共查询到20条相似文献，搜索用时 687 毫秒
1.
M. Ahmad M. K. Ansari Rajesh Singh L. K. Sharma T. N. Singh 《Geotechnical and Geological Engineering》2017,35(2):827-842
Weathering and durability are the key factors of the rock in the suitability and usefulness of different construction materials, building materials and engineering structures. A single test never predicts the entire factor for suitability of rock stone and aggregate in different uses. Thus, variety of physical, mechanical and chemical tests and indices of rocks are widely used to estimate and evaluate the rocks for the suitability of the required purpose. In all the cases, knowledge of durability and weathering properties are the most important along with the strength of the rock. Micropetrographic index and rock durability indicators (dynamic and static) are the one of the best methods to evaluate the rock for weathering and durability. To estimate these indices, variety of tests are performed such as petrographic examination test, point load index, sulfate soundness test, water absorption test, modified aggregate impact value test and test for specific gravity. Slake durability index and impact strength index tests were also performed for correlation with static and dynamic rock durability indicators due to its application and usefulness in the durability and strength of the rock materials. Micropetrographic index was obtained by petrographic examination test and correlated with all the physical and mechanical properties used for find out the durability indicators. The present study is to express the usefulness of these three indices in the classification of weathering and durability classes and estimation of durability indices by slake durability index, impact strength index and micropetrographic index. 相似文献
2.
Irb Kheoruenromne 《Chemical Geology》1987,60(1-4):319-326
Data of a study on red and yellow soils in the Northeast Plateau, Thailand, indicate that the soils are highly leached and well developed under oxidizing condition. They have been developed on slope wash materials and local alluvium underlain by cemented gravels and laterite. Appreciable amounts of Fe-oxides can be found in these soils, mainly in the form of goethite and hematite and in both silt and clay fractions. Other important constituents of these soils are quartz and kaolinite. The soil fabric contains argillan and ferri-argillan on skeleton grains and pore walls, indicating prolonged leaching and oxidizing state of the solum. Laterites found are both massive and pisolithic gravels. Since spot accumulation and separation of argillan and Fe-oxides were not observed in the soils it seems that the soils and laterite have been controlled by different sets of genetic processes. 相似文献
3.
Jacques De Medina Laura M. G. Motta João D. G. Dos Santos 《Geotechnical and Geological Engineering》2006,24(4):949-971
This paper summarizes the resilient and permanent deformation characteristics of laterite gravels, determined by cyclic loading in triaxial tests of compacted specimens. A study of laterite pavements was carried out on eight paved road sections in the state of Mato Grosso. Also reported is the influence of fine sand admixture, specimen size and soaking in two laterite samples from Roraima and Rondônia in the North of Brazil. The experimental relationships of resilient moduli against applied stresses are interpreted empirically for models what may be incorporated in a structural analysis of full depth of laterite pavement. 相似文献
4.
A.Bhaskara Rao 《Chemical Geology》1987,60(1-4):293-298
The structural classification previously proposed for laterite crusts in field exploration by the author has the objective of: (a) serving as a tool to geological mapping of the bed rock types; (b) recognition of greenstone belt units of economic interest; and (c) demarcation of target areas for mineral exploration. In localities of several small placer gold operations, outcrops of nodular and pisolitic laterite crusts are seen overlain occasionally by breccioid laterite, nodular laterite breccia, mottled cavernous laterite or banded concretionary laterite. Such nodular or pisolitic varieties, rich in goethite, characterise mafic to ultramafic parent rocks in/and greenstone belt units. This type of crust is thus the guide horizon in the laterite profile indicative of Au. Its surface expression accompanying the source rocks is occasionally significant and thus can be a promoter of small-scale mining and a metallotect and guide for exploration programmes. 相似文献
5.
