微波照射下矿物升温特性与岩石弱化效果研究综述

A Review on Mineral Heating Characteristics and Rock Weakening Effect under Microwave Irradiation

随着经济的快速发展,工程领域面对坚硬岩石的情况越来越多,传统机械开挖方式的效率和经济性难以保障,而微波辅助破岩具有较好的工程应用前景。岩石是由不同矿物组成的,不同矿物对微波的敏感程度不同,其敏感程度与矿物的族类、晶型和铁元素含量有关。当岩石处于微波场中时,不同敏感性矿物间的差异性膨胀能够在矿物边界和内部产生热应力,从而有效弱化岩石。影响岩石弱化效果的主要因素可分为微波条件和岩石条件两大类。一般而言,岩石强度随着微波功率与照射时间的增加而降低;相同能量条件下,高功率短时间的微波照射能够产生更好的弱化效果。岩石所含矿物的微波敏感性越高,敏感矿物的颗粒尺寸越大,及含量适当时,微波照射岩石的弱化效果越好;含水状态的岩石受到微波照射后,能够比干燥状态产生更大的损伤。微波的热效应有时还会使岩石中的矿物发生较大的物理或化学变化,进而对其升温特性及弱化效果产生影响。面照射试验表明微波能使大尺寸岩样在照射区域产生放射状裂纹,从而有效降低岩石强度,提高破岩效率。

With the rapid development of economy,there has been an increasing number of cases where extremely hard rock is encountered.Thus,traditional mechanical excavation methods can hardly guarantee their efficiency and economy.Microwave-assisted rock breaking is a promising technique.Rock is formed by different minerals which have different microwave sensitivity related to their species,crystal forms and iron content.When the rock is exposed to microwave irradiation,differential expansion between minerals of different sensitivity causes thermal stresses inside and along the boundaries of the minerals,thus effectively weakening the rock.Two main factors affecting the weakening effect are microwave parameters and rock properties.Basically,rock strength declines as microwave power and irradiation time increase;a high power and short irradiation can cause a better weakening effect when consuming the same energy.The weakening effect of microwave on rocks can also be enhanced by a certain content of microwave sensitive minerals and a coarser particle size.The physical and chemical properties of minerals are sometimes greatly affected by microwave heating,which in turn affects the heating characteristics and weakening effect of the rock.Surface irradiation tests reveal that microwave can induce radial pattern cracks on the irradiation zone of large-size rock sample,thereby reducing the rock strength and improving the rock breaking efficiency.