Acquiring high-resolution topography and performing spatial analysis of loess landslides by using low-cost UAVs

The Loess Plateau is a region in China prone to frequent geological disasters, where thousands of loess landslides can be found. Conventional field survey methods are inadequate for the requirements of fine spatial analysis of landslides. Due to its numerous advantages (fast, efficient, low cost, safe, and able to acquire high-resolution data), structure from motion (SfM) technique to photogrammetric orientation of flights and modeling applied to photographs taken by unmanned aerial vehicles (UAVs) equipped with a camera has become a powerful new tool for the generation of high-resolution topography that has emerged in recent years, which has become a powerful new technique for acquiring high-resolution topographic data. In this study, we conducted nearly two months of field UAV surveys of loess landslides on the Loess Plateau, eventually established 3D digital models for 11 loess landslides, and produced high-resolution digital orthophoto maps (DOMs) and digital elevation models (DEMs). High-resolution spatial analysis of the loess landslides (mainly including characteristic parameter extraction, topography profile analysis, surface feature analysis, and hydrologic analysis) was performed using Agisoft PhotoScan, ArcGIS 10.2, Global Mapper 17, and Origin Pro 9.0. The UAV technique allows us to further understand the micro-level internal spatial and structural characteristics of loess landslides. Moreover, not only does it allow us to accurately measure the characteristic geometric parameters but also enables us to detect the surface details of loess landslides (e.g., textures, fissures, and micro-landforms). Manifestly, we can also deduce the original structural characteristics and possible inducement mechanism of landslides based on a combination of high-resolution data acquired by UAVs, proper ground surveys, and theoretical knowledge. In summary, the low-cost UAVs are highly and especially suitable for surveys and digital terrain analysis of landslides on the Loess Plateau with sparse vegetation.     

A simple approach to evaluating leakage through thin impervious element of high embankment dams

Internal erosion is the most common reason which induces failure of embankment dams besides overtopping. Relatively large leakage is frequently concentrated at defects of impervious element, and this will lead to eventual failure. The amount of leakage depends not only on integrity of impervious element, but also on dam height, shape of valley, shape of impervious element and water level in reservoir. The integrity of impervious element, which represents the relative level of seepage safety, is not easy to be determined quantitatively. A simple method for generalization of steady seepage state of embankment dams with thin impervious element is proposed in this paper. The apparent overall value of permeability coefficient for impervious element can be obtained by this method with reasonable accuracy and efficiency. A defect parameter of impervious element is defined as an index to characterize seepage safety of embankment dams. It equals the ratio of the apparent overall value of permeability coefficient to the measured value in laboratory for intact materials. Subsequently, seepage safety of three dams is evaluated and the evolution of defect level of impervious element of dams is investigated. It is proved that the newly proposed method in this paper is feasible in the evaluation of relative seepage safety level of embankment dams with thin impervious element.     

Spatial and temporal variations of suspended solid concentrations from 2000 to 2013 in Poyang Lake,China

Concentrations of suspended solids in lakes can affect the latter’s primary productivity and reflect changes in sediment deposition. Determining the temporal and spatial distribution of suspended solid concentrations has important significance in lake water environmental management; this is particularly urgent for Poyang Lake, the largest freshwater lake in China. In this study, suspended solid concentration inversion models for Poyang Lake were created using a semi-empirical method with regression analysis between continuously measured suspended solid concentration data and multi-band moderate-resolution imaging spectroradiometer images for spring, summer, autumn, and winter from 2009 to 2012. The coefficient of determination (R²) is from 0.6 to 0.9 and the average relative error for the accuracy verification was between 10 and 30%. The seasonal distributions of suspended solid concentrations in Poyang Lake from 2000 to 2013 were then obtained using optimal reversal models. The results showed that the seasonal variation in suspended solid concentrations had a “W” shape in which high spring and autumn and low summer and winter values. The suspended solid concentrations increased annually from 2000 to 2013 and were mainly distributed in the northern and central portions of the lake, with lower values along the shorelines. Further analysis indicated that the large difference in water level between the wet and dry seasons is an important factor in explaining these seasonal variations. Moreover, the suspended solid concentrations were poorly correlated with water temperature and chlorophyll-a concentration but more highly correlated with the deferred chlorophyll-a concentration.     

Effect of climate change on water resources in the Yuanshui River Basin: a SWAT model assessment

The Yuanshui River Basin is one of the most important river basins ensuring food production and livelihoods in the Hunan and Guizhou Provinces of China. Based on digital elevation model, land use, soil, and meteorological data, the soil and water assessment tool was used to analyze the response of water resources in the basin to climate change. Specifically, the monthly runoff from the Yuanshui River Basin was simulated. Runoff measurements from the 1961–1990 series were used to calibrate model parameters, and measurements from the 1991–2010 series were used for model validation. The Nash–Sutcliffe efficiency coefficient, correlation coefficient, and water balance error were used to evaluate the simulation results; the values obtained for these parameters were 0.925, 0.929, and 2.0%, respectively, indicating that the established model can be applied successfully to runoff simulations. To evaluate the effects of climate change and human activities on runoff, 24 different climate scenarios were modeled. By comparing the model simulation results with the baseline scenario, the effects of climate change were analyzed by year, during the dry season, and during extremely dry conditions. The results showed that runoff decreased with increasing air temperature and decreasing precipitation, and that the effects of rainfall on runoff were greater than those of air temperature. Under the same baseline conditions, the effects of climate change on runoff were most pronounced during extremely dry months.     

