A soil boring log example is one of the most effective ways to understand how subsurface conditions are documented during a geotechnical investigation. While standards describe what should be included, reviewing a complete boring log with realistic data provides much more clarity for engineers, reviewers, and project stakeholders.
The soil boring log shown below is a representative example of a shallow to mid-depth geotechnical boring commonly performed for site development projects. This article walks through the key components of the log, explains how to interpret the data shown, and highlights how digital workflows improve accuracy and efficiency.
For a broader overview of soil boring logs and best practices, see our complete guide to soil boring logs.
This soil boring log illustrates a single boring advanced to 20 feet below ground surface using hollow stem auger methods with Standard Penetration Testing (SPT). Sampling was performed using split-spoon samplers in soil and core barrel sampling near refusal and bedrock.
The log includes:
This format and level of detail are typical of boring logs included in geotechnical engineering reports for foundations, pavements, and site feasibility evaluations.
At the top of the log, the header identifies:
This information ensures the boring can be accurately referenced on plans, cross-sections, and within the geotechnical report. Clear identification is critical when correlating subsurface conditions across multiple borings.
The log documents:
Recording drilling and sampling methods provides essential context for interpreting recovery, blow counts, and soil behavior. For example, SPT N-values shown on this log are directly tied to split-spoon sampling intervals.
The depth and lithology columns show changes in subsurface conditions with depth. In this example, the boring encountered:
Each soil layer is clearly delineated with depth intervals, allowing engineers to identify transitions and evaluate thickness and continuity.
SPT sampling intervals are marked on the log, with blow counts recorded for each 6-inch increment and summed to produce the N-value. Recovery values are also shown.
In this example:
These values are commonly used to estimate relative density, consistency, and bearing conditions.
Each soil layer includes a visual description that documents:
Consistent soil descriptions, such as those shown here, are essential for correlating conditions across borings and for supporting engineering judgment during design.
Groundwater depth is recorded both during drilling and after completion of the boring. In this example, groundwater was observed at approximately 7.1 feet below ground surface.
Groundwater information is critical for:
Multiple readings help distinguish between drilling-induced water and stabilized groundwater levels.
The log documents refusal and the encounter of igneous rock (diorite) near the bottom of the boring. The boring was terminated at 20 feet below ground surface after encountering very hard, slightly fractured rock.
Clear documentation of refusal and termination depth helps define:
When interpreting a boring log like this one, engineers should:
Interpreting boring logs requires engineering judgment supported by complete and consistent data.
This soil boring log avoids many common problems seen in field documentation, including:
These improvements are typically achieved through structured, digital data capture rather than paper forms.
Paper boring logs require manual transcription, often leading to errors and delays. Digital soil boring logs capture structured data directly in the field and carry it through lab testing and reporting.
To learn more about the operational advantages, see Digital Soil Boring Logs: Benefits for Geotechnical Firms.
Modern boring log software allows field crews to enter data once and maintain a single source of truth across field, lab, and project teams. Lab results, photos, and reports can all be connected directly to the boring record.
This approach supports more effective geotechnical data management and reduces rework throughout the project lifecycle. For more information on Aldoa's soil boring log solution visit our website and schedule a demo.