Road Craters and Bridge Demolitions
Road craters can be created be either a mined charge, camouflet charge or by a charge laid by auger-holes. A mined charge, as the name suggests would be laid by sinking a vertical shaft in the ground, followed by a horizontal shaft under the road leading to the explosive chamber. The explosive used would have been guncotton or equivalent e.g. dynamite No 1 or gelignite. The amount of explosive required was calculated by the ‘D’ formula with variables such as the width of ‘object attacked’, thickness of ‘object attacked’ etc. This method was very labour intensive. A camouflet charge was laid first by breaking the road surface then driving a length of pipe fitted with a driving cap and spearhead into the ground in which a small charge could be laid. This was then blown, forming a small mined chamber (the camouflet chamber) into which the main cratering charge was placed. This could be done by a party of one NCO and four men in about one hour. The third method, auger-holes, relied on boring a hole with an auger, lining the hole with metal tubing into which the charge was placed. Several auger holes could be placed side by side to increase the effect. A similar result could be obtained by pile driving a water pipe fitted with steel points and was particularly suited to fords.
An improvised method of road cratering was provided by making use of Naval depth charges. These were buried in the road with a metal pipe running up to the road surface. The pipe was covered with a metal plate. The charge was armed by placing a smaller charge into the pipe which could be blown electrically.
In Suffolk, road craters are frequently mentioned in unit Defence Schemes but the method of creating them is often not stated. The war diary of 2/8 Lancs does mention three camouflet tubes in position at one location.
Above: Method of creating a camoflet road crater
In 1942 it was noted in Lowestoft that some of the depth charge craters would do considerable damage to Naval facilities and the water / electricity supply as well as telephone communications. The metal pipes of these charges were filled with concrete to prevent them from being able to be fired but the depth charge itself remained in situ (are they still there!?).
The standard method of demolishing bridges was by a mined charge or bored charge at the bridge abutment – this had the result of not only destroying the bridge but also meaning that a replacement bridge would require a much larger span. Such major bridge demoloitions were only prepared on bridges which gave direct access to ports. Charges could also be be placed at the crown or haunch.
Bridge demolition - based on RE Pocket Book Pamphlet VI 1940