scholarly journals Compositional Features and Swelling Potential of Two Weak Rock Types Affecting Their Slake Durability

Geotechnics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 172-191
Author(s):  
Lena Selen ◽  
Krishna Kanta Panthi ◽  
Mai Britt Mørk ◽  
Bjørn Eske Sørensen
Keyword(s):  
Mineralogical Composition ◽  
Rock Material ◽  
Weak Rock ◽  
Swelling Potential ◽  
Weak Rocks ◽  
Rock Materials ◽  
Slake Durability ◽  
Rock Types ◽  
Mineral Components ◽  
Moisture Sensitive

Weak and weathered rocks are well known for their sensitivity to changes in moisture content. Degrading behavior is common in weak rocks with moisture-sensitive mineral components and present numerous stability problems. The slake durability is a measure of the resistance to weakening and disintegration of rock materials which quantitatively distinguishes durable from non-durable rock materials. Several rock material parameters interact on the process of disintegration when exposed to cyclic moisture changes, whereby the content of clay is believed to play a major role. This manuscript evaluates the overall material composition of flysch and serpentinite rocks cored from the wall of the shotcrete-lined headrace tunnel of a hydropower project, including minerals, structure, porosity, the presence of micro-discontinuities, and swelling potential, and links these properties to the slake durability. Further, the different methods used to assess compositional features affecting the durability of weak rocks are evaluated and discussed. The manuscript argues that the mineralogical composition and microstructures present in the intact rock and the content of moisture-sensitive constituents, as swelling clays, control the long-term durability of weak rock material. It is demonstrated that XRD assessments are not sufficient to detect the content of brucite and swelling components, and that methods as thin section and SEM analyses should be carried out in the assessment of weak and weathered rock mass.

scholarly journals “Trachytes” from Sardinia: Geoheritage and Current Use

2019 ◽  
Vol 11 (13) ◽  
pp. 3706 ◽  
Author(s):  
Nicola Careddu ◽  
Silvana Maria Grillo
Keyword(s):  
Volcanic Rocks ◽  
Mineralogical Composition ◽  
Building Stone ◽  
Step Method ◽  
Public And Private ◽  
Current State ◽  
Igneous Activity ◽  
Mineral Components ◽  
Granitoid Rocks ◽  
The Aesthetic

Sardinia was affected by an intense igneous activity which generated calc-alkaline products during the Oligo-Miocene period. The volcanic substance shows large variations, ranging from pyroclastic flow deposits, lava flows and domes. By composition, the deposits are all primarily dacites and rhyolites, with subordinate andesites and very scarce basalts. The rhyolite lavas show porphyritic and ash-flow tuffs. Ignimbrite structures are found in the dacitic domes and rhyolitic lavas. These rocks—commercially known as “Trachytes of Sardinia”—used to be quarried in all historical provinces, mainly in the central part of the island to be used as ornamental and building stone. They continue to be commonly used nowadays, but their use dates back to the prehistoric age. They are easily found in many nuraghi, “domus de janas”, holy wells, Roman works (mosaics, paving, roads, bridges), many churches built in Sardinia and practically in all kinds of structural elements in public and private buildings, such as walls, houses, and bridges. Contrary to the granitoid rocks, whose appearance is largely influenced by the mineralogical composition, the aesthetic feature of volcanic rocks is rather affected by the widest range of colors, structure and texture, i.e., shape, size and distribution of mineral components, porphyric index, etc. “Trachyte” is quarried opencast with the “single low step” method, with descending development, with prevalent use of double-disc sawing machines. Whenever the stone deposit allows higher steps, the chain cutting machine, in combination with diamond wire, becomes the preferred extraction solution. This study aims to at look Sardinian “trachytes” from a geoheritage perspective. After a geological-petrographic framework, the paper discusses the historical uses of “trachyte” in Sardinia. The current state of the art of “trachyte” quarrying, processing and usage in the Island is also described. An analysis of the “trachyte” production has been carried out. Finally, a consideration about how to enhance geotourism in the area is suggested.

scholarly journals An analysis on the slaking and disintegration extent of weak rock mass of the water tunnels for hydropower project using modified slake durability test

