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Japan, China and South-East Asia
Published in Ian Sims, Alan Poole, Alkali-Aggregate Reaction in Concrete: A World Review, 2017
Kazuo Yamada, Toyoaki Miyagawa
Xie et al. (2004) reported microcrystalline quartz and chalcedony in most aggregates along the Qinghai-Tibet railway. The Tibet plateau, occupying one fourth of China, forms the south-western area of China and has been called ‘the Roof of the World’. The Tibet plateau was formed by the collision of the Indian and Eurasian plates, with the Indian plate being subducted under the Eurasian plate. So, the Tibet plateau is formed by various deformed metamorphic rocks. In some coarse aggregates, the following rock types were observed: biotite-andesite, biotite-quartz-schist, fluidal structure tuff, welded tuff, metamorphic rocks, siltstone, diabase, rhyolite and biotite-quartz-diorite. In some sand, the following rock types are described: perlite, gneiss, siliceous rock, sandstone, tuff, rhyolite, phyllite, clay rock, pyroxenite, granite, diabase, quartzite, carbonatite, reddish marble, indicating a diverse variety of geological origins. From the viewpoint of ASR, in these old rocks, cryptocrystalline quartz and chalcedony are always suspicious as reactive minerals.
Effect of deep unloading zone on working performance of arch dam and abutment: A case study in the Yebatan Hydropower Station
Published in Heping Xie, Jian Zhao, Pathegama Gamage Ranjith, Deep Rock Mechanics: From Research to Engineering, 2018
Wen Zhang, Yuan Chen, Lin Zhang, Bao-quan Yang, Chong Zhang, Xiao-qiang Liu
The Yebatan arch dam is located in a symmetrical V-type canyon with high and steep slopes. The rock mass of the dam foundation is mainly composed of the quartz diorite. Some adverse geologic structures such as the deep unloading zones and faults are well-developed in both banks. As shown in Fig. 1, the two abutments are severely cut by the faults tectonics, decreasing the integrity of the rock masses. And the entire bearing capacity of two abutments is also be consequently influenced. In addition to fault tectonics, the deep unloading zones are developed within the conventional unloading zones in the slopes of both banks, mainly characterized by some gapped cracks or some broken zones filled with detritus. The rock mass in the deep unloading zones are mainly composed of the slight relaxed rock mass III1, the moderate relaxed rock mass III2S and the strong relaxed rock mass IVS. The mechanical properties of the deep unloading zones are poor (shown in Table 1). Moreover, the strong relaxed rock mass IVS in both abutments are located in the transmission direction of the arch thrust (shadow zones in Fig. 1). The adverse geologic conditions mentioned above, especially the deep unloading zones, are the major geological defect of the project. Due to the serious development of the deep unloading zones and high hydrostatic water pressure in the mid-low elevation of the project, the arch dam and abutment at EL. 2750 m are taken as research object to analyze the effect of deep unloading zone on working performance of the project.
Stave Falls intake excavation FLAC analysis—A case history
Published in Christine Detournay, Roger Hart, FLAC and Numerical Modeling in Geomechanics, 2020
At the intake, joint condition ranges from tight and unweathered to about 2 mm aperture with moderate weathering. Joint persistence ranges from about 20+ m for Set 1 joints to about 5 m for Set 3 joints. Joint spacing ranges from about 250 to 1500 mm. Minor shear zones with thickness up to 100 mm are also present in this orthogonal system. Spacing of the minor shear zones ranges from about 5 to 20 m. Random joints and shears are also present. Epidote and chlorite alteration of the quartz diorite rock mass occurs in local areas. Unconfined compressive strength ranges from about 50 to 200 MPa, and RQD ranges from about 30% to 100%.
Formation of Cu–Au porphyry deposits: hydraulic quartz veins, magmatic processes and constraints from chlorine
Published in Australian Journal of Earth Sciences, 2023
G. N. Phillips, J. R. Vearncombe, J. D. Clemens, A. Day, A. F. M. Kisters, B. P. Von der Heyden
The host rocks for porphyry Cu–Au deposits span a variety of settings in the crust and mantle. The dominant minerals that link the main, unaltered host rocks of diorite, quartz diorite, monzodiorite and granodiorite are plagioclase, lesser K-feldspar and minor to moderate quartz contents, with additional biotite and hornblende. Granodiorites that are not associated with Precambrian trondhjemite–tonalite–granodiorite series can have a variety of origins. These origins include fractionation from enriched mantle parental magmas, such as K-rich diorites, and possibly magma mixing, although this is disputed (e.g. Frost & Mahood, 1987). Brown (2001) pointed out that granitic magmas (granites to granodiorites) are the necessary complements to the melt-depleted granulites commonly formed in the deep crust (e.g. Arth & Hanson, 1972; Otamendi et al., 2009). For the majority of granodiorites (and other I-type granitic rocks), Clemens et al. (2011) showed that the only mechanism that simultaneously explains their major-element, trace-element, isotopic and mineralogical characteristics is partial melting of pre-existing meta-igneous crustal rocks, with variable entrainment of the solid products of the melting reactions. Recent summaries of the evidence can be found in Clemens (2012) and Brown (2013). Some of the more mafic plutonic rocks (such as diorites and monzodiorites), which also host Cu–Au porphyry deposits, are likely to represent magmas produced largely through partial melting of enriched mantle and subsequent differentiation or hybridisation (e.g. Shaw et al., 1993).