Assessment of Liquefaction Potential of Guwahati City: A Case Study

The liquefaction potential of saturated cohesionless deposits in Guwahati city, Assam, was evaluated. The critical cyclic stress ratio required to cause liquefaction and the cyclic stress ratio induced by an earthquake were obtained using the simplified empirical method developed by Seed and Idriss (J soil Mech Found Eng ASCE 97(SM9):1249–1273, 1971, Ground motions and soil liquefaction during earthquakes. Earthquake Engineering Research Institute, Berkeley, CA, 1982) and Seed et al. (J Geotech Eng ASCE 109(3):458–483, 1983, J Geotech Eng ASCE 111(12):1425–1445, 1985) and the Idriss and Boulanger (2004) method. Critical cyclic stress ratio was based on the empirical relationship between standard penetration resistance and cyclic stress ratio. The liquefaction potential was evaluated by determining factor of safety against liquefaction with depth for areas in the city. A soil database from 200 boreholes covering an area of 262 km² was used for the purpose. A design peak ground acceleration of 0.36 g was used since Guwahati falls in zone V according to the seismic zoning map of India. The results show that 48 sites in Guwahati are vulnerable to liquefaction according to the Seed and Idriss method and 49 sites are vulnerable to liquefaction according to the Idriss and Boulanger method. Results are presented as maps showing zones of levels of risk of liquefaction.     

滦河流域沉积物中重金属分布特征及风险评价

沉积物作为重金属污染物的源和汇,对水环境有着至关重要的影响.为了全面了解滦河沉积物中重金属污染现状,采用电感耦合等离子体质谱法对滦河干支流沉积物中重金属含量进行了测定,分析了其空间分布,并采用潜在生态危害指数法对滦河沉积物进行了评价.结果表明:滦河沉积物中Cr、Ni、Cu、Zn、Cd 和Pb的平均含量分别为60.40、26.15、48.07、76.42、0.30、25.55 mg/kg,其中Cu和Cd含量高于中国水系沉积物背景值.滦河干流的重金属含量空间分布自上游往下游呈逐渐增加趋势.潜在生态危害指数评价结果表明:不同重金属污染对滦河流域生态风险构成的危害由强至弱依次为:Cd＞Cu ＞Pb＞Cr＞ Zn,其中Cu、Pb、Cr和Zn为低生态危害等级,Cd以中等生态危害等级为主.总体上,滦河沉积物重金属处于中等生态危害等级,干流大黑汀水库和支流瀑河宽域处于强生态危害等级.     

Assessment and Prediction of Liquefaction Potential Using Different Artificial Neural Network Models: A Case Study

Soil liquefaction as a transformation of granular material from solid to liquid state is a type of ground failure commonly associated with moderate to large earthquakes and refers to the loss of strength in saturated, cohesionless soils due to the build-up of pore water pressures and reduction of the effective stress during dynamic loading. In this paper, assessment and prediction of liquefaction potential of soils subjected to earthquake using two different artificial neural network models based on mechanical and geotechnical related parameters (model A) and earthquake related parameters (model B) have been proposed. In model A the depth, unit weight, SPT-N value, shear wave velocity, soil type and fine contents and in model B the depth, stress reduction factor, cyclic stress ratio, cyclic resistance ratio, pore pressure, total and effective vertical stress were considered as network inputs. Among the numerous tested models, the 6-4-4-2-1 structure correspond to model A and 7-5-4-6-1 for model B due to minimum network root mean square errors were selected as optimized network architecture models in this study. The performance of the network models were controlled approved and evaluated using several statistical criteria, regression analysis as well as detailed comparison with known accepted procedures. The results represented that the model A satisfied almost all the employed criteria and showed better performance than model B. The sensitivity analysis in this study showed that depth, shear wave velocity and SPT-N value for model A and cyclic resistance ratio, cyclic stress ratio and effective vertical stress for model B are the three most effective parameters on liquefaction potential analysis. Moreover, the calculated absolute error for model A represented better performance than model B. The reasonable agreement of network output in comparison with the results from previously accepted methods indicate satisfactory network performance for prediction of liquefaction potential analysis.     

