Mobility and dynamic erosion process of granular flow:insights from numerical investigation using material point method

In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular flow.An index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of friction.The index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction weakening.An increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular flow.The mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular soil.However,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on gravity.The mobility of granular flow increases gradually by lowering the indexes of the apparent and repose coefficients of friction of granular flow while changing the surroundings,in turn,the dry soil,submerged soil and saturated soil,implying a gradually increased excessive mobility of granular flow with the friction weakening of granular soil.Presence of water in granular flow may be a potential catalyzer to yield a long run-out granular flow,as revealed in comparison of water-absent and water-present granular flows.In addition,the dynamic erosion and entrainment of based soil induced by granular flow subjected to the complex geological settings,i.e.,the aspect ratio,granular mass,gravity,friction and dilatancy resistance,and presence of water,were comprehensively investigated as well.

油气富集域早古生代以来的古地理演化及其对成藏的控制:南美-北非-中东-中亚特提斯域古地理与油气资源

鉴于中国的油气需求与国内外油气资源禀赋,合理有效利用国外油气资源以缓解国内能源需求压力,顺应能源转型与绿色发展趋势,成为国内各类油公司的时代责任与义务。地质研究是油气勘探开发的基础,因此组织了国外油气地质基础研究专栏。为便于读者更好地阅读领悟本期刊发的5篇海外区域研究论文,部分编者撰写了这篇关于5篇海外论文的整体研究背景、各自成果特色及其创新认识相关性的推介。

“古地理学术论坛”第1—17期评述

以《古地理学报》中文版、英文版编辑部为主,联合中国矿物岩石地球化学学会岩相古地理专业委员会、国际古地理学会和中国石油大学(北京)共同举办的“古地理学术论坛”,是促进古地理学创新发展、倡导开展公益学术讲座的学术交流平台。从2022年9月论坛开始至2024年1月共举办了17期,共计邀请21位专家学者(包括外国专家4位)在论坛作报告。报告内容紧密结合生产实践和科技前沿,既有高屋建瓴的沉积古地理学综述,也有与油气勘探关系密切的沉积体系与沉积环境、源汇系统、层序地层学、深水沉积研究,以及与深时古环境重建有关的事件沉积、遗迹化石、古野火、碳酸盐沉积、构造古地理学研究,还包括铝土矿成因等矿产沉积学研究。总体看来,系列报告理论联系实践,既立足基础又关注前沿,受到学者们较高的关注。

滑坡碎屑流消能桩结构动力计算与设计方法

滑坡碎屑流由于体积大、速度快和运动距离远的特性,常常在下游造成较大破坏形成严重的自然灾害。基于消能桩与滑坡碎屑流结构的动力相互作用过程,采用功能原理和结构力学方法,推导了消能桩对滑坡碎屑流能量耗散的理论计算模型。首先,通过冲击力计算模型获得滑坡碎屑流冲击力的垂向分布;其次,由悬臂梁挠曲变形的关系确定其抗弯反力;然后,根据滑坡碎屑流在坡面上流动的面积、厚度估算消能桩的反力,以及在反力方向上碎屑流通过的距离;最后,计算单根桩的动能耗散量。采用推导的公式进行消能桩的优化设计:综合考虑下游防护对象的位置和滑坡体的堆积位置,计算消能桩的“消能效益”,确定消能桩的数量;根据最大块石的冲击力作用,计算需要消能桩的排数,从而确定消能桩的排布设计。选取一个滑坡碎屑流实例,采用上述理论计算模型设计消能桩,计算出消能桩的数量和排数,并根据计算结果进行优化布设。结果表明,该模型适用于消能桩的优化设计与应用。

Seismically Induced Slope Instabilities and the Corresponding Treatments:the Case of a Road in the Wenchuan Earthquake Hit Region

On May 12, 2008, a magnitude 8.0 earthquake hit Wenchuan County, Sichuan Province resulted in great loss of life and properties.Besides, abundant landslides and slope failures were triggered in the most seriously hit areas and caused disastrous damages to infrastructures and public facilities.Moreover, abundant unstable slopes caused by the quake have the potential to cause damages for a considerable long period of time.The variety of these slopes and the corresponding treatments are connected with the topographical and geological conditions of the sites.It is decided to document and identify some of these major slope instabilities caused by the earthquake and their treatments.The paper shows the condition of a road in Dujiangyan through in situ explorations.The case history showed significant implications to the reconstruction of the quake-hit regions and future disaster prevention and management works.

