by Simon Jones
The use of spiling, or sheet piling, for working in ground consisting of unstable wet sand. From Tatham, ‘Tunnelling in the Sand Dunes of the Belgian Coast’.
The ability to work through the wet running sand of Flanders was the major achievement of the civilian miners in the British tunnelling companies. Firstly the sinking of shafts to depths of 100ft or more through the sand to the dry clay below stole the march on the German pioneers, and the Germans lagged behind in the use of steel tubbing to line the large shafts. Secondly, the very difficult technique of sheet piling, or spiling, through sand was mastered by the British and Commonwealth units.
British mining tools used in clay and sand. In Fig. A, D, E, and F are all push picks used by 176 Company for different activities. G is a cut-down grafting tool. Fig. B shows a modified grafting tool used by 171 Tunnelling Company for work in clay. From Trounce, Notes on Military Mining.
Grafting tools used in the Ypres Salient in October 1916, for a clay-kicking competition held between the Tunnelling Companies. From Mining Note No.66, 5 October 1916.
One very prominent way in which civilian practice improved military mining was the introduction of commercial blasting explosive for mining, which increased the power of charges. The French adopted cheddite, the Germans Westphalite and the British ammonal. These explosives also had the advantage of being safer to use, although accidents still occurred. The Germans also carried out successful trials with compressed air as an explosive. The new explosives and the unprecedented size of charges required new formulae to calculate the amount needed for the desired effect of each mine or camouflet. The fusing and circuits for the large mines were extremely complex and the British adopted the use of detonating cord (cordeau detonant) from the French for such charges.
Mechanisation was a response to the shortage of manpower and the desire to drive faster, deeper and longer than the opponent. Power in the form of electricity or compressed air could be used for drilling, ventilation and pumping. Air blowers in particularly needed to be quiet and the British often commented on the noise made by German rotary blowers. The British found large hand-operated blacksmith bellows often the most satisfactory and these were able to supply air up to 1,000ft. The British often also used compressors to provide air to the working face. The Germans and French were equipped with hand-operated boring equipment before the war and the British had commented on the need for it at exercises. The French found much equipment inadequate in hard ground, but adopted a variety of mechanized types. Their best equipment came into use after they had largely given up offensive mining and was used more for dugout construction.
French sappers using a Guillat- Génie hand borer to create a hole which could be used for ventilation or to house a periscope. From École de Mines, Supplément au Livre de l’Officier, 1917.
French Ingersoll screw drill, used from 1917. From École de Mines, Supplément au Livre de l’Officier, 1917.
Specialist officers knew the latest equipment. Norton Griffiths spent much of his prodigious energy sourcing the best pumps, boring equipment and much else and making sure that they were provided without delay. Füsslein complained that the British had superior equipment, for example pumps to dewater the deep levels, and that he could not obtain similar equipment from Germany. Trower, who was appointed in command of 252 Company, was the Paris representative of the Ingersoll Rand Company and quickly obtained compressors, which for use in hard chalk. All adopted drills powered by generator or compressor, which were used especially when working some distance away from the enemy and in conjunction with borehole blasting. Blasting was disliked by some British officers because it was inevitably heard by the other side and alerted them to the work. The French and British also experimented with types of forcing jacks, whereby pipes were driven along beneath the surface of the ground, which were used to blow charges. These appeared to offer a means of placing explosive charges against the enemy front line, to blow a breach into a trench and also to blow a communication trench across no man’s land. The British did not have success with them at St Eloi on 27 March 1916, where a Barrett Forcing Jack was supposed to blow a ready-made communication trench to the British Crater No.1, but succeeded only in blowing up a section of the British front line.9 The main problem with forcing jacks was that they could only be used effectively through soft ground. The Sentinel Pipe Pusher was developed for the same purpose by the British but attempts to use it on the Somme, where flints would deflect the head of the head of the pipe and drive it off course, met with little success. It was found that borers were more reliable than jacks and the most effective British, equipment was brought by the Australian Mining Corps. The invention of Captain Stanley Hunter of the Victorian State Mines Department, the ‘Wombat’, could drill a hole of up to 61/2in in diameter up to 200ft at about 3–4ft an hour through chalk. Communication trenches blown using the Wombat were used at Vimy on 9 April 1917.
French manual forcing jack incorporating a charge and a steel tip containing a microphone. From École de Mines, Supplément au Livre de l’Officier, 1917.
