drilled shaft

Posted by & filed under buildings.

Drilled shafts are vital when it comes to building the foundations of a structure solidly and securely.

There is a common issue, however, in this type of construction: conditions around the structure and within the structure itself.

It’s important for designers and planners of a project using drill shafts to consider various factors. These include the concrete used, the depth below the surface of the ground and any placement underwater.

Here are 5 key considerations for drilled shaft construction.

1: Concrete Filling and Passing Ability

Drilled shafts are unique in comparison to alternative reinforced concrete structures. Therefore, the right concrete is crucial.

A concrete mix, used with drill shafts, has to flow easily through the tremie. This means that the best concrete for drill shaft construction should be fluid. It’s also important that the correct reinforcement cage is utilized in the process.

On top of this, the concrete must be able to pass through the reinforcement without causing any blockages. Every area of the drilled shaft needs to be reached and so the concrete must be able to pass through any small openings in the structure.

2: Loose Sediment at the Bottom of the Drilled Shaft

Any sediment at the bottom of the drilled shaft must be less than three inches. Any potential concrete issues or defects can cause major issues down the line. This can be the case, whatever the quality of the tremie system you are using in the construction.

The drill shaft cannot become clogged with sand or grit and must remain clean. It will need to be cleaned before the tremie discharges any concrete or slurry.

If it doesn’t, any excess debris can rise up the column of concrete and cause major issues in the construction process or later on.

3: Environmental Considerations

It’s important that the structure and the drill shafts are able to withstand any detrimental impact from the environment. Low permeability is required here so that the potential for corrosion on the reinforcement is lessened. The concrete that you use must combine low permeability and high-density properties.

In addition to this, if the drilled shaft features a large diameter. This means that high levels of heat or hydration must be avoided. It’s important to consider the temperature of the concrete mix. This is most notably crucial in environments that get hot.

If the structure is designed to go underwater, the mix must resist combining with external fluid. It should be a cohesive mixture to avoid bleeding, segregation resistance and leaching.

4: Weight and Resistance

When considering the weight of the structure, it’s important to note that vibration in the boreholes of deep drilled shafts can’t be used. Thus, the concrete needs to consolidate and fill under self-weight. There are also guidelines for stiffness and strength that must be researched and adhered to.

5: Keeping Records

It’s important to maintain records that will tally the volume of the concrete in comparison with the shaft elevation. This helps identify any potential areas in a structure where the concrete is filling in cavities and voids. Keeping records will help you find any unusual conditions.

Foundation Structures Inc.

When you think drilled foundations, think Foundation Structures. Founded in 1996, FSI delivers a wide range of expertise to keep projects ahead of schedule and within budget.

FSI is one of the premier drilled shaft contractors servicing parts of the Northeast and Mid-Atlantic regions. We specialize in the construction of large and small diameter drilled shafts. We are also experts in drilled piers and drilled holes.

Contact us with any queries or questions; we are more than happy to help.