Are vibrations a problem for neighboring structures?

 

Generally not.  We have used our downhole vibrators within about 10 feet of existing structures with no damage at all.

What materials can you compact?

 

The ideal material is very clean sand and gravel.  When the percentage of fines exceeds about 6 to 10 percent, the ability to measure the degree of compaction using normal geotechnical testing decreases substantially.  However, surface settlements in these soil types often indicate that significant improvement is still being accomplished, even where test results have not changed.  On one of our projects, static cone penetration tests were repeated several years after completion of the project, and the results increased by 500% as compared with the tests conducted within weeks of completion.

Can you compact below the water table?

 

Yes, most vibrocompaction work is performed on soils below the water table.

Do you have to use water jetting?

 

Generally some type of jetting is necessary, but it is sometimes possible to use air jetting instead of water to reduce water management issues.

How deep can you do vibrocompaction?

 

Most projects require less than 50 feet of improvement, but it is possible to compact to depths of 100 feet or more.

How much improvement is possible?

 

In clean granular soils, tests indicate that relative densities of 80% or more are routinely achievable.