lacing

In underground mining, lacing consists of timber or steel cross-members installed horizontally across the open top of a passage to contain broken ore and prevent it from cascading into roadways below. The term is largely historical, more common in coal and metal mines of the nineteenth and early twentieth centuries, though the principle persists in modern operations. A laced passage keeps ore in its designated storage zone and protects workers and equipment from overhead falls.

The most common arrangement uses wooden planks or poles laid parallel to one another, spaced close enough that even small fragments cannot pass through. These pieces rest on the walls or props of the passage and are sometimes secured with wire or clasps to prevent shifting. In harder rock conditions or where higher loads were expected, miners used steel angles or H-beams instead of timber. The spacing depended on the size distribution of the broken ore: coarse waste rock required wider gaps than fine ore or slate.

Lacing was typically installed after ore was loaded into the passage from above, forming a temporary seal until the ore could be drawn out below. Once a passage began to be worked, lacing bore the weight of fresh material dropping onto it and slowly degraded under impact and moisture. Timbers rotted, sagged, or cracked; steel corroded or bent. Inspectors had to check regularly for broken pieces that might fall through and into the roadway beneath, creating a hazard and losing ore into unwanted locations.

The expense and labour of maintaining lacing encouraged miners to transition to more permanent segregation methods: dedicated ore passes lined with steel plating, or the use of ore bins and chutes with properly engineered support. Despite this shift, the term remains in use among older miners and in historical technical literature. Understanding lacing is valuable for anyone reading mine plans from the nineteenth century or managing heritage mining sites where the original timber framing still stands.