The Thin-section Identification of Rock and Its Grain-size Analysis in The West Route of South-to-North Water Transfer Project

Abstract

ABSTRACT:The basic characteristics of rock, such as lithology, strength, hardness and abrasion, are controled by the type, content, and grain-size of minerals in rock. Thin-section identification of rock was carried out with 124 pieces of samples from the West Route of South-to-North Water Transfer Project. The statistic and analysis of mineral composition and grain-size of rock clast were conducted. The statistic distribution curves of grain-size content and grain-size distribution graphs of different grain-size classes of quartz and feldspar clast were obtained according to the statistic analysis results. The categories and characteristics of different rocks were divided and described exactly. The research results show that the rocks in the West Route of South-to-North Water Transfer Project could be divided into three types, which are sandstone and greywacke, siltstone and slate. The grain-size distributions of quartz and feldspar are similar, and all of them are subject to normal distribution. The diameters of main mineral grains are within the level of fine sand size without exception. The percent frequency of grain-size distribution is more than 70%, and there are obvious traction -gravity flow characteristics for grain-size distribution of rock clast. There is relatively similarity in grain-size distribution of rock clast sampled from different regions, which illuminates that the different rocks are formed in the same stable sediment environment. The research results could provide references for optimal design and Tunnel Boring Machine construction in the West Route of South-to-North Water Transfer Project.