邯郸市饱和粉土地震液化判别与差异分析

采用标准贯入试验法、静力触探法及宏观判别法对邯郸市某工程粉土地基进行了液化判别,并对判别结果进行对比分析。根据判别方法所考虑的因素和特点,结合粉土的区域特征,提出了适合邯郸市饱和粉土的综合判别方法,从而提高了液化判别的可靠性。     

Effects of Non-Plastic Silts on Liquefaction Potential of Solani Sand

Loose saturated cohesionless soils are most susceptible to liquefaction, however there are strong historical evidence suggesting that soils containing fines such as silty sands are also prone to liquefaction during earthquakes. The liquefaction of silty sands has been observed in a number of recent case studies. This paper presents the effects of fine silts on liquefaction potential of sandy soil. Tests have been conducted on the vibration table at different accelerations and pore water pressure is measured. During the lab investigation, locally (Roorkee, India) available Solani Sand and Dhanauri Silt have been used. The soil samples have been prepared by varying silt content and the initial relative density. The results of the study performed are used to clarify the effects of non-plastic fines content on the Solani sand. As the silt content increases, the number of cycles required to produce maximum pore water pressure increases. For a particular level of excitation, rate of pore water pressure generation is maximum at critical silt content. It is observed that critical silt content to generate maximum pore water pressure is different for different accelerations. Further, effect of silt content is very much dependent on relative density.     

“沙洋电力跨越”塔位基础下饱和砂土液化势分析

本文将现场标准贯入试验结果与室内三轴振动压缩实验结果相比较,并进行水平地面下饱和砂土简化液化势分析。据此,一方面预测在一定烈度的地震荷载作用下该基础下的砂层发生液化的可能性,另一方面验证《工业与民用建筑抗震设计规范》(TJ11-74)在河滩地带的适用性。此外还利用经验公式进行计算比较,以及估计地下水位变化对抗液化能力的影响。     

The Evaluation of Liquefaction Potential for Marine Soil under Wave Loading

In this paper, the potential of marine soil liquefaction caused by wave loading is evaluated. This evaluation is based on the testing results from lab. And site of South Sea, China. This evaluation is also compared with the results from different methods.     

波浪荷载作用下海洋土的液化势估价

本文根据在我国南海北部湾某海区的工程地质调查工作以及大量室内和现场的实验成果,初步分析了重力式采油平台地基土在波浪循环荷载作用下可能受到的影响,并对不同分析方法所得的结果加以比较。对该海域的海洋土在一定波浪荷载作用下发生液化的可能性作出了初步估价。     

基于网格单元的总合式和非总合式结合的区域矿产资源潜力评价方法

区域矿产资源潜力有总合式评价和非总合式评价两大类方法.总合式评价方法简便易行,可以得到一个区域的资源潜力总量的估计,但是没有其在区域中的空间位置信息,区域矿产资源潜力评价早期主要是用总合式评价方法.随着资料数据的积累,特别是计算机和GIS技术的应用,能给出空间位置信息的非总合式评价越来越多的用于区域矿产资源潜力评价.非总合式评价主要把区域划分成同形等大的单元,在圈定成矿远景区单元基础上,用类比方法对成矿远景区单元进行矿产资源潜力数量预测评价.总合式矿产资源潜力评价是区域矿产资源潜力评价的主要方法,可以对区域内潜在的矿产资源量进行预测,但是只有一个总量,没有区域内矿产资源空间分布信息,不能结合各局部空间具体情况进行各种环境经济社会评价,因此需要将其预测的资源量空间定位化.非总合式矿产资源潜力评价虽然能够定位,但因其是用控制单元的探明资源量进行类比外推,所以无法对已知矿产资源量的单元内潜在的矿产资源量进行预测.提出了用基于网格单元的总合式和非总合式方法结合的矿产资源潜力评价方法,解决了总合式方法单元资源量预测值的空间定位和分配问题.并且以云南铅锌矿为例进行了计算,既得到了总量也得到了其空间分布量,修正了非总合式预测方法的不足,特别适用于对矿产资源进行环境、经济、社会等评价或者联合评价.以云南铅锌矿产资源潜力评价为实例进行了应用,得到初步结果.      

