红土化作用及红土的工程地质分类

根据有关红土的最新研究成果，结合在红土地区大量的勘察试验资料及现场对红土特性的深刻认识，提出了红土化作用的基本形式，并对红士的定义及现有对红土的主要分类方法及存在的问题进行讨论。在此基础上按红土化程度对红土进行分类。     

临川市网纹红土的工程地质特征

在大量岩土工程勘察实际资料的基础上,对临川市区网纹红土的工程地质特征进行了系统研究,结果表明,临川市网纹红土具有良好的工程地质性质,可以作为当地多层建筑的持力层。     

桂林地区红土砾石层的工程地质特征及其应用

桂林地区的红土砾石层以其独特的工程地质特征引起了许多中外学者的注意, 对它的成因至今还存在争议。本文主要讨论红土砾石层的工程应用, 即不仅可作为一般低层建筑物的天然持力层, 而且可以作为沟、塘等低洼地带的回填土料 ;而且厚度较大的红土砾石层坚硬部分可作为桩端持力层。     

鄱阳湖地区网纹红土的工程地质特性

本文通过对广泛分布江西省鄱阳湖地区的网纹红土物质成分和微结构特征的研究，从本质上揭示了纹网红土的工程地质特性。指出以往对地基潜力估计不足，大胆提出了要提高地基土强度的利用率，并提供了地基允许承载力（R）的参考值，减少在国民经济建设中的一系列不必要浪费。     

第四纪网纹红土的类型与网纹化作用

第四纪网纹红土在中国南方红土发育区内广泛分布,具有特殊的结构,是第四纪红粘土的重要组成部分,按照质地网纹红土可分为均质类网纹红土和非均质类网纹红土。测试结果显示:（1）均质类网纹红土的粒度组成以粉砂（5～50 μm）和粘粒（<5 μm）为优势粒级,砂（>50 μm）含量很小,不足3%;粒度频率曲线多数呈单峰正偏形态,众数峰值位于5.5～6.5之间,部分呈双峰形态,两个峰值分别位于6和8附近;CIA值较高（84.31%～89.26%）,ba值较低（0.19～0.30）;稀土元素平均含量和分布模式与风尘沉积相似,87Sr/86Sr值与佳县上新世红粘土接近;εNd（0）介于-10.54～-12.66之间,表明物质源区基本稳定;均质类网纹红土的理化特征体现了风成沉积的特性和风化成土作用的显著影响,可称之为加积型网纹红土。（2）非均质类网纹红土发育自冲洪积相、坡积相沉积物或基岩风化壳红土,土体粉砂含量明显减少,多小于50%,砂含量大大增加,>50 μm和>250 μm粒级的离散系数较高,指示了显著的非均质特征;CIA值多数大于84%,化学元素和风化指标的离散系数多小于10%,显示其经历了较为强烈和稳定的风化作用。第四纪网纹红土的形成先后经历了风化成土过程和网纹化过程,南方红土区在网纹红土发育期内具有整体湿润的气候条件。     

我国红土工程地质研究新进展及今后主要研究方向

通过大量的文献阅读,总结出了我国红土已有研究的主要进展,提出了今后的主要研究方向.我国红土研究取得的主要认识有以下几个方面：（1）湿热气候是红土形成的最主要的环境条件;（2）红土的形成是一个脱硅富铁铝的过程,高岭石、伊利石、绿泥石等粘土矿物是红土的主要组成物质;（3）团粒结构是红土的基本结构单元,它主要由粘土矿物通过静电引力、范德华引力连结或游离氧化物的胶结形成,具有很强的水稳定性和较高的力学强度;（4）红土是一种高分散度、低压缩性的区域性土,剖面上具有明显的力学分带性;（5）红土主要的工程地质问题是具有一定的胀缩性、底部常有软土和土洞分布、容易引起地基变形和地面塌陷.今后我国红土研究的主要方向是：红土形成年代和形成速率的研究、红土微结构定量化研究、红土剖面系统研究、红土的分区分类评价、红工测试技术的改进和开发、全国不同类型红土分布图的编制等.     

