The two most common materials a Tulsa commercial contractor will deal with are soil and concrete. The American Institute for Constructors or AIC gives three soil components and four types of soil and rock components below:
“…Soil contains three components: solid (weathered rock and decayed vegetation), liquid (water), and gas (air). Soils are commonly classified by category, type, and/or grain size. Three broad categories used in soil classification include the following:
- Cohesive soils: soils with very small particles that typically stick together, such as clay
- Cohesionless soils: soils that do not tend to stick together such as gravel, sand, and silt
- Organic soils: soils that contain organic material, such as peat Soil type is typically used to classify soil and rock deposits in excavations based on their stability. OSHA standards classify four types of soil and rock deposits:
- Stable rock: natural, solid material that can be excavated with vertical sides and remains intact while exposed
- Type A: undisturbed cohesive soils with an unconfined compressive strength of 1.5 tons per square foot (tsf) or greater
- Type B: cohesive soils with unconfined compressive strength greater than 0.5 tsf but less than 1.5 tsf; also include stable, granular, cohesionless soils; previously disturbed soils; and unstable rock
- Type C: cohesive soils with an unconfined compressive strength of 0.5 tsf or less, unstable soils, and saturated soils and rock
Soil grain sizes are used to identify the composition and properties of a soil sample. Grain sizes are determined by performing a sieve analysis and classified according to U.S. standard sieve numbers … Soils coarser than a No. 200 sieve size are considered coarse-grained soils, and soils finer than a No. 200 sieve size are considered fine-grained soils…
- Capillarity: the rise of water, against gravity, from a water source into the voids within a soil. Soils with high capillarity typically have a smaller grain size and higher permeability, such as silts and very fine-grained sands.
- Frost heave: the vertical expansion of soil due to the freezing of water within the soil…”
For the Tulsa commercial contractor, soil, the conditions, and the components effect every other structural component of the building. Without the soil information a Tulsa commercial contractor would be unable to successfully install a fully operable building. The way soil suitability is identified is described by the AIC as follows:
“… Soil investigation generally begins with a preliminary soil survey that typically includes general geologic and topographical information obtainable from federal, state, and local governmental agencies. Subsurface soil exploration is the next step in soil investigation and consists of three steps:
- Boring: drilling or digging a hole in the ground. Common types of borings include auger borings, wash borings, test pits, and core borings.
- Sampling: removing the soil from the hole. Samples may be classified as either disturbed (auger and wash borings) or undisturbed (test pits and core borings).
- Testing: the process of determining the properties and characteristics of the soil. Testing may be done in the field or in a lab. The most common field test used in the United States is the standard penetration test (SPT)… The final step in soil investigation is the soil investigation report, or geotechnical report. The geotechnical report identifies the methods used for testing; provides a description of the site geology and subsurface conditions; and provides analysis, design, and construction recommendations. Also included in the geotechnical report is a map of test locations and boring logs, if boring is used…for an example of a boring log. Boring logs indicate what type and at what depth different soil types and conditions can be expected. They should be reviewed early in the construction process and can assist a contractor in identifying the amount of available fill from excavations, type of excavation protection that will be required, locations of potential soil contaminants, extent of any rock excavations, dewatering requirements, and other constructability factors…”
Once the Tulsa commercial contractor has the geotechnical report, several factors about the building the can be determined. The geotechnical report or Geo-tech report will identify the bearing capacity of the soil and the composite layers of the site, and with their recommendations the type, size, and functionality of the building can be determined. Since budgets are a factor of any projects, where the project is located and therefore the soil make up a key component. The AIC list show two categories of foundations and several subcategories that would have impacts on budgets below:
“… Shallow foundations bear on suitable soil found at the base of a structure. Shallow foundations are typically less expensive than deep foundations. Common types of shallow foundations include the following:
- Isolated, single column or pad footing: a pad of concrete that spreads a concentrated load from the building above.
- Wall, strip, or continuous footing: a continuous strip of concrete that supports a continuous load above, similar to a load-bearing wall.
- Monolithic slab on grade: a concrete slab with thickened edges at loads above. Least expensive type of foundation. Typically used in areas with little or no ground frost.
- Crawl space or basement: a foundation wall, usually concrete or masonry, set atop a concrete strip footing. Typically used in areas with deep ground frost, low water table, and/or grade changes.
- Mat or raft foundation: large, often thick, foundation that supports the entire structure. Often used when column footings become large enough that they overlap or are more economical to pour as one unit.
Deep foundations are used to penetrate upper layers of unsatisfactory soils to allow the structure to bear on satisfactory soils or rock deeper in the earth. Common types of deep foundations include the following:
- Caisson: a drilled or dug cylindrical shaft with belled end and, if required, filled with concrete. Used to transfer loads though layers of unsatisfactory soils to satisfactory soils or rock below.
- Piles: a material, typically timber, steel, or concrete, driven into the ground through unsatisfactory soil until a firm bearing layer (end bearing pile) or sufficient friction resistance (friction pile) is encountered…”I
If the Tulsa commercial contractor is going to install deep foundations with concrete piles and large continuous spread footings on top of those piles, the cost to owner and impact of the overall budget will be significant.