Influence Of Rock Type Research Articles

Influence of rock type and geophysical properties on radon flux density.

The most significant source of human exposure to ionizing radiation is the radioactive gas radon (basically 222Rn) and its daughter decay products, creating more than half of the effective dose from all natural sources. Radon enters buildings mainly from dense rocks, which are below building foundations at depths of 1m and more. In this paper long-term measurements of radon flux density are analyzed, with radon exhalation from the surface of the most common rocks-loams, sandy loams, clays, clay shales, several types of sandy-gravel-pebble deposits, clay and rocky limestone. The influence of geophysical properties of rocks on radon flux density due to exhalation from surfaces of those rocks was studied. Based on the results obtained, a method of local assessment of the hazard from radon and its progeny in buildings is proposed, which is based on the geophysical properties of rocks below the foundations of those buildings.

Identification of mixed mode damage types on rock-concrete interface under cyclic loading

The study of the mixed mode Ⅰ-Ⅱ fracture damage characteristics of the rock-concrete interface under cyclic loading is essential to grasp the operation of gravity dams under seismic loading. To reveal the mixed mode fracture damage characteristics of the rock-concrete interface under cyclic loading, a four-point shear (FPS) test for rock-concrete specimens was carried out at first. The entire fracture damage process of rock-concrete specimens was monitored in real-time by acoustic emission (AE) and digital image correlation (DIC), the widely used nondestructive monitoring techniques. The mechanical test results show that the modal angle is related to the stiffness decay of rock-concrete specimens. The quantitative identification method of tensile and shear damage based on machine learning algorithm can quantitatively identify the damage types at the interface of rock-concrete specimens. The influence of rock type and modal angle on the interface damage mechanism was quantified by the damage identification method, and the spatial and temporal evolution of tensile and shear damage with cyclic loading was determined. The spatial and temporal evolution characteristics of the damage were compared with the DIC strain contours of the corresponding stages to reveal the mechanism of the influence of the damage evolution law on the crack expansion path.

Using field data and operational constraints to maximize hard rock TBM penetration and advance rates

In this paper, the influence of rock type and uniaxial compressive strength on the cutter penetration is investigated to provide a basic guideline for the optimum field cutter spacing. The successfully utilized cutterhead layout designs are also studied in various rock types and different categories of tunnel sizes for projects with relatively high performance. The results of the conducted analyses show that the maximum cutter penetration in uniaxial compressive strength values below 50 and above 150 MPa is achieved when the cutter spacing is close to 90 and below 80 mm respectively. The study on the layout design characteristics of the cutterhead shows the evenly distributed scheme is more used with success even in softer rocks (when the rock mass condition is good). In softer rocks, the extension of the openings may have to be well over 50% of the cutterhead radius to maximize its performance. It is also found that the linear speed of the cutters has a direct correlation with two major parameters of normal force index (NFI) and rolling force index (RFI). In this regard, two formulas are generated using statistical analysis of the data from around 260 tunnel projects to evaluate both NFI and RFI. The corresponding formulas have coefficients of determination of 77 and 68% respectively. These formulas are used in an optimization process to maximize cutter penetration using various operational constraints (cutter load capacity, cutterhead torque limit, cutter geometry constrains, and cutterhead penetration rate limits). The new findings of this study can provide a foundation to improve the design process of hard rock TBMs and to optimize their performance considering various project setting parameters.

Influence of rock type on regularities of excavator bucket tooth crown wear

Influence of rock type on regularities of excavator bucket tooth crown wear

Assessment of Environmental Geochemistry of Lead-Zinc Mining at Ishiagu Area, Lower Benue Trough, Southeastern Nigeria