浅谈风化壳红土型金矿的形成条件及找矿方向

在湿热的气候条件下,红土化作用可使金在风化壳中迁移再富集。发育完好的红土型风化壳常呈现三层结构,金主要富集在红土化较强烈的中上部。稳定的陆块、富金的原岩、湿热的气候、准平原的地貌等是重要的成矿条件。我国华南的赣中、闽西、粤西等地区是有利的成矿远景地区,红土型金矿埋藏浅,易勘探,易采易炼,是今后找矿值得重视的矿化类型。     

Shape analysis and multispectral classification in geological remote sensing

This paper discusses the usage of mathematical morphology in image processing of remotely-sensed data for geologic interpretation. Particular attention is given to noise-reducing transformations of spectral bands before and after different methods of classification, and to the usage of textural context. The development of a viable processing strategy requires a multidisciplinary approach and expert knowledge in different areas: (a) geology, geomorphology, and vegetation in a study area, (b) properties of the sensor for imagery photointerpretation, (c) spectral/spatial properties of the digital data within an integrated dataset (remote sensing and ancillary data), and (d) data-processing tools including mathematical morphology theory. Examples of geometric characterization of Canadian LANDSAT scenes are described in which shape measurements are obtained using a PC-based hybrid image-processing and geographic information system, termed ILWIS, which was developed at ITC, in the Netherlands. Classes from supervised and unsupervised classification are compared to guide in geological mapping. Classes over individual occurrences of broad vegetation-landform units are studied to aid in environmental mapping. Field knowledge is the context necessary to construct expert procedures to drive sequences of data-processing steps toward a target result such as optimal classification, enhancement, or feature extraction. The interaction between expert rules and the image-processing steps can be based on synthetic measurements of shape to quantize the information either spatially or spectrally. Many useful geometrical transformations of spatially-distributed data are extensions or generalizations of spatial analysis functions typical of geographic information systems.     

Micromorphological and chemical complexities of a lateritic profile from basalt (Jos Plateau, Central Nigeria)

A ferricrete-capped lateritic profile developed on basaltic saprolite is described.

Within both ferricrete and the immediately underlying soft laterite, two types of sesquioxidic cement are distinguished: the isopachous goethitic intergranular cement which is predominant and is interpreted as an indication of past phreatic conditions; and the Fe-stained meniscus cement which is interpreted as a sign of vadose conditions.

The observed features are suggested to reflect changing drainage conditions related to morphological rejuvenation of the profile, in full accordance with previous hypotheses developed on the basis of geomorphological consideration.     

二阶段聚类法在地质遗迹分类与开发中的应用

地质遗迹的科学分类是指导地质遗迹保护、利用与开发的重要依据.文章运用二阶段聚类法,选用地质遗迹的价值类型、开发成本、所在地经济与财政状况等因素为变量,以浙江省国家级地质遗迹为例研究地质遗迹的分类与开发,并对各类地质遗迹的保护、利用与开发提出具体建议.     

Pseudosinkhole occurrences in Brasilia,Brazil

Brasilia, the capital city of Brazil, is located in the central region of the country. Climate in the area is semitropical with an annual rainfall of 1500 mm. The geological environment in the area consists of low-grade metamorphic rocks. Slates of varying colors, metasiltstone, and quartzite beds are present. Over the Precambrian rocks is a lateritic layer varying in thickness from centimeters up to 30 m. Latosol dominates the existing plateaus, while laterite crusts and immature soils are dominant in the transition zones between plateaus and river valleys. Erosional problems related to the lateritic terrains were known prior to the settlement of the city in 1961. During 1986, erosion became a serious threat when several pseudosinkholes occurred in the urban area. Occurrence of pseudosinkholes resulted in condemnation of an area of 300,000 m² and the demolition of several buildings. Preliminary studies indicated at the time that underground erosion and pseudosinkholes were generated by shortening of the percolation path of groundwater due to the progress, toward the residential area, of large gullies. This produced an increase in the hydraulic gradient, resulting in the removal of latosol particles. Occurrence of pseudosinkholes in other areas of the city has led the Institute of Geosciences to investigate the problem in more detail. Studies have been conducted looking for correlation between pseudosinkhole occurrence and geologic, geomorphic, geotechnical, and urban development features. Recent results show a much more complex process then previously thought. Field data suggests that termite activity and recharge of the water table by inadequate disposal of residential sewer systems are directly related to the problem.     

