Channel morphology and bed sediment erodibility are two crucial factors that significantly affect debris flow entrainment processes. Current debris flow entrainment models mostly hypothesize the erodible beds are infinite with uniform slopes. In this study, a series of small-scale flume experiments were conducted to investigate the effects of bed longitudinal inflexion and sediment porosity on basal entrainment characteristics. Experimental observations revealed that sediment entrainment is negligible at early stages and accelerates rapidly as several erosion points appear. Continual evolution of flow-bed interfaces changes interactions between debris flows and bed sediments, rendering the interfacial shear action involved into a mixed shear and frontal collisional action. Lower bed sediment porosity will change the spatial arrangement and orientation of particle mixture, strengthen the interlocking and anti-slide forces of adjacent sediment particles, and promote the formation of particle clusters, all of which will increase bed sediment resistance to erosion. By examining the post-experimental bed morphology, the slope-cutting amounts and topographic reliefs are determined to positively correlate with longitudinal transition angles. These high topographic reliefs may indicate the propensity of triangular slab erosion, rather than strip-shaped slab erosion, in non-uniform channels with relatively steep erodible beds. Empirical formulas are obtained that denote the relationships among bed sediment strength, channel curvature radius, and sediment porosity through a multi-parameter regression analysis. This study may aid in clarifying the complex coupling effects of spatial variations in debris flow dynamics as well as sediment erodibility and bed morphology in non-uniform channels with abundant seismic loose material.
ABSTRACTThe work presents calculations of shaft support reliability index during partial extraction of protection pillar deposit and the related seismic phenomena. It has been assumed that the probability of failure caused by seismic phenomena depends on the velocity random variable of the shaft support vibrations. The random vibration velocity is a function of random variables of energy, shock distance and vibration frequency. Estimations of probability distributions for energy and frequency have been based on the actual measurement data from a mine. Failure probability has been estimated by means of methods based on so-called Hasofer-Lind reliability index β. 相似文献
Journal of Geographical Sciences - Ecosystem service values (ESVs) of bays and their response to sea reclamation are of great practical importance for forming bay eco-compensation policy and... 相似文献
Deep-water coarse-grained channels are embedded within a polygonal fault tier, and the polygonal faults (PFs) present non-polygonal geometries rather than classic polygonal geometry in plan view. However, PFs present differences when they encounter deep-water (coarse-grained vs. fine-grained) channels with different lithology, which has not been further studied to date. 3D seismic data and a drilling well from Beijiao sag of Qiongdongnan basin, South China Sea were utilized to document the plan view and cross-sectional properties of the PFs and their differences and genetic mechanism were investigated. Results show that, first, PFs can be divided morphologically into channel-segmenting PFs and channel-bounding PFs in plan view. The former virtually cuts or segments the axes of channels in high- and low-amplitudes, and the latter nearly parallels the boundaries of the channels. Both are approximately perpendicular to each other. Secondly, channel-bounding PFs that related to low-amplitude channels are much longer than those of high-amplitude ones; channel-segmenting PFs related to low-amplitude channels are slightly longer than the counterparts related to high-amplitude channels. Lastly, the magnitudes (e.g., heights) of the PFs are proportional to the scales (e.g., widths and heights) of low-amplitude channels, whereas the magnitudes of the PFs are inversely proportional to the scales of high amplitude channels. Coarse-grained (high amplitude) channels act as a mechanical barrier to the propagation of PFs, whereas fine-grained (low-amplitude) channels are beneficial to the propagation and nucleation of PFs. Additionally, the genetic mechanism of PFs is discussed and reckoned as combined geneses of gravitational spreading and overpressure hydrofracture. The differences of the PFs can be used to reasonably differentiate coarse-grained channels from fine-grained channels. This study provides new insights into understanding the different geometries of the PFs related to coarse-grained and fine-grained channels and their genetic mechanism.
