Mining at Lochnagar

The British took over the Somme area from the French during July and August 1915. On 24 July, 174 Tunnelling Company moved to the Somme front and established headquarters at Bray, taking over some 66 shafts at Carnoy, Fricourt, Maricourt and La Boisselle. Prior to the takeover, La Boisselle had been the scene of much mining activity and underground fighting. No-mans-land just south west of La Boisselle was very narrow, at one point no more than about 50 yards (46 metres), and had become pockmarked by many chalk craters. The French and German forces were constantly mining and countermining, and the area became known as the Glory Hole.

La Boisselle Trench Map

Nothing changed when the British took over, the underground war continued with offensive mining designed to destroy enemy strong points, and defensive mining to destroy enemy tunnels. Depths of tunnels ranged from 30 feet (9 metres) down to the deepest at 120 feet (36 metres). Around La Boisselle the Germans had dug defensive transversal tunnels at a depth of about 80 feet (24 metres), parallel to the front line.

French Officers using a Geophone in 1917

Tunnelling was a dangerous business, each side doing its best to detect and destroy enemy tunnels. On 4 February 1916, two officers and 16 men (See Appendix A) were killed, either being burnt or gassed when the Germans detonated a camouflet (a small explosive charge big enough to destroy enemy workings but not big enough to break the surface). Captain Richardson wanted to test the then very new listening device, the Geophone to see how accurate it was in pinpointing the direction from which sounds of enemy mining were coming. He had a three level mine system starting from Inch Street, La Boisselle, the deepest being just above the water level at around 100 feet (30 metres). Lieutenant Edward Lyall went to the deepest level and made deliberate noises, whilst Captain Richardson and Second Lieutenant Arthur Latham went into the middle level to see if they could use the Geophone to ascertain the direction from which Lieutenant Lyall’s noise was coming from. It was during this experiment that the Germans blew the large and unexpected camouflet that killed the 18 men.

Captain Thomas Charles Richardson (Left) and 2nd Lt Arthur Latham (Right)
The two officers killed in the camouflet at La Boisselle

For the 1 July 1916 attack two large mines were planned, one to the north of La Boisselle (Y Sap) and one to the south (Lochnagar). Both were ‘overcharged’ which means that more explosive was used than was necessary to just break the surface, so large rims were formed from the disturbed ground. The tunnel for the Y sap mine started in the British front line near where it crossed the Albert to Bapume road, but because of German underground defences it could not be dug in a straight line. About 500 yards (457 metres) were dug into no-mans-land before it turned right for about another 500 yards (457 metres). Some 40,000 lbs (18,144 kilograms) of ammonal (high explosive) was placed in the chamber beneath Y sap.

In addition to the two large mines, the Glory hole was also attacked with two smaller charges of 8,000 lbs (3,628 kilograms) each, designed to wreck German tunnels. Communication tunnels were also dug for use immediately after the first attack, but were little used. To try to ensure that the enemy did not find out about them, a high level of secrecy was maintained about their existence. So secret that Incredibly the attacking infantry did not know about them. An exception to this was the Russian sap from Kerriemuir Street which was eventually connected to Lochnagar Crater and the German front line. For some time this was the only means of crossing Sausage Valley. A battalion of the 19th Division and the 9th Chrshires passed through it, and it was used to evacuate the wounded.

The tunnel for the Lochnagar mine was started on 11 November 1915 by 185 Tunnelling Company, but was completed by 179 Tunnelling Company who took over in March 1916.

Video. The ‘îlot de La Boisselle. More at:- http://www.skphotoscom.co.uk

The shaft for the Lochnagar mine was sunk in the communication trench called Lochnagar Street. It was probably the first deep incline shaft, meaning that it was not sunk vertically but sloped down with an incline of between 1:2 and 1:3, to a depth of some 95 feet (29 metres). It was begun some 300 feet (91 metres) behind the British front line and 900 feet (274 metres) from the German front line.

In the Lochnagar inclined shaft, at about 50 feet (15 metres) below ground level, a gallery was driven towards the German strong point called the Schwaben Höhe. The final depth of the explosives chambers was about 52 feet (16 metres).

As the tunnellers drew nearer to the German line, progress was slowed due to the need to be as silent as possible whilst working. Pick axes could not be used, progress was made by lumps of chalk being prized out with a bayonet, caught without hitting the ground and passed back for disposal. Miners worked without boots, walking on sandbags, and talking was limited to a whisper. They could hear the Germans who were working below them in a transversal tunnel.

Crater – Side Elevation. No contemporary elevations drawings of the mining activity at Lochnagar exist, but after close study of existing documents, the drawing above is as accurate a representation of the arrangement of shafts and galleries that can be produced at the present time. The drawing will be updated should more information come to light. Image courtesy of Clive Gilbert and Peter Reed © 2010

When about 135 feet (41 metres) away from the Schwaben Höhe, the tunnel was forked to form two branches, the end of each branch was then enlarged to form a chamber for the explosives, the chambers being about 60 feet (18 metres) apart and 52 feet (16 metres) deep. When finished both chambers were overcharged, the left hand chamber with 36,000 lbs (16,330 kilograms) of ammonal and the right hand chamber with 24,000 lbs (10,886 kilograms) of ammonal. As the chambers were not big enough to hold all the explosives, the tunnels that branched to form the ‘Y’ were also filled with explosives. The tunnels did not quite reach the German front line, therefore the explosives were not directly under the trenches, but the blast dislodged enough material to form a 15 foot (4.6 metre) high rim and bury nearby trenches.

