2008-213 (5) - Laserfiche WebLink

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F 2) Drill Unit Positioning — The drill rig unit shall be positioned within the right-of-way or Owner's property to provide the desired bore route and pipe depth. Proper equipment anchoring is especially important for the existing sandy soils. 3) Drill Rods — The drill rods should be as least as strong as the equipment capability. The drill rod capabilities shall also be compatible with the planned bore route with respect to cumulative fatigue stresses. . 4) Drilling Fluid Usage — Drilling fluid shall be used to provide lubrication during the pilot boring, reaming and pullback operations to reduce the required torque and thrust of pullback loads. In addition, the drilling fluid shall stabilize the bore hole, cool the drill head (and internal circuitry), and remove cuttings and spoils. The crew must be trained in the proper use of drilling fluids and the appropriate types for various ground conditions. The Engineer shall be notified if excessive drilling fluid pressures or volumes are noticed. 5) Location and Tracking — In order to maintain the actual bore along the planned path, the pilot bore must be carefully tracked, and path confirmation established at least once each 15 ft interval. For paths with horizontal and vertical turns, or in critical areas including the vicinity of other obstacles, shorter intervals of 10 ft shall be used. Any misdirection of the drill head shall be corrected immediately. 6) Back Reaming — Where necessary, back reaming shall be performed to produce a hole size sufficiently large to readily install the pipe. Back reaming shall allow the bore hole to be created in stages, reducing the required torque and thrust loads at the machine. Back reaming operations shall help ensure that the capability of the machine is not exceeded due to the combined forces of increasing the hole diameter while pulling the pipe. Appropriate cutters and compactors compatible with the soil conditions shall be employed including proper usage of drilling fluid. Back reaming shall be used to reduce the possibility of voids or surface heaving or settlement, including unanticipated drilling fluid appearances. Hole diameter increments should be restricted to approximately 10 -inches or less during a single pass. The final hole diameter shall be 20% but in no case larger than 50% greater than the outer diameter of the pipe to provide clearance for pipe grips, allow spoils flow, and reduce the required loads during the pipe pullback operation. During back reaming, additional drill roads must be available at the pilot bore exit that are connected to a swivel at the rear of the reamer and pulled into the hole to maintain the path. Pipe Pullback 1) Gripping of Pipe — Due to the distance of the operation and the high pullback loads generated, secure gripping procedures must be used. Basket -type or internal only grips will not be allowed. The gripping method selected must allow the full tensile rating of the pipe to be developed. Appropriate types may include an internal/external clamping or bolting device, or a fused PE pipe adapter with a built- in pulling eye. In the latter case, a smaller diameter section of the adapter may serve as a breakaway link protecting the main section of pipe. 2) Swivel — A swivel is required between the reamer or compactor preceding the pipe to prevent the transmission of torsional loads to the pipe. The rating of the swivel 02400 — Directional Bore Crossings 02400 - 8