Geotechnical Engineering: Understanding What Lies Beneath

05 Jul 2023

Learn the importance of geotechnical engineering in design and construction projects, from site evaluations to foundation design, and more

The secret to a great construction project begins underground, what we don’t see. Geotechnical conditions such as foundations and groundworks play a crucial role in the proper design and construction of buildings, roads, runways, bridges, dams, and other engineering and architectural structures.

Geotechnical engineering is a specialized branch of civil engineering that focuses on the physical properties and behavior of soil and rock, as well as the design and construction of structures in contact with the ground to support the structures above it. It assesses the strength, stability, and other characteristics of a site’s soil and bedrock to determine how the load of the completed construction project will interact with the subsurface preventing any unacceptable movements that affect the future behavior of the structure.

Geotechnical engineering encompasses a wide range of services, including site evaluations, soil testing, foundation design, slope stability analysis, earthworks management, and more. These services provide crucial data points that enable architects, civil engineers, and contractors to design and build construction projects that are safe, cost-effective, durable, and sustainable.

Geotechnical engineering can identify safety hazards and mitigate their potential impact on budgets and schedules. It can help to prevent premature failure of foundations and pavements, catastrophic failures like building, bridges or road collapses, sinkholes, or landslides, and can include special design recommendations for sites that could potentially face natural disasters. Geotechnical value engineering can also determine the optimal design of foundations and earthwork alterations, helping to reduce costs, schedules, and even environmental impact.

Geotechnical Services

Let’s take a look at some of the core geotechnical services and the role they can play in the success of your next development.

Subsurface Evaluation & Exploration

Geotechnical engineers conduct detailed subsurface site evaluations to assess the geology and soil conditions at the proposed construction site. By collecting samples and conducting field and laboratory tests, they determine the physical and mechanical properties of the soil, such as its classification, density or consistency, permeability, and shear strength. This data then forms the basis for further, more detailed evaluations, engineering calculations (i.e., bearing capacity and settlement estimations), analysis, and assessments.

Foundation Design & Analysis

Geotechnical engineers employ their expertise to design and analyze the most suitable foundation system for a given site and the proposed project type. They consider various factors, including soil characteristics, groundwater levels, soil strength and elasticity properties, and the potential for settlement, ensuring that the structure can withstand and effectively distribute the final project’s expected loads to the ground without altering environmental conditions.

Geotechnical Engineering Reports, Studies & Analysis

• Preliminary Geotechnical Reports
  During initial site selection, geotechnical engineers can provide preliminary geotechnical surveys, with limited ground exploration and analysis. The resulting geotechnical report provides a basic understanding of the general geologic and geotechnical conditions of a proposed site before the owner moves forward with detailed site development plans.
  
  
• Comprehensive Geotechnical Reports
  Comprehensive geotechnical engineering reports come into play on new developments when the preliminary site layout and design have been complete and the general site conditions are understood. In this geotechnical evaluation, you’ll see a full à la carte menu of geotechnical services.
  
  Geotechnical engineers will plan and execute more advanced testing and analysis if deemed appropriate based on the preliminary study and any other information they have available. For example, subsurface evaluations, drilling, and sampling, soil characterization, and geologic studies can be undertaken to further analyze the physical properties of the site.
  
  Additional foundation and structural analyses might consist of shallow and deep foundations designs, settlement analysis, retaining wall design, and slope stability analysis. Foundation design, contamination assessments, pavement design and construction materials evaluations can also be performed. Once a geotechnical engineer is satisfied that they have all the necessary data and analysis, a full geotechnical report of findings, construction considerations, and designs can be developed and issued for the project.
  
  
• Linear Geotechnical Reports
  Lastly, linear geotechnical surveys like roadway/transportation studies and utility and pipeline corridor studies are conducted. Roadway, rail, pipeline, and utility infrastructure pose unique challenges for geotechnical engineering and environmental consultants as well. Spanning mile after mile, these projects can cross various geologic conditions and terrains, requiring unique earthwork solutions, permitting and regulatory compliance, and structural components like foundations, embankments, retaining walls, and flood and stormwater management.

Geotechnical Laboratory Testing

Geotechnical laboratory testing supports all of the above-mentioned services by testing soil samples for water content, soil classifications, compaction characteristics, and shear strength properties, amongst others. Proper field sample collection and speedy, detailed, reliable laboratory testing provide the data points necessary to develop numerical modeling and engineering judgements.

The Benefits of Geotechnical Engineering

Geotechnical engineering services are a must-do premium service to help ensure successful outcomes on structures behavior by discovering and addressing potential subsurface material challenges early on, optimizing foundation designs, and enhancing the overall performance and longevity of structures.

• Structural Integrity
  By assessing soil properties and designing appropriate foundations, excavations, and embankments, amongst others, geotechnical engineers contribute to ensure the structural integrity of buildings and infrastructure building a better and safer quality of life. Proper geotechnical engineering reduces the risk of settlement, uneven load distribution, instabilities, or structural failure, thus enhancing the overall safety and durability of the project, and the life of people.
  
  
• Budget and Schedule Optimization
  Geotechnical evaluations help identify potential challenges early in the design and construction processes, allowing for informed decision-making and proactive mitigation strategies. By understanding soil conditions and their implications, project teams can optimize designs, select appropriate construction techniques, and reduce the risk of unforeseen issues, assuring the safety of the public. This proactive approach can help minimize costly rework, scheduling delays, and expensive unexpected remediation efforts.
  
  
• Environmental Concerns & Regulatory Compliance
  Geo-environmental consulting combines environmental consulting, geotechnical engineering, drilling, and testing solutions for preliminary site characterization, Phase I and II Environmental Site Assessments and contamination assessments. This allows owners and contractors to implement appropriate natural resource protection measures, minimize soil erosion, remediate soil and groundwater contamination, and mitigate the risk of unforeseen issues that could impact site safety, budgets, and schedules.