【正文】 pounds per square inch .since that time the charging tube has been replaced by antistatic treated plastic hose of a special design. A charger includes a footoperated valve, reduction vavle with air hose, breech, connecting tube and charging hose. The semiautomatic charger permits the continuous insertion of explosive cartridge at the same rate as they are charged in the hole by the hose .Instead of a valve being used ,the cartridges pass through an air lock between two flaps. The air pressure in the charging hose is retained while cartridges are pressure in the charging hose is retained while cartridges are beins inserted .The semiautomatic charger permits considerably higher charging capacity than the normal type of charger. Explosives in the form of the form of loose material, usually ammonium nitrate explosives(ANFO), require special chargers. Two types can be differentiated: pressrure vessel machines and ejector units. Pressure vessel machines are particularly suitable for crystalline An 18 explosives with good charging capacity. Ejector units are operate by an ejector sucking up explosive from a container through a charging hose. The explosive is then blown through the charging hose into the drill hole .There are, also bined pressure ejector machines. The charging hose used for ANFO charging operations must conduct electricity and have a resistance of at least 1K?/m and ?/M. Nitro Nobel has developed a special pumping procedure which consists of a tanker vehicle which is used to pump explosive directly the drill holes. The charging capacity is very high in the case of large diameter drill holes. CONTROLLED BLASTING TECHNIQUTES Controlled blasting is used to reduce overbreak and minimize fracturing of the rock at the boundary of an excavation. The four basic controlled blasting techniques are: line drilling, presplitting, cushion blasting and smooth blasting. Line drilling, the earliest controlled blasting technique, involves drilling a row of closely spaced holes along the final excavation line, providing a plane of weakness to which to break. Line drill holes, 2or 4 diameters apart and contain no explosive. The blastholes adjacent to the line drillholes normally are loaded lighter and are on closer spacing than the other blastholes. The maximum depth for line drilling is about 30 ft .Line drilling involves no blasting in the final row of holes, and thus minimizes 19 damage to the final wall. Presplitting, sometimes called preshearing ,involves a single row of boreholes ,usually 2 to 4 in .in diameter ,drilled along the final excavation at a spacing of 6 to 12 borehole diameters .Dynamite cartridges 1to in . in size on 1 to 2 ft .centers usually are stringloadde on detonating cord ,although special smalldiameter cartridges with special couplers are available for total column loading .In unconsolidated formations ,closer spacings with lighter powder loads are required .The bottom 2 to 3 ft .of borehole usually is loaded somewhat heavier than the remainder .Stemming between and around the individual charges is optional .The top 2 to 3 ft . of borehole is not loaded ,but is stemmed. The depth that can bu presplit is limited by hole alignment ,with 50 ft .being about maximum .The presplit holes are fired before before the adjacent primary holes to provide a fracture plane to which the primary blast can break .In presplitting it is difficult to determine the results until the adjacent primary blast is shot .For this reason ,presplitting too far in advance is not remended .Presplitting seldom is done underground. Cushion blasting involves drilling a row of 2 – to 6in .diameter boreholes along the final excavation line ,loading with a light welldistributed charge ,pletely stemmed and firing after the main excavation is removed rather than before ,as in presplitting. The burden on the holes is slightly larger than the spacing .Wedges may be used to abut the charges to the excavation 20 side of the borehole and minimize damage to the final wall .Eeplosive loading is similar to that in presplitting .Cushion blasting has been done to depths near 100 ft .in a single lift with the largerdiameter boreholes because alignment is more easily retained .Cushion blasting seldom is done underground. Smooth blasting is the underground counterpart of cushion blasting .At the perimeter of the tunnel or drift ,closely spaced holes with a burdentospacing ratio near :1 are loaded with light welldistributed charges .Smooth blasting differs from cushion blasting in that (1) except at the collar ,the charges are not stemmed and (2) the perimeter holes are fired on the last delay in the same round as the primary blast .Total column loading is most mon ,although spacers may be used .The holes are stemmed to prevent the charges from being pulled out by the detonation of the previous delayed holes .Smooth blasting reduces overbreak in a drift and also provides a more petent back requiring less support .It involves more perimeter holes than does normal blasting. Combinations of controlled blasting techniques are used .In unconsolidated rock,line drilling sometimes is desirable between presplit or cushion boreholes . Corners sometimes are presplit when cushion blasting is used. TUNNEL BLASTING The most mon methed of driving a mining tunnel is a cyclic 21 operation in three sequences: (1) Drilling shot holes 。 5)時(shí)間依賴的反應(yīng)，由于流變學(xué)特性的地面必須加以考慮。 3)它是一個(gè)三維問(wèn)題。 難度設(shè)計(jì)的支持隧道是一個(gè)后果是以下幾個(gè)方面： 1)知識(shí)不足的行為，在地面條件下與開挖隧道。 許多工地工程師認(rèn)為，實(shí)證分析的收斂性是足夠的管理挖掘一條隧道，不那么在 意更精密的分析方法（ [ aftes ， 2021 年 ]和 [ graziani 等人， 2021 年 ] ） 。如果 采用移動(dòng)式工作 臺(tái)，其臺(tái)面有幾架棚子長(zhǎng)，其高度又能讓礦車從底下通過(guò)，則對(duì)掘進(jìn)工作會(huì)有好 處的。支護(hù)工作落后于工作面過(guò)遠(yuǎn)的地方，一般需要專業(yè)支架 隊(duì)。 12 這種工序顯然會(huì)減慢掘進(jìn)速度，但是除非巖層條件太差需要才用前 探板樁法或其他方法，一般坑木可標(biāo)準(zhǔn)化，并采用常規(guī)作業(yè)。 爆破后的第一道工序是撬落頂板上的浮石；在松軟的地 層中，利用前探梁、滑梁 或類似的裝置以