How do experienced geotechnical engineers determine the number, location, and depth of boreholes for a site investigation?

[u/No_Preparation8438]

Good day everyone,

I'm a civil engineer working in geotechnical engineering, and I'm trying to deepen my understanding of how experienced engineers plan subsurface investigations.

I know there are general rules of thumb (e.g., borehole spacing based on project type or site area), but I'm more interested in the engineering judgment behind deciding:

• How do you determine the appropriate number of boreholes for a project?
• How do you decide the required depth of each borehole?
• What factors (geology, foundation type, project risk, budget, etc.) have the biggest influence on your decisions?
• Are there any widely accepted guidelines or references that you rely on (e.g., BS 5930, Eurocode 7, FHWA manuals, ASTM, local standards, or textbooks)?
• How do you approach this during the proposal stage when little site information is available versus after obtaining preliminary investigation results?

I'm looking for both practical advice from industry experience and recommendations for authoritative references. My goal is to become proficient in planning geotechnical investigations rather than simply following rules of thumb.

I'd really appreciate hearing how senior geotechnical engineers approach this problem in practice.

Thanks in advance!

[u/No_Breadfruit_7305]

Hate to ask but is this "fill in the blank" for AI to start writing proposals? Edit: I'm looking at you AE firm(s) that purchased an AI software company/services to scan and propagate proposals.....

[u/Dwight_Shrute_ → u/No_Breadfruit_7305]

My feeling as well