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Modelling geologic surfaces
Published in Martin Lloyd Smith, Geologic and Mine Modelling using Techbase and Lynx, 2020
Fluctuation of grade levels as a function of support size can be a function of the physical characteristics of the material being sampled. For instance, drill core samples are consistent in diameter, but the sample length can vary from a few broken fragments that are assigned to an interval of a few centimeters to cores many meters in length. In many deposits, high grade zones are associated with lower rock strengths. Portions of the core that are associated with higher grade will tend to lack cohesion in the core while barren zones will produce longer cores. Since cores are logged and sampled largely in the same intervals as they are physically produced, there can be an inverse relationship between sample length and grade. In the case of gouge and mud seams, a positive correlation between assay and length could also be discovered.
Diagnosis, Appraisal, Repair and Management
Published in Ian Sims, Alan Poole, Alkali-Aggregate Reaction in Concrete: A World Review, 2017
Bruno Godart, Mario R de Rooij
Core samples are collected through drilling with a diamond bit. Before coring, any adjacent reinforcement buried in the concrete must be located using information from the drawings, checked with a cover meter. For coring in locations of structurally critical areas, coordination with or direction by the structural engineer in charge is necessary. To avoid excessive damage or fracturing of larger cores, the equipment used for coring should be well fixed to the structure during coring. It is desirable to take cores with a diameter at least three times the maximum size of the coarse aggregate used. To be able to remove the cores from the structure, drilling depth should be more than the diameter of the core. 100 mm diameter cores are often considered, but the use of larger size cores (e.g., 150 mm in diameter) will be beneficial in the case of expansion testing on cores at 38 °C and R.H. > 95 percent, as it will contribute to reducing the leaching of alkalis during the test, thus generating more reliable test data for estimating the potential for future expansion.
Prediction of Engineering Classification of Wedge Terrains of Eastern Ghats
Published in S.P. Kaushish, T. Ramamurthy, Tunnelling Asia’2000, 2020
The author during the execution of the project studied the rock masses insitu and 45 bore holes were driven at various locations in the region from Visakhapatnam to Koraput. Rock samples were collected from each bore hole at various depths depending on the rock strata. The total depth of bore hole varied from 30 to 46 m. About 25 to 30 rock core samples were obtained from each bore hole. On this rock core samples various experiments were conducted to determine engineering properties like field density, specific gravity, porosity, natural moisture content, uniaxial compressive strength, and point load index, standard penetration value, quantity of water discharge.
Design of an open-pit gold mine by optimal pitwall profiles
Published in CIM Journal, 2021
A. Agosti, S. Utili, D. Gregory, A. Lapworth, J. Samardzic, A. Prawasono
The design of pitwalls in open-pit mines involves multidisciplinary team of geologists, geotechnical engineers, and mining engineers (Randolph, 2011). The design process requires iterative steps alternating between the teams (Stewart, Hawley, Rose, & Gilmore, 2004). Typically, several boreholes are drilled as part of a site investigation, and laboratory tests are performed on the core samples to characterize the mechanical strength of the geomaterials encountered and the main stratigraphic layers. Then, a preliminary simplified design is generated, and a pit crest contour is drawn. The pit is then split into sectors to design the pitwalls (Stewart et al., 2004). It is wise to choose sectors having fairly constant lithologies so that a representative 2D cross-section can be determined for each sector. Successively, for each cross-section, a pitwall profile needs to be designed to maximize the steepness of the pitwall while ensuring a prescribed Factor of Safety (FoS) against slope failure.
Sedimentary environment and facies of the Huagang Formation in the northern central Xihu Depression, East China Sea Basin, China
Published in Australian Journal of Earth Sciences, 2020
Z. X. Zhao, C. M. Dong, C. Y. Lin, X. G. Zhang, X. Huang, B. J. Li, W. Guo, Z. Q. Zhu
The on-site tests used the fourth-generation DELTA series ore analyser from the American Innov-X company. A 60 m core was tested at 116 points. Relative to general geological samples, owing to the sampling and methods employed, drill core samples are likely to be affected by crude oil and drilling fluids and the artificial destruction and handling process cause the surface of the core to be uneven. The study area is a low-permeability tight sandstone gas reservoir; cores from this interval contain essentially neither asphalt nor residual crude oil. After cutting the core, a smooth test surface was obtained and tested directly with a hand-held X-ray fluorescence spectrometer using a 60 s test cycle to comprehensively examine the test efficiency and accuracy. The National People’s Republic of China National Standard material GBW07106 was used for precision testing.
Feasibility of novel techniques to predict the elastic modulus of rocks based on the laboratory data
Published in International Journal of Geotechnical Engineering, 2020
Generally, there are direct and indirect methods in order to determine the elastic modulus of intact rocks. Direct determination of elastic modulus is conducted in the laboratory on the core specimens; whereas indirect methods are commonly constructed on the basis of predictive equations and/or simulation results. Despite the high accuracy, direct measurement of E has some limitations. For example, preparation of core samples with high quality and proper dimensions is difficult in the fractured rocks that can lead to invalid results. Also, cores preparation and performing the laboratory tests are costly and time consuming in practice. In order to cover the time and cost related difficulties in direct measurement of E, indirect models were developed in the form of predictive models or/and empirical equations. These models are commonly constructed on the basis of the statistical models and artificial intelligence techniques (Sachpazis 1990; Katz, Reches, and Roegiers 2000; Karakus, Kumral, and Kilic 2005).