Mining activities have long been recognized as a major source of environmental contamination associated with heavy metals and metalloids. This study evaluated the relationship between the occurrence and mining of lead-zinc sulphide ores at Ishiagu, Nigeria, and heavy metal and metalloid contamination. A comparative study of two zones in the area, with and without mining activities was also made Water, soil, stream sediment and ore samples were analyzed, after acid digestion, using atomic absorption spectrophotometer (AAS).  The concentration levels of seven heavy metals and a metalloid namely Pb, Cu, Ni, Zn, Mn, Co, Cd and as were evaluated. While the highest concentration levels of As, Co and Pb (5.20 mg/l, 0.54 mg/l and 3.40 mg/l respectively) were found in water, those of Ni and Mn (2.26 mg/l and 5.48 mg/l respectively) occurred in soil.  For Cu and Zn, highest levels of concentration (2.80 mg/l and 0.41 mg/l respectively) occurred in stream sediments. The variations in the concentration levels of these elements in varying geologic media (soil, water and sediment) indicate influence of rock types, human activities and media physiochemical characteristics. Geostatistical analyses using QQPlot, semivariogram and kriging showed normal distribution of these elements. Distribution and dispersion patterns of the heavy metals indicated increase in concentration levels in the local stream flow direction. Pb, Cu, As, Cd, Mn, and Ni concentrations had reached pollutant levels in water based on WHO standards, while Zn level is below. Since the local people use untreated surface water and groundwater for drinking and other domestic purposes, soil for farming and lead for cosmetics, long term exposure poses significant health risk for humans, animals and plants.

Methods of Mechanical Mining of Compact-Rock—A Comparison of Efficiency and Energy Consumption

This paper compares the methods of mechanical mining of rock in terms of their efficiency, energy consumption, and the durability of the tools they involve. It presents the advantages of mechanical heading-driving methods. In the first part, we described the methods used to assess rock workability, and the influence of rock types and parameters on mining efficiency. Furthermore, we discussed the compact-rock mining process in terms of the energy it consumes. We provided the description of the most common mechanical methods, such as milling, static crumpling and undercutting, including the tools involved, and the requirements and limitations for the use of these methods. The paper presents unique machinery solutions designed to reduce the energy consumed by mining processes. In the final part of the paper, we propose a solution to select the mechanical method of rock mining as a function of rock type and parameters.

Biface Knapping Skill in the East African Acheulean: Progressive Trends and Random Walks

Over the 1.5-million-year duration of the Acheulean, there is considerable variation in biface finesse. It is not clear, however, if there is an improvement in biface knapping ability over time, or if variation between sites is largely unrelated to their age. The diversity and duration of the East African Acheulean presents an opportunity to examine this issue. Variables that reflect difficult aspects of biface knapping, and which were likely important goals for Acheulean hominins, were measured in order to assess skill. These variables—refinement (thinness), edge straightness, and symmetry—were compared across four East African Acheulean sites: Olduvai Gorge, Olorgesailie, Kariandusi, and Isinya. The influence of rock type, blank type, reduction intensity, aberrant scar terminations, and invasive flaking on these variables was assessed. Over relatively short timescales, confounding factors, including ones not possible to control for, tend to obscure any temporal signature in biface knapping skill. However, over the vast timespan of the Acheulean at Olduvai Gorge, a temporal trend was indeed apparent. Possible factors influencing this trend include the invention of new knapping techniques, the addition of adolescence as a life history stage, and evolving hominin cognition.

The use of index tests to determine the mechanical properties of crushed aggregates from Precambrian basement complex rocks, Ado-Ekiti, SW Nigeria

This study assessed the possibility of using index tests to determine the mechanical properties of crushed aggregates. The aggregates used in this study were derived from major Precambrian basement rocks in Ado-Ekiti, Nigeria. Regression analyses were performed to determine the empirical relations that mechanical properties of the aggregates may have with the point load strength (IS(50)), Schmidt rebound hammer value (SHR) and unconfined compressive strength (UCS) of the rocks. For all the data, strong correlation coefficients were found between IS(50), SHR, UCS, and mechanical properties of the aggregates. The regression analysis conducted on the different rocks separately showed that correlations coefficients obtained between the IS(50), SHR, UCS and mechanical properties of the aggregates were stronger than those of the grouped rocks. The T-test and F-test showed that the derived models were valid. This study has shown that the mechanical properties of the aggregates can be estimated from IS(50), SHR and USC but the influence of rock type on the relationships should be taken into consideration.

