The Westwood Mine aims to reuse the tailings storage facility #1(TSF #1) for solid waste storage, but,downstream of the Northwest dike is considered critical in terms of stability. This paper uses numerical modeling a...The Westwood Mine aims to reuse the tailings storage facility #1(TSF #1) for solid waste storage, but,downstream of the Northwest dike is considered critical in terms of stability. This paper uses numerical modeling along with geophysical monitoring for assessing the Northwest dike stability during the restoration phase. The impact of waste rock deposition in the upstream TSF #1 is considered. The geophysical monitoring is based on electrical resistivity methods and was used to investigate the internal structure of the dike embankment in different deposition stages. The numerical simulations were performed with SLOPE/W code. The results show a factor of safety well above the minimum recommended value of 1.5. Geophysical monitoring revealed a vertical variation in the electrical resistivity across the dike, which indicates a multilayer structure of the embankment. Without any current in situ data, the geophysical monitoring helped estimating the nature of the materials used and the internal structure of the embankment. These interpretations were validated by geological observation of geotechnical log of the embankment. Based on this study, it is recommended that the water polishing pond be partly filled before waste rock is deposited in TSF #1. In addition, to ensure the stability of the dike, the piezometric head monitoring prior to and during waste rock deposition is recommended.展开更多
An explicit demonstration of the changes in fish assemblages is required to reveal the influence of damming on fish species.However,information from which to draw general conclusions regarding changes in fish assembla...An explicit demonstration of the changes in fish assemblages is required to reveal the influence of damming on fish species.However,information from which to draw general conclusions regarding changes in fish assemblages is insufficient because of the limitations of available approaches.We used a combination of acoustic surveys,gillnet sampling,and geostatistical simulations to document the spatiotemporal variations in the fish assemblages downstream of the Gezhouba Dam,before and after the third impoundment of Three Gorges Reservoir(TGR).To conduct a hydroacoustic identification of individual species,we matched the size distributions of the fishes captured by gillnet with those of the acoustic surveys.An optimum threshold of target strength of 50 dB re 1 m 2 was defined,and acoustic surveys were purposefully extended to the selected fish assemblages(i.e.,endemic Coreius species) that was acquired by the size and species selectivity of the gillnet sampling.The relative proportion of fish species in acoustic surveys was allocated based on the composition(%) of the harvest in the gillnet surveys.Geostatistical simulations were likewise used to generate spatial patterns of fish distribution,and to determine the absolute abundance of the selected fish assemblages.We observed both the species composition and the spatial distribution of the selected fish assemblages changed significantly after implementation of new flow regulation in the TGR,wherein an immediate sharp population decline in the Coreius occurred.Our results strongly suggested that the new flow regulation in the TGR impoundment adversely affected downstream fish species,particularly the endemic Coreius species.To determine the factors responsible for the decline,we associated the variation in the fish assemblage patterns with changes in the environment and determined that substrate erosion resulting from trapping practices in the TGR likely played a key role.展开更多
基金financially supported by NSERC (Natural Sciences and Engineering Research Council of Canada) Engage grants
文摘The Westwood Mine aims to reuse the tailings storage facility #1(TSF #1) for solid waste storage, but,downstream of the Northwest dike is considered critical in terms of stability. This paper uses numerical modeling along with geophysical monitoring for assessing the Northwest dike stability during the restoration phase. The impact of waste rock deposition in the upstream TSF #1 is considered. The geophysical monitoring is based on electrical resistivity methods and was used to investigate the internal structure of the dike embankment in different deposition stages. The numerical simulations were performed with SLOPE/W code. The results show a factor of safety well above the minimum recommended value of 1.5. Geophysical monitoring revealed a vertical variation in the electrical resistivity across the dike, which indicates a multilayer structure of the embankment. Without any current in situ data, the geophysical monitoring helped estimating the nature of the materials used and the internal structure of the embankment. These interpretations were validated by geological observation of geotechnical log of the embankment. Based on this study, it is recommended that the water polishing pond be partly filled before waste rock is deposited in TSF #1. In addition, to ensure the stability of the dike, the piezometric head monitoring prior to and during waste rock deposition is recommended.
基金the National Science and Technology Supporting Program of China(No.2012BAD25B08)China Three Gorges Corporation Project(CT-12-08-01)State Key Laboratory of Freshwater Ecology and Biotechnology
基金supported by the National Natural Science Foundation of China (Grant No. 51079089)Key Project of the National Twelfth-Five Year Research Program of China (Grant No.2012BAC06B04)the Ecological and Environmental Monitoring Programs of China Three Gorges Project Corporation (Grant Nos. 241202004and SXSN/2726)
文摘An explicit demonstration of the changes in fish assemblages is required to reveal the influence of damming on fish species.However,information from which to draw general conclusions regarding changes in fish assemblages is insufficient because of the limitations of available approaches.We used a combination of acoustic surveys,gillnet sampling,and geostatistical simulations to document the spatiotemporal variations in the fish assemblages downstream of the Gezhouba Dam,before and after the third impoundment of Three Gorges Reservoir(TGR).To conduct a hydroacoustic identification of individual species,we matched the size distributions of the fishes captured by gillnet with those of the acoustic surveys.An optimum threshold of target strength of 50 dB re 1 m 2 was defined,and acoustic surveys were purposefully extended to the selected fish assemblages(i.e.,endemic Coreius species) that was acquired by the size and species selectivity of the gillnet sampling.The relative proportion of fish species in acoustic surveys was allocated based on the composition(%) of the harvest in the gillnet surveys.Geostatistical simulations were likewise used to generate spatial patterns of fish distribution,and to determine the absolute abundance of the selected fish assemblages.We observed both the species composition and the spatial distribution of the selected fish assemblages changed significantly after implementation of new flow regulation in the TGR,wherein an immediate sharp population decline in the Coreius occurred.Our results strongly suggested that the new flow regulation in the TGR impoundment adversely affected downstream fish species,particularly the endemic Coreius species.To determine the factors responsible for the decline,we associated the variation in the fish assemblage patterns with changes in the environment and determined that substrate erosion resulting from trapping practices in the TGR likely played a key role.
