Three-dimensional laser scanning and numerical investigation on the influence of freeze-thaw and hang-wall mining on the instability of an open-pit slope

The instability of the open-pit slope and associated disasters of complex orebodies such as hanging-wall mining are the key problems to be solved urgently in the development of western resources. In this work, taking the hanging-wall mining in the open-pit mine of Hejing iron mine, for example, the disaster mechanism influenced by the coupling freeze-thaw and hanging-wall mining is systematically studied by 3D laser scanning and numerical simulation. Firstly, the rock mass structure information such as dip, dip angle, spacing, and equivalent trace length characteristics was obtained using 3D intelligent recognition technology. Then, numerical simulation is employed to reveal the influence of freeze-thaw and excavation sequences on the overall stability of the open-pit slope. The stress, displacement, plasticity zone, and maximum shear strain patterns are revealed in detail. The results show that the excavation engineering will lead to frequent increase and unloading of the internal stress of the rock mass, and the gradual increase of the goaf area will cause great damage to the rock mass. The slope failure mode is strongly impacted by freeze-thaw weathering and orebody excavation

On the effect of water content on fatigue mechanical behaviors of mud-shale under stress disturbance conditions

This paper aims to reveal the fatigue damage and instability behaviors of mud-shale under multistage increasing-amplitude fatigue loading. The fatigue loading tests combined with real-time acoustic emission (AE) monitoring technique were employed to investigate the influence of water content on the deformation, damage, and fracture characteristics. Testing results show that rock fatigue life decreases with the increase of water content, and the hysteresis curve changes regularly with time. The failure process can be divided into three stages: initial stage, stable development stage and acceleration stage. The acoustic emission output activities were also influenced by the water content. The acoustic emission ring count and acoustic emission energy both decrease with increasing water ratio and the accumulative count and energy are the least for a sample having high water ratio. The acoustic emission activity shows a sudden increase trend at the amplitude-increasing moment, indicating the occurrence of strong damage within rock sample. The damage propagation within a cyclic loading stage is relatively small compared to the stress-increasing moment. The results are helpful to understand the fatigue mechanical responses of water-sensitive soft rock, as well as the slope stability of the open-pit mine. The research results have important theoretical and practical significance for promoting slope treatment and disaster prevention

Silencing of FGF ‐21 expression promotes hepatic gluconeogenesis and glycogenolysis by regulation of the STAT 3– SOCS 3 signal

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106851/1/febs12767.pd

Characterisation of the effect of redox potential on the emission of greenhouse gases using wireless sensing techniques

Soils act as both a source and sink of greenhouse gases (GHGs) and are widely considered to contribute to global warming. Soil N$_{2}$O emissions originate from microbial nitrification and denitrification processes. Reducing conditions in soils alter the biogeochemical processes and result in large emissions of N$_{2}$O and CH$_{4}$. Soil redox potential (Eh) measurements are a promising way to differentiate the major source mechanism in soil N$_{2}$O production and evaluate their functions within the N cycle and may contribute to the development of N$_{2}$O emission mitigation strategies. While soil GHG emissions have been studied in the recent past, the relationship between GHG productionand Eh has not been systematically studied in detail. Eh monitoring can improve the assessment of soil chemical potential variations and GHG emissions, especially for CH$_{4}$ emissions, which mainly occur when soil is in highly reduced conditions as a result of the soil submerged below the water table (WT) continually, and for N$_{2}$O emissions, that have two distinct source processes at different Eh, i.e. nitrification at high Eh, and denitrification at intermediate Eh values. The change between oxidizing and reducing conditions insoil can be monitored and quantified by soil platinum (Pt) electrodes in combination with a reference electrode and a datalogger system with high temporal resolution (less than 1 min). The objectives of this thesis were to systematically investigate soil surface GHG emissions and their relationship with the spatial distribution and temporal variation of Eh. Because it is challenging to establish controlled conditions in natural soils, this study is based on a series of step-by-step laboratory experiments, exploring the effects of soil water content, N fertilization, and Eh on GHG emissions, followed by longterm measurements of Eh and GHG emissions in the field. In laboratory experiments, soil was exposed to varying WT levels to evaluate the utility of Eh monitoring for interpretating soil GHG emissions. To quantify soil GHG emissions, the static chamber method was used, in which gas samples were collected manually and analyzed by gas chromatography (GC). These measurements opened the possibility to interpret the long-term monitoring Eh data and to evaluate their influence on soil GHG emission under controlled soil moisture conditions. The Eh decreased steadily after the soil was submerged under water. It was found that CO$_{2}$ emissions had no clear relationship with Eh variations, but were closely related to soil water potential. In addition, soil Eh variations showed different ranges of values at different depths. N$_{2}$O emission peaks occurred at different Eh ranges and were influenced by WT level changes or fertilization events. In order to obtain more accurate information on N$_{2}$O emission sources in cropland, we used an irrigation system in combination with the stable isotope labeling technique using a $^{15}$N-labeled fertilizer. This isotope tracer method provided better insight into N$_{2}$O source partitioning and provided an independent validation of the Eh-based N$_{2}$O source partitioning. It was found that the changes in soil Eh and N$_{2}$O emissions were induced by irrigation and fertilization events, and were also related to the vertical distribution of dissolved NO$_{3}^{-}$ and NH$_{4}^{+}$ in the soil profile. Soil Eh values proved to be a suitable basis for identifying the two dominant N$_{2}$O sources, i.e. hydroxylamine oxidation (during nitrification) and nitrite reduction (during denitrification). It can be concluded from the laboratory experiments that measurements of Eh with high spatial and temporal resolution can make an important contribution to the study and interpretation of the temporally and spatially diverse N turnover processes in soils. [...

