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Effects of igneous bodies on modification of modern slope morphology: Insights from the continental slope offshore Dongsha Islands, South China Sea

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Acta Oceanologica Sinica 2019年第5期38卷 109-117页

作者： Chao Liang Xinong Xie Hua Wang Guangjian Zhong Entao Liu Ming Sun Hai Yi Chunyu Qin Haiyang Cao Jie He Yanpu Zhao College of Marine Science and Technology China University of GeosciencesWuhan Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education China University of GeosciencesWuhan Faculty of Earth Resources China University of GeosciencesWuhan Guangzhou Marine Geological Survey China Geological Survey Institute of Sedimentary Geology Chengdu University of Technology

A statistical analysis for the morphological parameters extracted from numerous seismic profiles, and a highresolution seismic study of the southeastern slope of the Dongsha Islands(South China Sea) with water depth between approximately 500 and 3 100 m, has revealed the variation of morphological features due to the intrusion of igneous bodies and associated sedimentary processes. Three types of the continental slope are distinguished:(1) a rough and steep slope with multiple igneous bodies(Type 1),(2) a relatively smooth and gentle slope with the single igneous body(Type 2), and(3) a smooth and gentle slope without igneous bodies(Type 3). These igneous bodies, formed in the post-seafloor spreading of the South China Sea, are often characterized by high positive seismic amplitudes, and chaotic reflections with complex shapes. The igneous bodies in Type 1 separated the slope into two or more upper sub-sags and a lower main-sag, in which the sub-sags and main-sag could be filled with sediments transported by alongslope bottom currents at the same time. Whereas, the igneous body in Type 2 just separated the slope into an upper sub-sag and a lower main-sag, in which the sediments could be transported into the lower main-sag only after the upper sub-sag has been filled up. Type 3 represents a normal slope with common clinoform progradation. The modern slope morphologies in the study area are the results of adjustments of the continental slope due to the intrusion of igneous bodies and associated sedimentary processes. The distinctions among three types of modern slope morphologies indicate different depositional conditions and adjustments of slope morphologies.

关键词： igneous bodies modern slope morphology Dongsha Islands South China Sea

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Deriving the slope-mean shielded astronomical solar radiation spectrum and slope-mean possible sunshine duration spectrum over the Loess Plateau

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Journal of Mountain Science 2020年第1期17卷 133-146页

作者： CHEN Nan Key Laboratory of Spatial Data Mining & Information Sharing Ministry of Education Fuzhou University Spatial Information Research Center of Fujian Province Fuzhou University

Solar radiation is often shielded by terrain relief, especially in mountainous areas, before reaching the surface of the Earth. The objective of this paper is to study the spatial structures of the shielded astronomical solar radiation(SASR) and the possible sunshine duration(PSD) over the Loess Plateau. To this end, we chose six test areas representing different landforms over the Loess Plateau and the software package of Matlab was used as the main computing platform. In each test area, 5-m-resolution digital elevation model established from 1:10,000 scale topographic maps was used to compute the corresponding slope, SASR and PSD. Then, we defined the concepts of the slope-mean SASR spectrum and the slope-mean PSD spectrum, and proposed a method to extract them from the computed slope, SASR and PSD over rectangular analysis windows. Using this method, we found both spectrums in a year or in a season for each of the four seasons in the six test areas. Each spectrum was found only when the area of the corresponding rectangular analysis window was greater than the corresponding stable area of the spectrum. The values of the two spectrums decreased when the slope increased.Furthermore, the values of the stable areas of the spectrums in a year or in a season were positively correlated with the variable coefficients of the slope or the profile curvature. The values of the stable areas of the two spectrums in a year or in a season may represent the minimum value of test areas for corresponding future research on the spatial structures of the SASR or PSD. All the findings herein suggest that the spatial structures of the PSD and the SASR are caused by the interactions between solar radiation and terrain relief and that the method for extracting either spectrum is effective for detecting their spatial structures. This study may deepen our understanding of the spatial structure of solar radiation and help us further explore the distribution of solar energy in mountainous regions.

