沿山脊走向长输油气管道强震动力响应特征

沿山脊走向的长输油气管道在我国西部山区常有分布,强震作用下其动力响应直接关系到管道的安全运营,实际管道工程建设中亟需相关研究结果提供指导。依托云南玉溪龙马槽村段此类输油管道工程,考虑山坡的工程地质特征,对管道与坡体进行整体三维数值建模,采用有限差分方法FLAC3D进行数值模拟,基于汶川地震波,计算得到了水平地震加速度峰值、震后等典型时刻的管道位移、轴力、剪力和弯矩及坡体稳定性等地震动力响应特征。结果表明,管道内力最大值出现于震后时刻,地震作用使管道轴力达到较高水平,而剪力与弯矩值的量级仅占最大轴力的约1%;竖向地震波对管道内力影响较小,管道受力的不利部位出现在其与断层交界附近。地震过程中管道水平方向存在较多的弹性变形,竖向则存在较多的塑性变形,管道累计变形是影响其内力的主要因素,管道内力最大值出现于震后时刻。      

Study on the Liquefaction Properties of Silt at Yellow River Delta

The seabed of the Yellow River Delta is formed by the rapid deposition of sediments from the Yellow River. Recent researches have shown that the geological hazards in the Yellow River Delta are mainly related to the liquefaction of silty seabed under cyclic loading. In this paper, based on the theory of Stokes Viscous Principle, a self-design dragging ball apparatus was used to study the fluid characteristics of liquefied and post-liquefied silt more thoroughly. Wave flume and shaking table were used to apply wave loads and vibration loads. The pore pressure, earth pressure, and moving parameters of the dragging ball were recorded during tests. The effect of cyclic loads and excess pore pressure ratio on viscosity of silty soil is discussed. The constitutive model of flow characteristics of liquefied silt is also established. The results indicate that the apparent viscosity of silty soil is much higher than sand. Cyclic loads accelerated the process of silt liquefaction, resulting in the decrease in apparent viscosity. The excess pore pressure ratio (r_u) has effect on silt liquefaction. When the soil had not reached the completely liquefied state (r_u < 1), the apparent viscosity decreased with the increase of excess pore pressure ratio; when the soil had reached the completely liquefied state (r_u = 1), the shear stress decreased with the increase of strain rate. It was determined that silty soil characterized by shear thinning can be viewed as a type of non-Newtonian fluid. The equation of the shear stress and shear strain rates was established by fitting the test data.     

A Field Investigation on the Effects of Background Erosion on the Free Span Development of a Submarine Pipeline

The safety of submarine pipelines is largely influenced by free spans and corrosions. Previous studies on free spans caused by seabed scours are mainly based on the stable environment, where the background seabed scour is in equilibrium and the soil is homogeneous. To study the effects of background erosion on the free span development of subsea pipelines, a submarine pipeline located at the abandoned Yellow River subaqueous delta lobe was investigated with an integrated surveying system which included a Multibeam bathymetric system, a dual-frequency side-scan sonar, a high resolution sub-bottom profiler, and a Magnetic Flux Leakage(MFL) sensor. We found that seabed homogeneity has a great influence on the free span development of the pipeline. More specifically, for homogeneous background scours, the morphology of scour hole below the pipeline is quite similar to that without the background scour, whereas for inhomogeneous background scour, the nature of spanning is mainly dependent on the evolution of seabed morphology near the pipeline. Magnetic Flux Leakage(MFL) detection results also reveal the possible connection between long free spans and accelerated corrosion of the pipeline.     

孤永东输油管道穿越改造工程对黄河防洪影响评价

根据防洪影响评价有关规范,对输油管道穿越黄河河道处河势演变情况、主河槽摆动范围、主河槽及滩地冲刷深度等进行深入分析．提出管道穿越河道改造工程有关技术指标,就管道穿越工程对黄河的防洪影响做出综合评价并提出有关防治措施。     

Sedimentary Changes of a Sand Layer in Liquefied Silts

A flume experiment was conducted to investigate the restratification of liquefied sediment strata under a wave load with the focus on the interbedded strata of coarse and fine sediments formed in estuarine and coastal areas. The aim of this research was to study the characteristics and processes of liquefied sediment strata in terms of wave-induced liquefaction. In the experiment, the bottom bed liquefied under the wave action and the liquefied soil moved in the same period with the overlying waves, and the track of the soil particles in the liquefied soil was an ellipse. The sand layer consisting of coarse particles in the upper part, settled into the lower silt layer. The sinking of coarse particles and upward migration of the fine particles of the lower layer induced by liquefied sediment fluctuations are the likely reasons for sedimentation of the sand layer in liquefied silt.     

