Geotechnical Reporting

What Is Geotechnical Reporting?

Geotechnical Reporting is the formal, permanent record that transforms field exploration, laboratory testing, and engineering analysis into clear, actionable recommendations for design and construction. A high-quality report explains the subsurface model, describes methods and assumptions, quantifies uncertainty, and presents recommendations that are traceable to data.

Whether you are designing Shallow Foundations, Deep Foundations, Retaining Walls, or evaluating Slope Stability, the report is where decisions are documented, justified, and communicated to stakeholders. It ties together Site Characterization, Geotechnical Soil Testing, and the engineering models used to predict performance.

Great geotechnical reports are readable, reproducible, and review-ready—every recommendation links back to data and stated assumptions.

Purpose, Audiences & What Owners Expect

A geotechnical report must serve multiple audiences: owners, civil/structural designers, contractors, permitting agencies, and future teams maintaining the asset. Expectations include:

• Decision Support: Clear recommendations with options where uncertainty is material.
• Risk Transparency: Identification of key uncertainties, potential variances, and monitoring/contingency plans (see Geotechnical Risk Assessment).
• Constructability: Practical guidance on excavation, dewatering, ground improvement, and sequencing—tie to Geotechnical Earthworks where relevant.
• Code Context: Use durable references for hazards and building science such as USGS, FEMA, NIST, and transportation guidance from FHWA.

Recommended Geotechnical Report Structure

While formats vary by agency and project, the following structure covers the essentials and helps your report rank for search intent—engineers often search for “geotechnical report template,” “what to include,” or “soil report example.”

• Cover & Executive Summary: Project description, site location, scope, key findings, and top risks.
• Background & Site Conditions: Previous studies, regional geology, site history, and constraints. Cite authoritative sources such as USGS maps for geology and hazard context.
• Exploration & Testing Program: Borings, test pits, CPT, geophysics; lab tests like Atterberg Limits, Sieve Analysis, Standard Proctor Test, Triaxial Test, and Permeability Test.
• Subsurface Conditions: Stratigraphy, index properties, structure, and variability; integrate groundwater regime from Groundwater in Geotechnical Engineering.
• Engineering Analyses: Methods and software used (see Geotechnical Design Software and Geotechnical Modeling), parameters and correlations, load cases, and safety format (FS or LRFD).
• Design Recommendations: Foundations, slabs, retaining structures, pavements, and earthworks with allowable pressures, settlements, drainage, and seismic criteria.
• Construction Considerations: Excavation support, dewatering, compaction control, spoil handling, weather windows, and QA testing—tie to Compaction Test practices.
• Instrumentation & Monitoring: Piezometers, inclinometers, settlement plates, and acceptance thresholds; link to risk controls.
• Appendices: Boring logs, CPT plots, lab result summaries, calculations, software versions, and raw data tables.

Data, Figures & Logs That Make Reports “Stand Out”

The most common reason geotechnical reports get flagged in review is missing or untraceable data. Use consistent figure styles, legends, and units. Promote readability for non-geotechs without losing technical rigor.

• Location Plans: Show exploration points, utilities, and constraints; include coordinates and datum.
• Boring/CPT Logs: Standardized format with stratigraphy, recovery, RQD (if rock), SPT N, corrections, and groundwater levels.
• Stratigraphic Sections: Cross-sections that align with logs and interpretations.
• Lab Result Summaries: Grain size, Atterberg, strength, compressibility, and permeability plots.
• Groundwater Graphics: Seasonal ranges, response to recharge, and anticipated construction-stage levels.
• Analysis Figures: Slope stability surfaces, retaining wall pressure diagrams, settlement curves, and site response spectra (where applicable).

How to Present Engineering Analyses

Reports should concisely state the questions asked, methods chosen, parameters derived from testing, and results with sensitivity. Cross-reference related topics so readers can deepen context—e.g., settlement ties to Soil Consolidation and Settlement Analysis; seismic checks link to Seismic Testing and Liquefaction.

When using numerical tools, identify software name, version, element type, mesh density, boundary conditions, constitutive model, and validation against hand/LE checks. See Geotechnical Design Software and Geotechnical Modeling for methodology considerations.

QA/QC, Versioning & Traceability

Great reports are easy to audit. Adopt a standard naming convention and track versions, inputs, and outputs from the start. Store raw data, processed data, and final figures with clear folder structure. Summarize checks and reviews in the report.

• Data Provenance: Identify the origin of every parameter (lab test, correlation, code table).
• Sensitivity: Provide ranges and show how recommendations hold across credible bounds.
• Peer Review: Independent check using alternate methods (e.g., LE vs. FE), documented comments, and resolution.
• Monitoring Plan: When uncertainty remains, propose instruments and trigger levels linked to the risk register.
• Reporting Tools: Tables and figures produced directly from data analysis pipelines reduce transcription errors (see Geotechnical Data Analysis).

Common Pitfalls That Cost Time & Money

• Unstated Assumptions: Presenting a single value without noting groundwater, load case, or construction stage.
• Mixed Stress Frameworks: Combining total stress and effective stress parameters incorrectly.
• Ignoring Variability: Treating a heterogeneous site as uniform; not bracketing parameters.
• Figure–Text Mismatch: Logs or sections that don’t match narrative recommendations.
• Seismic Oversights: No documentation of Site Class or V_S30 basis—see Seismic Testing.
• Serviceability Gaps: Reporting allowable bearing without settlement evaluation; cross-link to Settlement Analysis.

FAQs: Geotechnical Reporting

How detailed should the exploration be for a small project?

Scope it to the risk: a light structure on uniform soils may need a modest program, while heavy loads near variable fill require more borings and lab work. Discuss assumptions and residual risks.

Should I use FS or LRFD in my report?

Follow the governing code/agency. Many building projects use allowable stress with global FS; transportation projects frequently use LRFD. Present both concepts where helpful and relate to Factor of Safety.

What monitoring should be included?

For risk-sensitive work, propose piezometers, inclinometers, or settlement points with trigger thresholds and response actions tied to the risk register and construction sequence.

Can I reuse parameters from a nearby project?

Only with caution. Document similarity and still obtain site-specific confirmation. Index/correlation values are not substitutes for representative testing.

What external sources are safe to cite long-term?

Hazard and building-science portals from USGS, FEMA, NIST, FHWA, and USACE are dependable anchors.

Conclusion

Geotechnical Reporting is where engineering judgment becomes a permanent, sharable asset. Structure the narrative around a defensible subsurface model, explicit assumptions, and clear ties from data to decisions. Use consistent figures, present sensitivity ranges, and align with codes using stable national resources like the USGS, FEMA, NIST, and FHWA. For deeper dives on supporting topics, explore our guides to Site Characterization, Soil Testing, Geotechnical Design Software, Geotechnical Modeling, and Ground Improvement Techniques. With a disciplined, traceable approach, your report will be useful today and trustworthy for decades.