【正文】 of the round .Usually ,one or more holes (largediameter) are left unloaded to provide relief for the loaded holes . Various binations of spacing ,alignment and holes loaded are possible. Innumerable typesofblastingrounds are used in underground headings .Even in the same heading the round may have to be altered as different rock charateristics important factor in any round is the firing sequence .In general ,the holes are fired so that each hole or series of holes is blasted to the free face provided by the preceding holes .The depth of drift rounds depends on the plete drifting cycle and drift general rule is that a round will not break much deeper than the least crosssectional dimension of the drift . Rounds can be arranged that provide certain muckpile shapes and positions for more efficient loading and cycles . In drifts requiring close support , rounds can be arranged to prevent damage. 爆破在巖巷掘進中的應用 1 破巖理論 破巖是用爆破的方法把煤、礦石或巖石破碎，以便于大部分物料的塊度小到便于裝載、處理和運輸。用機具傳遞能量使巖石或礦石破碎的方法，對于決定破巖效率至為重要。加壓的速度增加，使巖石強度顯著增加。近幾年來采用了半自動裝藥器，主要用于井下作業(yè)。第一種裝藥器由幾節(jié)鋁管連接而成并用 42磅／英寸 2的壓風把藥卷吹入炮眼。有兩種不同的裝藥器：壓力罐式裝藥器和注藥器。 3 控制爆破 控制爆破用于減少巷道超挖和使圍巖震裂減至最小程度。 預裂爆破，有時又稱為預剪切爆破，是在巷道的輪廓線上鉆一排炮眼，其直徑一般為 2至 4英寸眼距為炮眼直徑的 6~12倍，顯然市場上可買到柱狀裝藥所需的小直徑藥卷和專用的連接器，但一般仍采用直徑為 l— 11／，英寸的代那買特藥卷，間隔裝藥，藥卷間隔為 1~2英尺，以導爆線串系起來。因此建議預裂的超前距離不要太大。 光面爆破法就是井下的緩沖爆破法。但比普通方法需要多鉆一些周邊眼。 炮眼布置設計要做到：便于鉆跟，耗用炸藥最少，爆破后所形成的巷道斷面盡可能接近設計要求。 楔形掏槽或 v型掏槽內成對的斜角炮眼在底部相遇或接近相遇組成。一般有一個或一個以上槽眼 (大直徑眼 )不裝藥、為其他裝藥槽眼提供自由面。炮眼布置要使爆破下來的巖石堆的形狀及位置有利于更有效地裝運和循環(huán)作業(yè)。對任何一組炮眼來說，重要的因素是爆破順序。它適用于小斷面巷道。 常用的兩種掏槽方式是斜角眼掏槽和直眼掏槽。 4 巖巷爆破 最常用的巖巷掘進方法是三個工序的循環(huán)作業(yè)： (1)鉆炮眼、裝炸藥和爆破。雖然藥往中也可采用間隔物 (間隔裝藥 )，但最常用的是柱狀裝藥。可利用楔子把藥卷固定在眼中靠近爆破自由面一側，以減少爆破對巖壁的損壞?？卓?2~3英尺處不裝藥，但要充填炮泥。眼距通常相當于 2~4個炮眼直徑，不裝藥。裝填銨油炸藥的裝藥軟管必須能導電，其電阻最小為 1千歐米。這種半自動裝藥器不用閥門，而是讓藥卷通過一個位于兩個閘門之間的氣室。但炮棍與鉆孔相比不能做得太粗，因為這在裝藥作業(yè)中有可能捅壞和損壞導火索或電雷管腳線。人們經常綜合利用巖石的物理性質 (密度、壓痕，硬度、磨蝕硬度、孔隙度 )和機械性質，來謀取更好的破巖效果。隨著孔隙流體壓力增加，巖石的視強度就降低 因為它減弱了約束力的作用。能量的大小取決于巖石的性質和裝藥系統的類型。s surface or under the action of a fragmentation tool, causes an increase in rock strength .Apparent rock strength decreases as porc fluid pressure increases, since it decreases the effect of confining pressure. Although chemical effects of pore fluids influence rock strength, they generally are small pared to the confining pressure effect, except for a small minority of rock types .Increase in rock temperature causes a decrease in rock effect is very small because of the small ambient temperature changes found during mining. An increase in rate of load application causes an apparent increase in rock strength. Rock exhibits directional properties that in fluence the way it breaks. These are embodied in the concept of rock fabric ,which connotes the structure or configuration of the aggregate ponents as well as the physical or mechanical property manifestations. Rock fabric ont only relates to the preferred orientation of mineral constituents and their planes of weakness, but also to the configuration of discontinuities, microcracks and and bedding planes have great influence on fragmentation at field scale. Physical properties of rock (density,indentation,hardness,abrasivehardness and porosity ,)are frequently used in conjunction with mechanical properties to develop bett