Discrete Element Modeling of Debris Avalanche Impact on Retaining Walls

In China,gravity retaining walls are widely used as protection structures against rockfalls,debris flows and debris avalanches along the roads in mountainous areas.In this paper,the Discrete Element Method(DEM) has been used to investigate the impact of granular avalanches and debris flows on retaining walls.The debris is modeled as two dimensional circular disks that interact through frictional sliding contacts.The basic equations that control the deformation and motion of the particles are introduced.A series of numerical experiments were conducted on an idealized debris slide impacting a retaining wall.The parametric study has been performed to examine the influences of slope geometry,travel distance of the sliding mass,wall position,and surface friction on the impact force exerted on the wall.Results show that:1) the force achieves its maximum value when slope angle is equal to 60°,as it varies from 30° to 75°;2) an approximate linear relationship between the impact force and the storage area length is determined.

Surficial Stability Analysis of Unsaturated Loess Slopes Subjected to Rainfall Infiltration Effects

According to theory of unsaturated soil strength and Green-Ampt model, an analysis method based on limit equilibrium theory is introduced to consider rainfall infiltration effects in loess slope stability analysis. The relationships between wetting band depth and surficial stability of slopes are analyzed. It is found that the infiltration adds to the weight of the soil and at the same time reduces the shear strength provided by matric suction of the soil. The wetting band depth plays a key role in the stability of slopes. The minimum rainfall intensity and the minimum rainfall duration needed to infiltrate to the wetting front depth are calculated based on the Green-Ampt model. The method in this paper will contribute to the predication of slope stability considering rainfall characteristics.

Failure Mechanisms of Post-Earthquake Bedrock Landslides in Response to Rainfall Infiltration

Among the triggering factors of postearthquake bedrock landslides, rainfall plays an important role. However, with slope variation, the mechanism of its effects on the failure of rock landslides is not dear. Here, from the viewpoint of fracture mechanics, and based on post-earthquake conditions, the mechanisms of crack propagation, water infiltration and development of the sliding surface were investigated. Then, according to the upper boundary theorem, the effects of water infiltrated into fractures on the stability of rock slopes were analyzed quantitatively. Finally, an example is presented to verify the theory. The results show that the propagation and coalescence of cracks and the lubrication of incipient sliding surfaces are the main causes of the failure of post-earthquake rock landslides in response to rainfall.

Analysis of Danba Landslide

This paper using finite element method analyzed present slope and contrasted it with the original slope shape, plastic deformation figures and stress changes. At the same time, some deformation figures and stress figures were got, and the potential sliding surface and the stability coefficient were calculated. The conclusions are： This slope is provided with sliding conditions and began to slide when its foot was cut without any support in time. At the foot of the slope, some support measures must be taken to keep the slope steady and the slope surface need to be stabilzed to protect the lower people. These suggestions and conclusions are also useful to the slope constructions and succeeding inspecting works.

颗粒流冲击力研究现状及讨论

颗粒流包括滑坡、泥石流、碎屑流、雪崩等,通常对桥梁、公路、居民区具有较大危害。分析了颗粒流的运动过程及其侵蚀、堆积和爬高等特性;此外,对颗粒流冲击力计算模型及其野外观测结果进行阐述。结果表明:现有冲击力计算模型认为冲击力在结构全断面呈均匀分布,忽略了颗粒流的运动特性对冲击力的影响;大块石冲击力计算忽略了颗粒破碎和浆体垫层效应对冲击力的影响,造成巨大的计算误差;由于传统传感器的缺陷,现有野外观测结果也存在较大误差。对此本文提出野外观测需要通过引入或开发新式压力传感器以得到更准确的颗粒流冲击力大小及其分布形式,从而更精确的修正理论模型;理论计算模型研究工作需要考虑颗粒流浆体的垫层效应、流体与基底的相互作用及块石冲击破碎等对流体冲击力的影响,从而推导出更准确的冲击力计算模型,指导工程实际。