The two known massive Cu-Zn sulphide deposits in the steeply dipping strata of the Golden Grove District of Western Australia — the Gossan Hill Deposit and Scuddles Prospect — both have a multi-element secondary geochemical dispersion halo in the pisolitic layer of laterite of probable Tertiary age. The Gossan Hill geochemical anomaly is about 1.5 × 2 km and has a Bi-Sn-Mo-In-Sb-As-Cu-Au association. Mean compositions of pisolitic laterite samples range from 4 to 18 times background, with maxima for Bi, Sn and Mo reaching 90 to 100 times background. Relief of Gossan Hill, which rises some 80 m above the laterite plain, would have favoured dispersion during lateritization. Nevertheless at Scuddles, where the laterite surface has only a gentle slope across strike, an anomaly in pisolitic laterite measures 1 to 1.5 by 1.5 to 2.0 km. The anomalous association, Bi-Sn-Mo-Sb-As, is similar to that at Gossan Hill; the mean contents in pisolitic laterite samples from the Scuddles anomaly range from 2.3 to 8 times background, with maxima for Bi being 12 times background.At Gossan Hill, individual pisolites and the concretionary skins contain gossan fragments and cassiterite, indicating mechanical dispersion during interitization. However, anomalous Cu, Zn and As in goethites of the concretionary skins of pisolites and nodules from the centre of the anomaly indicate that there has also been hydromorphic dispersion.The geochemical characteristics of pisolitic laterite samples have been represented by empirically derived additive indices based on up to eleven chalcophile elements. One index is suggested as a method to increase anomaly size and simplify interpretation; a more specific index based on Bi, Sn and Se is suggested for defining more closely the actual centres of mineralization.For routine exploration of lateritic terrain where the dips of the host sequence are steep, 320-m spacing of samples on a triangular grid appears suitable for locating anomalies and generally defining their source. However, for reconnaissance exploration, the density of sampling could be significantly reduced for example to 1 km spacing. 相似文献
6.
M. A. Kamal M. A. Sulehri D. A. B. Hughes 《Geotechnical and Geological Engineering》2006,24(4):819-831
This paper summarizes an extensive series of common durability, shape and strength tests carried out on road aggregates from
quarries in northern Pakistan by Sharif et al. at the University of Engineering and Technology, Taxila. The data from these
standard tests have been correlated for a particular aggregate type to show the close relationship between these measured
physical characteristics. The paper outlines how, once these relationships have been established for a particular aggregate
source, it is feasible to simplify the testing or quality assurance regime and monitor only some of these characteristics
to assess the overall quality of the aggregate. The physical characteristics have then been combined into a linear relationship,
using coefficients estimated from the extensive data set in the paper, to give a single characteristic for an aggregate type
known as the Toughness Index (TI). The TI is therefore based on the main strength and durability characteristics of the aggregates
and can be used as an indicator of the overall quality of the aggregate. 相似文献
7.
传统的公路集料生产其质量不能满足现行公路沥青面层集料的质量要求。机制砂石将成为公路面层集料的主体。目前的机制集料生产企业多为小型企业，质量不稳定。根据集料生产工艺中的诸环节，提出质量控制的措施。 相似文献
8.
新近系上新世（N2）红土是实现我国西北地区保水采煤和生态环境保护的关键隔水层,研究红土的微观结构有利于分析其渗透性变化的内在机理。文章利用Matlab对不同渗透系数的N2红土的SEM图像进行了预处理和二值化分割,提取孔隙轮廓,得到其孔隙大小、排列、形态和类型等微观特征,并分析了红土的灰度熵、平均孔径、扁圆度、分布分维和概率熵等孔隙微观结构参数与渗透系数之间的关系。结果表明:图像灰度熵与渗透系数之间无明显变化规律,灰度熵在0.88~0.92之间;平均孔径在2.7~3.7μm之间,渗透系数随平均孔径的增加呈指数型增加;对孔隙大小按照微孔隙（<1μm）、小孔隙（1~4μm）、中孔隙（4~16μm）、大孔隙（> 16μm） 4组进行分类,发现小孔隙的数量最多,约占总孔隙数的50%以上,中孔隙和大孔隙的面积约占总孔隙面积的80%以上,渗透系数的增大主要与中孔隙和大孔隙有关;孔隙扁圆度在0.54~0.57之间,形状系数在0.63~0.75之间,孔隙主要呈扁椭圆状,渗透系数随扁圆度的增加呈指数型缓慢减小,随形状系数的增加呈线性减小;孔隙的分布分维数在1.00~1.40之间,随着分布分维的增加,孔隙由大变小,渗透系数随之呈指数型减小;不同土样的概率熵在0.97~0.99之间,孔隙缺乏明显定向性。 相似文献
9.