Larger tunnel boring machines were also tried by the Germans and the British.10 The Germans investigated the use of an electrical machine following the British mine blows at Hill 60 in April 1915, to overcome the difficulty that they experienced in pushing forward tunnels in the sector. On 4 June a detachment of three officers, 12 NCOs and 96 pioneers of the Experimental Pioneer Company (Pionier=Versuchs=Kompagnie) travelled to Erkelenz in the Rhineland, where they trained for two weeks at the works of the Internationale Bohrgesellschaft. A second detachment followed on 21 June. They were trained to operate a machine which seems to have measured about 1.20 x 3.50m and at the beginning of August the detachment began preparation of a dugout to house the machine on the eastern edge of Hill 60. The intention was to drive a tunnel of about 82m length to blow up the British position in front of the 143rd Infantry Regiment. Preparation of the dugout was long and difficult, as all of the spoil had to be removed in sandbags, presumably for the sake of secrecy. By 9 August it was at a depth of 2.20m and a dugout was also begun for transformers. Both were completed by 14 August. At the same time the high-voltage cable was laid from a farm on the Kortewilde–Zandvoorde road towards Klein Zillebeke. The cables suffered continuous damage from shellfire, and the bringing forward of the pipes, machinery and equipment was ‘infinitely laborious’.11 On 19 August the machine and cable were in place and two transformers were then installed. The machine was ready to begin cutting on 22 August at a depth of 4.20m with a gradient of one in twenty. Progress forward, however, was very slow and the machine had to be halted frequently for long periods in order to remove the build up of mud. Although a British camouflet at 2am on 26th did not delay work, two days later the machine had to be stopped owing, it appears, to unevenness of the soil causing the cutting head to race and become damaged. A second boring, parallel to the first, was begun on 5 September and advanced 56m in four days. The effect of the local conditions, however, meant that it had to be halted for maintenance and to lay new cables underground. Strong artillery fire also caused a halt, although it was unaffected by a powerful British camouflet on 11 September. Another drilling was set up for the 15th, 80cm beneath the first, on a gradient of one in fifty, but after only two days it had to be extracted because of ground water and running sand and a new foundation of reinforced concrete 1.20 x 3.50 by 0.25m was constructed. Heavy artillery meanwhile made transport more difficult and caused casualties. Large portions of the cables were buried and were frequently cut by shells. On 19th a new tunnel was begun and after about two days around 71m was excavated. After 55m power from the low tension cables from the transformers to the machine became very feeble. The power consumption rose metre by metre and this boring also had to be abandoned. Repair work had become necessary. Another British camouflet in the path of the tunnel did not affect the work, but it seems to have been accepted that the machine was not a success and on 2 October the company was ordered to the sector of the 39th D
ivision to take over mine workings on either side of the Menin Road. The machine was taken from Hill 60 back to Hollebeke and the bringing back of the power cables was only completed on 28 October. The machine seems not to have been tried again.
The British tried two tunnelling machines with no more success than the Germans. The first, tried at Petit Bois in a second shaft sunk at Van Damme Farm, operated at a far greater depth than the German machine, through the clay at 100ft depth. The compressed air-driven Stanley Heading Machine was lowered in parts down the shaft and first tried on 4 March 1916. It cut a 5ft diameter tunnel, moving forward at 2ft per hour. The machine, however, had a tendency to dive and each time it was stopped the newly exposed clay swelled and gripped it tightly, requiring it to be dug out by hand. The power output was insufficient and the fuses of the generator powering the compressor repeatedly blew. After 200ft had been managed Harvey ordered it to be abandoned in the tunnel.12 A second British machine, a Whittaker, was installed exactly a year later by the 1st Canadian Tunnelling Company at a similar depth, from a shaft in the embankment of the Ypres Canal opposite the Bluff, to carry out a 4,320ft projected drive towards the Dam Strasse. This machine was no more successful than the first at coping with difficult ground and was subsequently dismantled and removed.13
Military mining before 1914 was not practised at any great depth and did not anticipate detailed geological knowledge. Traditionally, the object in siege works was to drive tunnels which were as shallow as possible, and knowledge of the underlying strata was rarely needed. For the first time, tunnels were being driven at depths which would pass through several different layers and the location in Flanders of the Paniselien and Ypresian clay levels was crucial to the British Messines plan. Such geological knowledge was also required for constructing deep dugouts and detailed maps were drawn up by both sides to indicate where in Flanders their construction was feasible. Geological knowledge was also vital for the fundamental requirement of water supply. The British Army did not have geologists on its staff, which necessitated the co-opting of civilian experts. Once again the Territorial Force provided the bridge by which expertise was brought into the BEF, when Lieutenant W.B.R. King, formerly of the British Geological Survey and serving in the Royal Welch Fusiliers, was attached to the Engineer in Chief at GHQ from June 1915. The head start that the British had in reaching the clay levels at Messines was due in large part to shortcomings in geological knowledge in the German Army. A German geological investigation of the Messines–Wytschaete ridge prior to the British success in March 1916 would, in the view of one German military geologist, have enabled the Germans to take countermeasures in time to stop the British mining offensive.14 Serving as a temporary Major with the Australian Mining Corps was an eminent Professor of Geology from Sydney University, T.W. Edgeworth David. David made many important contributions to the geological knowledge of the British sectors of the Western Front. In particular he established the seasonal fluctuation of water levels in the chalk areas, which prevented the British systems being driven below the level at which they would be flooded by the rise in early spring.15
The Stanley Heading Machine. The machine was anchored to the sides and floor of the tunnel and the cutter arms rotated. Once the machine had cut the length of the cutter arms, the debris was removed and the machine was advanced forward. Designed to remove a 5ft diameter circular core of coal, it was less successful in clay. The machine used by 250 Tunnelling Company remains to this day 200ft below ground near Van Damme Farm. From Kerr, Practical Coal Mining (1905).
