Artificial neural networks and nonlinear regression techniques to assess the influence of slake durability cycles on the prediction of uniaxial compressive strength and modulus of elasticity for carbonate rocks

Understanding rock material characterizations and solving relevant problems are quite difficult tasks because of their complex behavior, which sometimes cannot be identified without intelligent, numerical, and analytical approaches. Because of that, some prediction techniques, like artificial neural networks (ANN) and nonlinear regression techniques, can be utilized to solve those problems. The purpose of this study is to examine the effects of the cycling integer of slake durability index test on intact rock behavior and estimate some rock properties, such as uniaxial compressive strength (UCS) and modulus of elasticity (E) from known rock index parameters using ANN and various regression techniques. Further, new performance index (PI) and degree of consistency (Cd) are introduced to examine the accuracy of generated models. For these purposes, intact rock dataset is established by performing rock tests including uniaxial compressive strength, modulus of elasticity, Schmidt hammer, effective porosity, dry unit weight, p‐wave velocity, and slake durability index tests on selected carbonate rocks. Afterward, the models are developed using ANN and nonlinear regression techniques. The concluding remark given is that four‐cycle slake durability index (I_d4) provides more accurate results to evaluate material characterization of carbonate rocks, and it is one of the reliable input variables to estimate UCS and E of carbonate rocks; introduced performance indices, both PI and Cd, may be accepted as good indicators to assess the accuracy of the complex models, and further, the ANN models have more prediction capability than the regression techniques to estimate relevant rock properties. Copyright © 2011 John Wiley & Sons, Ltd.     

An investigation of the relationship between uniaxial compressive strength and degradation for selected rock types

The relationship between uniaxial compressive strength and degradation was investigated for selected rock types, by using regression analyses to determine whether degradation was a useful predictor of compressive strength. In addition, the effects of aggregate particle size, number of hammer blows during the degradation test, engineering index properties, petrographic characteristics, and water saturation on the compressive strength-degradation relationship were evaluated. The results show that strong inverse relationships exist between compressive strength and degradation (measured on a 9.5-4.75-mm size aggregate) for sandstones and igneous/metamorphic rocks, but that no significant relationship exists for limestones/dolomites. The results also indicate a strong positive correlation between degradation and L.A. abrasion loss and can be used to establish a limit of allowable degradation for practical applications. Engineering index properties do not significantly affect the relationship between compressive strength and degradation but petrographic characteristics are important in explaining the strength and degradation behavior of the rocks studied. Water saturation decreases compressive strength and increases degradation to varying degrees.     

The effect of pH of water and mineralogical properties on the slake durability (degradability) of different rocks from the Lesser Himalaya, India

Slake durability is an important geotechnical parameter and is a measure of degradability of rocks due to the process of mechanical and chemical breakdown. It is closely related to the mineralogical composition and the texture of the rocks. In this paper, mineralogical examination along with slake durability tests under variable pH conditions, both in acidic and alkaline environments, on the limestone, shale and siltsone were evaluated to understand the relationship between mineralogy and the degradability of rocks. The study revealed that rocks rich in calcium carbonate and or magnesium carbonate are adversely affected in the acidic environment, whereas, the rocks rich in quartz, feldspar and muscovite are independent of the pH of the slaking fluid, which in turn, is more influenced by the texture of the constituent minerals. It has also been observed that fine grained rocks are more susceptible to degrade in comparison to the coarse grained rocks.     

Weathering effects on the strength and deformational behaviour of crystalline rocks under uniaxial compression state

Uniaxial compression tests were performed on different categories of weathering of three lithological units: Malanjkhand granite; Nagpur basalt; and Delhi quartzite, occurring in central and northern parts of India. The deformational behaviour is studied in terms of variation in tangent modulus (E_t50) and initial modulus (E_i) due to weathering. The power relationship between uniaxial compressive strength (σ_c) and E_t50 shows strong correspondence for weathering sequence of common rock types. This relationship has been established by regression analysis and significant correlation parameter (coefficient of determination, r²=0.87) for crystalline rocks. It is shown that there is a systematic decrease in stiffness ratio, that is, ratio of tangent modulus and uniaxial compressive strength with increased weathering state. Comparison of E_t50 and E_i values has shown that E_t50 decreases more gradually than E_i, and reduction is more drastic for E_i values with an increased degree of weathering in all the three rock types. The mode of failure has been found to be influenced by weathering extent in rocks. A brief account is given of the intrinsic characteristics of fresh and weathered rocks and mineralogical changes produced by weathering investigated quantitatively. Correlation drawn between the petrographical and mechanical indices has shown that mechanical properties are apparently dependent on the intrinsic characteristics of weathered rocks.     