关键词： Digital elevation model Shielded extraterrestrial solar radiation Spectrum Possible Sunshine duration slope Loess Plateau

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Effect of slope gradient on the subsurface water flow velocity of sand layer profile

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Journal of Mountain Science 2020年第3期17卷 641-652页

作者： HAN Zhen CHEN Xiao-yan HUANG Yu-han LUO Bang-lin XING Hang HUANG Yong-chao College of Resources and Environment/Key Laboratory of Eco-environment in Three Gorges Region(Ministry of Education) Southwest UniversityChongqing 400716China College of Water Resource and Civil Engineering China Agricultural UniversityBeijing 100083China Chongqing Surveying and Design Institute of Water Resources Electric Power and Architecture Chongqing 401120China

Subsurface water flow velocity influences the hydrodynamic characteristics of soil seepage and the interaction between subsurface water flow and surface runoff during soil erosion and sediment transport.A visualized method and equipment was adopted in this study to observe the subsurface water flow.Quartz sand was used as the test material of subsurface water flow and fluorescent dye was used as the indicator for tracing subsurface water flow.Water was supplied at the same flow discharge to the three parts at the bottom of the test flume,and the subsurface water flow were determined with four slope gradients(4°,8°,10°,and 12°).The results showed that the seepage velocity gradually increased with increasing slope gradient.The pore water velocity at different depths of sand layer profile increased with increasing slope gradient,whereas the thickness of the flow front gradually decreased.For the same slope gradient,the pore water velocity in the lower layer was the largest,whereas the thickness of the flow front was the smallest.Comparative analysis of the relationship between seepage velocity and pore water velocity at different depths of sand layer profile showed that the maximum relative difference between the measured pore water velocity and the computational pore water velocity at different depths of sand profile in the experiment was 4.38%.Thus,the test method for measuring the subsurface water flow velocity of sand layer profile adopted in this study was effective and feasible.The development of this experiment and the exploration of research methods would lay a good test foundation for future studies on the variation law of subsurface water flow velocity and the determination of flow velocity in purple soils,thus contributing to the improvement of the hydrodynamic mechanism of purple soils.

关键词： Subsurface water flow Pore water velocity Seepage velocity slope gradient Sand layer

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Research on the slope spectrum of the Loess Plateau

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Science China(Technological Sciences) 2008年第S1期51卷 175-185页

作者： TANG GuoAn,LI FaYuan,LIU XueJun,LONG Yi & YANG Xin Key Laboratory of Virtual Geographic Environment,Nanjing Normal University,Ministry of Education,Nanjing 210046,China Key Laboratory of Virtual Geographic Environment Nanjing Normal University Ministry of Education Nanjing China

A new concept dealing with digital analysis of loess terrain,slope spectrum,is presented and discussed in this paper,by introducing its characteristic,represen-tation and extracting method from DEMs. Using 48 geomorphological units in dif-ferent parts of the loess as test areas and 5 m-resolution DEMs as original test data,the quantitative depiction and spatial distribution of slope spectrum in China's Loess Plateau have been studied on the basis of a series of carefully-designed experiments. In addition,initial experiment indicates a strong relationship between the slope spectrum and the loess landform types,displaying a potential importance of the slope spectrum in geomorphological studies. Based on the slope spectrums derived from the 25 m-resolution DEM data in whole loess terrain in northern part of Shaanxi,13 slope spectrum indices were extracted and integrated into a compre-hensive layer with image integration method. Based on that,a series of unsuper-vised classifications was applied in order to make a landform classification in northern Shaanxi Loess Plateau. Experimental results show that the slope spec-trum analysis is an effective method in revealing the macro landform features. A continuous change of slope spectrum from south to north in northern Shaanxi Loess Plateau shows an obvious spatial distribution of different loess landforms. This also proves the great significance of the slope spectrum method in describing the terrain roughness and landform evolution as well as a further understanding on landform genesis and spatial distribution rule of different landforms in the Loess Plateau.