大型滑坡长期演变的地质力学行为及成灾模式研究年度报告

该年度投入了大量的人力和物力开展文献资料总结和野外调查工作,初步将西部山区大型滑坡地质结构类型划分为"弱面"控制型、"关键块体"型、"软弱基座"型和"采空区"控制型四大类。将滑坡成灾模式划分为变形体-潜在威胁模式、滑坡-随动破坏模式、滑坡-高速碎屑流模式、滑坡-堰塞坝堵江模式和滑坡-高涌浪模式等5个模式。完成了对贵州习水县程寨滑坡、贵州关岭县岗乌镇大寨滑坡和重庆武隆鸡尾山滑坡地质结构类型及成灾模式的详细调查分析工作。获取了滑坡岩土体物性参数,为后续研究打下了基础。在滑坡的启动和运动机理研究方面,主要完成了模型试验设备的设计和加工,基于连续介质力学和离散元的滑坡动力过程模拟,针对声波液化模型在大型滑坡中的应用及滑坡模拟中物质状态方程的替代问题的研究和采用大型模型槽及离散元方法对大型滑坡产生的碎屑流运动特征的研究等工作。该年度所取得的研究成果有助于加深人们对大型滑坡地质结构类型和成灾模式的认识和理解,拓宽现有的对大型滑坡启动和运动的模拟方法,推动大型滑坡成因机理研究向前发展。

科学家办好一流科技期刊的典范——忆《古地理学报》创刊主编冯增昭先生

《古地理学报》创刊主编冯增昭先生于2023年1月5日逝世。他作为我国有突出贡献的科学家和教育工作者,为国家的科技进步和石油事业做出了突出的贡献。他退休后先后创办了《古地理学报》中文版和英文版,并于2022年7月成立“国际古地理学会”。他始终怀着高昂的办刊斗志和满腔的爱国情怀,坚持高标准办刊、开放办刊、严谨办刊、融合办刊和情怀办刊,在他的有生之年把《古地理学报》办成了地质学领域的高水平期刊。我们永远怀念冯增昭先生!

Congratulation on the 60^(th) anniversary of the China University of Petroleum with publication of Sedimentology of China (Second Edition)

【正】For the last 4-5 years,we,the editors of the Journal of Palaeogeo graphy(in Chinese)and the Journal of Palaeogeography(in English),and the teachers from College of Geosciences,China University of Petroleum(Beijing)altogether,taking spare time after our routine editing and teaching work,participated in the designation,organization,writing,editing and revision processes of the Sedimentology of China(Second Edition).We put great efforts into this great work which represents the latest research results of various domains of sedimentology in China.We specially published this

中国科技期刊“造船出海”的3个关键问题

中国科技期刊“造船出海”问题引起期刊界与国家高度关注。本文分析了“借船出海”的弊端,认为中国科技期刊“造船出海”要解决3个关键问题:打造中国自主的国际化出版与传播平台、加快打造中国的国际化科技期刊和建立中国科技期刊国际影响力评价机制并纳入科研评价体系。只有切实解决好这3个关键问题,才能从根本上扭转中国科技期刊国际化面临的不利局面。

《古地理学报》的编辑思想探析

期刊编辑思想是主编领导下的期刊编辑部的集体思想结晶,目前研究相对较少。文章初步总结了《古地理学报》的编辑思想,集中体现在5个方面:学术质量乃生命,千锤百炼出精品,科学性第一在细节,服务至上永牢记,形式俭朴始终如一。这一编辑思想是《古地理学报》20多年来发展的智慧结晶,指导着《古地理学报》的每一步发展和进步。