Salient. Victoria University Student Newspaper. Volume 36, Number 9. 1ts May 1973

Demolitions and Engineering — (Save this article for academic interest)

Demolitions and Engineering

(Save this article for academic interest)

Train Derailment

A number of factors influence train derailment. Security measures, such as patrols and track walkers, may be expected wherever there is resistance; activity. Mountainous terrain offers steep grades, sharp curves, bridges, culverts, and tunnels which are ideal locations for derailment. In other areas a long level section of track may be the only vulnerable point, and it is suitable if the train moves through the area at high speed. Derailment on double-track lines should be accomplished on curves to that a single train will obstruct both tracks. Three derailment techniques are described in this section.

a. Technique. 3-5-2 (fig. 24). This method uses three charges weighing 1.25 kilograms each, placed and tamped under every fifth crosstie.

(1) The charges are linked together with detonating cord. A firing device with detonator is taped to detonating cord leads on both ends of the chain. The charges may be detonated from either end by an electrical firing circuit or by a pressure device actuated by the weight of the train wheels. The detonating cord should be extended on each end of the charges for a distance of at least 10 meters. The firing device should be placed at the end of the detonating cord nearest the approaching train. This is to insure that the charges blow in front of the train and not under it. The charges are placed under their respective ties and firmly tamped into position. The explosion will remove the rails at least 1 meter beyond the outside charges, disrupting at least 6 meters of rail. Additionally, the ties are broken and a crater is formed.

The depth of the crater depends on the type of ballast material in the railbed. Since the charges are not placed in contact with the rail, the rail is lifted upon detonation. The pressure breaks the rail just beyond the outside charges.

(2) The disadvantages of this technique are the time required and noise associated with the placement of the charges. Once the charges are cm placed, they may be left in position for extended periods.

b. Technique, 10-2-1 (fig.25). This method uses a total of ten 0.5 kilogram charges, each charge placed against the rail over every second crosstie.

(1) The charges are linked together with detonating cord. The charges are wedged or lashed to the web of the rail directly over the crossties. Detonating cord priming leads must extend from both ends of the chain. A pressure firing device may be used.

(2) The advantages of this technique are speed and silence in emplacement. The disadvantage is that the charges are visible to trackwalkers.

Foreign Explosives

Foreign explosives and equipment should be used when available. Except for minor differences, foreign material is similar to American.

a. Principal Explosives. Many countries make TNT, dynamite and plastic explosives similar to American explosives. Table III shows standard explosives. It does not indicate the packaged size or form of the different explosives.

b. Characteristics of Foreign Explosives. A particular explosive produced by one nation is usually similar in characteristics to the same explosive produced in another nation. Minor differences in purity, density, ingredients, etc., may influence the performance of an explosive slightly; but the important characteristics particularly those of sensitivity and stability, are generally the same.

1. TNT. TNT is probably the most common explosive. It may be formed in different shapes, but its characteristics are similar to TNT manufactured in the United States since, chemically, they are the same (trinitrotoluene).

(2) Plastic explosives. Plastic explosives are manufactured by many countries and used for frontline demolition work. Their characteristics and performance are similar to those manufactured in the United States.

(3) Picric acid. TNP (Trinitrophenol) is slightly more powerful than TNT with a velocity of about 7,000 meters per second. It is a lemon-yellow, crystalline substance which may be identified by its tendency to dye water or material it may contact. It combines readily with some metals to form picrate (explosive) salts which are extremely sensitive to shock, friction, and heat. For this reason careful attention must be paid to packaging (usually paper or zinc Is used) and storage. Otherwise, TNP has the same general characteristics as TNT.

(4) Guncotton. The power of guncotton, which is a cellulose of high nitration, is directly influenced by moisture. Dry guncotton generally detonates at a velocity of 7,300 meters per second; when wet, the velocity velocity of detonation is about 5,500 meters per second. Dry guncotton is extremely sensitive to shock and should be used only for booster pellets and blasting caps.

(5) Nitroglycerin explosives. Standard, ammonia, and gelatin (Gelignite) dynamites are common in foreign countries. Granular or free-running dynamite is conventional for borehole loading and replaces black powder in some areas of the world. It usually is less sensitive than other dynamites because of the increase of ammonium nitrate or other compounds necessary to make it pour. Nobel's 808 is similar to blasting gelatin, being of a higher density though somewhat less sensitive. It has a hard, rubber like texture which tends to soften as the temperature is increased. Its color normally varies between green and brown.

