What on Earth to Do with Dirt

Geotechnical engineering is a very important, but sometimes overlooked parked of any construction project. Geotechnical engineering, AKA geotechnics, is a branch of civil engineering that deals with the behavior of earth materials. It combines the principles of soil mechanics and rock mechanics to solve engineering problems.

Geotechnical engineering is especially important when considering how to build the foundation of most construction projects. The foundation of any construction project should be the utmost concern for anyone involved in a project from a developer to a homeowner who is adding an addition to their home.

First let's discuss the two types of soils. There are cohesive and cohesionless soils.

• Cohesion Soils

• Include clays, silts, marl and muck

• Can be compressed

• Hard to control

• Organic makeup

• Cohesionless Soils

• Includes sands and limestones

• Granular and don't compress

• Easy to work with

There are also two foundation types, deep and shallow foundations. Either soil type can require either type foundation based on several different factors (see below):

• Deep Foundations

• For soils that can't support loads

• Foundation loads exceed traditional footings

• Building Settlement

• Examples

• Augercast pilings- hole that is drilled to a required depth or degree of resistance and then filled with fluid grout to ground level.

• Used when soil is weak & compressible or when there is water to transfer load from those weak soil strata to stronger, less compressible soil layers.

• Precast concrete piling- displacement pile that comes in a variety of shapes that are hammered directly into the ground.

• Used when weak soil is very deep

• Steel H piling- square structural beams designed to reach deeper soil strata than other types of pilings.

• Used for deep soil penetration that other piles can't reach

• Cassions- watertight retaining structure used to work on foundations below water.

• Used in construction of foundations for bridge piers or concrete dams

• Micro piles-very small grouted pile with internal reinforcement.

• Helical piles- consists of a round steel shaft and helical blades.

• Shallow Foundations

• Economic Factors are important

• Loading & soil types will permit

• Soil treatments will work

• Examples

• Grade bearing- concrete foundation with rectangular cross section running around the perimeter of the house under exterior walls.

• Used where the surface soil's load-bearing capacity is less then the anticipated design loads.

• Isolated column pads- used to carry and spread concentrated loads

• Common with columns or pillars

• Continuous wall footings- supports more than two columns on a wall thus creating stability for the foundation.

Now that we have discussed soil and foundation types, you can see why it is so important to find a geotechnical engineer you can trust. The fate of your foundation rests completely on the condition of your soil. That being said, living in South Florida presents it's own challenges to geotechnical engineering because of our high water table. At SPEC we have been designing the foundations of South Florida since 1979. We have worked on projects from the I-595/I-75 interchange to several recently completed high rise structures in our metropolitan areas.