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Groundwater monitoring of an open-pit limestone quarry: Water-rock interaction and mixing estimation within the rock layers by geochemical and statistical analyses

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Title: Groundwater monitoring of an open-pit limestone quarry: Water-rock interaction and mixing estimation within the rock layers by geochemical and statistical analyses
Authors: Eang, Khy Eam Browse this author
Igarashi, Toshifumi Browse this author →KAKEN DB
Kondo, Megumi Browse this author
Nakatani, Tsurugi Browse this author
Tabelin, Carlito Baltazar Browse this author →ORCID
Fujinaga, Ryota Browse this author
Keywords: Water-rock interaction
Groundwater mixing
Interbedded layer
Geochemist's workbench
Rock slope stability
Issue Date: Nov-2018
Publisher: Elsevier
Journal Title: International journal of mining science and technology
Volume: 28
Issue: 6
Start Page: 849
End Page: 857
Publisher DOI: 10.1016/j.ijmst.2018.04.002
Abstract: Water-rock interaction and groundwater mixing are important phenomena in understanding hydrogeological systems and the stability of rock slopes especially those consisting largely of moderately watersoluble minerals like calcite. In this study, the hydrogeological and geochemical evolutions of groundwater in a limestone quarry composed of three strata: limestone layer (covering), interbedded layer under the covering layer, and slaty greenstone layer (basement) were investigated. Water-rock interaction in the open-pit limestone quarry was evaluated using PHREEQC, while hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to classify and identify water sources responsible for possible groundwater mixing within rock layers. In addition, Geochemist's Workbench was applied to estimate the mixing fractions to clarify sensitive zones that may affect rock slope stability. The results showed that the changes in Ca2+ and HCO3 concentrations of several groundwater samples along the interbedded layer could be attributed to mixing groundwater from the limestone layer and that from slaty greenstone layer. Based on the HCA and PCA results, groundwaters were classified into several types depending on their origin: (1) groundwater from the limestone layer (L-o), (2) mixed groundwater flowing along the interbedded layer (e.g., groundwater samples L-7, L-11, S-3 and S-4), and (3) groundwater originating from the slaty greenstone layer (S-o). The mixing fractions of 41% L-o: 59% S-o, 64% L-o: 36% S-o, 43% L-o : 57% S-o and 25% L-o: 75% S o on the normal days corresponded to groundwaters L-7, L-11, S-3 and S-4, respectively, while the mixing fractions of groundwaters L-7 and L-11 (61% L-o: 39% S-o and 93% L-o: 7% S-o, respectively) on rainy days became the majority of groundwater originating from the limestone layer. These indicate that groundwater along the interbedded layer significantly affected the stability of rock slopes by enlarging multi-breaking zones in the layer through calcite dissolution and inducing high water pressure, tension cracks and potential sliding plane along this layer particularly during intense rainfall episodes.
Type: article
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 五十嵐 敏文

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