Notice of Retraction and Apology
To all Visitors of our Site: I declare that our website contained information that was inaccurate, and in retrospect, was offensive and disrespectful to our longtime Customer and highly qualified construction Client, Obayashi Corporation of Japan, along with their Joint Venture (JV) Partners, Taisei Corporation and Kosei Corporation. The referenced Project Site name is Hiroshima Expressway 5 Shield Tunnel Project and the Robbins Technical Article titled https://www.robbinstbm.com/grout-or-not/, which states as if the JV selected the wrong type of TBM for the Hiroshima Project.
We retract the statements made in our article such as, “Contractors who are used to tunneling in soft ground may not realize that when using a Slurry TBM in rock, inspections must be frequent due to increased cutter consumption. We have seen this borne out on recent projects such as the Hiroshima Expressway Line 5 in Japan” because these statements were not based on facts and were incorrect. This statement reads as if the contractor did not review other optional TBM types, when in fact, the JV did indeed study all TBM types and methods to excavate this Express Tunnel.
There were additional incorrect statements made in the Article as follows:
- The same paragraph of the Article continues,”…, and they (contractor) were expecting up to 13 bar water pressure. This high pressure water zone was only in a small section of the overall tunnel length, about 5 percent.“
- The Article further states, “The contractor in Hiroshima had grouted off from the surface a planned safe zone in which to inspect the cutterhead without requiring a hyperbaric intervention, but this strategy did not go according to plan. The abrasive rock damaged the cutters and cutterhead before they could reach the safe zone, resulting in unplanned delays“.
- The same paragraph of the Article continues, “…grout off from the surface a planned safe zone…“.
The reason for choosing a Slurry type TBM was not solely based on the high water pressure but was also a result of the JV’s extensive review of all aspects of the tunnel requirements.
There was no plan to grout a “safe zone/safe haven” from the surface as other plans for cutter changes were in place and such plans have proven to be effective over numerous cutter change events.
Robbins commits to have more peer review and where a Client is involved, to have the Client review prior to presenting such data on our website.
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