Detecting the noises made by the enemy underground was a crucial form of intelligence and miners spent long periods attempting to discern the location and activities of their opponents. Listening became the most important means of gaining information on the activities of the opponent underground. It was also the most nerve-wracking activity of underground warfare, requiring a man to crouch in a tunnel for long periods, often alone, and in close proximity to the enemy. Graffiti surviving deep in the Vimy Ridge system of 172 Tunnelling Company indicates only a small number of men employed on listening, working in pairs, and on duty for many consecutive days in the same chamber. As well as good hearing, only a small number of men possessed the temperament to make effective listeners. The hearing and interpretation of sounds was highly subjective and Capitaine Thobie ranked his listeners according to how reliable they were. He placed the best in galleries where the tangle of surrounding tunnels was most complex, as they had to distinguish between noises from their own adjacent galleries and those of the enemy. In the most dangerous places:
…a kind of fever of anxiety and fear reigned permanently. The listener’s attention was constantly drawn by the workers, to listen to the slightest movement indicating the presence of the enemy miners. At the start of day, all went well; but, as the hours passed, the constant reminder of the burden of responsibility by all those who carried out their task with the greatest possible activity acted on the listeners. Any routine incident of this terrible existence in the trenches 30 or 35 metres from the enemy: a mortar bomb or rifle grenade bursting in the vicinity, all contributed to tightening the nerves and wore down the resolve of the listener towards his task which was to report the slightest noise heard. The result, especially at night where the danger of raids increased, was to excite the listener to the point where he imagined that he heard noises. He warned the workers and the foreman NCO, and as obviously each felt relieved of the individual burden of responsibility of claiming to hear something, there arose a strong conviction of the certainty that noises had been heard which had no basis in reality. These misapprehensions had to be combated in order not to fall into the same error oneself, because a charge, placed without reason at a point where the enemy had not yet reached, led to waste of time and a partial destruction of our own system without any profit.16
Listening records had to be carefully kept, so that patterns could be detected, and it was important that they were handed on to relieving units. Where there was anxiety over mining, engineers would frequently be asked to investigate sounds by the infantry, who believed that they were being undermined. Often these would be discovered to be harmless activity in an adjacent dugout, or on occasion a nest of rats. Where miners did discover signs of activity, however, they might not reveal to the infantry that the enemy was beneath their trenches, for fear of inducing panic.
The geophone in use to establish the relative depth of enemy workings. It was more usually placed on the tunnel floor. From École de Mines, Supplément au Livre de l’Officier, 1917.
The French listening device improvised from a water bottle. From École de Mines, Supplément au Livre de l’Officier, 1917.
Mine listening was greatly improved by technological development. At first the ear was simply placed flat against the wall or floor or in a basin of water. The first French listening aid was a water bottle filled with water, to which were attached stethoscope ear pieces.
A French device which greatly improved Allied listening ability was invented by Jean Perrin, Professor of Physical Chemistry at the Sorbonne, in 1915. The geophone enclosed mercury between two mica membranes linked to stethoscope earpieces to magnify sound waves by about two and a half times.17 By using two such discs, a listener with training and aptitude could detect both distance and direction and, by taking compass bearings on the same sounds from adjacent galleries, listeners could pin-point the direction of the sound with far more accuracy. In practice this required very powerful self-control from the listener. Lying alone in a gallery which was known to be in danger from enemy mining, the listener first had to become used to the instrument detecting his own heartbeat or any creaking of his clothing or a leather belt. An electrical version of the geophone, the seismomicrophone, was not as sensitive and lacked the benefit of stereo listening, but could be placed in galleries in which it was unsafe for a listener to remain, either because of the proximity of the enemy or dangerous levels of gas. These detectors were connected to a central listening st
ation and would activate an alarm when noises were detected in the gallery. The Germans used a version developed by Dr Erich Waetzmann of Breslau University, the Horchgerät Waetzmann, manufactured by Siemens and Halske, and were using central listening stations by the end of 1915.18
The seismomicrophone, invented by the French and also used by the British. The vibration of a lead mass (M) held in rubber rings was recorded by a microphone formed of two carbon discs (P) which was transmitted to a receiver. From École de Mines, Supplément au Livre de l’Officier, 1917.
The British drew up guidance on the range of noises in chalk or clay. Picking in chalk travelled the furthest: it could be heard 150ft away with the naked ear and 300ft away with a geophone. Shovelling was audible at 70ft or 120ft with the geophone. Talking was perceptible at 12ft or 50ft with the geophone.19 In sandy clay the distances were about two and a half times less20 and work in clay was always more liable to break into the galleries of the opposing side. In the chalk areas it was far more difficult to place a mine directly beneath the enemy trenches and most blows tended to be in no man’s land.