软质岩石工程地质分类新方法探讨

本文通过对软质岩石工程地质性质的研究,在软质岩石的地质成因分类和力学分类基础上进行了全面的多指标、综合性的工程地质分类,为软质岩石的进一步分类、研究提供了较可靠工程分类的依据。     

华南花岗岩残积土红土化程度的地带性与香港该类土不发育的原因

从华南花岗岩残积土红土化程度的地域变化规律出发 ,通过香港与华南沿海各地花岗岩残积土的化学成分及红土化指标对比 ,作者发现香港花岗岩残积土无论厚度、类型 ,还是红土化程度都具有与所处气候环境不协调的特点。文章进一步讨论了香港花岗岩残积土不发育的原因和对工程性质的影响.     

花岗岩的Sr-Yb分类及其地质意义

研究表明,中酸性岩浆岩(包括SiO2＞56%的中酸性火山岩和侵入岩)的Sr和Yb是两个非常有意义的地球化学指标,如果大致按照Sr=400×10-6和Yb=2×10-6为标志,可以划分出4类花岗岩,即高Sr低Yb(Sr＞400×10-6,Yb＜2×10-6)、低Sr低Yb(Sr＜400×10-6,Yb＜2×10-6)、低Sr高Yb(Sr＜400×10-6,Yb＞2×10-6)和高Sr高Yb(Sr＞400×10-6,Yb＞2×10-6)型花岗岩.其中,从低Sr高Yb型中还可以分出非常低Sr高Yb(Sr＜100×10-6,Yb＞2×10-6)的一类.因此,按照Sr和Yb含量的不同,可以将花岗岩分为5类.文中着重探讨了这5类花岗岩形成的源区深度问题,指出按照残留相组成和花岗岩地球化学特征,可以将花岗岩形成的压力分为3或4个级别即(1)高压下与石榴石平衡的花岗岩具有高Sr低Yb的特征;(2)在中等或较高压力、麻粒岩相(由斜长石+石榴石+角闪石+辉石组成)条件下,花岗岩具低Sr低Yb或高Sr高Yb的特点(取决于原岩成分);(3)低压下,残留相有斜长石无石榴石(角闪岩相),花岗岩为低Sr高Yb类型的;(4)与蛇绿岩有关的在洋壳剖面浅部由辉长岩部分熔融形成的M型花岗岩,具有非常低Sr高Yb的特点,形成深度约2～5km,可能是非常低压条件下形成的.研究表明,淡色花岗岩大多分布在低Sr低Yb区,部分正长岩和钾玄岩分布在高Sr高Yb区.藏南淡色花岗岩可能形成的压力较高.文中探讨了岩浆与深度的关系,得出了一些初步的认识,指出需要进一步研究的问题.为了得到经得起考验的结论,还需要更多资料的积累,更多理论的探讨和更多实验的佐证.     

