What Happens During a Geotechnical Soil Investigation?
Before construction begins, engineers need to understand what lies beneath the surface of a property. While a site may appear ready for development, the soil conditions below ground can vary significantly and influence how a project should be designed and constructed.
At AWM Engineering, geotechnical investigations help support residential, commercial, and land development projects by evaluating subsurface conditions and providing engineering recommendations tailored to each project's needs.
Step 1: Reviewing the Project Requirements
A geotechnical investigation begins with understanding the proposed project. Before fieldwork is scheduled, the engineering team considers the type of construction planned, the property's location, and the information needed to support design.
For example, a custom home, commercial building, parking lot, and large residential subdivision may require different investigation approaches. The number and depth of soil borings, sampling methods, and laboratory tests depend on the project requirements and anticipated ground conditions.
Reviewing these details helps establish an appropriate scope of work for the investigation.
Step 2: Performing Fieldwork and Soil Borings
Once the investigation is planned, fieldwork can begin. A drilling crew visits the property to collect information about the soil beneath the ground surface.
Soil borings are completed at selected locations and depths to help identify the different soil layers present at the site. During drilling, samples may be collected for further evaluation, and field observations are recorded to document the conditions encountered.
Depending on the investigation scope, fieldwork may also include measurements or observations related to groundwater and other subsurface conditions.
The information collected during this stage provides the foundation for the laboratory analysis and engineering evaluation that follow.
Step 3: Evaluating Soil Samples in the Laboratory
After samples are collected, appropriate laboratory testing helps determine the engineering properties of the soil. The specific tests depend on the project and the materials encountered during drilling.
Testing may evaluate characteristics such as:
Moisture content: The amount of water present in a soil sample.
Soil classification: The properties used to identify and categorize soil types.
Plasticity: How certain fine-grained soils respond to changes in moisture.
Soil strength: Properties that help engineers evaluate how soil responds to applied loads.
Compaction characteristics: Information used to establish appropriate moisture and density targets when applicable.
These results help engineers interpret the site conditions and develop recommendations appropriate for the proposed construction.
Not every project requires every type of laboratory test. The testing program is selected based on the investigation objectives and the soil conditions encountered.
Step 4: Analyzing the Findings
Once the field observations and laboratory results are available, the geotechnical engineer evaluates the information together.
This analysis helps develop an understanding of the subsurface soil profile and identify conditions that may affect the project. Depending on the site, considerations may include variations in soil strength, moisture-sensitive soils, groundwater, settlement potential, and the suitability of existing or proposed fill materials.
For projects in the Houston area, evaluating moisture-sensitive clay soils can be particularly important. However, conditions differ between properties, making site-specific investigation essential.
The goal is to interpret the available data and determine how the findings should influence the project's design and construction planning.
Step 5: Preparing the Geotechnical Report
The findings are typically documented in a geotechnical engineering report. This report communicates the investigation results and provides recommendations relevant to the proposed project.
Depending on the scope of work, a report may include:
A summary of the investigation methods and locations of soil borings.
Descriptions of the soil layers encountered.
Relevant field and laboratory test results.
Observations regarding groundwater conditions, where applicable.
Foundation recommendations and design considerations.
Guidance related to site preparation, fill placement, and compaction.
Pavement or other site improvement recommendations, when included in the scope.
The report gives the project team a technical reference for making design decisions. Recommendations are specific to the investigation findings and intended project; they should not automatically be applied to a different property or construction type.
Step 6: Using the Results During Design and Construction
A geotechnical investigation does not end with collecting samples or completing a report. Its findings can inform decisions throughout the design process and, when appropriate, during construction.
Architects, civil engineers, structural engineers, developers, and contractors may use the report to coordinate design requirements and plan site preparation. For example, geotechnical recommendations may help guide foundation design, building pad preparation, pavement design, or fill placement.
If actual soil conditions encountered during construction differ from those anticipated in the report, additional evaluation may be needed to determine the appropriate next steps.
Coordinating geotechnical information with the broader project team helps ensure that decisions are based on documented site conditions rather than assumptions.
When Should You Schedule a Geotechnical Investigation?
It is generally beneficial to evaluate subsurface conditions early enough for the findings to inform design. Waiting until construction is underway may limit the available options if unexpected conditions are discovered.
A geotechnical investigation may be appropriate for:
New custom homes and residential developments.
Commercial buildings, retail centers, and office projects.
Industrial facilities and warehouses.
Subdivisions and multifamily developments.
Parking lots, roadways, and other paved areas.
Projects involving significant grading or fill placement.
Property due diligence when subsurface conditions are relevant to development decisions.
The appropriate scope and timing depend on the project, applicable requirements, and the information needed by the design team.
Geotechnical Investigations With AWM Engineering
Understanding subsurface conditions is an important part of preparing for construction. A geotechnical soil investigation gives the project team site-specific information that can help guide engineering decisions from initial planning through design and construction.
AWM Engineering provides geotechnical and civil engineering services for residential, commercial, and land development projects in Houston and throughout Texas. Our team works to deliver practical, technically sound recommendations based on each project's needs and site conditions.
If you're planning a construction or development project, contact AWM Engineering to discuss your property and determine what type of geotechnical investigation may be appropriate.
AWM Engineering — Practical Engineering Solutions for Your Next Project.