洋山港海域现代沉积物运移趋势

地形、物源和水动力条件是洋山港海域现代沉积环境的主要控制因素，粉粒和粘粒是现代沉积物的主要组成部分，潮流是起动和搬运现代沉积物的主要动力，悬移是现代沉积物最主要的搬运方式，跃移是次要搬运方式，现代沉积物的起动和沉积过程交替频繁。研究区现代沉积物长期净运移趋势表明：研究区东部的黄泽洋向洋山港海域的输沙趋势显著；洋山港岛链峡道深槽的形成，系由峡道东部和西部的现代沉积物各向峡道两端分异运移所致；小洋山—唐脑山—线将是今后港区泥沙淤积的主要部位之一。     

A Comparative Study of Soil Liquefaction Assessment Using Machine Learning Models

Geotechnical and Geological Engineering - Liquefaction of saturated granular soils is marked by the total loss of shear strength of soil under dynamic cyclic or transient loading conditions due to...     

剪切波速测试技术及场地土液化势判别

文章简要地介绍了剪切波测试技术的基本原理、野外测试方法及其在工程中的主要用途.结合工程实例,对于在资料处理中碰到的场地液化势判别的问题,采用石兆吉判别式,丁伯阳判别式,谢生荪判别式及标准贯入试验法等目前运用较多的多种液化判别方法进行对比分析,最后得出在本次工程中石兆吉判别式结果最切合本次工程,其结果予以采用,并且就液化判别问题提出了一些建议.     

黑潮源区沉积物古菌多样性调查及研究

为了研究西太平洋黑潮源区不同深度沉积物中古菌群落结构的多样性,应用16S rDNA文库技术,对IMAGES XIV航次采集的岩芯MD06-3047进行基因文库的构建和分析,得到260个克隆,经分析处理后得到56个OTUs(Operational Taxonomic Units).基于16S rRNA序列的同源性比较,绘制系统进化树,进行统计学分析.研究结果显示,西太平洋黑潮源区的本哈姆高原(Benham Rise)沉积物中有丰富多样的古菌群落,在1m内的沉积物中分布着9种古菌类群.古菌序列归属于泉古菌(Crenarchaeota)和广古菌(Euryarchaeota),并以泉古菌为主(占总序列的91.5％).其中,泉古菌包含MGI、MBG-B、MCG和UCII-b 4个类群,并且主要由MGI构成(占总序列的40.8％),而广古菌包含MBG-D、SAGMEG、DHVEG、MBG-E和VAL Ⅲ 5个类群,各类群所占总序列比例均较低(占总序列的0.4％～5.4％之间).研究结果对于理解西太平洋黑潮源区沉积物中古菌多样性有重要意义,并为今后研究古菌群落与环境之间的关系提供科学依据.     