Evaluation of graphical and multivariate statistical methods for classification of water chemistry data

A robust classification scheme for partitioning water chemistry samples into homogeneous groups is an important tool for the characterization of hydrologic systems. In this paper we test the performance of the many available graphical and statistical methodologies used to classify water samples including: Collins bar diagram, pie diagram, Stiff pattern diagram, Schoeller plot, Piper diagram, Q-mode hierarchical cluster analysis, K-means clustering, principal components analysis, and fuzzy k-means clustering. All the methods are discussed and compared as to their ability to cluster, ease of use, and ease of interpretation. In addition, several issues related to data preparation, database editing, data-gap filling, data screening, and data quality assurance are discussed and a database construction methodology is presented. The use of graphical techniques proved to have limitations compared with the multivariate methods for large data sets. Principal components analysis is useful for data reduction and to assess the continuity/overlap of clusters or clustering/similarities in the data. The most efficient grouping was achieved by statistical clustering techniques. However, these techniques do not provide information on the chemistry of the statistical groups. The combination of graphical and statistical techniques provides a consistent and objective means to classify large numbers of samples while retaining the ease of classic graphical presentations. Electronic Publication     

Modified rock mass classification system by continuous rating

It is not the purpose of this paper to propose a new rock mass classification system but rather to improve the existing ones by incorporating some simple quantitative interpretations. The geomechanics classification system of naturally fractured rock masses is modified to decrease personal judgement involved in its calculation. Instead of six parameters in the classical rock mass rating (RMR) system, only five basic parameters are considered in the proposed system, which are namely, rock quality designation (RQD) value with the underlying frequency distribution function of intact lengths; uniaxial or point load strength of intact rock material; conditions of the most unfavorable joints; groundwater condition; and joint orientation. Classical lump-rating system is replaced by continuous grading system which leaves no ambiguity for an inexperienced engineer in allocating grades based on quantitative field or laboratory measurements. Finally, necessary charts are presented for obtaining straightforward design values concerning average stand-up time and corresponding unsupported span of excavations in fractured rock mass; cohesion as well as friction angle of the rock mass. The continuous RMR system is very convenient for calculators or in writing computer software. The proposed methodology reduces the scale of subjectivity and leads to a unique rock mass design value.     

Engineering geological parameters affecting the response of Τhessaloniki's urban fill to a major seismic event

In urban areas where there has been continuous occupation of the land for centuries, there are likely to be large areas of filled ground. Fills may have arisen inadvertently from the rubble of demolished buildings and the slow accumulation of refuse. Old urban fills of this type may contain soil, rubble, refuse and even whole parts of past constructions. Despite the fact that areas covered with such deposits are generally prone to severe problems, especially under conditions of dynamic loading, still their influence, as a foundation material on the seismic behaviour of modern buildings is practically unpredictable.Thessaloniki is an old historical city of Macedonia, Greece with no less than 2300 years of continuous urban evolution. A thick and heterogeneous layer of artificial deposits covers the biggest part of the historical centre of the city, as is the case for many old historical cities. The presence of this extensive formation influences the urban development, as it constitutes the foundation of the majority of the buildings of the historical centre, and its investigation is essential for most of the major constructions proposed. The complexity and heterogeneity of Thessaloniki's fill makes the assessment of its engineering behaviour a rather complicated task. This is due to the big range of values of accumulated geotechnical data but also to the fact that these data have been produced by unrelated methods and applied tests.The aim of this paper is to assess the engineering performance of Thessaloniki's fill based on its behaviour as foundation material to a major seismic event. This is carried out by the evaluation of the influence of engineering geological parameters to the damage distribution of the 1978 earthquake, based on the official database which recorded the condition of all the buildings of the historical centre. The statistical elaboration of the damage distribution was carried out following a classification scheme for the fill, based on the fill's classes produced by this scheme, the fill's thickness and the combination of both.The results are given in terms of damage ratios i.e. the ratios of the number of buildings in each damage status per total number of buildings inspected. The correlation of the engineering response with the thickness of the fill showed that there is a significant increase of the percentage of damaged buildings with increasing thickness. However, further analysis of these results showed that the above increase does not apply to all classes equally, which actually suggests that different parts of the fill behave differently in respect to the fill thickness. These results clearly show that a classification scheme and the determination of the boundary conditions should be used as a combined tool from an engineering geological point of view, in order to form a basis for the better understanding of the engineering behaviour of such deposits, the interpretation of geotechnical data and the design of more sophisticated investigations.