关键词： Loess Plateau slope spectrum slope DEM loess landform

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Influence of rock property correlation on reliability analysis of rock slope stability: From property characterization to reliability analysis

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Geoscience Frontiers 2018年第6期9卷 1639-1648页

作者： Adeyemi Emman Aladejare Yu Wang Department of Architecture and Civil Engineering City University of Hong Kong

Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of rock slope stability. However, the characterization of joint probability distribution of c and φ through which their correlation can be estimated requires a large amount of rock property data, which are often not available for most rock engineering projects. As a result, the correlation between c and φ is often ignored or simply assumed during reliability studies, which may lead to bias estimation of failure probability. In probabilistic rock slope stability analysis, the influence of ignoring or simply assuming the correlation of the rock strength parameters(i.e., c and φ) on the reliability of rock slopes has not been fully investigated. In this study, a Bayesian approach is developed to characterize the correlation between c and φ, and an expanded reliability-based design(RBD) approach is developed to assess the influence of correlation between c and φ on reliability of a rock slope. The Bayesian approach characterizes the sitespecific joint probability distribution of c and φ, and quantifies the correlation between c and φ using available limited data pairs of c and φ from a rock project. The expanded RBD approach uses the joint probability distribution of c and φ obtained through the Bayesian approach as inputs, to determine the reliability of a rock slope. The approach gives insight into the propagation of the correlation between c and φ through their joint probability into the reliability analysis, and their influence on the calculated reliability of the rock slope. The approaches may be applied in practice with little additional effort from a conventional analysis. The proposed approaches are illustrated using real c and φ data pairs obtained from laboratory tests of fractured rock at Forsmark, Sweden.

关键词： Reliability-based design Rock slope Correlation Failure probability Bayesian approach Joint probability distribution

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Analysis of slope Stability with Dynamic Overloading from Earthquake

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Journal of Earth Science 2012年第3期23卷 285-296页

作者：赵体孙进忠张彬李程 School of Engineering&Technology China University of Geosciences

The analysis of slope earthquake stability is one of the most important research subjects in geotechnical engineering and earthquake engineering.Two different concepts of slope earthquake stability are put forward：strength reserve stability and dynamic overloading stability.The first concept of slope earthquake stability has been widely accepted,and relative analysis methods are also well de-veloped;the second one,however,is seldom mentioned until now,and the failure criterion and the analysis method based on this concept are yet to be explored.What are researched are just the failure criterion and the analysis method of dynamic overloading earthquake stability.The criterion of critical earthquake peak acceleration for the dynamic overloading stability of a slope and its analysis method,the load increasing method（LIM）,are put forward.The dynamic overloading earthquake stability of a loess slope at Changshougou（长寿沟） in Baoji（宝鸡） City,Shaanxi（陕西） Province,China,is analyzed with LIM.The analysis result reveals that the dynamic overloading earthquake stability of the slope is quite high to the action of the earthquake ground motion,with exceeding probability of 10% in the next 50 years.

关键词： slope dynamic overloading earthquake stability load increasing method criticalearthquake peak acceleration.

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Stable-thickness study of masonry block on the inner slope of dikes

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Journal of Oceanology and Limnology 2019年第6期37卷 1921-1928页

作者： SUN Tianting LIU Qingjun WANG Dengting Nanjing Hydraulic Research Institute Nanjing 210029China Key Lab of Port Waterway and Sedimentation Engineering of MOTNanjing 210024China

Dike failure caused by overtopping is likely to result in major casualties and property losses.Aiming at this fact,a series of physical model experiments were conducted on stable thickness of masonry block on the inner slope of the dike.According to the erosion of block embankment with different thicknesses,the relation between the stable thickness of masonry block pitching of the inner slope and the average overtopping discharge is discussed.New equations subject to irregular waves are presented for average overtopping discharge,based upon the analysis of mean overtopping discharge and comparison of present overtopping discharge formulas at domestic and abroad.Finally,a calculation equation of the stable thickness of the dry masonry block stone of inner slope subject to irregular waves is given.In conclusion,the formula matches well with the experiment result,which is capable of functioning as an important reference for structure designs of the dike in China.