2019 ◽  
Vol 79 (4) ◽  
pp. 1919-1937 ◽  
Author(s):  
Lena Selen ◽  
Krishna Kanta Panthi ◽  
Gunnar Vistnes
Keyword(s):  
Rock Mass ◽  
Test Method ◽  
Weak Rock ◽  
Hydropower Project ◽  
Durability Test ◽  
Slake Durability ◽  
Operational Life ◽  
Heterogeneous Rock ◽  
Weak Rock Mass ◽  
Slake Durability Test

AbstractWater tunnels built for hydropower passing through weak and heterogeneous rock mass pose challenges associated to slaking and disintegration, as they are first exposed to dry condition during excavation and are then filled with water to produce hydropower energy. Over the period of operational life, these tunnels are drained periodically for inspections and repair leading to drainage and filling cycles. The weakening of rock mass caused by cycles of drying, saturation and drainage may lead to the propagation of instabilities in the tunnels. Therefore, it is important to study the slaking and disintegration behavior of the weak rock mass consisting of clay and clay-like minerals. This paper assesses the mineralogical composition of flysch and serpentinite from the headrace tunnel of Moglicë Hydropower Project in Albania. Further, to determine the slaking and disintegration behavior of these rocks, extensive testing using both the ISRM, Int J Rock Mech Min Sci Geomech Abstr 16(2):143-151, (1979) suggested test method and a modified variant of this test are performed. Finally, comprehensive assessments, discussions and comparisons are made. It is found that the modified slake durability test better suits for the tunnels built as water conveying systems such as hydropower tunnels.

scholarly journals Petrology of Exposed Basement Rocks around Shintaku of North Central Nigeria

2013 ◽  
Vol 5 (3) ◽  
pp. 489-497
Author(s):  
O. Odedede
Keyword(s):  
Granite Gneiss ◽  
Mineralogical Composition ◽  
Petrographic Analysis ◽  
Structural Elements ◽  
North Central ◽  
Porphyritic Granite ◽  
Geologic Time ◽  
Rock Types ◽  
Basement Rocks ◽  
Porphyritic Texture

The study area is part of the Basement Complex of North Central Nigeria. The study aims at identifying the rock types and interpretation of the structural elements. The major rock units in the area comprises of porphyritic granite, gneiss and schist. Structural evidence shows that the rocks are deformed and where intruded by the granite. Petrographic analysis reveals the existence of feldspar phenocrysts in a groundmass of quartz and biotite. The granite is composed of quartz (25-35%), plagioclase (15-20%), orthoclase (10-20%), microcline (5-25%), biotite (15-20%) and other accessory minerals. The granites displayed a porphyritic texture while the schist and gneisses exhibit planar and linear structures. Variation in structural trend and mineralogical composition is due to the series of deformational activities which has affected the rocks during geologic time. Keywords: Monzogranite; Porphyritic; Deformation; Fractionation.  © 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.  doi: http://dx.doi.org/10.3329/jsr.v5i3.15233 J. Sci. Res. 5 (3), 489-497 (2013)  

scholarly journals ESTIMATION OF THE EFFICIENCY OF MECHANICAL ACTIVATION OF SILICA-CONTAINING ROCKS

2021 ◽  
Vol 6 (5) ◽  
pp. 19-27
Author(s):  
A. Shamanina ◽  
Arkadiy Ayzenshtadt ◽  
V. Kononova ◽  
V. Danilov
Keyword(s):  
Mechanical Activation ◽  
Surface Activity ◽  
Raw Materials ◽  
Functional Dependence ◽  
Construction Materials ◽  
Mineralogical Composition ◽  
Optimal Time ◽  
Energy Potential ◽  
Mineral Components ◽  
Time Parameters

