To expand on my first-look research into the tunnelling carried out by miners during WW1:
Although many miners were refused permission to fight for their country during the First World War, the military did employ some specialist miners to tunnel beneath enemy lines (a particular example is No Man’s Land) and plant explosives and mines beneath the opposition’s defence positions. Once these sections of the trenches were destroyed, infantry would advance towards the enemy front-line.
It could take as long as a year to create a tunnel and place a mine.
At the same time as digging their own tunnels, miners vitally had to listen out for enemy tunnellers. At times, they collided with oppositional tunnels and underground fights took place; these tunnels were then usually destroyed with explosive charges.
On the ‘listening’ process:
“The tunnelling war was a game of blindfold cat and mouse. The only way to detect one’s enemy underground was by listening. In every tunnelling company considerable numbers of specially-selected men were employed solely on this vital task. Using at first just the naked ear and subsequently sensitive technical devices, listening became a highly developed and efficient art. Installed at the end of their tiny gallery, a trained listener would take notes of the compass bearing and estimated distance of suspect sounds. Comparing the notes of several listeners allowed triangulation of a sound’s origin, and thus an indication as to the location of the enemy, the direction he was heading, and the speed at which he was working. The favoured British listening aid was the Geophone (below). Employing two sensors a listener was able to ascertain the direction of hostile activity by moving the sensors until sound levels appeared equal in both ears. A compass bearing was then taken. When gauging distance only, both earpieces were plugged into a single sensor; this was a skill only gained by experience.
By the end of 1916 the scale of mine warfare had expanded to such an extent that there were not enough listeners to man every post, and central listening stations were devised. Working electronically like a telephone exchange, the signals from up to 36 remote sensors (Tele-geophones and Seismomicrophones) could be distinguished and recorded by just two men.”
Here are some interesting illustrations I was given by Tony at Elvington & Eythorne Heritage Centre. The first depicts the ‘clay-kicking method’ (aka ‘working on the cross’) of the tunnelling process used in WW1, and the second shows a steel shaft construction:
Some further information on the ‘clay-kicking method:
“Clay-kicking (also known as ‘working on the cross’) was a specialist method used in England for driving tunnels for sewer, road and railway works through clay-based geology. In late 1914 the technique was proposed to the army by the creator of the Tunnelling Companies, John Norton-Griffiths, a British engineering entrepreneur who at that time was employing clay-kickers on one of his company’s contracts: the refurbishment of Manchester’s main sewer. Norton-Griffiths persuaded the military that this technique – and his men – were perfect for the clays of Flanders. By February 1915, and as a result of continuing severe enemy mining action, the suggestion was at last taken up. The first batch of kickers – called “Moles’ by Norton-Griffiths – left Manchester on a Thursday; by the following Monday they were already working underground in France – at Givenchy.
In employing the power of the legs to work a specially shaped and finely sharpened spade known as a ‘grafting tool’, clay-kicking allowed a small tunnel to be driven quickly and with minimal effort. The tool was pushed rather than kicked into the working ‘face’ with the feet, each ‘spit’ of clay being then levered out by a prising movement. Progress was thus much faster than digging by hand. Most importantly, however, the technique was almost silent in its application. Digging with a pick or mattock demanded that the earth be struck, creating noise which could be heard by enemy listeners. The Germans never used clay-kicking as it was not a technique employed in civil engineering; indeed, it remained unknown to them for the entire war.”
Gas in the mines:
“Underground, tunnellers faced many a threat: entombment, obliteration, health problems brought on by the workload, working environment and poor air quality; there was even the risk of drowning. But the biggest killer was actually gas poisoning; not the designed toxic vapour variety used in cloud and shell form by troops on the surface, but carbon monoxide (CO), an invisible, odourless and tasteless substance that was naturally produced by every explosive action – even the firing of a simple rifle bullet. In mines that broke the surface, or in the case of a shell burst, carbon monoxide quickly dissipated into the atmosphere; after an underground explosion, however, it is trapped – in the geology and in the tunnels.”
Image and info source: The Tunnellers Memorial, Givenchy http://www.tunnellersmemorial.com/tunnelling-companies/