冻融循环对二灰和改性聚乙烯醇固化盐渍土力学性能的影响

随季节性变化的冻融循环作用对土体结构有显著的影响。为降低盐渍土对环境温度的敏感性并将其应用于工程中,提出以石灰、粉煤灰和改性聚乙烯醇(MPA)为固化材料的联合固化方法。先通过无侧限抗压强度(UCS)和微观扫描试验评价固化效果,构建固化材料的参数范围,再将抗剪强度(黏聚力和内摩擦角)与正交试验相结合,分析各因素的影响,明确最佳组合参数。结果表明:石灰+粉煤灰+MPA联合固化有助于提高盐渍土的强度,联合固化盐渍土的UCS为1 130.25 kPa,是盐渍土(218 k Pa)的5.18倍;联合固化盐渍土的冻融强度满足工程规范(JTG 3430-2020)要求。冻融循环作用下联合固化盐渍土的UCS稳定值为700k Pa,且3次循环后的波动范围在5%左右。适宜配比下联合固化盐渍土的抗剪强度(黏聚力和内摩擦角)在3次冻融循环后为208.2 kPa和38.56°。各因素的敏感性由高到低依次为养护时间、石灰掺量、MPA掺量、干密度、含盐量和冻融循环次数,随石灰、粉煤灰和MPA掺量的增加,联合固化盐渍土强度增大并趋于稳定,固化参数的优化可有效弱化冻融作用对滨海盐渍土的影响。结合抗压及抗剪强度试验结果,...     

新疆中天山南缘乌瓦门地区蛇绿岩中超镁铁岩的成因:来自岩石矿物学和地球化学的证据

本文对新疆中天山南缘乌瓦门蛇绿混杂岩中的超镁铁岩进行了岩石矿物学和地球化学研究,对其成因和形成环境进行限定。乌瓦门蛇绿混杂岩中的超镁铁岩为蛇纹石化二辉橄榄岩,由橄榄石(Fo=89.1~90.6)、斜方辉石(Wo0.4-2.4En87.2~90.7Fs8.9-10.9;Mg#=89.0~91.0)、单斜辉石(Wo49.1-51.3En16.0~48.4Fs0.9-4.3;Mg#=90.2~92.1)和尖晶石(Mg#=71.8~77.5;Cr#=9.3~13.4)组成。主量元素组成上,以低Mg O(37.74%~41.34%)、高Al2O3(2.58%~3.39%)、高Ca O(2.23%~3.68%)和高Ti O2(0.05%~0.11%)为特征。微量元素上,亏损稀土元素(REE总量为1.73×10-6~4.63×10-6),亏损不相容元素(如,Rb=0.4×10-6~1.39×10-6,Zr=0.73×10-6~3.28×10-6,Hf=0.04×10-6~0.11×10-6),富集相容元素(如,Cr=2516×10-6~2793×10-6,Co=84.6×10-6~119×10-6,Ni=1641×10-6~2261×10-6)。矿物学和地球化学特征一致指示,乌瓦门蛇绿混杂岩中的超镁铁岩为经历过低程度(5%~10%)部分熔融作用的残余地幔橄榄岩,形成于洋中脊环境,是MOR型蛇绿岩中的地幔橄榄岩。     

The influence of foliation on the fragility of granitic rocks, image analysis and quantitative microscopy

Fabric-dependent anisotropy is important in understanding the mechanical behaviour of foliated rocks because the foliation creates mechanically weak discontinuities. Using optical microscopy, a foliation index (FIX) was calculated for a group of granitic rocks in southern Sweden that displays a range of textures from foliated to nonfoliated. Image analysis from scanning electron microscope with backscattered detector (SEM/BSE) images was used in order to measure the rock texture of these samples. The analyses were compared with the Los Angeles (LA) test, which measures resistance of rock aggregate to fragmentation. The results demonstrate that the measured grain size, shape and spatial arrangement are important parameters controlling the fragility of the rock. Both the texture and foliation must be taken into account to obtain a significant relationship with the mechanical analyses. We suggest that this alternative method could be a helpful tool for predicting a rock's suitability as an aggregate as it gives a better understanding of the material properties compared to mechanical testing.     