关键词： mean overtopping discharge block revetment inner slope stable thickness

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Evaluation of mountain slope stability considering the impact of geological interfaces using discrete fractures model

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Journal of Mountain Science 2019年第9期16卷 2184-2202页

作者： WANG Lu-yu CHEN Wei-zhong TAN Xu-yan TAN Xian-jun YUAN Jing-qiang LIU Qi State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China University of Chinese Academy of Science Beijing 100049 China Research Center of Geotechnical and Structural Engineering Shandong University Jinan 250100 China

The stability of rock slope is often controlled by the existing discontinuous surfaces, such as discrete fractures, which are ubiquitously distributing in a geological medium. In contrast with the traditional approaches used in soil slope with a continuous assumption, the simulation methods of jointed rock slope are different from that of in soil slope. This paper presents a study on jointed rock slope stability using the proposed discontinuous approach, which considers the effects of discrete fractures. Comparing with traditional methods to model fractures in an implicit way, the presented approach provides a method to simulate fractures in an explicit way, where grids between rock matrix and fractures are independent. To complete geometric components generation and mesh partition for the model, the corresponding algorithms were devised. To evaluate the stability state of rock slope quantitatively, the strength reduction method was integrated into our analysis framework. A benchmark example was used to verify the validation of the approach. A jointed rock slope, which contains natural fractures, was selected as a case study and was simulated regarding the workflow of our framework. It was set up in the light of the geological condition of the site. slope stability was evaluated under different loading conditions with various fracture patterns. Numerical results show that fractures have significant contributions to slope stability, and different fracture patterns would lead to different shapes of the slip surface. The devised method has the ability to calculate a non-circular slip surface, which is different from a circular slip surface obtained by classical methods.

关键词： Rock slope stability Discrete fractures Discontinuous approach Equivalent model Slip surface

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Dynamic response of a slope reinforced by double-row antisliding piles and pre-stressed anchor cables

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Journal of Mountain Science 2019年第1期16卷 226-241页

作者： FAN Gang ZHANG Jian-jing QI Shun-chao WU Jin-biao College of Water Resource and Hydropower Sichuan University School of Civil Engineering Southwest Jiaotong University

Large-scale shaking table tests were conducted to study the dynamic response of a slope reinforced by double-row anti-sliding piles and prestressed anchor cables. The test results show that the reinforcement suppressed the acceleration amplification effectively. The axial force time histories are decomposed into a baseline part and a vibration part in this study. The baseline part of axial force well revealed the seismic slope stability, the peak vibration values of axial force of the anchor cables changed significantly in different area of the slope under seismic excitations. The peak lateral earth pressure acting on the back of the anti-sliding pile located at the slope toe was much larger than that acting on the back of the anti-sliding pile located at the slope waist. The test results indicate an obvious load sharing ratio difference between these two anti-slide piles, the load sharing ratio between the two anti-sliding piles located at the slope toe and the slope waist varied mainly in a range of 2-5. The anti-slide pile at the slope waist suppressed the horizontal displacement of the slope surface.

关键词： slope stability Anti-sliding pile Anchor cable Seismic design Shaking table test Earthquake

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Simulation study of the void space gas effect on slope instability triggered by an earthquake

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Journal of Mountain Science 2019年第6期16卷 1300-1325页

作者： ZHOU Zhou WANG Xiao-qun WEI Yu-feng SHEN Jun-hui SHEN Man College of Environment Geology and Civil Engineering Chengdu University of TechnologyChengdu 610059China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu 610059China

This study aims at exploring the void space gas effect of earthquake-triggered slope instability and providing a new method for studying the formation mechanism of earthquake-triggered landslides. We analysed the basic characteristics, kinematic characteristics, initiation mechanisms and physical mechanical parameters of the Daguangbao landslide, generalized a landslide prototype, and established a geological model and performed simulation tests. Based on the seismic wave propagation theory of rock-soil mass, rock fracture mechanics and the effective stress principle, we found that the void space gas effect is due to the occurrence of excess void space gas pressure when the dynamic response of seismic loads impacts the void space gas in weak intercalated layers of the slope. The excess void space gas pressure generated by the vibration(earthquake) damages the rock mass around the void space with a certain regularity. The model test results show that the effective shear strength of the rock mass can be reduced by 4.4% to 21.6% due to the void space gas effect.

关键词： Earthquake landslide slope weak intercalated layer Void space gas effect Void-gas dynamic response Excess void space gas pressure Gas-rock interaction mechanism

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