Rocks of various chemical and mineralogical composition are widely used as raw materials in the construction materials industry. At the same time, preliminary mechanical activation of mineral raw materials to a finely dispersed state contributes to a change in the energy potential of the system and affects the tendency of the surface of a finely dispersed system to transformations. Studies of the physicochemical activity of mechanically activated rocks allow to determine the rational areas of use of mineral components. The paper presents the results of evaluating the efficiency of mechanical activation of silica-containing raw materials by the values of surface activity (ks), defined as the ratio of the value of the free surface energy to the specific mass energy of atomization. Fine powders are obtained by grinding in a planetary ball mill to a different specific surface area of quartz sand (1200 – 3000 m2/kg) and polymineral sand (700 – 1335 m2/kg). The presence of a functional dependence of the surface activity on the time parameters of mechanical activation of the studied rocks is shown. The mechanical activation of the feedstock at the optimal time of its grinding makes it possible to achieve a given value of the surface activity. It is recommended to use the ks parameter as a criterion for assessing the efficiency of the process of mechanical activation of silica-containing rocks

Guidelines for Open Pit Slope Design in Weak Rocks

2018 ◽  
Keyword(s):  
Surface Water ◽  
Mine Planning ◽  
Rock Slope Stability ◽  
Open Pit ◽  
Weak Rock ◽  
Primary Control ◽  
Water Control ◽  
Open Pit Mines ◽  
Weak Rocks ◽  
Slope Design

Weak rocks encountered in open pit mines cover a wide variety of materials, with properties ranging between soil and rock. As such, they can provide a significant challenge for the slope designer. For these materials, the mass strength can be the primary control in the design of the pit slopes, although structures can also play an important role. Because of the typically weak nature of the materials, groundwater and surface water can also have a controlling influence on stability. Guidelines for Open Pit Slope Design in Weak Rocks is a companion to Guidelines for Open Pit Slope Design, which was published in 2009 and dealt primarily with strong rocks. Both books were commissioned under the Large Open Pit (LOP) project, which is sponsored by major mining companies. These books provide summaries of the current state of practice for the design, implementation and assessment of slopes in open pits, with a view to meeting the requirements of safety, as well as the recovery of anticipated ore reserves. This book, which follows the general cycle of the slope design process for open pits, contains 12 chapters. These chapters were compiled and written by industry experts and contain a large number of case histories. The initial chapters address field data collection, the critical aspects of determining the strength of weak rocks, the role of groundwater in weak rock slope stability and slope design considerations, which can differ somewhat from those applied to strong rock. The subsequent chapters address the principal weak rock types that are encountered in open pit mines, including cemented colluvial sediments, weak sedimentary mudstone rocks, soft coals and chalk, weak limestone, saprolite, soft iron ores and other leached rocks, and hydrothermally altered rocks. A final chapter deals with design implementation aspects, including mine planning, monitoring, surface water control and closure of weak rock slopes. As with the other books in this series, Guidelines for Open Pit Slope Design in Weak Rocks provides guidance to practitioners involved in the design and implementation of open pit slopes, particularly geotechnical engineers, mining engineers, geologists and other personnel working at operating mines.

scholarly journals Durability Assessment of Clay-Bearing Soft Rocks By Using New Decay Index

2018 ◽  
Author(s):  
Mojtaba Heidari ◽  
Aliakbar Momeni ◽  
Yazdan Mohebbi
Keyword(s):  
Physical And Mechanical Properties ◽  
Test Methods ◽  
Index Test ◽  
Durability Test ◽  
Weak Rocks ◽  
Slake Durability ◽  
Decay Index ◽  
Durability Assessment ◽  
Engineering Projects ◽  
Slake Durability Test

Clay-bearing rocks are known as most important problematic weak rocks. Due to the importance of disintegration of clay-bearing rocks in engineering projects, several simple test methods have been proposed to assess durability of these rocks. In this study, a comprehensive research program was conducted on twenty different clay-bearing rocks to assess their disintegration characteristics under laboratory conditions. In order to carry out the research, at the first step some physical and mechanical properties of the studied rocks were measured. After that, three durability test methods were employed. These tests include the standard slake durability test to obtain index durability (Id2 ), slake durability test with sieving the remained materials in drum to obtain disintegration ratio (DR) and new time series slake durability test to obtain decay index (DI). The results of this research indicated that for most of samples, using the standardized slake durability index test (Id2 ) may not be adequate to understand the disintegration characteristics of clay-bearing rocks and shows overestimated values. The new decay index (DI) has overcome the most limitations of the standard slake durability test and clearly will realize deterioration potential of clay bearing rocks. Finally, based on the results of decay index a new durability classification was proposed.

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