山东省定陶地区富锶土壤地质成因研究

为研究山东省定陶地区土壤富锶的地质成因,更好地规划潜在富锶土壤种植区域,指导农业生产,发展绿色经济,本文在对该区土壤样品的相关元素化验分析的基础上,进行了定陶地区富锶土壤的沉积环境分析、黄河故道变迁分析和水化学分析.通过研究分析发现,土壤中富集的锶非当地风化沉积而成,而是从锶含量较高的区域搬运而来.历史上黄河故道曾流经...     

An experimental study on the wave-induced pore water pressure change and relative influencing factors in the silty seabed

In this study, a flume experiment was designed to investigate the characteristics of wave-induced pore water pressure in the soil of a silty seabed with different clay contents, soil layer buried depths and wave heights respectively. The study showed that water waves propagating over silty seabed can induce significant change of pore water pressure, and the amplitude of pore pressure depends on depth of buried soil layer, clay content and wave height, which are considered as the three influencing factors for pore water pressure change. The pressure will attenuate according to exponential law with increase of soil layer buried depth, and the attenuation being more rapid in those soil layers with higher clay content and greater wave height. The pore pressure in silty seabed increases rapidly in the initial stage of wave action, then decreases gradually to a stable value, depending on the depth of buried soil layer, clay content and wave height. The peak value of pore pressure will increase if clay content or depth of buried soil layer decreases, or wave height increases. The analysis indicated that these soils with 5% clay content and waves with higher wave height produce instability in bed easier, and that the wave energy is mostly dissipated near the surface of soils and 5% clay content in soils can prevent pore pressure from dissipating immediately.     

Vertical Migration of Fine-Grained Sediments from Interior to Surface of Seabed Driven by Seepage Flows–‘Sub-Bottom Sediment Pump Action'

A scientific hypothesis is proposed and preliminarily verified in this paper: under the driving of seepage flows, there might be a vertical migration of fine-grained soil particles from interior to surface of seabed, which is defined as ‘sub-bottom sediment pump action' in this paper. Field experiments were performed twice on the intertidal flat of the Yellow River delta to study this process via both trapping the pumped materials and recording the pore pressures in the substrate. Experimental results are quite interesting as we did observe yellow slurry which is mainly composed of fine-grained soil particles appearing on the seabed surface; seepage gradients were also detected in the intertidal flat, under the action of tides and small wind waves. Preliminary conclusions are that ‘sediment pump' occurs when seepage force exceeds a certain threshold: firstly, it is big enough to disconnect the soil particles from the soil skeleton; secondly, the degree of seabed fluidization or bioturbation is big enough to provide preferred paths for the detached materials to migrate upwards. Then they would be firstly pumped from interior to the surface of seabed and then easily re-suspended into overlying water column. Influential factors of ‘sediment pump' are determined as hydrodynamics(wave energy), degree of consolidation, index of bioturbation(permeability) and content of fine-grained materials(sedimentary age). This new perspective of ‘sediment pump' may provide some implications for the mechanism interpretation of several unclear geological phenomena in the Yellow River delta area.     

Undersea Buried Pipeline Reconstruction Based on the Level Set and Inverse Multiquadric Regularization Method

The electric inversion technique reconstructs the subsurface medium distribution from acquired data. On the basis of electric inversion, objects buried under the earth or seabed, such as pipelines and unexploded ordnance, are detected and located in a contactless manner. However, the process of accurately reconstructing the shape of the target object is challenging because electric inversion is a nonlinear and ill-posed problem. In this work, we present an inverse multiquadric (IMQ) regularization method based on the level set function for reconstructing buried pipelines. In the case of locating underwater objects, the unknown inversion area is split into two parts, the background and the pipeline with known conductivity. The geometry of the pipeline is represented based on the level set function for achieving a noiseless inversion image. To obtain a binary image, the IMQ is used as the regularization term, which 'pushes' the level set function away from 0. We also provide an appropriate method to select the bandwidth and regularization pa-rameters for the IMQ regularization term, resulting in reconstructed images with sharp edges. The simulation results and analysis show that the proposed method performs better than classical inversion methods.     

