2418.01 DESCRIPTION.
Installation of pipe culverts by jacking shall consist of furnishing and placing culvert pipe of the size, type, and design specified in the contract documents, in accordance with the provisions of this section.

This operation requires that the pipe culvert, as a unit or in sections, be forced through the existing embankment from side to side by application of force to the projecting end, the necessary excavation being performed by removal of the excavated material through the pipe as it progresses.

2418.02 MATERIALS.
Pipe for culverts to be installed by jacking shall meet requirements of Sections 4141 or 4145 for the type specified and the following requirements:

Pipe may be either in a single unit or sectional. If sectional, it shall have joints of a type that will assure positive engagement of the sections during and after the jacking process. Square end pipe without proper connecting devices will not be permitted. Pipe having projections on their exterior surfaces which will require an excavation larger than the body of the pipe will not be permitted.

2418.03 CONSTRUCTION
Before jacking is started, the pipe or initial section of pipe shall be carefully aligned on a prolongation of the line and grade shown in the contract documents or staked by the Engineer, and shall be held by braces, guideways, and other devices, to follow these lines and grades as close as possible as it progresses through the embankment.

The number and capacity of jacks used shall be adequate to exert sufficient force to overcome the greatest resistance to be encountered, considering both the weight (mass) of the pipe and the friction on its exterior surface.

Care shall be taken that the jacks and struts are placed against the backslope or buried anchors so that the thrust is applied parallel with the center line of the pipe and distributed equally among the jacks.

2418.04 JACKING CULVERTS.
The pressure exerted by the jacks shall be applied uniformly over the end of the pipe by a collar, or shall be distributed to a number of points around the perimeter by cross timbers. Application of pressure with the metal of the jack in direct contact with the pipe will not be permitted with either concrete or corrugated pipe. Suitable cushioning material shall be inserted between the jack and pipe. Spalled concrete or crumpled metal, which will result in an unsatisfactory joint when the succeeding section of pipe is placed, shall be cause for rejection and removal of the section that is damaged.

Excavation for a limited distance ahead of the forward end of the pipe will be permitted when the soil is sufficiently stable to stand without danger of caving. In this case, the hole shall be trimmed to the outside diameter of the pipe to reduce resistance to jacking and to maintain contact between embankment material and outside surface of the pipe. In soft or unstable soil, the pipe shall be allowed to cut its way through the soil to avoid danger of caving and subsidence of the overlying embankment and roadway. If the pipe is of metal with a coating of corrosion resisting material, care shall be taken to protect this coating from damage during jacking and excavating processes.

A small, high pressure, low volume water jet (4 gal/min maximum (15 L per minute maximum)) may be used to cut the soil within a steerable shield at the leading edge of the pipe being jacked. The water and the operation shall be controlled so there is no change in the condition of the soil adjacent to the pipe and no flow of water along the outside of the pipe.

Obstructions to the progress of the pipe, such as roots, boulders, or parts of former structures, shall be removed. Deviations from line or grade to pass obstructions shall be avoided if such deviation will result in unsatisfactory fitting joints. The use of explosives for removing obstructions is prohibited.

Provisions shall be made for keeping the excavation free from surface and seepage water during the jacking operation.

After the excavation is opened, the placing and jacking of the pipe shall follow immediately to avoid unnecessarily disturbing the stability of the embankment and roadbed.

Backfilling that may be necessary shall be done in accordance with Article 2402.09. Surplus excavated material may be uniformly spread in the immediate vicinity of the work, as directed by the Engineer.

2418.05 ACCURACY OF PLACEMENT.
When the location and grade line of the culvert have been determined by the position or elevation of the available outlet, insertion of the pipe shall be from the outlet end.

When the location and grade have been determined by the position of the inlet and the elevation to which water must be lowered at the upstream end, insertion of the pipe shall be from the inlet end.

In either case, deviation from designated flow line elevation and location at the initial point shall not exceed 0.1 foot (30 mm).

The alignment and elevation of the forward end of the pipe shall be kept under control throughout its passage through the embankment. Accumulated errors which cause the forward end of the pipe to deviate from the intended elevation or location by more than 25% of the internal diameter of the pipe may be cause for rejection.

Deviation from the prescribed line that reverses the fall of the grade line through the culvert shall be cause for rejection.

Openings more than 1/4 inch (5 mm) in width between adjacent sections of concrete pipe shall be filled with 1:2 cement/sand mortar.

2418.06 METHOD OF MEASUREMENT.
The quantity of jacked pipe culvert, in feet (meters), will be the measured length of culvert installed, excluding aprons, to the nearest foot (0.1 m). The quantity of jacked pipe culvert will be determined along the axis.

Normal excavation for jacked pipe culvert will not be measured for payment, but shall be considered incidental to pipe culverts installed by jacking. Excavation for boulders smaller than one-third the diameter of the pipe being installed, or parts of existing structures identified in the contract documents will not be measured for payment, but shall be considered incidental to the price bid for jacked pipe culvert. Excavation and removal of boulders larger than one-third the diameter of the pipe being installed, or parts of existing structures not identified in the contract documents will be paid for in accordance with Article 1109.03, B.

2418.07 BASIS OF PAYMENT.
The Contractor will be paid the contract unit price for jacked pipe culvert of the type and size specified per linear foot (meter). This payment shall be full compensation for materials, labor, and equipment necessary to complete the work. Culverts that consist of both jacked pipe culvert and conventionally placed pipe culvert will include separate bid items for each portion.