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BoulderRefusal: Foundation Obstruction Risk Predictor for Melange Sites

A predictor that tells construction companies how often they will hit large boulders when drilling foundations.

A tool that predicts how often drilled shafts and piles will hit obstruction-size boulders on a melange site, so foundation contractors can plan equipment and price boulder risk up front instead of absorbing refusals as change orders.

EngineeringRock Mechanics and Modeling
Urban Stormwater and Fluid ManagementDeep foundations and commercial construction — drilled shaft and pile obstruction risk, equipment planning, and contingency pricing on melange sites.

Concept

A constructability-risk tool for deep foundations on melange-underlain sites. The user enters the foundation footprint area and the volumetric block proportion observed in test pits, borings, or excavation test panels. The tool applies the Franciscan melange scaling law (block/matrix threshold 0.05√a, tentative fractal dimension D ≈ 1.3) to estimate how many obstruction-size boulders — blocks larger than the auger or casing can handle, e.g., > 0.3–0.5 m — each drilled shaft or driven pile is likely to encounter, and converts that into a recommended plan: rock augers and core barrels on standby, pre-drilling, a switched pile type, or a priced contingency. Because the distribution is scale-independent, a handful of test pits predicts obstruction rates across the whole footprint. The deliverable is a boulder-risk line item for the foundation bid, replacing the current practice of discovering boulders one refusal at a time.

Why now

Paper [0] demonstrates that block-size distributions in Franciscan melanges are individually fractal and collectively scale-independent across mapped areas from cm² to km², with a block/matrix threshold of 0.05√a and a tentative generic fractal dimension of 1.3 — so the frequency of obstruction-size boulders beneath a foundation footprint can be roughly estimated from the site area and volumetric block proportion alone. [2] frames the underlying commercial pain: the ability to identify the nature of spatial soil variation is 'almost nonexistent,' so contractors currently carry boulder risk as unpriced contingency. In the San Francisco Bay Area, where major buildings and infrastructure are founded on Franciscan bedrock, a quantitative pre-estimate turns that hidden risk into a plannable, priceable quantity.

Written by GLM · 14 Oct 2026

AI assessment

Backed by 2 papers85

A highly focused, commercially viable tool that converts a specific geological scaling law into a pricing and equipment planning utility for foundation contractors.

Evidence strength
5/5
The idea directly applies the specific scaling law (0.05√a) and fractal dimension (1.3) detailed in the provided text to a concrete engineering problem.
Market pull
4/5
Foundation contractors and engineers face significant financial risk from 'refusals,' making a tool that converts uncertainty into a priceable line item highly attractive.
Novelty & moat
2/5
The mechanism and underlying research are nearly identical to 'BoulderAhead' (tunneling), simply shifting the application from TBMs to drilled shafts/piles.
Feasibility
5/5
The tool is essentially a calculator based on a known formula; an MVP could be built as a simple software module or spreadsheet.
Wedge clarity
5/5
The wedge is extremely sharp: a 'boulder-risk line item' for foundation bids on melange sites.
Simplicity / focus
5/5
The product is a single-purpose predictor with a clear input and a clear output, avoiding any 'platform' bloat.

Scored by Gemma 4 · 14 Oct 2026. Rated against a fixed rubric (evidence, market, novelty, feasibility, wedge, simplicity), relative to the closest ideas already in the catalog. A prior estimate to compare ideas before real-world signal arrives.

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Who benefits

  • Malcolm Drillingcompany

    A San Francisco Bay Area foundation contractor whose drilled shafts and caissons in Franciscan bedrock face boulder obstructions; obstruction forecasts directly inform equipment plans and bid contingency.

  • ENGEOcompany

    A Bay Area geotechnical engineering firm that would use obstruction estimates to advise developers on foundation type selection and cost risk for melange sites.

  • Arupcompany

    Designs deep foundations for major Bay Area buildings; quantitative boulder frequency supports choosing between drilled shafts, piles, and other foundation options.

  • Fugrocompany

    A site characterization and geotechnical due-diligence firm; could bundle the estimator into site assessment reports for melange-underlain parcels.

  • Webcor Builderscompany

    A San Francisco general contractor that carries foundation cost risk; a pre-priced boulder line item reduces change-order exposure on melange sites.

Research it builds on

  1. Estimation for Stochastic Soil Models
    Gordon A. Fenton · 1999 · 262 citations
    All ideas from this paper →
  2. The engineering significance of the scale-independence of some Franciscan melanges in California, USA
    Edmund W. Medley, Eric S. Lindquist · 2026 · 97 citations
    All ideas from this paper →
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feasibility