Environment
Ayodele Owolabi; Olumuyiwa Temidayo Ogunro; Gbenga Stephen Ayode
Abstract
Sustainable development is one that meets the needs of the current generation without compromising the ability of future generations to meet their own needs. The geospatial approach was used to evaluate the degree of sustainability of the mining operations in Okpella, Nigeria. 2011, 2016, and 2021. Normalized ...
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Sustainable development is one that meets the needs of the current generation without compromising the ability of future generations to meet their own needs. The geospatial approach was used to evaluate the degree of sustainability of the mining operations in Okpella, Nigeria. 2011, 2016, and 2021. Normalized Difference Vegetation Index (NDVI) revealed mean values of 0.36557, 0.32961, and 0.41674, respectively. This vegetation cover of shrubs, grassland, and relatively healthy vegetation remained after the mining activities in the research area. The surface water in the area is under stress due to the anthropogenic activities like mining, which is known to demand large amounts of water for mineral recovery and processing. Additionally, the Normalized Difference Moisture Index (NDMI) revealed that the mean values for the years 2011, 2016, and 2021 were, respectively, 0.01415, -0.32949, and -0.15331. The research area's NDMI showed little water stress. The Soil Moisture Index (SMI) for 2011, 2016, and 2021 indicated a moderate moisture content in the soil (0.73682, 0.58690, and 0.58897, respectively). The Land Surface Temperature (LST) data revealed that the LST levels (from 28.623 oC to 32.525 oC) had been rising. During the three years under study, aquatic bodies had the lowest LST values, whereas bare land and populated regions had the greatest LST values. According to the results of the NDVI, NDMI, and MNDWI investigations, this increase was caused by the intermediate vegetation levels and extremely low surface water. It is necessary to develop an environmental policy to mitigate the negative consequences of mining on land covers.
Rock Mechanics
K. Bour; K. Goshtasbi
Abstract
The design of underground spaces is mainly carried out using empirical, analytical, and numerical methods. The convergence confinement method (CCM) is an analytical technique that is widely utilized in analyzing the stability of underground spaces. However, the main challenge in the stability analysis ...
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The design of underground spaces is mainly carried out using empirical, analytical, and numerical methods. The convergence confinement method (CCM) is an analytical technique that is widely utilized in analyzing the stability of underground spaces. However, the main challenge in the stability analysis is the selection of an accurate constitutive model for rock mass, and particularly, its post-failure behavior. The existence of water plays a significant role in the stability analysis, whereas this effect is not usually considered in the CCM method. In this research work, a circular tunnel in a saturated medium is modelled and compared with its dry condition. Two types of constitutive models namely elastic perfectly plastic (EPP) and strain softening (SS) are used and compared in order to investigate the effect of water and post-failure behavior on the stability of tunnels. With this respect, the codes are written and incorporated in the constitutive models and various analyses are carried out. The results achieved from the analyses show that the elastic reaction of ground in the presence of water in both constitutive models are the same and that the ground reaction curves (GRCs) and longitudinal deformation profiles (LDPs) are similar. However, the trend of GRC is different in the case where the rock failure occurs and the face of the tunnel goes beyond 0.5D. According to the results obtained, the maximum displacement in a saturated medium with different K values for the SS model is more than that for the EPP model.
