陕北烧变岩水—岩作用的劣化特性

鄂尔多斯盆地东北缘陕晋蒙交界地区存在大量煤火高温烘烤形成的烧变岩。与原岩相比,烧变后的岩体结构破碎孔隙发育,在长期水–岩作用下,形成了大量危岩体。以陕北神木大柳塔地区的烧变岩为对象,开展了50次干湿循环试验,测试不同循环次数后烧变岩物理性质与力学性质及其变化,探讨不同烧变程度烧变岩劣化特性。结果表明：烧变岩质量、硬度、力学性质下降,表面亮度降低,粗糙度与红黄色度增强;基于低场核磁共振技术(NMR)测试,烧变岩孔隙体积比例曲线右移,最大孔径扩张;微孔向大孔转化,大孔含量与总孔隙率升高;烧变作用使岩体孔隙发育,且提高了烧变岩的抗侵蚀能力,降低了色度、质量、粗糙度、硬度、力学性质的变化程度。长期水–岩作用可对烧变岩的物理力学性质与孔隙结构造成明显改变,烧变程度与初始孔隙结构能够影响劣化效果。根据研究不同烧变岩的劣化过程,得出加固低烧变程度岩体表面、加固沉积层理与原有裂隙、堵塞高烧变程度岩体孔隙,可降低水-岩作用的侵蚀破坏强度。

Deterioration characteristics of water-rock interaction on combustion metamorphic rocks in northern Shaanxi

There are a lot of combustion metamorphic (CM) rocks formed by high temperature baking of coal fires in the border area of Shaanxi, Shanxi and Inner Mongolia in the northeastern margin of Ordos Basin. Compared with the virgin rock, the rock mass subjected to combustion metamorphism is broken in structure, with pores developed, and a large number of dangerous rock masses are formed under the long-term water-rock interaction. Herein, 50 dry-wet cycle experiments were carried out with the CM rocks in Daliuta Area of Shenmu in Shaanxi Province. Meanwhile, the changes in the physical and mechanical properties of CM rocks were tested after different cycles, and the deterioration characteristics of CM rocks with different degrees of combustion metamorphism were discussed. The results show that: the CM rock has the quality, hardness and mechanical properties lowered, the surface glossiness and brightness decreased, and the roughness and red-yellow degree increased. According to the low-field nuclear magnetic resonance (NMR) testing, the pore volume proportion curve of the CM rock shifts to the right and the maximum pore size expands. That is, the micropores change to macropores, with the macropore content and total porosity increased. Besides, the combustion metamorphism causes the development of pores in the rock mass, improves the anti-erosion ability of the CM rock, and reduces the variation of chromaticity, quality, roughness, hardness and mechanical properties. The long-term water-rock interaction could significantly change the physical and mechanical properties, as well as the pore structure, of the CM rocks. Moreover, the degree of combustion metamorphism and the initial pore structure could affect the degree of deterioration. According to the study on the deterioration process of different CM rocks, it is concluded that the erosion and fracture intensity of water-rock interaction could be reduced by strengthening the surface of rock mass with low degree of combustion metamorphism, reinforcing the sedimentary bedding and the original fissures, and plugging the pore of rock mass through high degree of combustion metamorphism.