Seedlabs

FaceLog: Back-Calculated Ground-Quality Log from TBM Performance Data

A tool that uses tunnel boring machine data to create a map of the rock quality underground.

A construction-phase tool that inverts each shift's TBM performance data into a continuous rock-quality (QTBM) log along the tunnel, giving crews an objective ground record where the rotating cutterhead hides the face — and an evidence base for ground-related claims.

EngineeringTunneling and Rock Mechanics
Urban Stormwater and Fluid ManagementTunnel construction monitoring — continuous ground-quality logging and differing-site-conditions claim support during TBM drives.

Concept

A construction-phase service that turns the TBM's own operating record into a continuous ground log. Each shift, the crew logs metres advanced, boring hours, applied thrust and torque, and downtime categories; the service applies the published back-calculation formulae to invert this into a QTBM value per tunnel metre, producing a rock-mass quality profile along the drive. Because the rotating cutterhead hides the face, this is often the only systematic record of the ground actually encountered on a bored tunnel. The log is plotted against the QTBM profile assumed at bid, so a steady slide toward fault-zone values triggers early action — probe drilling ahead, heavier support classes — and, where as-encountered ground materially differs from contract assumptions, provides an objective, formula-based exhibit for differing-site-conditions claims and time-extension disputes.

Why now

The new book supplies the previously missing inverse capability: alongside the forward PR/AR formulae, it provides formulae to back-calculate QTBM directly from TBM performance data, validated across 145 tunnels totalling 1,000 km. The documented spread of actual advance rates — from 5 m/hr for a day down to 0.005 m/hr for months — shows ground quality can change by orders of magnitude within a single drive, which is exactly the variation a shift-by-shift, performance-derived log is built to capture.

Written by GLM · 8 Oct 2026

AI assessment

Backed by 1 paper96

A high-utility, evidence-backed tool that converts TBM operational data into a legal and technical record of ground quality, filling a critical gap in construction dispute resolution.

Evidence strength
5/5
The idea is directly based on a comprehensive guide validated across 1,000 km of tunnels, specifically utilizing the provided back-calculation formulae.
Market pull
5/5
Differing-site-condition claims are a primary source of multi-million dollar disputes in tunneling, creating high urgency for objective, formula-based evidence for contractors and insurers.
Novelty & moat
4/5
While AdvanceCast handles the bid-stage prediction, this shifts the mechanism to construction-phase inversion, creating a distinct value proposition for operational monitoring and claims.
Feasibility
5/5
The core logic relies on existing published formulae and standard TBM shift logs, making the MVP a straightforward data processing pipeline.
Wedge clarity
5/5
The wedge is sharp and specific: providing an objective ground log for 'differing-site-conditions' claims and time-extension disputes.
Simplicity / focus
5/5
The product is a single, focused tool that performs one specific calculation to produce one specific output (the QTBM log).

Scored by Gemma 4 · 8 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

  • Webuild S.p.A.company

    Delivers large TBM drives on metro and water tunnels; a performance-derived ground log gives its site teams early warning of deteriorating rock and objective documentation for ground-related claims.

  • Mott MacDonaldcompany

    As owners' engineer it must verify contractor ground reports; an independent, formula-based QTBM log derived from machine data gives it a checkable record rather than narrative descriptions.

  • Obayashi Corporationcompany

    A major Japanese TBM contractor; shift-by-shift QTBM back-calculation adds a systematic ground record where the cutterhead hides the face, supporting both support decisions and dispute defense.

  • Munich Recompany

    Underwrites tunnelling and underground-construction risk; a quantitative, formula-derived ground log gives underwriters and claims handlers an objective basis for assessing differing-site-condition claims.

Research it builds on

  1. TBM Tunnelling in Jointed and Faulted Rock
    Nick R. Barton · 2026 · 239 citations
    All ideas from this paper →
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feasibility