Influence of petrographic characteristics on physico-mechanical properties of ultrabasic rocks from central Greece

Ultrabasic rocks show a variety of engineering properties that may affect quarrying operations, tunnelling, mining, slope stability and the use of rock as a construction material. The physico-mechanical properties are influenced by the mineralogical and textural characteristics as well as the weathering of the rock. For this reason, the relationships between petrographic and physico-mechanical properties of fresh (peridotites) and serpentinized (serpentinites) ultrabasic rocks from central Greece, were investigated using correlation analysis. Thin sections, from the 47 samples, were prepared and examined under the polarizing microscope with the aim of describing the main mineralogical composition, the grain size, the serpentinization percentage and the structure of the rocks. The mineralogical and textural characteristics of some of them were also studied by X-ray diffraction analyses and the scanning electron microscope. The 47 samples were tested to determine dry and saturated unit weight, effective porosity, uniaxial compressive strength and static modulus of elasticity. The relationships between these properties and the petrographic characteristics are described by simple regression analyses. The research demonstrates that the physico-mechanical characteristics are strongly influenced by the petrographic characteristics except for mineral grain size. Negative linear correlations exist between serpentinization percentage and dry unit weight, while the effective porosity has a strong positive relationship with degree of serpentinization. Positive relationships are also obtained between the mechanical properties and dry unit weight and micropetrographic index I _ps, while the increase of effective porosity causes a decrease in the index I _ps (logarithmically in peridotites, and exponentially in serpentinites). The mechanical properties are exponentially related (negatively) to the serpentinization percentage in serpentinites and logarithmically (negatively) in peridotites. The serpentine plays a very important role in strength and elasticity modulus reduction, while the primary minerals have a smaller effect on the mechanical properties.     

Determination of the thermal conductivity from physico-mechanical properties

Samples of limestone, dolomite, dolomitic limestone, marble, travertine, sandstone, siltstone, andesite, basalt and porous basalt from different parts of Turkey were tested to obtain their UCS, porosity, water absorption, density, P-wave velocity and thermal conductivity (TC). It was observed that while TC increased with density, P-wave velocity and UCS, it decreased with increasing porosity. Equations are presented to allow an assessment of TC from these physico-mechanical properties.      

酸性溶液浸泡下原状黄土物理力学特性试验研究

黄土中存在大量碳酸钙胶结物,该胶结物对黄土力学性状的影响很大。采用浓度为0.1,1和2 mol/L的盐酸溶液,开展了原状黄土试样的浸泡试验,测定了不同时间浸泡溶液中钙离子的浓度,开展了经不同时间浸泡土样的颗粒分析试验、固结试验及剪切试验,分析了酸性溶液浸泡下原状黄土力学特性及其变化规律。试验表明：黄土中胶结物主要是以粒径小于0.01 mm的颗粒存在,在酸性溶液浸泡作用下,土中钙质胶结物逐渐被溶蚀,试样中细小颗粒逐渐减少,尤其是颗粒直径小于0.005 mm的含量明显减少,浸泡液酸性越强,土体中钙质胶结物溶蚀的速度越快并且溶蚀得越充分。胶结物在土体中的作用主要是连接骨架颗粒,因此,胶结物对土体的黏聚力影响较大,而土体内摩擦角受胶结物溶蚀的影响不明显。经盐酸溶液浸泡后,试样的黏聚力随浸泡时间延长持续降低,浸泡60 d后,土体的黏聚力逐步趋于稳定。经0.1,1,2 mol/L盐酸溶液浸泡120 d后,试样的黏聚力分别降低约47%,63%,87%,且呈现出浸泡液酸性越强,黏聚力减少越多的情形。胶结物的溶蚀引起土体孔隙增加,压缩系数增大。随着胶结物的减少,土体的快剪应力-应变关系逐渐由应变硬化型向应变软化型转变。     

Effect of pH on the physico-mechanical properties of marble

The physico-mechanical properties of rocks are important parameters in the planning and design of mining and civil constructional works. These properties are adversely affected by acidic and alkaline environments. In the present study, marble rock specimens were tested in the laboratory after treatment with different pH solutions for 15 h. The physico-mechanical properties of the marble were determined in both acidic and alkaline conditions. The study revealed that the strength properties are higher at pH 7 and lower in acidic and alkaline conditions. The strength reduction in acidic conditions is greater than that in the alkaline conditions.      