Mineral nutrient mobilization by plants from rock: influence of rock type and arbuscular mycorrhiza

Rock colonization by plant roots and their associated microbiota is one of the major drivers of mineral weathering, nutrient cycling, soil formation and ecosystem stability. Yet the mechanisms of bio-uptake of lithogenic elements from rocks with differential nutrient availabilities and limitations are yet to be established. Here we present results from a mesocosm experiment that examined lithogenic element dissolution and uptake (P, K, Ca, Mg, Mn, Fe, Na, Ti, Al and Si) in Bouteloua dactyloides (buffalo grass) grown on four different granular porous media (basalt, rhyolite, granite and schist) comprised of primary mineral assemblages as influenced by arbuscular mycorrhiza (AM; Rhizophagus irregularis). Our results demonstrated that nutrient mobilization (chemical denudation + plant uptake) in such oligotrophic systems is governed by nutrient supply in the parent material, nutrient availability in pore water solution, and plant physiology. Overall, total major lithogenic element mobilization in planted columns (with and without AM) exceeded abiotic controls in all substrates. Differences in total mobilization among substrates occurred as follows: Fe, Na, Ti and Al reached high values in planted treatments in basalt, P and Mn in rhyolite, Ca and K in granite and K in schist, suggesting enhanced dissolution of primary minerals in the presence of plants. Element biomass enrichment of Mn, Fe, Ti and Al appeared to be higher in basalt than the rest of the substrates; however, high Al availability limited Ca and Mg uptake and plant growth in this rock media. Presence of mycorrhiza enhanced shoot biomass in rhyolite due to increased P uptake, and increased concentrations and total uptake of lithogenic elements in plants in all rocks but granite. As expected, AM significantly increased plant root concentrations of P, K, Ca, Mn, Fe, Ti, Al in basalt, and Mn shoot concentrations in rhyolite, as well as root total uptake of K, Ca, Mg, Mn, Fe, Na, Ti, Al and Si in basalt. At the same time, AM decreased Ca, Ti and Al concentrations in shoots grown in rhyolite, a possible protection mechanism against Al toxicity. The importance of AM in nutrient uptake is also reinforced by positive correlations between AM infection rate and P, Ca and Mn total uptake across all substrates. Moreover, total mobilization of Ca, Mg and Mn in rhyolite, was significantly higher in the AM versus non-AM treatment, contrary to K, Ca, Mg, Na and Si in schist. Our work demonstrates how mineral weathering and associated nutrient release is promoted by plant processes, further enhanced by plant associated with symbiotic AM, and yet more pronounced in basalt and rhyolite compared to granite and schist.

Influence of Rock Types on the Penetration by Linear Shaped Charge Jet with Uneven Thickness Clad in Cutting Excavation

In order to analysis the crack lengths of the different rocks which penetrated by the linear shaped charge jet with uneven thickness clad for cutting excavation, the ANSYS/LS-DYNA code was used to simulate the penetrating process which three kinds of rocks had been penetrated. The results show that: through simulating the penetrate process by eight kinds of linear shaped charge jet with uneven thickness clad, the longest crack was found in Gneiss, the shortest crack was found in Iron ore and the crack length of Granite in between. For the linear shaped charge in this record, the good effect was obtained through taking the uneven thickness clad which vary rate was 2%.The linear shaped charge jet with vary rate of less than 2% slightly was suitable for Gneiss, the linear shaped charge jet with vary rate of more than 2% slightly was suitable for Iron ore, and if Granite was penetrated by linear shaped charge jet with uneven thickness clad, the shaped charge which has 2% vary rate would be more appropriate. It is believe that through the features of penetrated rocks mentioned in the paper, new rock material can be applied easily for pre-splitting blasting engineering in cutting excavation.