黄河一级支流水土保持“3S”分析应用

改善黄河流域生态环境是推动西部大开发的有力保证。本文以黄河一级支流为单元,以秃尾河、皇甫川和窟野河为重点研究对象,介绍了如何利用GPS、RS和GIS相结合的技术,动态监测黄河流域水土流失情况,为黄河流域环境治理提供科学依据。     

1980-2015年黄河流域降雨侵蚀力时空变化分析

本文利用1980-2015年黄河流域及周边166个气象站点36 a的降雨资料,采用日降雨侵蚀力计算模型,对克里金插值后的栅格数据,通过利用主成分分析法、isodata聚类和最大似然法实现区域划分,并在此基础上应用重心模型研究了黄河流域降雨侵蚀力的时空变化。研究结果表明：黄河流域内不同区域的年降雨侵蚀力差异较大,最小的区域在200 MJ·mm·hm^-2·h^-1左右变化,最大的区域可达3000 MJ·mm·hm^-2·h^-1,年降雨侵蚀力具有由西北向东南递增的趋势。年降雨侵蚀力大的区域其侵蚀力值在不同年份中波动范围也大。西宁、呼和浩特等所在的一区、二区和三区的年降雨侵蚀力的重心总体上呈现向东北方迁移趋势。太原、西安所在的四区、五区其重心总体上呈现向西南方迁移趋势,其年降雨侵蚀力重心迁移范围小,重心点分布更紧密。各区域年降雨侵蚀力重心的迁移范围在空间和时间尺度上总体呈现由西北向东南方向逐渐缩小趋势。     

武汉主城区液化潜能分区研究

搜集并整理武汉主城区地震安全性评价控制性钻孔SPT-N资料,配合武汉市地震动参数小区划成果,采用规范法对各场地土层在罕遇地震作用下液化可能性进行判别。以液化指数作为分区指标并结合各场地坐标,绘制武汉主城区液化潜能分区图。分区图初步预测了罕遇地震发生以后,可能发生液化的区域及其严重性,且表明无论是分布面积还是液化潜能,长江右岸均大于长江左岸。通过与4次历史大震液化资料的对比分析,武汉主城区可能液化场地具有地下水位埋深浅、液化土层分布范围广、埋藏深度大的特点。     

黄河三角洲生态区孔隙热储地热开发对地面沉降的影响分析

黄河三角洲地区地热资源丰富,热储类型以孔隙热储为主,开采潜力巨大。同时黄河三角洲地区由于成岩差、土层新,地热开发引发的地面沉降问题逐渐引起人们的重视。研究表明:现状条件下,黄河三角洲地区地面沉降以地层(土体)自然固结与地面建筑物载荷有关,地热开发对地面沉降影响微小,南部的广饶地区过量开采地下水是引起地面沉降的主要原因。     

Feasibility Study on Common Methods for Wave Force Estimation of Deep Water Combined Breakwaters

China's newly enacted Breakwater Design Specifications(JTS154-2011) explicitly state that breakwaters with water depths greater than 20 m are categorized as deep-water breakwaters, and emphasize that design principles, methods and construction requirements are different from those of common shallow water breakwaters. However, the specifications do not make any mention of how to choose wave force calculation methods of deep-water breakwaters. To study the feasibility of different formulae for wave force estimation of deep water combined breakwaters, the wave force calculated by the Sainflou's, Goda's, modified Goda's and specifications' methods are compared for various water depths and wave heights in this paper. The calculated results are also compared with experimental data. The total horizontal forcing and the pattern of pressure distributions are presented. Comparisons show that the wave pressure distributions by the four methods are similar, but the total horizontal forces are different. The results obtained by the Goda's method and the specified formulae are much closer to the experimental data. As for the wave force estimation for the deepwater mixed embankment foundation bed parapet, the Goda's formula is applied in the case with a water depth of less than 42 m. The Specifications method is suitable for standing waves. In the wave force estimates of breastworks, Sainflou's and the modified Gaoda's formulae are no longer applicable for the foundation bed of mixed embankment.     

黄河三角洲地区软土的初步研究

黄河三角洲地区是正在加紧开发的经济区,大中型建筑日益增多,而软土在该区广泛分布,厚度较大,易发生不良工程地质问题。本文就黄河三角洲地区软土的成因、厚度、埋藏条件、分布规律及发育过程进行了初步研究,总结了该区软土的物理力学特性及若干物理力学指标的经验关系,并对其主要工程地质问题及措施提出了建议。     