Research on mining-induced deformation and stress,insights from physical modeling and theoretical analysis

The dynamic change of mining-induced stress is the main reason for large deformation of surrounding rock. To investigate the influence of mining-induced stress and deformation is important for appropriate supportive design. It also helps to raise the safety and productivity of longwall mining operations. In this paper, Weijiagou Coal Mine in Southwest China was selected as the case study. In order to research on the deformation and breakage of overlying strata, physical modeling test was carried out on the self-developed rotatable physical similar test system. By using digital image correlation (DIC) technique, the deformation of strata and development of cracks in the process of coal seam excavation were acquired, meanwhile, mining-induced stress was also monitored by pressure cell and strainmeter. According to the mechanical structure of stope, the height of the destressed zone has a significant influence on stress distribution. In order to minimize the discrepancy between the physical model test and theoretical analysis, the dimension of the plastic zone of roadway was added into the mining panel width, and the gap between the experimental and theoretical results reduced.     

中亚造山带伊犁北缘早古生代海相斑脱岩地质意义

伊犁地块位于西天山北部,通常认为其北缘经历了晚古生代活动陆缘的演化,但对其早古生代构造沉积演化（尤其是同位素定年）的研究仍较为薄弱.在伊犁北缘果子沟地区的奥陶系黑色硅质页岩中发现多层斑脱岩（蚀变凝灰岩）夹层,奥陶系发生了强烈褶皱变形,在其中一个倒转向斜的核部和翼部选取两层斑脱岩进行了锆石U-Pb测年.2个斑脱岩样品中的锆石显示岩浆锆石的特征,其加权平均年龄分别为458±2 Ma和460±2 Ma.结合前人研究成果,认为该斑脱岩的沉积时代为中奥陶世末期（达瑞威尔阶顶部）,该时代与温泉地区大陆弧岩浆岩年龄基本一致,是准噶尔洋在中-晚奥陶世向伊犁地块之下俯冲的又一证据;该斑脱岩与全球范围内的大规模火山活动时代一致,该期火山活动可能是中-晚奥陶世全球气候变化与生物大灭绝的重要原因.      

Numerical investigation of the hydrodynamic response of an impermeable sea-wall subjected to artificial submarine landslide-induced tsunamis

Landslides - Landslide-induced tsunamis are common natural hazards that potentially affect the safety and stability of waterfront structures. A numerical tank was constructed using FLOW-3D to...     

喜马拉雅东部三叠系涅如组地球化学和碎屑锆石U-Pb年代学特征及构造意义

喜马拉雅中—新生代地层沉积于印度被动大陆边缘,三叠系沉积物物源分析是冈瓦纳大陆裂解和古地理研究的重要载体.特提斯喜马拉雅东段上三叠统涅如组碎屑岩的物质来源和沉积背景具有较大的争议,本次研究采集隆子县斗玉乡晚三叠世粉砂质板岩进行碎屑锆石U-Pb年代学和全岩主微量元素地球化学分析.涅如组碎屑锆石年龄具有两个明显的峰值:206～224Ma(峰值213 Ma)和462～567Ma(峰值512 Ma),表明涅如组沉积时代为晚三叠世诺利期.涅如组w(SiO2)含量较低(平均值为57.7％),w(Al2O3)值较高(17.2％),轻稀土元素富集,重稀土元素亏损,轻稀土/重稀土元素平均值为8.1.高场强元素中Nb,Ta,Ti亏损,Zr,Hf,Th,U富集;大离子亲石元素中Ba,Sr亏损,Rb和K富集.综合分析认为源区岩石以酸性岩浆岩为主.本次研究认为上三叠统涅如组浊流相沉积形成于裂谷环境,代表新特提斯洋的打开;标志着拉萨板块从冈瓦纳大陆北缘裂解,并开始向北漂移.     

Arsenic contamination caused by roxarsone transformation with spatiotemporal variation of microbial community structure in a column experiment

Arsenic contamination from roxarsone in livestock manure is common, and livestock manure continuously accumulates in the open environment. Evaluations of the environmental processes of As mobilization and transformation are critical for predicting the fate of As compounds after roxarsone degradation. In this study, spatiotemporal variations in As species and microbial community structure were characterized using laboratory column experiments with background soil collected from Yanggu County (northern Shandong Plain, China), a region of intense poultry production. Organic and inorganic arsenic were detected by high-performance liquid chromatography (HPLC) and HPLC with hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS), respectively. High-throughput sequencing technology was used to describe microbial diversity. Results showed that roxarsone was transformed completely within 7 days, and As(Ⅲ) and As(Ⅴ) were the major degradation products. The concentration of As(Ⅲ) was much lower than that of As(Ⅴ). The As(Ⅲ) concentration increased significantly after Day 14, whereas the As(Ⅴ) concentration increased significantly after Day 84, indicating that As(Ⅲ) was initially produced. The microbial community structure changed significantly as roxarsone transformed into various As compounds. A critical and dominant bacterial strain, norank_f__Family_XVⅢ, was found to be related to the degradation of roxarsone into As(Ⅲ). This study improves our understanding of the fate of As species released from poultry litter to soil and groundwater, which is a threat to human health and environment.     

Machine learning reveals the influences of grain morphology on grain crushing strength

Acta Geotechnica - Grain morphology has significant impacts on the mechanical behaviors of granular materials. However, its influences on grain breakage are still poorly understood due to the...