高液限红黏土用于路基填筑时,因其不良的水理特性,需要掺石灰或水泥改良。但红黏土成团现象十分突出,进行灰土拌和时不易达到均匀状态,影响预期改良效果。通过对不同直径的红黏土土团及石灰改良土土团进行承载比试验,结果表明：干密度随着土团直径尺寸的增大呈现先增大后减小的特征,红黏土和石灰土的最大干密度对应的土团直径处在0.2～ 5 mm范围内;而最大承载比CBR值对应的土团直径分别处在5～10 mm和2～5 mm的范围内。石灰土和红黏土的吸水率、膨胀率均随着土团尺寸的增大,呈现先减小后增大的整体变化趋势。在2～10 mm的范围内,两种土的膨胀量最小。石灰改良只对直径小于5 mm的土团的膨胀特性起到明显的抑制作用。可见,现场施工中严格控制土团的大小对保证土体的强度和水稳定性具有十分重要的意义。 相似文献
10.
红黏土易失水收缩开裂,不仅降低了其整体强度,还为雨水入渗提供了通道,加剧了其承载能力的弱化。因此,如何抑制红黏土收缩,成为解决问题的关键。纳米氧化硅颗粒尺寸极其细小,隶属纳米范畴。充分发挥纳米氧化硅的尺寸优势,以期纳米氧化硅微粒能够进入红黏土团粒内,抵抗红黏土的失水收缩行为。为此,选用不同干质量掺入比（纳米氧化硅:红黏土分别为0:100、2:100、3.5:100、5:100、6.5:100）,将纳米氧化硅混入红黏土后压实成型（干密度1.44 g/cm3和1.46 g/cm3）。比较压实红黏土-纳米氧化硅混合物的收缩特性与孔隙分布情况。试验发现,纳米氧化硅可以抑制红黏土的收缩行为;而且随着掺入量增加,其缩限值也逐渐提高。红黏土-纳米氧化硅混合物的表观形貌照片显示,纳米氧化硅掺量大于5%时,红黏土团粒内孔隙赋存有大量纳米氧化硅颗粒。同时,孔隙分布曲线还表明,分布于孔径0.03 ?m的孔隙明显减少,说明纳米氧化硅主要充填孔径大于0.03 ?m的孔隙。纳米氧化硅改善红黏土的收缩性属于物理方法,有别于石灰处治等化学方式,更具有环境友好的潜在优势。 相似文献
11.
Field and laboratory investigations of the Triassic Budra Formation of Wadi Budra, south-west Sinai, have demonstrated the existence of surface pedogenic laterites developed within‘overbank facies’of fluviatile sediments during times of hiatus. The laterite profiles, up to 7 m thick, comprise a zone of high-iron concentrations (21.47–73.17%) which includes a concretionary unit and either overlies a zone of slightly mottled host rock or rests directly upon unaltered sandstone; a pallid zone is noticeably absent. The primary depositional horizontal fabric of the finely laminated sediments of the‘overbank facies’ has strongly influenced the final fabric of the laterite. The pronounced alternations of iron-rich pisolitic and iron-deficient laminae highlight the influence of inherent fabric (primary bedding) on pedogenesis. The micromorphology of the laterites is characterized by bimasepic plasmic fabrics, abundant elongate voids partially infilled with cryptocrystalline kaolinite and an abundance of randomly oriented skew planes. Illuviation of clay minerals to considerable depths is evident. Sesquioxidic and kaolinitic glaebules, concentrated within the concretionary units of the laterite have a flattened ellipsoidal shape and occur as both massive and concentrically structural varieties. At Gebel Mussaba Salama to the north, zoned iron mineralization occurs at various levels within the fluviatile sandstones which underlie the‘overbank facies’. This is interpreted as being a non-pedogenic, ground water alteration phenomenon induced by a rising water table within the buried alluvial channels. Iron mineralization, probably records minor fluctuations of the water table during standstill periods. Lateritization in the Triassic Budra Formation provides important evidence that the widely recorded late Triassic lateritization and bauxitization event of the neighbouring East Mediterranean countries, extended south to the continental areas bordering the Tethyan Ocean. 相似文献
12.