Stable-Isotope-Aided Investigation of the Effect of Redox Potential on Nitrous Oxide Emissions as Affected by Water Status and N Fertilization

Soils are the dominant source of atmospheric nitrous oxide (N2O), especially agricultural soils that experience both waterlogging and intensive nitrogen fertilization. However, soil heterogeneity and the irregular occurrence of hydrological events hamper the prediction of the temporal and spatial dynamics of N2O production and transport in soils. Because soil moisture influences soil redox potential, and as soil N cycling processes are redox-sensitive, redox potential measurements could help us to better understand and predict soil N cycling and N2O emissions. Despite its importance, only a few studies have investigated the control of redox potential on N2Oemission from soils in detail. This study aimed to partition the different microbial processes involved in N2O production (nitrification and denitrification) by using redox measurements combined with isotope analysis at natural abundance and 15N-enriched. To this end, we performed long-term laboratory lysimeter experiments to mimic common agricultural irrigation and fertilization procedures. In addition, we used isotope analysis to characterize the distribution and partitioning of N2O sources and explored the 15N-N2O site preference to further constrain N2O microbial processes. We found that irrigation, saturation, and drainage induced changes in soil redox potential, which were closely related to changes in N2O emission from the soil as well as to changes in the vertical concentration profiles of dissolved N2O, nitrate (NO3−) and ammonium (NH4+). The results showed that the redox potential could be used as an indicator for NH4+, NO3−, and N2O production and consumption processes along the soil profile. For example, after a longer saturation period of unfertilized soil, the NO3− concentration was linearly correlated with the average redox values at the different depths (R2 = 0.81). During the transition from saturation to drainage, but before fertilization, the soil showed an increase in N2O emissions, which originated mainly from nitrification as indicated by the isotopic signatures of N2O (δ15N bulk, δ18O and 15N-N2O site preference). After fertilization, N2O still mainly originated from nitrification at the beginning, also indicated by high redox potential and the increase of dissolved NO3−. Denitrification mainly occurred during the last saturation period, deduced from the simultaneous 15N isotope analysis of NO3− and N2O. Our findings suggest that redox potential measurements provide suitable information for improving the prediction of soil N2O emissions and the distribution of mineral N species along the soil profile under different hydrological and fertilization regimes

Insight into the Effect of Natural Fracture Density in a Shale Reservoir on Hydraulic Fracture Propagation: Physical Model Testing

