Tieback Installation – 30 Years of Innovation
Integral Construction, Inc. has engineered, drilled & installed thousands of tiebacks throughout the Seattle & Puget Sound Region over the past 30 years. We have developed specialized drilling techniques that allow for tieback installations in difficult site access situations. Integral Construction Inc. has engineered tieback construction applications for residential, commercial, industrial, City/County Municipal governments, state agencies, and public utilities.
A tieback is essentially a horizontal wire strand or rod anchor used to reinforce retaining walls for lateral stability. With one end of the tieback secured to the wall, the other end is anchored to stable earth materials. Tiebacks are typically installed into drilled small diameter holes, less than 12 inches, extending a sufficient distance so that the anchor zone is within earthen materials with sufficient pull out resistance. After the hole is drilled, the tieback tendon is installed and cement grout is then pumped under pressure into the tieback anchor holes so that the rods can utilize soil resistance to prevent tieback pullout and wall destabilization. The tied-back structure resists forces that would otherwise cause the wall to lean.
In many areas of Puget Sound creating retaining structures requires the use of Tieback Anchors to add strength to Soldier Pile or Concrete retaining walls. In most of the Puget Sound Basin the hard subsurface material into which the Tiebacks are to be established is either medium to dense sand or a hard blue-gray clay called Lawton Clay. Helical Tieback Anchors can be used effectively in these materials.
There are, however, several areas where the fine silts from underneath the glacier were compacted into a very dense rock like material called Glacial Till. In areas where there is rock or Glacial Till, the Helical Anchors will not work and in those areas we use an Anchor which has a rock bit followed by a hollow steel tube where grout is injected. These Anchors are called Injection Boring Anchors. There are many machines for installing this type of Anchor. As with the Helical Anchors, Integral Construction has specialized in providing our services where there is difficult access for standard equipment.
We use a portable air driven Jack Leg Drill, portable water jet cleaning, and a portable grout pump to install IBO anchors on slopes and in difficult access areas. In the Hard Glacial Till areas these types of anchors can deliver 4,000 lb. to 6,000 lb. of pull-out load capability per foot of embedment into these hard materials. We have installed and tested hundreds of these types of Tieback Anchors.
Integral IBO example. In the above picture you see a catch basin for the city that was located in a slide zone that had moved; breaking the lines. Integral was able to install IBO Tiebacks to stabilize the catch basin so that the lines could be attached and put back into use.
Advantages of the IBO :
- Simple drilling system
- Suitable for cramped and limited-access conditions
- Low manpower requirement
- Good connection with surrounding soil due to drilling and grouting
- Soil improvement thanks to rotary impact driving and flushing
- Piles can be lengthened or shortened on site
- Suits all ground conditions
- Rapid, effective ground and structural stabilization(ground improvement)
- Single step casing free operation significantly improves productivity
- Suitable for difficult and restricted access situations
- Ability to use smaller drilling rigs reduces mobilization costs
- Extreme low settlement characteristics – less than 5mm working load
- Enhanced mechanical bond with surrounding ground
- Minimal disturbance during installation
- No requirement for double corrosion protection in permanent works
- On site fabrication provides design flexibility
- Wide variety of drill bits to suit different ground conditions
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Lic # INTEGCI159K3