西藏雅鲁藏布缝合带三叠系朗杰学群沉积岩古生物、地球化学特征及其物源区和构造背景分析

随着近年来对朗杰学群的解体,发现前人对于朗杰学群、涅如组、修康群及洛林岩群的研究存在混淆,研究对象是否为朗杰学群应重新审慎,同时,几者是否为同一构造背景产物仍存在较大争议。本文对朗杰学群命名地(贡嘎县姐德秀镇-朗杰学乡一带)的朗杰学群重矿物特征、地球化学特征及古生物化石进行了研究。朗杰学群砂岩主量元素和微量元素化学成分低于地壳克拉克值,SiO₂含量平均为74.14%,K₂O/Na₂O值平均为0.70,反映砂岩成熟度较低,没有经历明显的成岩后生改造;化学蚀变指数(CIA)较集中,平均为71.55,属低级-中等风化程度,指示气候和构造环境都处于相对稳定状态;古环境分析显示,100Mg/Al₂O₃值平均为7.85,CaO/Fe+CaO值平均为0.314,表明朗杰学群形成于中等盐度的深水厌氧环境,且由北向南沉积水体逐渐加深;重矿物以锆石为主,其次为金红石,分选磨圆较差,ATi指数为93.3～98.97,ZTR指数为48.01～85.75,反映朗杰学群物源区的火山岩较为丰富,且搬运距离较...     

湖南城步火成岩锆石SHRIMP U-Pb年龄及其对江南造山带新元古代构造演化的约束

目前对新元古代中期江南造山带构造演化及钦杭结合带南西段构造性质存在不同认识。本文对湘西南城步地区新元古代火山岩和花岗岩进行了锆石SHRIMPU-Pb年龄测定并厘定其构造环境,从而为区域构造演化提供了约束。城步新元古代花岗岩侵入于云场里组变质火山-沉积地层中。云场里组变质火山岩与花岗岩的锆石SHRIMPU-Pb年龄分别为828±10Ma和805.7±9.2Ma。构造环境的地球化学判别图解表明花岗岩形成于岛弧环境;区域地质背景指示云场里组可能形成于活动陆缘弧前盆地。以城步火山岩和花岗岩研究为基础,结合区域地质资料,提出新元古代中期江南造山带西段构造演化过程:872～835Ma期间为陆缘盆地;835～820Ma期间俯冲造山,江南造山带形成基性—超基性岩和早阶段岛弧花岗闪长岩,东侧的城步地区为弧前盆地;820～810Ma期间江南造山带发生弧-陆碰撞;810～800Ma期间江南造山带进入后碰撞环境并形成晚阶段强过铝(黑云母)花岗岩,东侧城步地区因华南洋洋壳俯冲而形成新的岛弧;800Ma后华南进入伸展裂陷盆地演化阶段。上述认识揭示出扬子陆块东南缘的连续岛弧增生过程,同时为钦杭结合带南西段雪峰期"残留洋盆"属性提供了新证据。     

