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Nisael A. Solano Mohammad Soroush Chris R. Clarkson Federico F. Krause Jerry L. Jensen 《Computational Geosciences》2017,21(3):567-593
A high-resolution simulation model of a heterogeneous low-permeability rock sample is used to investigate the effects of physical and biogenic sedimentary structures on scaling and anisotropy of absolute permeability at the core scale. Several simulation sub-samples with random locations and volumes were also selected for evaluation of the effects of scale and lithological composition on the calculated permeability. Vertical and horizontal permeability values (from whole core simulation) are in good agreement with routine core analysis (RCA) measurements from offsetting cores. Despite relatively good reservoir quality associated with geobodies of biogenic and relic bedding structures, results from the full diameter core simulation demonstrate that their limited volumetric abundance and restricted connectivity prevent these features from controlling fluid flow in these rocks. In fact, permeability seems to be dominated by the tighter encasing matrix, which exhibits average permeability values very close to those reported from RCA. Geometric averaging offers a better representation for the upscaling of horizontal permeability datasets; whereas, both geometric and harmonic averaging work similarly well for the vertical measurements. The methodology used in this work is particularly applicable to the detailed characterization of reservoir rocks with a high degree of heterogeneity caused by biological reworking and diagenesis. 相似文献
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Environmental geochemistry of Zarshuran Au-As deposit, NW Iran 总被引：2，自引：1，他引：2
Zarshuran deposit is the most famous and important As-Au mine in Iran. However, there is no information on the impact of mining activity on the surrounding environment, especially on water systems. This paper attempts to document the concentration of arsenic and associated elements in waters and sediments resulting from the mining history of Zarshuran, a period covering hundreds of years. Water and sediment samples collected from Zarshuran Stream indicate high content of some potentially toxic elements, especially of As which ranges from 0.028 to 40 ng/l in water and 182 to 36,000 mg/kg in sediment samples. Mining activity, exposure of a large volume of mining wastes to weathering, and the anomalously high background of trace metals in the mining area are considered to be the main sources of heavy metal pollution. 相似文献
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This study considered the possibility of using visible and near infrared (VNIR) spectral absorption feature parameters (SAFPs) in predicting the concentration and mapping the distribution of heavy metals in sediments of the Takab area. In total, 60 sediment samples were collected along main streams draining from the mining districts and tailing sites, in order to measure the concentration of As, Co, V, Cu, Cr, Ni, Hg, Ti, Pb and Zn and the reflectance spectra (350–2500 nm). The quantitative relationship between SAFPs (Depth500nm, R610/500nm, R1344/778nm, Area500nm, Depth2200nm, Area2200nm, Asym2200nm) and geochemical data were assessed using stepwise multiple linear regression (SMLR) and enter multiple linear regression (EMLR) methods. The results showed a strong negative correlation between Ni and Cr with Area2200nm, a significant positive correlation between As and Asym2200nm, Ni and Co with Depth2200nm, as well as Co, V and total values with Depth500nm. The EMLR method eventuated in a significant prediction result for Ni, Cr, Co and As concentrations based on spectral parameters, whereas the prediction for Zn, V and total value was relatively weak. The spatial distribution pattern of geochemical data showed that mining activities, along with the natural weathering of base metal occurrences and rock units, has caused high concentrations of heavy metals in sediments of the Sarough River tributaries. 相似文献
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Acta Geotechnica - In general, there are two classical solutions in soil mechanics to predict the shear band orientation in dense granular materials: the Coulomb and Roscoe theories. The present... 相似文献
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Thermal springs are attractive geological features interesting for tourists because of their balneological and therapeutic applications. In Iran, the thermal springs surrounding Mount Sabalan are famous and unique in this regard. Two clusters of thermal springs consisting of 16 springs and mostly used as spas occur in Neer and Meshkinshahr areas. In order to investigate the seasonal changes of field and chemical parameters and to trace element concentrations in dry and wet seasons, springs were sampled twice in May and November. Field data including T, EC, pH and Q were measured on-site and major cations and anions were analysed in the laboratory along with 72 trace elements. Cations show the following order of abundance: Na ? Ca ≥ K > Mg and anions follow the order of Cl > HCO3 > SO4. Trace element concentrations indicate that most of the elements show concentrations well beyond the standard guideline values for drinking water. pH, T, spring discharge and elevation are not correlated with each other and with other parameters, indicating that they have had no role on concentrating or depleting trace elements in spring waters. While the two sets of samples were taken within a 6 month interval, the elements and parameters show slight or no variation from the first period to the second and in some cases, they show less than 5 % decrease or increase in