Foreign Accessories

a. Primers. Many foreign explosives are as insensitive to shock as TNT. Since some foreign blasting caps are only equivalent to the standard, commercial, American, numbers 6 and 8 caps, the Insensitive foreign explosives cannot be detonated consistently by using the American caps. A small amount of a more sensitive explosive must be used as the link between the charge and the cap; this is called a booster or primer. Foreign demolition charges of the cast kind require the use of a booster and are manufactured with a booster recess.

b. Blasting Caps. Foreign blasting caps are often identical to the American number 6 and 8 caps. They may be of dry guncotton or some other compound pressed into a cardboard, metal or paper shell. Some of the Russian caps are made of cardboard and paper and may be of slightly different lengths and diameter.

c. Burning Fuse. It is important to recognise instantaneous fuse manufactured by some countries for booby trapping and incendiary purposes. They burn at fast speeds; some burn as fast as 61 meters per second. When ignited it may appear to explode. To minimize accidents, all fuse should be tested before being used with explosives. Activate unidentified fuse with a firing device from a safe distance or with a known time fuse with a 45 degree splice.

Handling Foreign Explosives

a. General. The characteristics of an unknown explosive must never be taken for granted, and should be subjected to the expedient lest methods outlined below.

b. Procedure for Handling Unknown Explosives. Unknown explosives should be tested as follows:

(1) Examine the packaged unit (case, block, cartridge) for exuded liquids. If there is reason to believe that an oozing explosive is dynamite (i.e. contains considerable nitroglycerin) it should be destroyed.

(2) Subject 0.5 kilograms of the explosive to rifle fire. If it fails to detonate after five or more hits, it may be considered insensitive to shock and friction. Dynamite containing nitroglycerin should detonate on the strike of a bullet.

(3) Place approximately 28 grams of the explosive on paper or some other combustible material and ignite it. This permits the tester to withdraw to a safe distance before the flame reaches the explosive. Take note of the following burning characteristics: color of flame, rate of burning, whether or not the explosive melts, amount and color of smoke etc. These may be similar to the burning qualities of known explosives and an indication of the content of the unknown explosive compound.

(4) Attempt to detonate a unit of the unknown explosive with a blasting cap. If this fails increase the number of blasting caps by one for each successive attempt until detonation occurs.

ChemicalFormalNormal sourcePotassium chlorate................Kclo3Drug store*, hospital, swimming pool, and gymnasiumPotassium Permanganatekmno6 KNO3Same as KCLO3.Potassium nitrate Fertilizer manufacturer and explosive plants. Fertilizer manufacturer and glass foundries.Potassium nitrateNANO3 (NH4)NO Fe3O3 Ferric aluminum Same as KNO3.Powered aluminum Same as KNO3.Powered aluminumAlElectrical equipment, auto and paint manufacturer, paint store Auto manufacturer, machine shoo, commercial chemical house.MagnesiumMg GlycerineC2H4(OH)2 H2SO4Drug store, soap and/or candle manufacturer.Sulphuric acid Garage, machine shop, school or hospital. Match manufacturer add explosive plants. Sodiumm chlorate.NaCLO2 Sulphur Drug store, natch manufacturer.

Table II. Chemical Formulas.

(based on U.S. Army Field Manual FM 31-20 December 1965) U.S.BritishFrenchGermanItalianJapanese Russian Tnttut Trotyl*TotitePull Pulver Spreag Munition 02.Tritole Tritdo*Chakatauyaku TOL Tryty*Crdosite C3* C4*Plastic explosive or PE—2A*Cyclonite* Hexogen C6* Plastitc* Nipolit*Hexagense* T-4*Koehitaubakuyapho Cyelonite* O-Shitauyaku*Hexogen Kamsikite*Tetryl TetrytolCompositive ecplosive or C.E.MeiayakuTETPPETN Pestotie* Primaseoed* (Detondting sord)PETN Pentotite Cordtex' (Detonating sord)KnallsundaehourShoe-i- Yaku**Ten DSH* 1943**Ammoslyu sitrase AmstolNitste d'amston iuse.Amantoc SaltpeterNitrate FNP* JeWistSS* Tjjgsaj MsjssfSloaVaa Mxau- Got i.ai.i'boaster DtHwau1 M*atW*Dyasaan'DyaaaeSr*OaWmira- Qgmtmm t*Aaatesawtaa fwttt**aMrttkyaka Oaaira**- ? ??SaaTltVK*I'r*-r** Compounded with other explosives. ** Undetermined if this is demolition explosive or detonating cord. Note; no information available on Chieom or Eastasiancom Items.

Table III. World's Principal Civil (Commercially-produced) Explosives.

Figure 24 3-5-2 Technique for train derailment.

Figure 24 3-5-2 Technique for train derailment.

Figure 25 10-2-1 Technique for train derailment.

Figure 25 10-2-1 Technique for train derailment.