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21.
REE mineralization in the carbonatites of the sung valley ultramafic-alkaline-carbonatite complex,Meghalaya, India 总被引：1，自引：0，他引：1
The Early Cretaceous Sung Valley Ultramafic-Alkaline-Carbonatite (SUAC) complex intruded the Proterozoic Shillong Group of rocks and located in the East Khasi Hills and West Jaintia Hills districts of Meghalaya. The SUAC complex is a bowl-shaped depression covering an area of about 26 km2 and is comprised serpentinised peridotite forming the core of the complex with pyroxenite rim. Alkaline rocks are dominantly ijolite and nepheline syenite, occur as ring-shaped bodies as well as dykes. Carbonatites are, the youngest intrusive phase in the complex, where they form oval-shaped bodies, small dykes and veins. During the course of large scale mapping in parts of the Sung Valley complex, eleven carbonatite bodies were delineated. These isolated carbonatite bodies have a general NW-SE and E-W trend and vary from 20–125 m long and 10–40 m wide. Calcite carbonatite is the dominant variety and comprises minor dolomite and apatite and accessory olivine, magnetite, pyrochlore and phlogopite. The REE-bearing minerals identified in the Sung Valley carbonatites are bastnäsite-(Ce), ancylite-(Ce), belovite-(Ce), britholite-(Ce) and pyrochlore that are associated with calcite and apatite. The presence of REE carbonates and phosphates associated with REE-Nb bearing pyrochlore enhances the economic potential of the Sung Valley carbonatites. Trace-element geochemistry also reveals an enrichment of LREEs in the carbonatites and average ΣREE value of 0.102% in 26 bed rock samples. Channel samples shows average ΣREE values of 0.103 wt%. Moreover, few samples from carbonatite bodies has indicated relatively higher values for Sn, Hf, Ta and U. Since the present study focuses surface evaluation of REE, therefore, detailed subsurface exploration will be of immense help to determine the REE and other associated mineralization of the Sung Valley carbonatite prospect. 相似文献
22.
The Effect of Specimen Size on Strength and Other Properties in Laboratory Testing of Rock and Rock-Like Cementitious Brittle Materials 总被引：1，自引：0，他引：1
William?J.?DarlingtonEmail author Pathegama?G.?Ranjith S.?K.?Choi 《Rock Mechanics and Rock Engineering》2011,44(5):513-529
The effect of specimen size on the measured unconfined compressive strength and other mechanical properties has been studied
by numerous researchers in the past, although much of this work has been based on specimens of non-standard dimensions and
shapes, and over a limited size range. A review of the published literature was completed concentrating on the presentation
of research pertaining to right cylindrical specimens with height:diameter ratios of 2:1. Additionally, new data has been
presented considering high strength (70 MPa) cement mortar specimens of various diameters ranging from 63 to 300 mm which
were tested to failure. Currently, several models exist in the published literature that seek to predict the strength–size
relationship in rock or cementitious materials. Modelling the reviewed datasets, statistical analysis was used to help establish
which of these models best represents the empirical evidence. The findings presented here suggest that over the range of specimen
sizes explored, the MFSL (Carpinteri et al. in Mater Struct 28:311–317, 1995) model most closely predicts the strength–size relationship in rock and cementitious materials, and that a majority of the
empirical evidence supports an asymptotic value in strength at large specimen diameters. Furthermore, the MFSL relationship
is not only able to model monotonically decreasing strength–size relationships but is also equally applicable to monotonically
increasing relationships, which although shown to be rare do for example exist in rocks with fractal distributions of hard
particles. 相似文献
23.
