Trenchless Delivery Methods – Part II: Types

By Arvid Veidmark III, President at SSC Underground

It is no surprise that trenchless technology is taking the industry by storm. When it comes to determining the most optimal method, it is imperative to first take all the considerations into account. Once it has been decided as the best route to take, how do you know which solution will produce the best results for your project to stay on track

Here's a list we’ve compiled to expand on the main trenchless delivery types, along with quick points on the pros and cons for each to keep in mind. As always, we recommend partnering with a trusted trenchless technology company that is a local expert in delivering underground construction.

For more information on the initial considerations step of this process,
read Trenchless Delivery Methods – Part I.

4 Main Types

Horizontal Auger Boring (HAB)

Well-known and commonly referred to as “Jack and Bore,” Horizontal Auger Boring (HAB) is a solid trenchless installation option for steel casing of 12” to 72” in diameter, starting at 20’ out to 500’ in length. Casing is installed in 10’ or 20’ joints and bore pits are 40’ long x 14’ wide. 

Pros: Proven, established method used when installing steel casing under freeways, canals, or railroad tracks; effectively can provide installation in a fairly quick time frame given the right soil condition.

Cons: Requires not only expert knowledge and experience but the proper HAB machine for the specific conditions; may not provide precise line and grade accuracy; limitations for length of drive that can be achieved

Pipe Jacking/Utility Tunneling

Pipe jacking (PJ) and utility tunneling (UT) are trenchless construction methods that uses a motorized head with an operator inside the jacking pipe or tunnel. Since the method requires personnel entry, the casing or tunnel size starts at a 48” diameter, even though it is theoretically possible for a person to enter a 36” or 42” diameter tunnel. It would be very difficult for a person to work safely and efficiently.

Pros: Designed to tunnel through anything from sand to hard rock; still widely used today due to its speed; smaller disturb zone; requires less rock support than drilling and blasting

Cons: Significant setup and dismantling time; limited range of available tunnel cross-section shapes; alternatives may be faster depending on rock mass quality

Small Boring Unit (SBU)

For small diameter scenarios, an auger attachment that can be used to avoid hand tunneling is a Small Boring Unit (SBU). It is typically used on underground utility installations, between 100’ and 300’ in length, ideal for waterlines and dry utilities.  Sizes range from 24” up to 66”. Bore pit: 44’ long x 14’ wide.

Pros: Can easily cut hard rock faster in small diameter drives than any other method available; the most time- and cost-effective way to bore through hard rock like limestone, cobbles, caliche, and river run

Cons: Cannot be used for large diameter tunneling; line and grade accuracy is not precise

Did you know?: SSC Underground is the first to offer this technology in Arizona and is the leading auger boring company in Phoenix!

Hand Tunneling

Hand tunneling is the main alternative to auger boring and is essentially described as a person manually excavating from the face of the tunnel with a hand tool. This is ideal when mechanical excavation is not an option but must be completed. Bore pit: 40’ long x 14’ wide but has the capability to be shrunk if the site requires it.

Pros: Longest trusted; safest method since the technician can clearly see any potential hazards ahead; only method where line and grade accuracy can be guaranteed; ability to handle all soil types

Cons: 4’ to 6’ per shift is typical production; sizes start at 42” but most companies will only start at 48” for safety 

So when it comes to your unique project, the first step is always taking into account all the considerations, and then it will lead to making an educated decision on which trenchless delivery method will be right for the situation.

Keeping these pros and cons in mind, it is important to understand there is always more to consider below the surface and it is not always a clear answer to uncover. For that reason, we recommend partnering with a trusted trenchless technology company that is a local expert in delivering underground construction.

For more information on the initial considerations step of this process,
read Trenchless Delivery Methods – Part I.