Characterisation of river reaches: The influence of rock type

Abstract The characterisation of geomorphological, hydrological and ecological properties of river systems represents a popular and important research direction in fluvial studies, particularly with regards to contemporary international environmental legislation. Recent research has also drawn attention to the unique ecological value and high level of environmental threat associated with groundwater-fed catchments, emphasising the importance of underlying rock type in the development of river typologies. A standardised field method for assessing physical river habitat quality known as River Habitat Survey (RHS) has been developed in the UK and provides an extensive data set of surveyed river reaches. This paper uses information from the RHS database to explore the influence of rock type on reach-scale sedimentological and vegetation characteristics. A range of reach-scale indices are derived from the RHS database for analysis, supported by landscape variables which provide detail on the catchment context. River reaches were then classified into broad lithological groups which reveal statistically significant differences along two key gradients in environmental conditions: an energy gradient associated with stream power and sediment calibre which is inversely related to in-channel vegetation roughness, and a riparian vegetation gradient that also reflects the inverse relationship between instream and riparian vegetation cover. The results emphasise the differences in reach-scale geomorphological and ecological structure between groundwater-fed and surface water-fed catchments, supporting the inclusion of underlying reach lithology in the development of river typologies.

Influence of rock types and structures in the development of drainage network in hard rock area

Remote sensing techniques has proved to be an extremely useful tool in morphometric analysis and groundwater studies. Remote sensing techniques with an emphasis on lineament identifications can play a great role in groundwater prospecting in semi-arid hard rock areas of Purulia district. In the present study, morphometric analysis using remote sensing technique has been carried out in parts of Baghmundi block, Purulia district, West Bengal. The parameters worked out include Bifurcation ratio (Rb), Stream length (Lu), Form factor (Rc), Circulatory ratio (Rc), and Drainage density (D). The morphometric analysis suggests that fractured, resistant, permeable rocks cover the area, the drainage network not so affected by tectonic disturbances. Using satellite imageries of two dates of IRS, different hydrogeomorphological units have been delineated. Among different hydrogeomorphic units (i) very shallow weathered pediment and (ii) Structural hills/ residual hills/inselbergs have very poor ground water prospects, while moderately weathered pediplains and valley fills are good prospective zones for groundwater exploration.

Influence of shear velocity on rock joint strength : Curran, J H; Leong, P K Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10–15 April 1983V1, PA235–A240. Publ Rotterdam: A. A. Balkema, 1983

The influence of the rate of shear displacement on the frictional resistance of rock discontinuities was examined by testing jointed samples of three rock types in a dynamic direct shear machine. The influence of rock type, joint roughness, apparent area of contact, normal stress level and gouge infilling were investigated. The experiments consistently showed that the frictional resistance is dependent on the slip velocity. This rate-dependency was observed within a certain rate of shear velocities below and above which the frictional resistance was essentially independent of the rate of shear displacement. A model based on mechanical instabilities is proposed to explain the observed behaviour. The number of the covering abstract of the congress is TRIS no. 385148. (Author/TRRL)

Geosynclinal Filling: Some Stratigraphic-Structural Relationships: ABSTRACT

A geosyncline does not develop by mere crustal sag but rather by movement along faults. Contemporaneous faults are known to have been active during development of the large Ouachita and Gulf Coast geosynclines and development of the small but active Los Angeles, Hanna, and Ardmore basins, which are tectonically similar. The sedimentary fill of tectonically similar geosynclines, however, may be quite different. The Los Angeles Basin along the continental margin received thick turbidite deposits before it was filled to shelf depths. During its rapid subsidence, the Hanna Basin within the landlocked western interior filled with alluvial deposits. The Ardmore Basin during the late Paleozoic received shallow marine and coastal (paralic) sediments. Disharmonic folds involving the thick, ductile Springer-Goddard Shale indicate the influence of rock type in forming local structural features. While the Springer Shale was being deposited in the Ardmore Basin, turbidites were being deposited along the length of the Ouachita geosyncline. After water depths shoaled, shallow marine beds of the Atokan were deposited. The over-all regressive sequence of the Tertiary in the Gulf Coast geosyncline has resulted in paralic sediments overlying ductile, offshore, and deep-water shales. This relation may have been the cause of structures formed independently of salt tectonics. Such features are thought to be analogous to those failures recognized causing failures in foundation engineering and to the Recent mudlumps of the Mississippi River. End_of_Article - Last_Page 358------------