Water (in the solid, liquid and vapour state) is one of the main factors that drive construction materials to deterioration. To assess the quality and durability of a repair rendering mortar, thus ensuring its protective function in the masonry structure, it is fundamental to study the behaviour of this mortar towards water. Mortars were elaborated with a calcitic dry hydrated lime, a calcareous aggregate, a pozzolan, a lightweight aggregate, a water-retaining agent and a plasticiser. The effect of different binder-to-aggregate proportions on the mortars’ hygric behaviour was assessed by performing free water absorption and drying, capillary uptake, hydraulic conductivity and water vapour permeability tests. Another aspect that was considered in the assessment of mortar quality was the drying shrinkage that was measured by means of a non-standardised device. It has been found that a larger amount of water is absorbed by mortars with higher lime content, whilst faster drying and higher permeability to water and water vapour are obtained in mortars with higher aggregate content. The hygric behaviour as well as the drying shrinkage of mortars has been interpreted taking into account the differences in microstructure and pore system between mortars. 相似文献
13.
考虑酸浓度和养护时间的影响,通过室内试验对比研究了酸污染红土的颗粒组成、比重和界限含水率等物理特性。研究结果表明:不洗盐、加分散剂,酸浓度较低时粉粒含量减小,酸浓度较高时粉粒含量增大;随养护时间延长,浓度较低时粉粒含量减小,浓度较高时粉粒含量先增后减;洗盐后粉粒含量减小,不加分散剂粉粒含量增大。酸污染红土的比重、液塑限与塑性指数随酸浓度的增大和养护时间的延长总体都呈减小的趋势。酸污染红土物理性质的变化可以从酸污染红土所存在的腐蚀、成盐和溶解三个阶段来解释。 相似文献
14.
In the present work, the relationship between intrinsic factors, mechanical properties and durability of Miocene sandstones used in the architectural heritage of Tunisia, specifically in the Roman aqueduct of Oued Miliane and Uthina site, are studied. The petrographic study and the characterisation of porous network have been carried out using optical microscopy, mercury intrusion porosimetry and laser scanner confocal microscopy (LSCM). The hygric behaviour has also been determined from water absorption under vacuum, drying, capillary water absorption and water vapour permeability. The mechanical properties have been assessed from compressive strength and abrasion tests. Rock durability has been evaluated from salt crystallization (sodium sulphate) accelerated aging tests. The results show good hygric behaviour characterised by a high evaporation rate and almost no retention of water; due to the macroporous character of the rock and the good connectivity of the pore network. Because of the poor lithification, the stone has a very low mechanical strength which makes it very vulnerable to the salt crystallization effects. The absence of chemically unstable minerals preserves the rock from chemical alteration. The durability of the building stone is mainly conditioned by salt loading of the monument. 相似文献
15.
Samples of pyroclastic rocks from Abakaliki area (Nigeria) were subjected to geological and geochemical tests to determine the suitability and durability of the rocks as concrete aggregate. Petrographic analysis shows fine-grained texture and predominance of plagioclase (21–60 %) and shaley-muddy lithic fragment, while geochemical analysis classifies the rocks as alkaline. Analysis indicates that the pyroclastics would likely perform marginally well as concrete aggregates, especially in heavy Portland cement concrete and bituminous concrete. This is due to appreciably high values of natural moisture content, low bulk density, relative density and specific gravity, which suggests low durability, high voids and less aggregate absorption in concrete and bitumen mixes. The rocks are rated as moderate to high strength material on the basis of their unconfined compressive strength values, but are very likely to have low durability as buttressed by poor sulphate soundness test results, probably due to high amount of weak minerals. Analyses reveal that the Abakaliki Pyroclastics are not completely satisfactory as concrete aggregates source, despite their origin, texture, strength and economic availability. Hence, caution is required when they are used in concrete projects. 相似文献
16.