Predicting the physico-mechanical properties of rocks from electrical impedance spectroscopy measurements

Electrical resistivity values of eight different samples cored from a fault breccia were measured using an impedance analyser. The uniaxial compressive strength, elastic modulus, point load strength, Schmidt hammer value, P-wave velocity, density and porosity values of the samples were determined in the laboratory. Electrical resistivity values were correlated with the corresponding physico-mechanical properties using the method of least-squares regression and the derived equations were checked by the t and F-test. A strong logarithmic relation between uniaxial compressive strength and resistivity was found. The relation between elastic modulus and resistivity is significant and follows a logarithmic function. Density was linearly, and porosity was exponentially correlated with resistivity.It may be concluded that electrical resistivity can be used as a representative measure of rock properties, particularly for characterizing rocks for which regularly shaped specimen are difficult to obtain. However, the effect of different rock types on the correlations must be further investigated. Additionally, the effect of certain minerals on the rock's resistivity must be taken into account, especially when testing dry or partially saturated rocks.     

Correlations between petrographic and geometrical properties of ophiolitic aggregates from Greece

The study investigated the influence of petrographic characteristics on the geometrical properties of ultrabasic and basic ophiolitic aggregates from Greece. Quantitative petrographic analysis indicates that the studied lithologies display various percentages of secondary mineral phases. Statistical analyses indicate that the geometrical characteristics of ultrabasic rocks tend to improve as the micropetrographic index I _rep , the degree of serpentinisation, the ratio of soft to hard minerals and the ratio of secondary to primary minerals decrease. The aggregate particles of the basic lithotypes tend to be more elongated and flaky when the ratio of soft to hard minerals increases. The higher flakiness and elongation index values of the ultrabasic samples are attributed to the high percentage of serpentine, the local preferred orientation of the olivine grains and the existence of oriented transgranular microcracks.     

Effect of freezing-thawing on the physico-mechanical properties of a Morianic clayey loam

Laboratory-derived dependencies of the change in grain-size distribution, water properties, density, and equivalent cohesion of frozen morainic clayey loam on the number of freeze-thaw cycles are presented.     

Prediction of strength properties of some schistose rocks from petrographic properties using artificial neural networks

Petrographic features of a rock are intrinsic properties, which control the mechanical behaviour of the rock mass at the fundamental level. This paper deals with the application of neural networks for the prediction of uniaxial compressive strength, tensile strength and axial point load strength simultaneously from the mineral composition and textural properties. Statistical analysis has also been conducted for prediction of the same strength properties and compared with the predicted values by neural networks to investigate the authenticity of this approach. The network was trained to predict the uniaxial compressive strength, tensile strength and axial point load strength from the mineralogical composition, grain size, aspect ratio, form factor, area weighting and orientation of foliation planes (planes of weakness). A data set having 112 test results of the four schistose rocks were used to train the network with the back-propagation learning algorithm. Another data set of 28 test results of the four schistose rocks were used to validate the generalization and prediction capabilities of the network.     