Here, laboratory tests were conducted to examine the effects of natural fracture density (NFD) on the propagation of hydraulic fracture (HF), HF and natural fracture (NF) interaction, and the formation of the stimulated reservoir volume (SRV). Laboratory methods were proposed to prepare samples with dense, medium and spare discrete orthogonal fracture networks. After conducting a true triaxial hydraulic fracturing experiment on the synthetic blocks, the experimental results were analyzed by qualitative failure morphology descriptions, and the quantitative analysis used two proposed new indices. On the pump pressure profiles, it reflected the non-linear interactions between HFs and NFs well. For rock blocks with a dense DFN density, pump pressure curves present fluctuation shape and the degree of interaction between HF and NF is strong; however, for model blocks with a sparse DFN density, the pump pressure curves present a sudden drop shape. In addition, different propagation behaviors of NFs—offset, divert, branch, and cross NF—can be observed from the fractured model blocks. By using a proposed index of “P-SRV”, the relationship between NFD and the fracturing effectiveness was further confirmed. Furthermore, the most striking finding is that mixed mode I–II and I–III fracture types can be formed in the naturally fractured model blocks. The experimental results are beneficial for grasping the influential mechanism of NFD on the propagation of HF and for developing more accurate and full 3D-coupled simulation models for unconventional oil and gas development

Stable-Isotope-Aided Investigation of the Effect of Redox Potential on Nitrous Oxide Emissions as Affected by Water Status and N Fertilization

Soils are the dominant source of atmospheric nitrous oxide (N2O), especially agricultural soils that experience both waterlogging and intensive nitrogen fertilization. However, soil heterogeneity and the irregular occurrence of hydrological events hamper the prediction of the temporal and spatial dynamics of N2O production and transport in soils. Because soil moisture influences soil redox potential, and as soil N cycling processes are redox-sensitive, redox potential measurements could help us to better understand and predict soil N cycling and N2O emissions. Despite its importance, only a few studies have investigated the control of redox potential on N2Oemission from soils in detail. This study aimed to partition the different microbial processes involved in N2O production (nitrification and denitrification) by using redox measurements combined with isotope analysis at natural abundance and 15N-enriched. To this end, we performed long-term laboratory lysimeter experiments to mimic common agricultural irrigation and fertilization procedures. In addition, we used isotope analysis to characterize the distribution and partitioning of N2O sources and explored the 15N-N2O site preference to further constrain N2O microbial processes. We found that irrigation, saturation, and drainage induced changes in soil redox potential, which were closely related to changes in N2O emission from the soil as well as to changes in the vertical concentration profiles of dissolved N2O, nitrate (NO3−) and ammonium (NH4+). The results showed that the redox potential could be used as an indicator for NH4+, NO3−, and N2O production and consumption processes along the soil profile. For example, after a longer saturation period of unfertilized soil, the NO3− concentration was linearly correlated with the average redox values at the different depths (R2 = 0.81). During the transition from saturation to drainage, but before fertilization, the soil showed an increase in N2O emissions, which originated mainly from nitrification as indicated by the isotopic signatures of N2O (δ15N bulk, δ18O and 15N-N2O site preference). After fertilization, N2O still mainly originated from nitrification at the beginning, also indicated by high redox potential and the increase of dissolved NO3−. Denitrification mainly occurred during the last saturation period, deduced from the simultaneous 15N isotope analysis of NO3− and N2O. Our findings suggest that redox potential measurements provide suitable information for improving the prediction of soil N2O emissions and the distribution of mineral N species along the soil profile under different hydrological and fertilization regimes

Lattice Boltzmann modeling of the effective thermal conductivity for fibrous materials

This paper presents a full set of numerical methods for predicting the effective thermal conductivity of natural fibrous materials accurately, which includes a random generation-growth method for generating micro morphology of natural fibrous materials based on existing statistical macroscopic geometrical characteristics and a highly efficient lattice Boltzmann algorithm for solving the energy transport equations through the fibrous material with the multiphase conjugate heat transfer effect considered. Using the present method, the effective thermal conductivity of random fibrous materials is analyzed for different parameters. The simulation results indicate that the fiber orientation angle limit will cause the material effective thermal conductivity to be anisotropic and a smaller orientation angle leads to a stronger anisotropy. The effective thermal conductivity of fibrous material increases with the fiber length and approach a stable value when the fiber tends to be infinite long. The effective thermal conductivity increases with the porosity of material at a super-linear rate and differs for different fiber location distribution functions. (c) 2006 Elsevier Masson SAS. All rights reserved