Underground Jumbo Development

SME Mining Engineering Handbook, Table 10.4-1, p. 933, after Atkinson 1992. Bank density is the rock as it sits in the ground, before it is blasted and swells, which is the same thing Table 12.2-1 calls rock density (wet) and the right number for this page. Pick the closest rock in Step 1 and it fills itself in. This table publishes every density twice, in tonnes per cubic metre and pounds per cubic yard, and the two agree across all 37 rows to within 1.7%, the gap being the book rounding the pounds column to the nearest hundred. The printed page also carries swell, fillability and digability columns; they describe loading the broken rock rather than drilling it, so they are deliberately not reproduced here.

SME Mining Engineering Handbook, Table 7.2-1, p. 439. The metres per minute column is converted from the printed metres per hour, because m/min is the unit Table 12.2-2 states penetration rate in. The printed footnote is what makes these numbers mean the same thing as the field in Step 3: "drilling rates are for actual drilling and do not include time for drill retraction, boom relocation, collaring, etc. Drilling rates decrease as rock mass strength increases and may increase or decrease depending on the number and orientation of joints/blocks." This page counts boom relocation and collaring separately, as boom setup per hole, so do not fold them into the rate as well or you pay for them twice. The surface crawler and down-the-hole rows on the printed page are for bench drilling and are left out. Note that the worked example drills a 3.05 m round, shorter than the 4 m these rows quote as typical.

SME Mining Engineering Handbook, Table 12.2-1, p. 1153. Loading this page reproduces every row of it. The printed overbreak is 5%, not the 5.6% our first transcription carried: 22.5 m² × 2.8 t/m³ × 1.05 gives the printed 66.2 t/m exactly, and 5.6% does not. Read off the printed page and corrected.

SME Mining Engineering Handbook, Table 12.2-2, p. 1154. Two rows here are printed values this tool does not reproduce and does not use: drill metres per engine hour, and average penetration rate per boom. Neither follows from the other cells on the page — the boom rate comes out at 0.93 m/min on every route through the table we could find, against a printed 0.71 — so they are shown as published and left out of the chain rather than having a derivation invented for them.

SME Mining Engineering Handbook, Table 12.2-3, p. 1154. Measured at a mine where every jumbo had at least five faces available to it, so it was never waiting on a muck cycle.

SME Mining Engineering Handbook, Table 12.5-1, p. 1220, in 2009 US dollars at ±25%, for fairly fractured and weathered ground in central Nevada requiring regular bolting with split sets on 1.2 m centres. This table publishes every rate twice, in dollars per metre and dollars per foot, and the two agree to better than 1% on all six rows above, which is an independent check that a transcription cannot pass by accident. The seventh printed row, for pump stations and shops, is deliberately not carried here: it is quoted per unit of volume, and the book's own metric column converts it with the linear foot-to-metre factor instead of the cubic one, making it roughly eleven times too small.

All from the SME Mining Engineering Handbook, p. 1153. The single-heading numbers are the ones to hold this tool against. A model built on five available faces describes a jumbo that never waits; a decline being driven off one face is a different machine doing a different job.