Effect of elevated temperature on physico-mechanical properties of blended cement concrete

Pozzolanas are readily available for use in concrete in the local markets for strength and/or durability enhancement. Although safety and security against disasters are not new, they still presuming a challenge. For instance, the fire resistive properties of concrete are of prime interest.Through this work, the effect of different kinds of pozzolana on the fire resistive properties of concrete was studied. Four types of pozzolana were incorporated into the concrete mixtures, i.e. metakaolin (MK), silica fume (SF), fly ash (FA), and ground granulated blast furnace slag (GGBS). Each of the employed pozzolana was used in two ratios: 10% and 20%, either in the form of cement replacement or as an addition without affecting the cement content. A total of 17 mixes were cast.For all mixtures, compressive strength is evaluated after 28 days of water curing. The mixtures’ compressive strengths were also evaluated after exposure to elevated temperatures: 200 °C, 400 °C, 600 °C, and 800 °C. The residual compressive strengths after heat exposure are evaluated. The formed cementitious phases after incorporation of pozzolana and the heat-induced transformations are investigated via the X-ray diffraction technique (XRD).Test results demonstrate the impact of each type of the employed pozzolana on the heat resistive properties of concrete in addition to their influence on the strength development of the investigated mixes. Therefore, a decision could be made regarding optimizing the benefits specific to each type of pozzolana and their employment method.     

Variation on physico-mechanical properties of Kota stone under different watery environments

The physico-mechanical properties of rocks play an important role in planning and designing of civil constructional works. These properties are adversely affected by acidic and alkaline environments, where they are exposed for a longer time. The natural forces and agents of weathering have degrading effect on the appearance and structural soundness of Kota stone. These agents include rain, temperature, wind and atmospheric pollutants. Weathering agents almost never work individually or in isolation, they always act in combination with one another or with other agents of deterioration.

The durability of building stones is primarily judged by its reactivity with acidic and basic water of different pH values. The conditions are very obvious in any of the large scale construction and use of building stone like sandstones and Kota stones. During the mining of carbonate hosted mineral deposits, the interaction of ground water with ore minerals affect the surrounding environment and rock types. This may cause problem in exploitation of minerals and may cause failure of slope or pillars. To avoid such problems, the prior study of effect of ground water charged with ions released from ore minerals on carbonate rock is important.

In this paper, an attempt has been made to see the variation in the physico-mechanical properties of Kota stone under different watery environment. In the present study, the NX size cylindrical cores were prepared with the help of diamond core drilling machine as per ISRM standard. For each mechanical property, eight samples were prepared and tested. The prepared samples were put into the oven for 24 h at 104 °C to eliminate the moisture present and later submerged in to the water having different pH values ranging from nearly 0.89–12 for 24 h under stirring mode till it gets full saturation at room temperature. The study reveals that there is prominent change in strength properties under acidic and alkaline environments. Rock is considered as a neutral substance so at pH 7, Kota stone shows maximum strength due to non-reactive nature of the solution. Majority of rock mass is not neutral but some of the rock mass shows very minor changes in its strength. The chemical composition of the rock mass dominates the reaction process when it is submerged in varying pH solution.     

Characteristics of the composition,structure, and physico-mechanical properties of permafrost rock soil in massifs

Investigations of the composition, structure, and physico-mechanical properties of permafrost rock soil in massifs are codified. Tables are presented for characteristics of frozen and thawed rock soils, and are compared with the deformability, strength, and other characteristics of frozen rock soils on the basis of investigations on specific projects. It is demonstrated that after thawing, strong permafrost rocks are frequently transformed into weak saturated soils.     

Effect of the treatment of wood shavings on the physico-mechanical characteristics of wood sand concretes

This study investigates the effect of a wood shaving treatment on the physico-mechanical characteristics of wood sand concretes. The two main objectives of this work are to improve a lightweight sand concrete and to valorise local materials and industrial wastes. Three wood shaving contents, two types of sand concretes (dune and river sand concrete) and a preliminary wood shaving treatment have been used. Sand, cement, filler, admixture and water composed the sand concrete matrix. The shaving treatment appreciably increases the mechanical strength of the studied composites without a large influence on thermal conductivity. The shrinkage of the composite is considerably reduced and the wood–matrix adherence is improved. At low wood contents, the dune sand concrete remains always slightly more insulating and less strong than the river sand concrete. At higher wood contents, the two concretes present almost similar properties.     

