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21.
Studying the stress redistribution around the longwall mining panel using passive seismic velocity tomography and geostatistical estimation 总被引：3，自引：0，他引：3
Navid Hosseini Kazem Oraee Kourosh Shahriar Kamran Goshtasbi 《Arabian Journal of Geosciences》2013,6(5):1407-1416
Generally, knowledge of stress redistribution around the longwall panel causes a better understanding of the mechanisms that lead to ground failure, especially to rockbursts. In this paper, passive seismic velocity tomography is used to demonstrate the state of stress around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. To determine the location of seismic events and execute the process of tomography, double-difference method is employed as a local earthquake tomography. Since passive sources are used, the ray coverage is insufficient to achieve the quality images required. The wave velocity is assumed to be the regionalized variable and it is therefore estimated in a denser network, by using geostatistical estimation method. Subsequently, the three-dimensional images of wave velocity are created and are sliced into the coal seam. These images clearly illustrate the stressed zones that they are appropriately in compliance with the theoretical models. Such compliance is particularly apparent in the front abutment pressure and the side abutment pressure near the tailgate entry. Movements of the stressed zones along the advancing face are also evident. The research conclusion proves that the combined method, based on double-difference tomography and geostatistical estimation, can potentially be used to monitor stress changes around the longwall mining panel continuously. Such observation could lead to substantial improvement in both productivity and safety of mining operations. 相似文献
22.
Mohammadreza Gharibreza Mohammad Zaman Mahmood Arabkhedri Shahriar Sobh-Zahedi 《国际泥沙研究》2022,37(3):370-382
Abkenar open water(AOW)has a 35 km2distribution and is the largest part of the Anzali Lagoon in the southern coastal zone of the Caspian Sea.The effects of deforestation in the upstream basin of the AOW were assessed by measuring the rate of sedimentation,sediment contamination,and ecological risk for aquatic life and end-users using radioisotopes Cesium-137 and Lead-210.The chronology of the AOW sediment column was studied using the Constant Rate of Supply model.Correlations between environmental changes and the sedimentary regime of the study area highlight the contribution of the AOW authorized international and local wood harvesting companies pre-and-post 1950 in the catchment in terms of the rate of sediment supply and the influx of toxic metals.Historical evidence shows that two specific layers formed during World Wars I and II with the mean rates of 0.185±0.04(±STD)and 0.32±0.02 kg/(m2·y),respectively.The highest influx of alkali elements and toxic metals(nickel,cadmium,lead,zinc,and copper)into the basin occurred in 1945.Two layers of gray mud(16-50 cm)and organic-rich dark loss mud(0-16 cm)correlated well with the programmed wood harvesting projects.These layers accumulated from 1953 to 2000 with a mean rate of 0.6±0.2 and 2±0.7 kg/(m2·y).Thus,aquatic life and end-users have been exposed to moderate to extremely high levels of toxic metals and a moderate level of contamination since the 1950s. 相似文献
23.
E. Karimzade M. Sharifzadeh H. R. Zarei K. Shahriar M. Cheraghi Seifabad 《Arabian Journal of Geosciences》2017,10(9):206
Groundwater flow is a major issue in underground opening in fractured rocks. Because of finding the fracture connectivity, contribution of each fracture in flow, and fracture connectivity to excavation boundary, the prediction of water flow to underground excavations is difficult. Simulation of fracture characteristics and spatial distribution is necessary to obtain realistic estimation of inflow quantity to tunnel and underground excavations. In this research, a computer code for three-dimensional discrete fracture network modeling of water inflow into underground excavations was developed. In this code, the fractures are simulated as ellipsoid while geometrical properties of the fractures are reproduced using a stochastic method. Properties such as the size, orientation, and density of the fractures are modeled by their respective probability distributions, which are obtained from field measurements. According to the fracture condition, the flow paths in rock mass are determined. The flow paths are considered as channels with rectangular sections in which channel width and fracture aperture determine geometry of channel section. Inflow into excavation is predicted ignoring matrix permeability and considering the hydrogeological conditions. To verify presented model, simulation results were compared to a part of the Cheshmeh-Roozieh water transfer tunnel in Iran. The results obtained from this research are in good agreement with the field data. Thus, the average of the predicted inflow has just an approximation error equal to 17.8%, and its standard deviation is 8.6 l/s, which is equal to 21% of the observed value that demonstrates low dispersion of the predicted values. 相似文献
24.
Pure and Applied Geophysics - 相似文献
25.
