What’s the Difference Between a Geotechnical Investigation and a Geophysical Survey?

Whether you’re breaking ground on a commercial, residential, or public project, understanding the surfaces you’re building upon is crucial. Gaining a thorough understanding involves conducting a stringent site investigation to discover the subsurface conditions present on-site. One of the first steps in construction planning is to conduct a geotechnical investigation to get a sense of the soil consistency, groundwater levels, potential hazards, and general conditions. The geotechnical investigation scope of work may vary based on a number of factors, so working with an experienced team is key for meeting all regulations and producing a sound structure. But what’s the difference between a geotechnical investigation and a geophysical survey?

The geophysical survey definition and purpose is to get a “picture” of what the soils “look” like under the surface. Specialists use highly sensitive electronic tools to produce a detailed image or map that enables engineers to understand the physics behind the subsurface conditions. Below, our team will further discuss the geotechnical survey scope of work and geophysical survey definition to help you prepare for your next job.

Purpose of a Geotechnical Investigation

Geotechnical site investigations are commonly referred to as or geotechnical “surveys”. A site investigation is tasked with discovering the current soil status and subsurface conditions. Surface-level and subsurface field tests will be conducted during a geotechnical investigation and soil samples will be taken and studied to determine the feasibility of building on a site. Geotechnical investigations come in many forms, but regardless of the method, they all typically share a common goal of analyzing one or more of the following:

  • Composition
  • Bedrock depth and composition
  • Conditions of groundwater depths
  • Impact of adjacent sites
  • Slope conditions
  • Construction requirements

From that analysis, a geotechnical engineer will develop a plan to reduce risks, avoid hazards, and construct a sound foundation. Hazards can include floods, groundswells, slides, permafrost, shrinkage, and erosion. As each of these occurrences can be highly likely depending on the site, discovering the way your soil will react is absolutely essential for constructing a durable, safe, and long-lasting structure — and is almost always a requirement to obtain building permits.

Purpose of a Geophysical Investigation

Now that we’ve rounded out the scope of work, let’s take a closer look at the difference between a geotechnical investigation and geophysical survey. As we’ve discussed, the geophysical survey definition is more about how we can obtain a “picture” of the subsurface conditions, rather than understanding their behavior once built upon. Graphs, maps, and images produced from a geophysical survey shed light on potential hazards beneath the ground surface without drilling borings or performing other subsurface testing.

Geophysical surveys provide insight into magnetic and gravitational fields that radiate from the earth’s core, which offer inherently important information concerning seismic activity and internal structures. Along with this, the results of a geophysical survey can be applied to understand the position of underground objects, mitigate seismic risk, and produce 3D imaging of subsurface data. Geophysical surveys can be conducted from the air, on the ground, and sometimes through boreholes.

Consult With Central Geotechnical Services on Your Next Project

If you need insight into the subsurface conditions at your job site, work with the experts at Central Geotech. Our team has experience working on projects of every scale around the globe. We can help you understand the conditions at your site and build a risk-mitigation plan for a successful build. If you have any questions about site surveys and investigations, contact us today to talk shop.