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Geotechnical Engineering & Soil Testing

Geotechnical Engineering is a branch of Civil Engineering that is focused on what is below the ground surface. Geotechnical investigations are conducted to observe the soils, rocks, and other materials that are beneath the Earth’s surface. At Alta Design, we design and implement geotechnical investigations that will provide all of the necessary information to assess the suitability of those subsurface materials for the support of your project. Depending on the site constraints and project specifications, geotechnical investigations may include test pits and/or test borings. 

Test pits are holes that are opened in the ground by a back-hoe or track-hoe excavator, to a pre-determined depth, allowing us to observe the soil types and depths, and the presence of any limiting conditions such as groundwater or bedrock. Soil samples are easily collected from the wall of the excavation or from the excavated soil.

Test borings are performed by driving a split-barrel sampling tube into the ground, using a 140-pound drop hammer, in 6-inch increments. The number of drops - or "blows" - is counted per 6-inch increment, which allows us to estimate the density of the soils encountered, while simultaneously collecting soil samples. Typically, after advancing the split-barrel sampler an incremental depth of 2 feet, 4- to 8-inch diameter holes are drilled into the ground to advance the hole deeper. Holes are drilled using solid and/or hollow-stem augers attached to a drill rig that is usually track-mounted or truck-mounted. This procedure is then repeated until the hole reaches an overall depth specified by the engineer. 

Soil samples from both test pits and test borings are visually evaluated and classified by Alta. Additional laboratory testing of soil samples is facilitated, as needed.

We also perform infiltration testing – such as double-ring infiltrometer testing or hydraulic conductivity testing – to determine the rate at which stormwater may percolate into the ground surface at your property, and we can install temporary wells to monitor your groundwater levels.

Following the geotechnical investigation, we provide a Geotechnical Engineering Report, as applicable, which would detail the results of the geotechnical investigation and would offer recommendations and design parameters for the design and construction of the proposed project, including recommendations regarding foundation support; earthwork; slope stability; groundwater control; settlement analyses; and general design parameters.

On the left is a groundwater monitoring hole with PVC casing. On the right is a double-ring infiltrometer test in-progress.

The information provided by these Geotechnical Engineering Reports is utilized in Site DesignStormwater Management Engineering calculations and design, and Structural Engineering Analysis & Design.  

If you have a Geotechnical Engineering project that is not mentioned on this page, do not hesitate to CONTACT US. The services described are not all-inclusive.

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