K.M.A.S.Bandara P.G.Ranjith T.D.Rathnaweera W.A.M.Wanniarachchi S.Q.Yang 《地学前缘(英文版)》2021,12(6):376-393
Crushing and embedment are two critical downhole proppant degradation mechanisms that lead to a significant drop in production outputs in unconventional oil/gas stimulation projects.These persistent production drops due to the non-linear responses of proppants under reservoir conditions put the future utilization of such advanced stimulation techniques in unconventional energy extraction in doubt.The aim of this study is to address these issues by conducting a comprehensive experimental approach.According to the results,whatever the type of proppant,all proppant packs tend to undergo significant plastic deformation under the first loading cycle.Moreover,the utilization of ceramic proppants(which retain proppant pack porosity up to 75％),larger proppant sizes(which retain proppant pack porosity up to 15.2％)and higher proppant concentrations(which retain proppant pack porosity up to 29.5％)in the fracturing stimulations with higher in-situ stresses are recommended to de-escalate the critical consequences of crushing associated issues.Similarly,the selection of resin-coated proppants over ceramic and sand proppants may benefit in terms of obtaining reduced proppant embedment.In addition,selection of smaller proppant sizes and higher proppant concentrations are suggested for stimulation projects at depth with sedimentary formations and lower in-situ stresses where proppant embedment pre-dominates.Furthermore,correlation between proppant embedment with repetitive loading cycles was studied.Importantly,microstructural analysis of the proppant-embedded siltstone rock samples revealed that the initiation of secondary induced fractures.Finally,the findings of this study can greatly contribute to accurately select optimum proppant properties(proppant type,size and concentration)depending on the oil/gas reservoir char-acteristics to minimize proppant crushing and embedment effects. 相似文献
24.
Xu Jiang Dai Guoliang Gong Weiming Zhang Qi Haque Asadul Gamage Ranjith Pathegama 《Acta Geotechnica》2021,16(3):653-677
Acta Geotechnica - Shaft resistance generally dominates at the service loads of rock-socketed piles and therefore is always a topic of large research interest. This paper reviews the research... 相似文献
25.
26.
Manukonda Suresh Kumar Ashitha Gopinath Nenthramkunnath Ranjith Safar Ummar Puthiya Veetil Nidheesh 《洁净——土壤、空气、水》2023,51(3):2100169
The integrated steel industry is considered as one of the important industrial sectors, and its outputs are inputs for other sectors including construction, engineering, medical and scientific equipment, and defence. Massive production, consumption, and export of steel signify a country's economic index. This review outlines the World's steel production quantities, the processes involved, and wastewater generation from the industry and its treatment. Wastewater generated from steel plants is highly complex and requires intensive treatment before discharge into natural water bodies. Technologies adopted for treating wastewater generated from steel industries are deliberated, focusing on coking wastewater treatment. Microbial mediated processes provide an effective means of degrading the contaminants, but the toxicity of certain compounds during higher pollutant load inhibits its further treatment. However, these processes can be integrated with either electrochemical technologies or advanced oxidation processes (AOPs), which can reduce the toxicity level. Hence, when a highly concentrated and complex mixture of contaminants is considered, an integrated approach is a resourceful option in terms of cost-effectiveness and treatment efficiency. 相似文献
27.
An experimental study of single and two-phase fluid flow through fractured granite specimens 总被引：3，自引：2，他引：1
P. G. Ranjith 《Environmental Earth Sciences》2010,59(7):1389-1395
Triaxial tests on the two-phase flow of air and water through fractured granite specimens were performed to discover whether
the two-phase fluid flow within rock fractures was laminar or turbulent. The two-phase flow characterization was carried out
based on the macroscopic two-phase steady state flow model and the homogeneous steady state flow model. Rock specimens with
a single natural fracture (joint roughness coefficient, JRC < 10) were tested using two-phase, high pressure triaxial rig.
Experimental results show that the estimated Reynolds numbers for various inlet fluid pressures are well below 1000. The findings
of this study reveal that both single and two-phase flow through rock fractures (JRC < 10) can be characterized as laminar
flows at moderate inlet fluid pressures. However, for single-phase air flow, an increase in inlet air pressures may result
in the formation of turbulent flow. 相似文献
28.