Wave uplift force on horizontal panels: a laboratory study

Accurate estimation of wave uplift force is essential to the designs of reliable coastal and marine structures. We presents a series of laboratory work here on the impact of regular waves on horizontal panels, from which an empirical formula to estimate accurately the wave uplift force on panels is established. The laboratory measurements show that the wave uplift force depends mainly on the incident wave height, the wave period, the wave length, the panel width, and the clearance between the subsurface of the panel and the still water level. Among these factors, the impact of the panel width on uplift forces is relatively complicated. Result shows that the relative panel width(i.e., the ratio of panel width to wave length) plays a more important role in estimating the wave uplift force. Based on our comprehensive laboratory measurements, we further developed an empirical formula to compute wave uplift force on horizontal panels through dimensionless analysis. Compared with other empirical formulas, this formula uses dimensionless variables of clear physical meanings, thus can describe the interaction between waves and the panels in a better way. In addition, the efficiency of the formula to estimate wave uplift force on horizontal panels is verified against existing works. Therefore, the findings in this study shall be useful for understanding the mechanism of wave uplift force on horizontal panels and numerical model validation.     

黄河上游及源头区生态环境质量综合评价

本文简要介绍了利用遥感和地理信息系统技术进行黄河上游及源头区生态环境质量综合评价中,评价因子的获取及其分值和权值的确定,评价模型的建立及评价等级的划分。评价结果表明,该区环境质量具有垂直分带规律,人类不合理的经济活动是影响环境质量的重要因素。     

济南市华山湖开挖建设渗漏分析研究

该文在查明区域水文地质条件、湖区地下水的类型、分布、埋藏条件、含水层及隔水层特征、岩性结构以及地下水的补给、径流、排泄条件的基础上,通过现场试验,确定了天然状态下湖区各含水层之间的水力联系、黄河侧渗补给量及湖区向小清河的排泄量,结合数值模拟,预测了湖区维持设计蓄水位21.5m时黄河的侧渗补给量、湖区向小清河的排泄量及湖区对周边地下水位的影响。结果表明,天然状态下,黄河侧渗补给量为748.23m~3/d,湖区向小清河排泄量大约为52.03m~3/d,黄河侧渗补给量远大于湖区向小清河的排泄量。数值模拟结果表明,湖区维持设计蓄水位21.5m时,不同水文年湖区接受的侧渗补给量均大于湖区的渗漏量,且对周围地下水位的影响不超过1.5m,因此,湖区维持设计蓄水位21.5m时可不考虑防渗措施。     

Provenance of Sediments Filling a Paleo-Channel that Formed on the Western Yellow Sea Continental Shelf During the Last Glacial Period

Several buried paleo-channels are located on the continental shelf of the western Yellow Sea. Research on the paleochannels is significant for both theoretical studies and practical applications. In this paper, we analyse and discuss the mineralogy of sediments in a core (SYS-0803) recovered from a buried paleo-channel on the continental shelf of the western Yellow Sea. The aim is to determine the provenance of sediments that fill the paleo-channel. The heavy mineral assemblage of sediments in the core consists of schistose minerals, common hornblende, epidote, and ilmenite. The light mineral assemblage consists of plagioclase, quartz, lithic fragments, and K-feldspar. Analysis of the compositional maturity of the sand fraction revealed a quartz/feldspar ratio of < 1. A relatively high percentage of smectite is recorded throughout the entire paleo-channel fill, with the greatest percentage in the middle to lower parts. The detrital mineral assemblage and clay mineral content indicate that the paleo-channel sediments were sourced mainly from the Huanghe River during the last glacial period.     

Disaster reduction stick equipment: A method for monitoring and early warning of pipeline-landslide hazards

Oil and gas pipelines are of great importance in China, and pipeline security problems pose a serious threat to society and the environment.Pipeline safety has therefore become an integral part of the entire national economy. Landslides are the most harmful type of pipeline accident, and have directed increasing public attention to safety issues.Although some useful results have been obtained in the investigation and prevention of pipeline-landslide hazards, there remains a need for effective monitoring and early warning methods, especially when the complexity of pipeline-landslides is considered.Because oil and gas pipeline-landslides typically occur in the superficial soil layers, monitoring instruments must be easy to install and must cause minimal disturbance to the surrounding soil and pipeline. To address the particular characteristics of pipelinelandslides, we developed a multi-parameter integrated monitoring system called disaster reduction stick equipment. In this paper, we detail this monitoring and early warning system for pipeline-landslide hazards based on an on-site monitoring network and early warning algorithms.The functionality of our system was verified by its successful application to the Chongqing Loujiazhuang pipeline-landslide in China. The results presented here provide guidelines for the monitoring, early warning, and prevention of pipeline geological hazards.