M. D. Gidigasu 《Engineering Geology》1980,15(3-4):173-194
The paper discusses the laboratory and pavement constructional evaluation of residual lateritic gravels over phyllite.
Laboratory classification, compaction and bearing test results indicate that the natural materials are unsuitable by standard gravel acceptance specifications for road base construction. However, the bearing properties can be improved to meet base-material specifications through treatment with about 5% cement. Results of construction control studies also revealed that the laboratory compaction properties of both the raw and cement-stabilised gravels are easily reproduced in the field using fairly light, smooth-wheel rollers. This means that the complaints by contractors of difficulty in achieving design specifications using similar plants during construction is not justified.
Notwithstanding the results of the studies reported herein, it is not possible at the moment to suggest any construction control specifications for these gravels until more data on their in-service performance in the roadway has been collected and analysed over a number of years. 相似文献
17.
以云南红土为研究对象,考虑干湿循环次数、干湿循环幅度等影响因素,利用TSZ-2型全自动三轴仪,开展干湿循环下饱和红土的不排水三轴试验,研究干湿循环作用对饱和红土剪切特性的影响。试验结果表明:不固结不排水条件下,随干湿循环次数增加和干湿循环幅度增大,饱和红土的应变软化现象增强,应力-应变曲线的初始斜率、孔压峰值增大,剪切峰值、峰值轴向应变、黏聚力、内摩擦角减小;干湿循环次数的影响大于干湿循环幅度的影响。干湿循环下饱和红土剪切特性变化的实质在于红土与水之间的相互作用,包括脱湿过程中水的逃逸作用、红土颗粒的吸附作用、红土体的硬化作用及收缩作用和吸湿过程中水的楔入作用、润滑作用、软化作用及红土体的膨胀作用,干湿循环过程中上述作用不断加深加剧,严重损伤了红土体的微结构,最终改变了饱和红土的不排水剪切特性。 相似文献
18.
针对不同加砂比例的云南红土,在相应最优含水率及最大干密度的初始条件下,采用土工试验与相关理论研究相结合的方法,运用Excel分析试验数据,揭示干湿循环作用与加砂红土物理力学特性变化之间的关系。结果表明:在干湿循环过程中,不同加砂比例的红土比重均呈先上升后下降的趋势,干密度均呈上升趋势,抗剪强度及抗剪强度参数均呈下降趋势,并最终都在循环10次左右趋于稳定。在干湿循环次数一定条件下,加砂比例越大的红土,其黏粒降幅越小,粉粒和砂粒增幅也越小,裂隙数量越少,土样越密实。抗剪强度及抗剪强度参数降幅最大的是加砂比例为15%的红土,降幅最小的是加砂比例为10%的红土。 相似文献
19.
20.
This paper is concerned with the mechanical properties of the Great Limestone in northern England. After first outlining the geological structure of the limestone at East Layton in north Yorkshire, the problem of the basal dolomitization of the limestone is introduced and the geochemistry of the rock profile evaluated. It is shown that chemical alteration due to dolomitization is accompanied by a mechanical weakening of the rock and a reduction in the quality of the bond between a tar or bitumen coating medium and the surface of the stone. The two types of rock are compared via specific gravity, moisture absorption, unconfined compressive strength, aggregate impact and aggregate crushing tests. The results from a detailed series of shear box tests taken through from peak to residual shear strength are interpreted through the fundamental strength properties of calcite and dolomite to show that whereas in the size range 200B.S. sieve, dolomite is a little weaker than limestone due to internal weakness associated with volume change; the situation is reversed as the particles decrease in size to form an aggregate of single dolomite crystals which are inherently more resistant to shear. 相似文献