(A) A heavy timber shaft at both ends of the tunnel will be provided in order to prevent failure of the embankments and to maintain access to the tunnel. The tunnel liner plates shall be installed by tunnel methods using an approved method to support the face of periphery of the excavation, which support shall be adequately strong, braced, and shored. This support shall be maintained during non-working hours in order to prevent cave-ins. The contractor shall have approved plans of a method to support the face and periphery of the excavation, before doing any work.
(B) The excavation for the tunnel liner plate shall be advanced in increments not greater than 2 feet, and the liner plates shall be installed immediately after each increment of excavation. Excavation shall be carried on in such a manner that voids behind the liner plates will be held to a minimum. Such voids shall be completely filled with grout placed under pressure.
(C) It is a requirement that at least 2 grout plugs be provided per ring to appropriately fill voids between the liner plate and the excavation.
(D) It is the responsibility of the specific utilities, or agencies responsible for construction work, to direct the contractor to begin the grouting operation as soon as a sufficient length of tunnel liner plate has been installed that will insure a proper seal. Grouting in general shall proceed progressively with each adjacent set of holes provided in the liner plates. All voids shall be completely filled within the working day with grout. It will be necessary that a bulkhead be made sufficient to insure the proper seal in order that all voids will be completely filled with the grout being placed under pressure. The grouting equipment shall have a minimum capacity of 1/2 cubic yard in order to assure that adequate grouting materials will be placed within a reasonable period of time to avoid the setting up of grouting from the previous grout batch. Upon completion of grouting, all holes shall be plugged with the fitting provided.
(Ord. —, passed 6-30-2009) Penalty, see § 54.99