关于砂（粉）土地震液化的判别公式——审稿后的思考

对于液化判别,不论是用什么方法,也不论是砂土或粉土,其基础都是根据已有的有限震例调查资料。可以说,这完全是一种经验关系,甚至可以说这仅是一种非常粗略的概率判别或趋势判别。即使是列入《规范》[1]的判别方法,对于一个具体实例来说,都可能存在着相当的误判概率。作为一个岩土工程师,我们要求的是根据各种因素的判别结果,作出合理的工程判断。如果文献[2]的重点也是强调根据各种因素进行综合判断,那无疑是完全应该肯定和鼓励的。但如果是讨论SPT法和CPT法哪个更好,则可能是不一定必要的。因为对于这些判别方法(公式)的来由和当时的概…     

攀西地区晚新生代沉积研究回顾与问题讨论

攀西地区晚新生代沉积是研究青藏高原东南缘隆升演化历史及其周缘环境响应、中国第一第二阶梯地貌格局演变和高原东南缘水系变迁的天然地质记录,具有重要科学意义。对该区晚新生代河湖相沉积,尤其是昔格达组和大箐梁子组的研究历史、岩性内涵、形成时代、古地理与古气候意义等进行了较全面的回顾。在此基础上对晚新生代冰碛物记录的冰川发育过程、青藏高原东南缘新构造运动和隆升历史、水系格局变迁等过程进行了评述。针对该区晚新生代沉积研究中存在的问题和分歧,提出了今后研究的方向,认为在详细的地层学和地貌学等综合研究基础上开展高精度的年代学研究是当前攀西地区晚新生代沉积研究的重点。     

Stratigraphy of the Lower Cretaceous Sediments from the Carpathian Bend Area, Romania

The Lower Cretaceous sediments of the Ceahl?u Nappe (from the bend region of the Romanian Carpathians) were investigated from lithological and micropaleontological (calcareous nannoplankton) points of view. Our investigations revealed that the studied deposits were sedimented within the latest Tithonian-Albian interval. The calcareous nannofossil assemblages of the turbidite calcareous successions (the Sinaia Formation) were assigned to the NJK-?NC5 calcareous nannofossil zones, which cover the Late Tithonian-Early Barremian interval. The sandy-shaly turbidites, which followed the calcareous turbidites of the Sinaia Formation, are Early Barremian-Early Albian in age (interval covered by the ?NC5-NC8 calcareous nannofossil zones). Because the studied deposited are mainly turbidites, many reworked nannofossils from older deposits are present in the calcareous nannofloras. Thus, some biozones (i.e., NC5), defined based on the last occurrences of nannofossils, could not be identified. The calcareous nannofossil assemblages are composed of Tethyan taxa (which dominate the nannofloras) and cosmopolitan taxa. During two intervals (the Late Valanginian and across the Barremian/Aptian boundary), Tethyan and cosmopolitan nannofossils, together with Boreal ones, were observed. This type of mixed calcareous nannoplankton assemblage is indicative for sea-level high-stand, which allows the nannofloral exchange between the Tethyan and Boreal realms, within the two-above mentioned intervals.     

Holocene Ash from Lacustrine Sediments of the Okhotsk Area: Distinctive Features

Doklady Earth Sciences - The results of a multidisciplinary study of two Holocene tephras from lacustrine sediments of the Northern Okhotsk area are presented. A comprehensive characterization of...     

黄河三角洲地区砂土路基液化机理探讨及处置

从砂土路基液化机理人手,结合黄河三角洲地区地基土工程地质特征,对该地区路基砂土液化做现场振动试验,找出影响砂土路基液化的影响因素,主要内因有土体的密实度、含水量和土体中是否存在软弱区;主要外因有荷载的大小、作用时间和荷载频率。并针对砂土液化的内外因,结合青银高速公路强夯处理案例展开分析,提出了处理方法。     

煤层气产能潜力模糊数学评价研究——以河东煤田柳林矿区为例

在系统分析影响煤层气产能潜力开发地质因素的基础上,确立了以二级评价指标地质储量参数和开发参数为支撑的煤层气产能潜力模糊评价体系及对应的三级评价指标,采用模糊数学方法对各评价指标进行了权重赋值,建立了用于煤层气产能潜力评价模糊数学评价模型。利用该模型,对河东煤田柳林矿区的煤层气产能潜力进行了评价,认为该矿区3-5#煤层煤层气产能潜力较大,为该矿区煤层气开发的有利层段。