the second sampling period. Correlation coefficient and principal component analysis of analytical data indicate that EC, K, Cl, HCO3, As, B, Ba, Br, Li, Na, Rb, Sr and V show very strong mutual correlation coefficients implying their relationship and common source and fate in the hydrothermal fluid that carries them out of the geothermal system. Moreover, they all fall in the component 1 of PCA. This group of elements is supposed to be derived from the magmatic-hydrothermal system through the interaction of hydrothermal fluids with the rocks they have passed through. The mean As value is 160-fold higher than the guideline values (10 μg/l) and Mn and Sb shows an exceedance of 12- and 11.5-fold, respectively. Arsenic shows a variation of 5–5,834 μg/l. Hence, it is supposed that potentially toxic elements may have adverse effects on tourists using the springs as a treatment or recreation. Indeed, the discharge of springs with high values of As and other elements represents a threat for downstream water uses. The higher concentrations of most elements including As, Pb, S, Cl and Sb and the higher pH values found in Neer area springs seem to be more related to an older hydrothermal system present in this area than the Meshkinshahr system that is still active today. 相似文献
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Seyed Mohammad Fattahi Abbas Soroush Ning Huang Jie Zhang Sona Jodari Abbasi Yang Yu 《地球表面变化过程与地形》2021,46(13):2565-2581
Crusts play a crucial role in the reduction or control of wind erosion. In this regard, the resilience and durability of crusts are of prime importance. Crusts have high resilience and durability against wind flow shear stresses; however, they are prone to abrasion induced by saltating particles. Therefore, estimating crust durability in abrasion rupture has practical importance. In this study, a cyanocrust and a biocemented sand crust were subjected to a controlled flux of saltating particles for different sandblasting periods to provide a framework for predicting crust rupture. The velocity and pre- and post-collision energy of the saltating particles were measured using high-speed photography. The changes in the strength of the crusts after different periods of sandblasting were determined using a scratch test. The results suggested that the average strength of the cyanocrust and biocemented sand crust became 0.25 and 0.7 of their corresponding initial values after 30 min of sandblasting. Also, the average stiffness of the cyanocrust and biocemented sand crust decreased to 0.5 and 0.9 of their initial values, respectively. Furthermore, the amount of impact energy absorbed by the crusts increased by the deterioration of the crusts. Compiling the results of the wind tunnel experiment and scratch tests yielded an exponential equation which can be used to estimate crust durability in a given condition of saltation. Based on this equation, the cyanocrust and biocemented sand crust will break down entirely after 23 and 449 min, respectively, at a wind velocity of 6.8 m/s and a saltation flux of 1 g/s/m. 相似文献
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A Moisture Index Classification System for Rocks (MiC System) 总被引：1，自引：0，他引：1
Summary. Interaction of rocks with water is leading to a reduction in physical and mechanical properties, and quantifying this effect
has always been a problem for design purposes in rock engineering projects. Despite the fact that a number of considerable
works have been carried out in this field, they are not thorough and general. In this paper, a new rock classification system
is presented in order to evaluate wet rock properties.
Laboratory studies showed that six parameters may be recognized as major controlling parameters for wet rocks, including:
water absorption, porosity, weathering degree, swelling index, number of microfissures, and average grain size. Many tests
were performed and a sensitivity analysis was carried out on the data obtained. This analysis characterized the rock sensitivity
when changing each parameter and consequently, a rating value was assigned to each parameter.
By adding these rating values, a rating between zero and 100 is allocated to each rock as Moisture index (Mi). The closer
this index is to 100, the more sensitive rock will be to moisture. On the basis of this index, rocks are divided into five
classes including: very good, good, fair, weak and very weak. 相似文献
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Several experimental methods have been proposed for consolidation test such as: constant loading rate, constant gradient and
constant rate of strain (CRS). Unfortunately, there are no unique criteria for performing the CRS consolidation test. Also,
there are considerable differences among the standards proposed for the test. In the present paper, authors have tried to
find the reasons for differences among standards, by studying the basic assumptions made on the characteristics of the pore
water flow during consolidation process. In the course of study, CRS consolidation tests were carried out under different
strain rates on remolded samples. The results of the tests have indicated that the Darcy’s law is not valid throughout the
CRS test and therefore, any consolidation equation based on Darcy’s law would not provide accurate results. The results of
the current experiments also showed that with regard to the applied strain rates, there are three different flow regimes governing
the process named as: pre-linear (non-Darcy flow), linear (Darcy flow) and post-linear (non-Darcy flow). Experimental results
also showed that distinction between boundaries of linear and nonlinear flow is possible from the excess pore pressure developed
during the tests. 相似文献