The auger boring method for installing casing has been in existence for more than 70 years, and during those 70 years we have seen the size, scope, and accuracy improve dramatically. When preparing for an auger bore several key factors will help you complete you bore on grade, on time, on-budget and last but not least safely.
Auger Boring Prep Steps
- Call 811 to locate existing utilities
- Determine site prep for receiving materials, machinery, secure storage and spoil disposal/storage. The contractor must have adequate space at the bore pit for equipment to move safely around the area for staging and spoil disposal.
- The depth and side slope of the bore pit is determined. Shallow bore pits may be tapered, but most bore pits will require proper wall shoring to protect workers from trench collapse. Pits should be designed to the Federal Regulations OSHA Code 29CFR, Part 1926 Subpart P.
- Setting the backstop and the base for the auger boring machine is a critical element to a successful auger bore. Low to medium thrust bores may use steel sheeting, steel plate or wooden timbers may be adequate. Longer and large diameter bores may require a concrete backstop. Thrust loads from some of the larger Auger Bore Machines exceed 1.5 to more than 2 million lbs of thrust. A sump for pumping ground water is placed in the rear corner of the pit depending on the slope.
- Exit Pit- Most bores require an exit pit at the end of the bore. Safety requirements for an exit pit are the same as an entrance pit. During the boring process no personnel should be in the exit pit unless absolutely necessary. The unexpected entry of the boring head into the exit pit can cause serous injury or death.
- Equipment Setup- Most sites will require excavators or cranes to set the auger boring machines, casing and auger. Use the appropriate chains and slings for installing the equipment, many machines are separated into separate lifts to lighten the maximum lift needed. When loading auger into casing it must have a cross member welded in the casing to prevent the auger from sliding inside the casing during loading into the pit.
- Auger boring machines are designed for cased bores and highly discouraged for free boring. Free boring has a much higher chance for the auger bore machine to catch and turnover.
- It is often recommended to use lubrication on the outside of the casing to reduce friction between casing and the soil, this will reduce the thrust loads. There are many options for lubrication solutions based on soil conditions.
- Auger boring machines safety equipment include but are not limited to:
- Emergency stop switches positioned at the operator and on some machines around the front and back of machine on each side.
- Operator presence lanyard is used to shut down the engine if the operator leaves the operating station.
- Winch or rack drive systems use delayed light and sound warnings to notify personnel that the machine is readying to move.
- Keepers, hold downs and trap track are all methods for securing machine to the track, never operate the machine if the keepers or hold downs are not engaged to the track. A machine that is operated without being engaged to the track is not a safe method and may turnover.
- Fire Extinguishers are located on the auger boring machine
- Spoil removal safety door, restrict personnel to dangerous moving parts area as well protect against flying objects from spoil chute directly to the bore pit.
- Tilt sensor shuts down machine if degree of tilt angle exceeds a certain degree
- Read and understand manufacturer’s manual, understand all the safety decal meanings on the machine prior to operating.
Auger boring is a commonly used method to install cased utility bores. The addition of pilot bore systems like the Akkerman 240GBM used in concert with auger boring machines greatly enhance the accuracy for today’s auger boring projects.