安徽铜陵中生代侵入岩地质地球化学特征再认识及成因讨论

安徽铜陵地区是我国最著名的铜多金属矿产地,岩浆岩出露广泛,岩浆作用与成矿关系密切.作者广泛收集了前人对铜陵地区中生代岩浆岩的研究资料和成果,并在此基础上进行了仔细的岩相学观察和深入的岩石学、岩石化学和微量元素及同位素地球化学研究,系统总结了该区中生代侵入岩的地质地球化学特征,并探讨了其成因机制.研究认为:①铜陵地区中酸性侵入岩形成于晚侏罗世-早白垩世(135 ～ 147Ma),岩浆活动持续时间大约为10～15Ma;岩体沿近东西向深断裂呈带状分布,浅成侵入产出,受多期不同方向和性质的断裂控制.②依据Q-A-P图解确定区内侵入岩主要为辉石闪长岩、石英(二长)闪长岩和花岗闪长岩3类中酸性闪长质岩石,均属亚碱性高钾钙碱性系列.③3类侵入岩具有相似的微量元素、稀土元素和Pb-Sr-Nd-O同位素地球化学特征,反映原始岩浆起源于富集岩石圈地幔,受到壳源物质的混染.④3类侵入岩可能是地壳深部带状岩浆房不同岩浆层中的岩浆与构造运动诱发的深断裂相沟通并随机地上升、脉动式侵位形成的;深部岩浆房中的带状岩浆层可能是由于温度梯度引起扩散对流作用进而发生一定程度的熔离分异作用所致;岩浆演化过程中存在镁铁矿物及磷灰石和锆石等矿物的结晶分异作用.⑤铜陵地区中生代岩浆活动的大地构造背景是大陆板块内部,岩浆作用与晚侏罗纪古太平洋板块的俯冲作用密切相关,但同时受区域前中生代基底构造的制约;侵入岩原始岩浆起源于挤压向拉张转换的动力学背景下的岩石圈地幔加厚之后的减压熔融并底侵下地壳岩石.     

Concentration and association of minor and trace elements in Mukah coal from Sarawak, Malaysia, with emphasis on the potentially hazardous trace elements

The ash yield and concentrations of twenty-four minor and trace elements, including twelve potentially hazardous trace elements were determined in Mukah coal from Sarawak, Malaysia. Comparisons made to the Clarke values show that Mukah coal is depleted in Ag, Ba, Be, Cd, Co, Mn, Ni, Se, U, and V. On the other hand, it is enriched in As, Cr, Cu, Pb, Sb, Th, and Zn. Among the trace elements studied, V and Ba are associated predominantly with the clay minerals. Manganese, Cr, Cu, Th, and Ni are mostly bound within the aluminosilicate, sulphide and/or carbonate minerals in varying proportions, though a portion of these elements are also organically bound. Arsenic, Pb and Sb are mostly organically bound, though some of these elements are also associated with the sulphide minerals. Zinc is associated with both the organic and inorganic contents of the coal. Among the potentially hazardous trace elements, Be, Cd, Co, Mn, Ni, Se, and U may be of little or no health and environmental concerns, whereas As, Cr, Pb, Sb and Th require further examination for their potential health and environmental concerns. Of particular concern are the elements As, Pb and Sb, which are mostly organically bound and hence cannot be removed by physical cleaning technologies. They escape during coal combustion, either released as vapours to the atmosphere or are adsorbed onto the fine fly ash particles.     

Geochemistry and zircon U-Pb ages of adakitic rocks from the Dulan area of the North Qaidam UHP terrane, north Tibet: Constraints on the timing and nature of regional tectonothermal events associated with collisional orogeny

Geochemistry and U-Pb ages of leucosomes and tonalites in a high pressure granulite unit of the Dulan area have been determined to constrain the tectonothermal evolution related to collision and thickening of lower crust in the North Qaidam Mountains (NQD). Leucosomes and tonalites show a marked chemical resemblance to adakites: (1) high La/Yb and Sr/Y, and low Y and HREE; (2) high Al₂O₃ and low Mg^# values with obvious positive Eu anomalies; and (3) slightly positive ε_Nd(t) values. Zircon U-Pb analysis of leucosomes and tonalites yielded ²⁰⁶Pb/²³⁸U ages of 428-437 Ma and 436-437 Ma respectively, which constrain the emplacement ages of the adakitic rocks. Petrological, geochronological and geochemical characters indicate that the adakitic rocks may have been derived from partial melting of a thickened mafic lower crust (> 50 km), suggesting a dominating source regime of synchronous high-pressure mafic granulites. Contemporary magmatism in other units of the NQD shows evidence of a widespread tectonothermal event during early Silurian (420-450 Ma) that includes metamorphism, magmatism and anatexis related to collision and thickening of lower crust.