https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17368 2D (rock failure process analysis), was used to simulate the initiation and propagation of fractures around a pre-existing single cavity and multiple cavities in brittle rocks. Both static and dynamic loads were applied to the rock specimens to investigate the mechanism of fracture evolution around the cavities for different lateral pressure coefficients. In addition, characteristics of acoustic emission (AE) associated with fracture evolution were simulated. Finally, the evolution and interaction of fractures between multiple cavities were investigated with consideration of stress redistribution and transference in compressive and tensile stress fields. The numerically simulated results reproduced primary tensile, remote, and shear crack fractures, which are in agreement with the experimental results. Moreover, numerical results suggested that both compressive and tensile waves could influence the propagation of tensile cracks; in particular, the reflected tensile wave accelerated the propagation of tensile cracks.]]> Wed 11 Apr 2018 13:17:24 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:45646 i.e., low (N1), middle (N2), and high (N3) N additions (10, 30, and 90 kg N hm^-2 a^-1, respectively) and an unfertilized control (CK; 0 kg N hm^-2 a^-1), were conducted in the desert grassland of Karamay, Xinjiang, in northwest China. Then, the amounts of 16 priority USEPA PAHs, the total amount of PAHs (∑PAHs), and three biotic-abiotic factors, including soil environmental factors, enzyme activities, and microbial functional diversity, were investigated to demonstrate the effects of N fertilization on PAHs degradation in the desert grassland. The results showed that, the amounts of ∑PAHs and 14 priority USEPA PAHs significantly decreased along the gradient of N addition (N2 ≤ N3 < N1 < CK)(P < 0.01), except for undetected acenaphthylene and acenaphthene, in all N additions treatments. This suggested N fertilization was advantageous to the decrease of soil PAHs in arid desert grassland. Low molecular weight PAHs/heavy molecular weight PAHs > 1.00, whereas 0.40 < fluoranthene/(fluoranthene+pyrene) < 0.50 in CK plots in both April and September, suggesting that PAHs mainly originated from a petroleum pollutant. ∑PAHs in the desert grassland soil equaled to (28.91±2.32) mg/kg in September in Karamay, indicating that the local soil had a heavy pollution level of PAHs. In most situations, the amounts of ∑PAHs and 14 priority USEPA PAHs had a significant regression relationship with soil organic matter, ammonium nitrogen, nitrate nitrogen, total nitrogen, available phosphorus, and urease activity in the generalized linear mixed models (GLMMs) (P < 0.05). The regression function of PAHs to biotic-abiotic factors varied among PAH types. Overall, our results showed that PAH degradation was a complex process in desert grassland soil, which was interactively determined by their own characteristics, plant roots, and microorganisms. N deposition might improve nutritional availability, with positive interactions with plant roots, microorganisms, and PAHs degradation, and the subsequent decrease in PAHs concentration along an N addition gradient.]]> Wed 02 Nov 2022 15:24:16 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:55759 Thu 20 Jun 2024 10:24:12 AEST ]]>