Investigation of deposits for traditional extraction activities (metals and coal) has generally been based on determining grade, or content, of the required material. In order to apply the grade concept to an ornamental rock such as slate, it is first necessary to define the variables that determine both the geotechnical recovery rate for the rock mass — which conditions the size of the extracted blocks – and the aesthetic features of the slate — which define the quality of the slabs as potential roofing material.
For this research, geotechnical and aesthetic data for a slate deposit were collected from 16 continuous core borehole samples. A fuzzy expert system was then developed using this data, defining the rock mass recovery rate and slab quality in accordance with the criteria of a slate expert, producing as a final output a zonation of the deposit in terms of top quality slate, medium quality slate or waste.
A mathematical model based on fuzzy logic was chosen due to the fact that the boundaries between different quality groups in a deposit are not clearly distinguished. Moreover, quality also depends on a company's infrastructures for transformation of the blocks, and also on its commercial strategies. 相似文献
The minerals of Oldoinyo Lengai natrocarbonatite lavas are unstable under atmospheric conditions. Subsolidus mineral assemblages in natrocarbonatites were studied in 105 samples from contemporary eruptions ranging from present day to about 100 years old. The subsolidus minerals in natrocarbonatites were formed (i) along cracks on the lava surface from hot gases escaping during cooling, (ii) as atmospheric alteration by solution of water-soluble minerals, in particular halides and gregoryite, and by hydration of nyerereite under the influence of meteoric water and (iii) by reaction with fumarole gases. After solidification, the lavas were cut by a network of thin cracks, the edges of which are covered by polymineralic encrustations. Samples collected 2–24 h after eruption contain nahcolite, trona, sylvite, and halite with accessory kalicinite and villiaumite. Atmospheric humidity results immediately (≥ 2 h after eruption) in alteration of black lavas that is marked by the appearance of white powdery thermonatrite with nahcolite on the lava surface. Subsequent reaction (weeks, months, years) of natrocarbonatite with meteoric water and the atmosphere results in the formation of pirssonite, gaylussite, shortite, trona, thermonatrite, nahcolite and calcite. Generally, the first important step is the formation of pirssonite and the end-members are calcite carbonate rocks or loose aggregates. Fumarolic activity is common for the active northern crater of the volcano. Reaction of hot (54–141 °C) fumarolic gases with natrocarbonatite leads to the formation of sulphur, gypsum, calcite, anhydrite, monohydrocalcite, barite and celestine. Changes in mineralogy of the natrocarbonatite lead to substantial chemical transformation. The most obvious chemical changes in this process are the loss of Na, K, Cl and S, combined with an increase in H2O, Ca, Sr, Ba, F and Mn. The oxygen and carbon isotopic composition of altered natrocarbonatites shows a significant shift from the primary “Lengai Box” to high values of δ18O and δ13C. Calcite exhibits δ13C values between − 2‰ and − 4‰ PDB and δ18O values of + 23‰ to + 26‰ SMOW. The observed assemblages of secondary minerals formed by reaction with atmosphere and meteoric water, the changes in chemical composition of the natrocarbonatite and field observations suggest that alteration of natrocarbonatite is an open-system low-temperature process. It takes place at temperatures between 8 and 43 °C with the addition of H2O to the system and the removal of Na, K, Cl and S from the carbonatites. Low-temperature thermodynamic models developed for alkali carbonate systems can be used for the interpretation of Oldoinyo Lengai subsolidus mineralization. 相似文献
This paper presents a forward model for subsidence prediction caused by extraction of hydrocarbons. The model uses combinations
of analytic solutions to the visco-elastic equations, which approximate the boundary conditions. There are only a few unknown
parameters to be estimated, and, consequently, calculations are very fast. The semi-analytic model is applicable to a uniform
and layer-cake stratigraphy, with visco-elastic parameters changing per layer, and an arbitrary depletion pattern. By its
capabilities to handle a multi-layered visco-elastic subsurface, the semi-analytic model fills the gap between the analytic
single-layered elastic models available to date and the more elaborate numerical, e.g. finite element, models. 相似文献
An increasing number of palaeo-climatic records have been reported to identify the Holocene climate history in the arid Xinjiang region of northwest China. However, few studies have fully considered the internal linkages within the regional climate system, which may limit our understanding of the forcing mechanisms of Holocene climate change in this region. Here, we systematically consider three major issues of the moisture/precipitation, temperature and near-surface wind relevant to the Holocene climate history of Xinjiang. First, despite there still has debated for the Holocene moisture evolution in this region, more climatic reconstructions from lake sediments, loess, sand-dunes and peats support a long-term regional wetting trend. Second, temperature records from ice cores, peats and stalagmites demonstrate a long-term winter warming trend during the Holocene in middle- to high-latitudes of Asia. Third, recent studies of aeolian sedimentary sequences reveal that the near-surface winds in winter gradually weakened during the Holocene, whereas the winter mid-latitude Westerlies strengthened in the Tienshan Mountains. Based on this evidence, in the arid Xinjiang region we propose an early to middle Holocene relatively cold and dry interval, with strong near-surface winds; and a warmer, wetter interval with weaker near-surface winds in the middle to late Holocene during winter. Additionally, we develop a conceptual model to explain the pattern of Holocene climate changes in this region. From the early to the late Holocene, the increasing atmospheric CO2 content and winter insolation, and the shrinking of high-latitude continental ice-sheets, resulted in increasing winter temperatures in middle to high latitudes in the Northern Hemisphere. Subsequently, the increased winter temperature strengthened the winter mid-latitude Westerlies and weakened the Siberian high-pressure system, which caused an increase in winter precipitation and a decrease in near-surface wind strength. This scenario is strongly supported by evidence from geological records, climate simulation results, and modern reanalysis data. Our hypothesis highlights the important contribution of winter temperature in driving the Holocene climatic evolution of the arid Xinjiang region, and it implies that the socio-economic development and water resources security of this region will face serious challenges presented by the increasing winter temperature in the future. 相似文献
The geothermal resources in Fujian Province are mainly hydrothermal resources of medium-low temperature. To better understand the whole process and conditions of heat control in the middle and deep crust, this study focuses on the analysis of heat accumulation model in Hongtang Area of Xiamen, and the main conditions of the model such as faults and sags are explored and interpreted in detail by using gravity and wide-field electromagnetic methods. 4 main faults (F33, F2, F12 and HT-F1) and 10 secondary faults (HT-F2, HT-F3, HT-F4, HT-F5, HT-F6, HT-F7, HT-F8, HT-F9, HT-F10 and HT-F11) were inferred, and the distribution range of sags was delineated. The convective geothermal system is composed of four components: Heat source, geothermal reservoir, heat-conductive fault and heat retaining cover, which form a quaternary heat accumulation model. According to the model, the intersection of the main faults F12, HT-F1 and F33 can be delineated as the primary target area of geothermal exploration, while the intersection of the secondary faults (F12 and HT-F6; F12 and HT-F2; HT-F9, HT-F10 and F12; F12 and HT-F11; F33 and HT-F3; HT-F8 and HT-F3; HT-F2, HT-F10 and HT-F1) can be delineated as the secondary target area. Borehole DR01, which is located in the primary target area, shows that the water temperature increases from fast to slow in the depth range of 0–500 m, and stays at 36℃ below 500 m. The reliability of the heat accumulation model and the target area was tested via geothermal boreholes, which is of great significance to the exploitation and utilization of geothermal resources in Hongtang Area of Xiamen. 相似文献