Soil boring logs are the backbone of geotechnical investigations. They document subsurface conditions, identify restrictive layers, and inform design decisions that affect safety, cost, and schedule. Yet many teams still rely on clipboards and spreadsheets, which introduces errors and delays.
This guide explains what to include on a boring log, how to plan field exploration, and how to interpret results. It also shows how modern software like Aldoa helps geotechnical firms create accurate boring logs faster and connect field and lab data in one workflow.
A soil boring log is a record of subsurface conditions observed and sampled during drilling. It typically includes location and elevation, drilling method, sample intervals and recovery, blow counts, lithology, groundwater conditions, photos, and notes that together form a defensible profile for design.
The right number depends on site size, variability, structure loads, and local guidance. For small facilities or infiltration practices, one to two explorations might suffice. As area and complexity grow, add locations to capture variability and confirm depth to bedrock and groundwater. A practical rule: increase spacing in uniform sites and tighten spacing in filled, urban, or geologically complex areas.
Tip: If you discover unexpected materials or refusal, add offset borings to reduce uncertainty.
| Method | Typical depth | Speed | What it is good for | Notes |
|---|---|---|---|---|
| Soil probe | ≤ 3 ft | Fast | Shallow profile checks | Limited data, not for design on its own |
| Hand or power auger | ≤ 50 ft | Moderate | Unconsolidated soils | No blow counts with hand auger |
| Test pits | ≤ 20 ft | Fast | Visual logging and bulk samples | Requires excavation equipment and safety controls |
| Direct Push (DPT) | 60–100+ ft | Fast | Continuous sampling with minimal cuttings | No SPT N-values |
| Rotosonic | 100+ ft | Fast | Continuous core through difficult formations | Mobilization costs can be higher |
| Hollow Stem Auger with SPT | 100+ ft | Moderate | Foundation investigations, infiltration decisions | Provides SPT N-values and flexible sampling |
Choose methods that match project goals. If you need blow counts for density or consistency, plan for SPT with hollow stem auger.
If possible, have a geotechnical engineer onsite during drilling to coordinate locations, adjust intervals when conditions change, and document observations. Clear instructions for drillers will improve outcomes:
A defensible log has consistent identifiers and complete metadata:
Pro tip: Use standard forms and controlled vocabulary for soil descriptions to keep logs consistent across crews and projects.
Restrictive layers such as dense clays, cemented zones, perched water, or bedrock limit infiltration and can cause perched groundwater. When interpreting logs:
Moving from paper to digital improves accuracy and speed:
Aldoa is a modern data and workflow platform built for geotechnical and construction materials testing teams. It centralizes your boring log process from scheduling through reporting.
Plan and dispatch: Create work orders, assign the right driller or technician, and attach maps and forms so crews know exactly what to collect.
Capture field data once: Log sample intervals, recovery, and SPT N-values in structured forms. Attach photos and site notes. Initiate lab tests from the field to give the lab a head start.
Connect lab results automatically: As tests are completed, results flow back into the boring log and the project record. No retyping. Fewer errors.
Generate reports faster: Produce professional boring logs, well diagrams, and project summaries ready for client delivery or inclusion in geotechnical reports.