Anisotropy Effects on Microseismic Event Location 总被引：2，自引：0，他引：2
Seismic anisotropy in sedimentary environments is significant—microseismic waveforms often show strong shear-wave splitting,
with differences reaching 40% between horizontally and vertically-polarized shear-wave velocities. Failure to account for
this anisotropy is shown to result in large microseismic event location errors. A method is presented here for determining
the five elastic parameters of a homogeneous, vertical transverse-isotropic (VTI) model from calibration shot data. The method
can also use data from mining-induced seismic events, which are then simultaneously located. This simple model provides a
good fit to arrival times from coal-environment data, and results in dramatic shifts in interpreted event locations. 相似文献
26.
China Ocean Engineering - Conventional design of pier structures is based on the assumption of fully rigid joints. In practice, the real connections are semi-rigid that cause changes in dynamic... 相似文献
27.
Environmental impact assessment of open pit mining in Iran 总被引：2，自引：0，他引：2
Mining is widely regarded as having adverse effects on environment of both magnitude and diversity. Some of these effects
include erosion, formation of sinkhole, biodiversity loss and contamination of groundwater by chemical from the mining process
in general and open-pit mining in particular. As such, a repeatable process to evaluate these effects primarily aims to diminish
them. This paper applies Folchi method to evaluate the impact of open-pit mining in four Iranian mines that lacked previous
geo-environmental assessment. Having key geologic resources, these mines are: Mouteh gold mine, Gol-e-Gohar and Chogart iron
mines, and Sarcheshmeh copper mine. The environmental components can be defined as public health and safety, social relationships,
air and water quality, flora and fauna hence, various impacting factors from the mining activities were estimated for each
environmental component. For this purpose, each impacting factor was first given a magnitude, based solely on the range of
possible scenarios. Thereafter, a matrix of weighted factors was derived to systematically quantify and normalize the effects
of each impacting factor. The overall impact upon each individual environmental component was then calculated by summing the
weighted rates. Here, Folchi method was applied to evaluate those environmental conditions. Based on the acquired results,
the present paper finally concludes that amongst four case histories in Iran, Sarcheshmeh copper mine significantly affects
the environment, with critical level of air pollution there. 相似文献
28.
Maintaining a fixed position near the sea floor is a critical capability during the deployment of remotely operated or intelligent (autonomous) undersea vehicles in a variety of missions, including inspection and repair of undersea structures, data collection, and surveillance. We present an automatic optical station-keeping system for application to submersible vehicles in deep waters by exploiting the information in sea floor images. Readily measurable spatio-temporal image gradients are used to detect and compute the vehicle's translational and yaw motions using a direct motion vision technique. The vision system has been implemented on a Windows-NT Pentium platform, and the estimated positions and yaw angles are communicated via a serial link to the control system, running on a PC-386. Accurate station-keeping is demonstrated in experiments with a three-thruster floating vehicle in a 6-ft×12-ft×6-ft water tank 相似文献
29.
Shahriar Negahdaripour Caroline Barufaldi Ali Khamene 《Oceanic Engineering, IEEE Journal of》2006,31(3):533-550
Estimating the relative positions and (or) trajectory of a camera from video images is a fundamental problem in motion vision. Of special relevance is the closed-form solution for planar scenes, for processing fly-over imagery from airborne and underwater robotics platforms, automated airplane landing utilizing runway landmarks, photomosaicing, etc. However, the method's robustness can break down in certain scenarios, e.g., due to inherent translation-rotation ambiguity of visual motion with short baselines and narrow field of view. The robustness can be improved by devising methods that compute a smaller set of motion parameters, utilizing other sensors to measure the remaining components. This paper addressed key issues in six degrees of freedom positioning from fly-over imagery by integrating vision with rotational angle sensors. First, we propose and utilize robust closed-form solutions for estimating the motion and orientation of a planar surface from the image flow variations up to first order, given measurements of pitch and roll motions. We also describe a calibration technique to enable the integration of angle sensor and visual measurements. Next, an error analysis enables us to evaluate the impact of inaccurate pitch and roll measurements on the estimates from the new closed-form solutions. Finally, the performance of our new methods and the integrated positioning system are evaluated in various experiments with synthetic and real data 相似文献
30.
Work on the development of passive-vision sensing capabilities that can increase the autonomy of an undersea vehicle is reported. Two classic machine-vision problems for recovering motion and the shape of objects from their images are considered, in light of formulations that incorporate effects due to the illumination attenuation and nonuniform lighting commonly encountered in undersea environments. Based on the formulations, methods are proposed for recovering the orientation of a planar patch from its image shading and for estimating the image motion, a useful tool in dynamic scene analysis 相似文献