Position of the charges and tunnels under the Crater
A = Point were the tunnel from Lochnagar Street divides into two branches
B = Explosive Chamber holding larger charge of 36,000lbs (16,330kg) of high explosive
C = Explosive Chamber holding the smaller charge of 24,000lbs (10,886kg) of high explosive
X = Distance between the two explosive chambers 60ft (18m)
Y = Longer branch of the tunnel 60ft (18m) long
Z = Shorter branch of the tunnel 40ft (12m) long
Image courtesy Clive Gilbert © 2010



Captain James Young pressed the plunger at 0728 (local time), the two charges combined formed one massive crater. Spoil from the blast spread over a diameter of 450 feet (137 metres), obliterating some 300 to 400 feet (110 to 122 metres) of German line and nine dugouts. How many were killed? Who knows! However, it is said that it covered nine deep dugouts, each capable of holding an officer and 35 men, a total of nine officers and 315 men.



Based on ‘The work of the Royal Engineers in the European War, 1914-1919, Military Mining, 1922’

The Crater left now measures some 300 feet (91 metres) across the highest point of the rim and 70 feet (21 metres) deep from the top of the rim. The Lochnagar Crater is the biggest man made crater made by a single aggressive explosion. However, another mine, at St Eloi which was blown on 7 June 1917 contained 95,600 lbs (43,363 kilograms) of ammonal, some 35,600 lbs (16,150 kilograms) more than at Lochnagar, but the resulting crater was smaller.

Weekly Mine Report 179 Coy. Strength RE 19 officers 384 OR, attached infantry 214 OR, total 19 officers 598 ORs. Designation of working: Lochnagar; Map Ref. X.20.c; Depth: 50 feet (15 metres); nature of ground: hard chalk;

Tunnellers of 179 Tunnelling Company Albert c.1916. courtesy Barry Maule

Report:
A straight gallery had been driven for a total distance of 500 feet (152 metres) in front of our front line trench. A Y branch was then driven to within an estimated distance of 100 feet (30 metres)of the German trenches, when chambers were excavated. These two branches of the Y totalled 100 feet in length. This distance, and the last 34 feet (10 metres) of the straight in gallery, were excavated with the bayonet only, for silent work. Latterly the enemy was heard very plainly working at a slightly lower level than ourselves Subsequent examination points to his work having been of the nature of a defensive mine system in which it is probable that the sounds we heard were caused by his work on a transversal gallery as they did not seem to come any closer (as would have been the case had he been driving an attack gallery) but rather to cross our front. The objects of the mine were:
1.  to destroy the enemy trench and to knock out his machine guns at this point, where his trench formed a pronounced salient
2. to destroy his underground system whatever it might be
3. to kill any troops he might have sheltering underground from our bombardment.

As the work of excavating the chambers required to receive the necessary charges was very slow, it became necessary to place portions of the charges in each of the two branches of the Y (galleries – the chambers not being large enough to accommodate them). And as the one branch was roughly normal to the enemy trench, and the other inclined thereto, the charge was divided into 24,000 lbs (10,886 kilograms) in the former and 36,000 lbs (16,330 kilograms) in the latter. These charges were tamped solid for 350 feet (106 metres) outside the junction of the Y branches.

Twelve detonators in series, each with a guncotton primer attached, were distributed among each charge, the two charges being in parallel. A second and reserve system of detonators was also connected in case of accident to the first. The mine was fired at -2 minutes on Z day, and was wholly successful. An enormous crater was formed, extending considerably behind the enemy trench, which, with its occupants and machine guns etc, was entirely destroyed for a considerable length, as well as all his dugouts for a considerable distance beyond the actual crater being entirely closed, and large portions of his trench being buried. There can be no doubt that the mine generally caused him considerable loss, and by the violence of the shock to his garrison, and the shelter afforded by the lips of the Crater itself, enabled our attacking infantry to reach his trenches here, and to pass over them in the first assault, with comparatively light loss. Such loss as was incurred must have been caused by fire from his flank. The infantry were also on Z night to establish themselves inside this crater, forming an advance position in front of our original trenches. Observations have been taken to the boundaries of this crater but so far each attempt to measure the same with a view to estimating the affect [sic] of the charge has been prevented by the amount of fire the enemy has still, until today [5/7], been able to bring to bear at the point. These investigations we hope to continue at a subsequent moment.

[sgnd] H M Hance Major OC 179 Co RE 5/7/1916

Were the mines exploded on the first day of the Battle of the Somme, a success? The official historian when writing on the 7 large and 11 small mines that were fired on 1 July 1916 at the start of the battle of the Somme, stated: ‘they were too much scattered up and down the front to produce a noticeable effect’.

Check Military Mining for more on how mining developed on the western Front.

Appendix A

Men and Officers of 185th Tunnelling Company. © IWM

Men of the 185th tunnelling company who lost their lives to a German camouflet at La Boisselle on 4 February 1916

Sources

• UNDERGROUND WARFARE 1914-1918: By Simon Jones.
• MILITARY MINING 1914-19: By the Institute of Royal Engineers, Chatham.
• WAR UNDERGROUND The Tunnellers of the Great War: By Alexander Barrie.
• TUNNELLERS: By Captain W. Grant Grieve and Bernard Newman.
• BENEATH FLANDERS FIELDS: By Peter Barton, Peter Doyle & Johan Vandewalle.
•  AUSTRALIAN WAR MEMORIAL: www.awm.gov.au/
• SOLDIERS DIED IN THE GREAT WAR 1914-19. CD.