A geotechnical investigation is imperative before you commence any type of construction or building project. Considerable structural damage can be a trigger to homes built on poor foundations. The strength of these foundations begin with the type of soil the footings are placed upon. Moisture content in clay soils, in particular, can swell or shrink with dampness changes and settlement can ensue due to compressed soil or fill.
Geotechnical analysis is essential prior to contemplating house designs or construction plans. Soil conditions can dictate the foundation design and cost. The geotechnical report includes a site investigation of the subsurface soil and lime-rock properties that exist beneath the surface of the property. The soils exploration is performed in order to ascertain the engineering properties of how the subsurface elements and foundations will interact with the proposed construction. A geotechnical soil evaluation report encompasses a subterranean site analysis, which is then tested and verified by a geotechnical engineer. The principal reason for the test is to comprehend how ‘sensitive’ the soil is.
Soil boring evaluations identify incompatible subsurface soil conditions that have the potential to trigger settlement of the helical pile footings and concrete foundations. The assessment is also prepared to confirm that there are not any physical conditions or organics that could impair or disrupt the proposed construction.
SOIL BORING PROCEDURE
The soils narrative for a single family residence typically entails two soil borings, 30’ and 50’ deep. These assist to determine what the subsurface soils appear like on that lot/job project. The shortcoming to soils test is the analysis only tells you what the soil looks like in that specific bore hole. The single hole may not characterize the entire site and usually there is a difference from one bore hole to another.
In-situ (in the situation, or at site) testing methods incorporate penetration tests such as Standard Penetration Tests (SPT), which penetrate via drilling, direct push or punch. These assessments calculate the physical properties of the subsurface soil directly, minus removal. This delivers the advantages of producing a more precise reflection of soil circumstances underground.
EXPLAINING SOIL REACTIVITY
“Reactive Soil” is the way soil reacts with changing moisture content. The phrase ‘reactive soil’ doesn’t have anything to do with it being radioactive.
Soil reactivity is an indication how the soil on the building site is apt to shrink, shift or expand. All clay-based soils have the possibility to change volume and shift with fluctuations in the amount of moisture in the soil and are regularly called ‘reactive soils’ because of this. If poor soil reactivity is existing on your site then it can be a serious hindrance when building, specifically when it comes to concrete slab or multi-story structures. This soil condition requires serious review, as a different type of engineered foundation slab may be required. Most new structures in Southwest Florida with this type of underlying soil conditions are usually piling supported.
In the beginning phases of planning, it is essential to employ a licensed geotechnical engineer to perform a soil report on the property you propose to build on. The engineered report will identify the physical characteristics of the soil on your building development site. It will also include the natural constitution of the earth, and other necessary factors of the construction site. The soil report usually incorporates and specifies the foundation piling type and installation depth, for pile supported structures. In more compressed soils, a slab on grade foundation plan is engineered. Generally, the geotechnical engineer also performs the pile installation monitoring and provides a letter of certification verifying the foundation piles were installed to engineers specifications.
Our geotechnical team consists of highly experienced geotechnical engineers who participate in the vital role in the initial design and planning phases of a construction project. We recommend performing soil borings (Geotechnical Evaluation) at the site to provide engineered recommendations to facilitate in building pad preparation as well as helical pile foundation design.
Our geotechnical engineers primary focus is on providing on clients with the design of ground improvement techniques and helical pile bearing capacity with in-situ soil data without solely estimating pile capacity on installation torque only.
Foundation examinations, helical piling performance monitoring, and a practical approach are equally significant for the positive completion and engineering certification of projects.
NO GEOTECHNICAL SOIL BORING PRIOR TO CONSTRUCTION EXAMPLE
Recently, a specialty helical contractor encountered serious ramifications on an out island foundation project. The owner refused to engage the services of a geotechnical engineer and relied on the islands coconut telegraph to determine foundation piling depth. ( A recent helical project on the island was completed with helical piling projecting 45 foot into substrate to secure bearing capacity) The owner directed the general contractor to secure bids to install helical piling to a prescribed depth of 42 foot.
The specialty contractor mobilized equipment and product to the remote project site to commence construction. The first piling was unable to secure 6 ton loads at 28 foot of penetration. The second attempt saw the helical installed to a depth of 84 foot without torque or load bearing capacity being acquired. The 84 foot piling only secured a capacity of 3 tons.
The project was temporary ceased to allow structural engineer to compile additional data and provide a new engineered foundation plan. The original design designated nineteen (19) piling for the construction of 900 square foot stilt home.
After five long days the structural engineer came back with a revised plan of thirty-eight (38) additional piling for this light weight wood structure. The additional project cost would be close to $40,000.00, an astronomical cost increase for the owner.
This is a true and costly experience that could have been avoided with proper geotechnical information. It is imperative before you commence any type of construction or building project, that you secure the services of a licensed geotechnical engineering firm.