Like any other coal, the highly heterogeneous nature of brown coal can sometimes make it difficult to interpret the results
of laboratory experiments. More homogeneous samples with properties reproducible in the laboratory would provide significant
advantage, especially in understanding the effects of various factors in the properties of coal. An attempt was made to develop
reconstituted coal (RC) samples in the laboratory through an extensive material development and laboratory testing programme.
The latter consisted of mainly uniaxial compression tests. The main objective in developing the RC material is to use it in
future research on CO2 sequestration in unmineable coal seams. A highly homogeneous coal sample would make it much easier to identify, for example,
the effect of CO2 sorption on the mechanical, flow and transport properties of coal. Uniaxial compression tests were conducted on some brown
coal samples to determine the approximate mechanical properties. The results revealed an average uniaxial compressive strength
of 1.46 MPa, an average elastic modulus of 77.43 MPa and a Poisson’s ratio of 0.16. The measured properties were used as a
reference for the development of RC samples. An extensive laboratory experimental programme was conducted to develop RC samples
with the desirable mechanical properties. Portland cement was used as the cementing agent for the RC. Different variables
such as percentage of cement, water content, compaction load and curing time were taken into account when developing RC samples.
Uniaxial compression tests were carried out to ensure that the RC samples were reasonably homogeneous and the properties were
similar to those of natural coal. Percentages of cement by weight of coal such as 4, 6 and 8% were attempted and a 4% cement
mix with 50% water was considered most suitable for the RC samples. Average compressive strength of 0.8 MPa (28-day strength)
and an average elastic modulus of 34 MPa were achieved for the RC samples. Further efforts at improvement would involve better
matching of the uniaxial compressive strength and elastic modulus of RC samples with the natural coal samples. 相似文献
29.
Laboratory testing is often used to derive the mechanical properties of rock. Testing conditions heavily influence the results of such laboratory experiments in which factors, including the water content, diameter of samples, slenderness of sample and strain (or loading) rates are of great importance. This paper evaluates the influences of four major test conditions: water content, strain rate, sample diameter and sample slenderness, on the peak uniaxial compressive strength (UCS) and modulus of elasticity (MoE) of sandstone. Following the Taguchi approach, an experimental study was conducted on cylindrical sandstone specimens, and the results were interpreted using signal-to-noise ratio (S/N) and analysis of variance (ANOVA). The results reveal that water content is the most influential test condition for peak UCS and the influence of sample diameter, slenderness and strain rate decreases in the cited order. MoE is greatly affected by sample slenderness, whereas the other three test conditions show an approximately similar and smaller influence. These characteristics were further verified by the ANOVA results. These behaviours are consistent with the results reported in the literature. Finally, the Taguchi approach, which is a very useful and versatile technique, which has not been effectively applied in rock mechanics and rock engineering, was successfully used to evaluate the influences of different test conditions on the peak UCS and MoE of laboratory rock samples. 相似文献
30.
微量陨石激光熔样稀有气体测定方法是一种可以在微米尺度上对几毫克陨石样品进行准确稀有气体同位素分析的方法,克服了传统全岩熔融法在测量时存在样品用量大、前处理过程复杂和样品稀有气体分布不均导致不同组分的宇宙射线暴露历史无法进一步区分等问题。但是由于该方法所用样品体积小和样品用量低,要求实验室具有超低本底的稀有气体提取系统,目前国内在微量陨石稀有气体分析技术方面尚处于起步阶段。本文采用金刚石激光样品窗成功研制了超低本底的气体提取系统,通过系统体积标定和天平称量误差、热本底、干扰元素、质量歧视及质谱灵敏度等参数的校正,在中国科学院地质与地球物理研究所建立了微量陨石激光熔样稀有气体测定方法,并对毫克级微量钙长辉长无球粒陨石Millbillillie粉末标样进行了稀有气体同位素含量和比值测定,计算获得准确一致的宇宙暴露年龄。该方法的建立,将为我国迅速发展的比较行星学和深空探测提供重要技术支撑。 相似文献