I've heard a lot about Rammed Aggregate Columns, shouldn't I use them instead of dynamic compaction?

 

Rammed Aggregate Columns, which we install under the trade name Terrapiers, can also be an excellent solution when ground improvement is needed.  However, Terrapiers commonly cost 2 to 10 times the cost of dynamic compaction, and we would never advise the more costly option unless it was necessary.  As the only contractor who uses both methods, we are uniquely qualified to assist your design team in determining the most appropriate ground improvement solution for your project.

Isn't Dynamic Compaction the same as Rapid Impact Compaction (RIC)?

 

It’s similar, in that both processes use impact to improve the soils.  However, RIC uses a relatively light weight (7 tons) falling a very small distance (3 to 4 feet), so its effect is very limited.  Its manufacturer suggests a maximum depth of compaction of 3 meters in very clean sands, decreasing rapidly with increasing fines content.  Dynamic compaction, on the other hand, uses weights of 6 to 20 tons falling from heights of up to 80 feet, and can achieve a significantly greater depth and degree of improvement.

How do you know it has been successful?

 

The geotechnical consultant may specify a variety of subsurface testing techniques to verify that the improvement has been achieved.  Unfortunately, experience has shown that in many cases, the testing does not accurately indicate the amount of improvement, unless it is done weeks or even months after the compaction is done.  The simplest, and perhaps the most reliable indication of improvement is through elevation surveys of the compaction. Area.  If the surface has been lowered, significant improvement has occurred.

Will it work on my site?

 

Dynamic compaction can work in most soil types, but the suitability depends on many factors, including soil type, groundwater conditions, proposed construction type, and type and location of other nearby buildings.  We routinely assist owners, general contractors, and design consultants in deciding just what type of ground improvement is the most suitable for a specific project.

Can I do it myself?

 

You can certainly buy a crane and build yourself a weight and try it.  On the other hand, we’ve invested a lot of years in learning both the technical and practical aspects of the process, and made plenty of mistakes along the way.  Do you really want to go through that learning process on your own for just one project?

What about vibrations?

 

Vibrations are not as high as most people would expect.  We have worked within 50 feet of existing buildings, and withing 15 feet of underground utilities without causing damage.  A much bigger concern in most cases is public perception, because you can feel the vibration long before its strong enough to cause damage.  IT is often very important to document conditions of surrounding buildings before dynamic compaction, and to monitor vibrations throughout the construction process.

I have to compact below the groundwater table, it can't work there, right?

 

We have done hundreds of projects in which the soils below the groundwater were improved.  However, when planning a project where the groundwater is near the surface, it becomes important to conduct the compaction in a series of phases.  After each phase of compaction, we wait until the piezometric pressure returns to normal before applying additional compaction effort.

How do you know when to stop?

 

We plan our compaction program using a combination of published guidelines and corporate experience, but we continually monitor the tamper penetration, ground heave, and other visible indications to verify that the ground is reacting as we anticipated.  Based on those visual observations, we may decide to do additional compaction in some or all of the compaction area.

Who designs the program, and who is responsible for the results?

 

In many cases, a geotechnical consultant designs the details of the compaction program.  In those cases, the consultant should take responsibility for the resulting performance.  On the other hand, we offer complete design services, and can provide engineering evaluations of the completed compaction operations.