIER. AT LEAST 3 OF OUR OWN COMPANY FLTS CLAIMED TO HAVE HAD NEAR MISSES WITH THE AREA. THE COMPANY RPTED THAT 10 TIRES WERE DAMAGED AND HAD TO BE CHANGED. SUPPLEMENTAL INFORMATION FROM ACN 287361: APPARENTLY; BECAUSE OF THE DUSK CONDITIONS; ASSOCIATED LOW VISIBILITY; AND THE APPARENT LACK OF MARKINGS OR LIGHTING TO WARN OF THE DEBRIS ASSOCIATED WITH A RAMP REPAIR SITE; WE WERE UNABLE TO SEE IT. I BELIEVE IT IS POSSIBLE THE RAMP RADIO OPERATOR WAS UNAWARE OF THE REPAIR SITE. OR AT THE VERY LEAST DID NOT KNOW OF THE HAZARD IT WAS CREATING IN POOR VISIBILITY CONDITIONS. THE SITE SHOULD HAVE BEEN BETTER MARKED AND WARNING LIGHTS INSTALLED AND OPERATING. TAXI INSTRUCTIONS FROM RAMP CTL SHOULD HAVE INCLUDED THE DIVERSION AROUND THE SITE AS PER THE 20-8 COMMERCIAL ARPT PAGE.