Road humps–or accidental “speed bumps”–are expensive, time-consuming errors that shouldn’t happen in the first place. Though less common these days than during the telecom boom (when it seemed like anyone with access to a backreamer could install conduit without much supervision), there are still some conditions under which road humping can occur. Drilling the pilot shot usually goes smoothly–it’s during the backream process that road humps are most likely to happen. Pay attention to these causes and indications to avoid costly repairs during your job.
Wrong tool for the ground
The most common cause of a road hump is the use of the wrong tool for the ground. Each piece of HDD tooling is specially designed to perform best in particular ground conditions. Pay attention to these specifications. For example, if you use a tool meant for cobble conditions, thinking it will easily cut through clay or sand, you’re going to experience problems that can create a speed bump. Instead of performing a quality drilling action combined with the appropriate amount of fluid to carry out cuttings, your tool will likely just ball up. Your backreamer will simply push the material to the side, compacting it into areas with the least resistance.
Going too fast
Allow your HDD tooling to perform the function for which it was designed. Never try to rush a job in the interest of saving time or money. When you don’t allow the equipment to carry out cuttings with the appropriate amount of fluid, it forces all the material toward the machine, building up pressure in the ground that can cause a hump.
Inadvertent returns—or “frack outs– can be a telltale sign that you’re creating a hump. Usually, when you hump the road, you’ll see a frack out as well. If not, continuing without adjustment is likely to lead to humping. However, keep in mind that humps can happen even without any sign of fluid leaks.
Improper fluid mixing
Make sure you have the right ratio of fluid, especially in clay conditions. If your fluid ratio isn’t correct, your tool will ball up–essentially making it the wrong tool for the ground. Your HDD tooling should be cutting, mixing, pumping cuttings out of the hole, all at the appropriate speed for the job. Cuttings that remain in the hole, combined with heat from spinning, can cause your slurry to harden like pottery clay. Do this long enough on a job and it’s like trying to pull a giant doorknob through the ground. You’ll displace soil–and create a speed bump.
Road humps can be caused by engineers who mistakenly underestimate the amount of cover needed in relation to the diameter of the pipe and type of ground. Some soils will compress more than others. This should be factored into the job strategy before you begin and should be adjusted if you run into any surprises while drilling. Pay close attention to the soil types at every depth and along the entire distance of your pilot bore before selecting the most appropriate HDD tooling for your job.
Surging pressure readings could be a signal that you’re getting into conditions that you didn’t anticipate. Use this as a sign to slow down and evaluate why your pressure is high. Cycle several lengths of drill rod whenever fluid pressure is too high or surging. This can often relieve a blockage and fluid pressure, lessening the stress on surrounding ground cover.
Road humping can happen in any type of ground while backreaming a hole of any size, but it’s most common when drilling larger holes. Though humps in landscaping or uncovered surfaces might not seem like a big deal, create a speed bump on a highway or major city street and you have a significant repair job ahead. Use the right backreamer, take your time and pay attention to any anomalies in your equipment readings and you should have a smooth road ahead.