Hybrid effect of carbon nanotube and nano-clay on physico-mechanical properties of cement mortar

In this work, several nanomaterials have been used in cementitious matrices: multi wall carbon nanotubes (MWCNTs) and nano-clays. The physico-mechanical behavior of these nanomaterials and ordinary Portland cement (OPC) was studied. The nano-clay used in this investigation was nano-kaolin. The metakaolin was prepared by thermal activation of nano-kaolin clay at 750 °C for 2 h. The organic ammonium chloride was used to aid in the exfoliation of the clay platelets. The blended cement used in this investigation consists of ordinary Portland cement, carbon nanotubes and exfoliated nano metakaolin. The OPC was substituted by 6 wt.% of cement by nano metakaolin (NMK) and the carbon nanotube was added by ratios of 0.005, 0.02, 0.05 and 0.1 wt.% of cement. The blended cement: sand ratio used in this investigation was 1:2 wt.%. The blended cement mortar was prepared using water/binder ratio of 0.5 wt.% of cement. The fresh mortar pastes were first cured at 100% relative humidity for 24 h and then cured in water for 28 days. Compressive strength, phase composition and microstructure of blended cement were investigated. The results showed that, the replacement of OPC by 6 wt.% NMK increases the compressive strength of blended mortar by 18% compared to control mix and the combination of 6 wt.% NMK and 0.02 wt.% CNTs increased the compressive strength by 29% than control.     

云南个旧锡矿花岗岩地球化学特征及构造环境研究

文章通过对个旧锡矿西区贾沙二长花岗岩和东区老卡花岗岩地球化学特征的对比研究分析表明,前者Al₂O₃、TFe、K₂O、Na₂O的含量略高,后者SiO₂、TiO₂、CaO的含量略高;两者均具富集Cs、Rb、Th、U、Pb而亏损Ba、Sr等大离子亲石元素的特征,高场强元素分异明显;前者稀土总量、轻稀土含量和δEu值均高于后者,后者重稀土的含量明显高于前者。从个旧地区花岗岩的形成环境来看,该区花岗岩从西到东,从北到南具有从燕山期碰撞造山晚期逐渐过渡到碰撞造山期后的演化趋势,暗示岩浆期后气成成矿流体和盆地流体最终在个旧东区南部集中,成矿可能具有一定的方向性,该区可能为今后的重点找矿区域。     

西藏打加错东I型花岗岩的地球化学特征及构造意义

打加错东岩体位于冈底斯—下察隅晚燕山—喜马拉雅期岩浆弧南亚带,侵入岩广泛分布,年龄介于56-65Ma,属于始新世。打加错东岩体具有钙碱性-高钾钙碱性、过铝质,SiO_2含量为65. 49%~70. 32%,K_2O/Na_2O1,碱度率AR数值为2. 02~2. 73,铝饱和指数A/CNK值介于0. 80~1. 08之间,A/NK值介于1. 34~1. 72之间。微量元素整体较为亏损,稀土元素总量总体偏低,显示轻稀土富集、重稀土弱亏损的特征。本文研究认为打加错东始新世侵入岩来源于基性岩部分熔融,同时有部分壳源成份夹物,构造环境为火山弧环境,同时向碰撞环境过渡,具有双重性特点。它们的形成与喜马拉雅时期,雅鲁藏布江洋块继续向北俯冲有关,形成打加错东地区规模最为强烈的岩浆活动。     

A new method to test rock abrasiveness based on physico-mechanical and structural properties of rocks

A new method to test rock abrasiveness is proposed based upon the dependence of rock abrasiveness on their structural and physico-mechanical properties. The article describes the procedure of presentation of properties that govern rock abrasiveness on a canonical scale by dimensionless components, and the integrated estimation of the properties by a generalized index. The obtained results are compared with the known classifications of rock abrasiveness.