The Sap and the Mine (1915)
The Illustrated War News, 24 March 1915
Although this article isn't specifically about the CEF, it has been tagged as such to keep it with other First World War material.
When the enemy's trenches are only at a distance of a hundred yards or so, real trench-warfare may be said to begin. It is characterised by the making of saps which permit of an advance under cover towards the enemy's lines; and it is then that the sappers play their great part. Every thirty or forty yards the sap-heads are joined by parallels. When the saps are near enough to the enemy to enable him to stop the advance by throwing grenades and bombs on the workers, the sappers start an entrance to a mine-gallery to lead to a mine-chamber for explosives the power of whose charge varies with the depth of the chamber beneath the ground. These chambers are generally placed under a salient, or under points particularly guarded (a fortified house, machine-gun shelter, fortlet, castle, etc.) of the enemy's line. Their number depends on the results to be obtained, and the importance of the action. The explosion of the mine-chambers gives the signal of attack, at the same time as producing craters in the ground, destroying the flanking adjustments of the enemy, and making a breach in the wire-entanglements which protect his front, These craters are immediately occupied and organised, thanks to the surprise-attack, and one or several lines of trenches are sometimes taken.
The method of driving a mine-gallery employed by the Royal Engineers is, briefly, as follows. First, a steel shield is placed over the head of the sap, from beneath which the sapper cuts the earth, inclining his trench downwards. When he has sloped it down to about eight feet, he prepares for mining. He begins by placing a stout timber framework, consisting of a top sill, two side-pieces, and a ground sill, against the face of the earth (now widened to about six feet) and drives heavy sheeting-planks with a maul, to support the earth over his head as he works beneath them, propping them with uprights as he moves forward. The process is repeated as often as necessary. Having thus made a kind of ante-chamber for the collection of gear, pumps, trucks, and so on, he begins to drive the ordinary mining-gallery, either by means of frames and sheeting-planks, as before, or by placing a series of cases like the four sides of a stout box framed together at the angles. The task is extremely trying, as the space within which the miner works measures only four feet in height and two feet in breadth, the light is only that of candles, and the air soon becomes very foul, in spite of fans and bellows. The man at the face, therefore, only works for a short spell. The earth dug out is removed in little handtrucks, and has to be carefully disposed of so as, not to let the enemy get wind that. a mine is in progress. When the gallery has reached the point required near the enemy s trench, a small mine-chamber is driven from it sideways just big enough to contain the charge, the laying of which is always done by an officer. When the box is packed, the electrical fuse is inserted and the insulated cable laid. Then comes the work of "tamping"…i.e., filling up the gallery for some distance with sand-bags, to prevent the explosion from breaking back towards the sappers and to force it to tear its way out through the enemy's trench. If the distance from the mine-chamber to the trench is 15 ft., with 20 ft. of earth overhead, the tamping has to extend for about 30 ft. along the gallery. When all is ready, the mine is fired, and the infantry, with fixed bayonets, dash forward to occupy the crater which the explosion forms.