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排序方式: 共有109条查询结果,搜索用时 109 毫秒
31.
This study presents a time-dependent approach for seismic hazard in Tehran and surrounding areas. Hazard is evaluated by combining background seismic activity, and larger earthquakes may emanate from fault segments. Using available historical and paleoseismological data or empirical relation, the recurrence time and maximum magnitude of characteristic earthquakes for the major faults have been explored. The Brownian passage time (BPT) distribution has been used to calculate equivalent fictitious seismicity rate for major faults in the region. To include ground motion uncertainty, a logic tree and five ground motion prediction equations have been selected based on their applicability in the region. Finally, hazard maps have been presented.  相似文献   
32.
This study aims to develop a new earthquake strong motion-intensity catalog as well as intensity prediction equations for Iran based on the available data. For this purpose, all the sites which had both recorded strong motion and intensity values throughout the region were first searched. Then, the data belonging to the 306 identified sites were processed, and the results were compiled as a new strong motion-intensity catalog. Based on this new catalog, two empirical equations between the values of intensity and the ground motion parameters (GMPs) for the Iranian earthquakes were calculated. At the first step, earthquake “intensity” was considered as a function of five independent GMPs including “Log (PHA),” “moment magnitude (MW),” “distance to epicenter,” “site type,” and “duration,” and a multiple stepwise regression was calculated. Regarding the correlations between the parameters and the effectiveness coefficients of the predictors, the Log (PHA) was recognized as the most effective parameter on the earthquake “intensity,” while the parameter “site type” was removed from the equations since it was determines as the least significant variable. Then, at the second step, a simple ordinary least squares (OLS) regression was fitted only between the parameters intensity and the Log (PHA) which resulted in more over/underestimated intensity values comparing to the results of the multiple intensity-GMPs regression. However, for rapid response purposes, the simple OLS regression may be more useful comparing to the multiple regression due to its data availability and simplicity. In addition, according to 50 selected earthquakes, an empirical relation between the macroseismic intensity (I0) and MW was developed.  相似文献   
33.
A carbonaceous chondrite was recovered immediately after the fall near the village of Diepenveen in the Netherlands on October 27, 1873, but came to light only in 2012. Analysis of sodium and poly‐aromatic hydrocarbon content suggests little contamination from handling. Diepenveen is a regolith breccia with an overall petrology consistent with a CM classification. Unlike most other CM chondrites, the bulk oxygen isotopes are extremely 16O rich, apparently dominated by the signature of anhydrous minerals, distributed on a steep slope pointing to the domain of intrinsic CM water. A small subset plots closer to the normal CM regime, on a parallel line 2 ‰ lower in δ17O. Different lithologies in Diepenveen experienced varying levels of aqueous alteration processing, being less aqueously altered at places rather than more heated. The presence of an agglutinate grain and the properties of methanol‐soluble organic compounds point to active impact processing of some of the clasts. Diepenveen belongs to a CM clan with ~5 Ma CRE age, longer than most other CM chondrites, and has a relatively young K‐Ar resetting age of ~1.5 Ga. As a CM chondrite, Diepenveen may be representative of samples soon to be returned from the surface of asteroid (162173) Ryugu by the Hayabusa2 spacecraft.  相似文献   
34.
This paper presents the results of a series of numerical experiments using the synthetic rock mass (SRM) approach to quantify the behaviour of jointed rock masses. Field data from a massive sulphide rock mass, at the Brunswick mine, were used to develop a discrete fracture network (DFN). The constructed DFN model was subsequently subjected to random sampling whereby 40 cubic samples, of height to width ratio of two, and of varying widths (0.05 to 10 m) were isolated. The discrete fracture samples were linked to 3D bonded particle models to generate representative SRM models for each sample size. This approach simulated the jointed rock mass as an assembly of fractures embedded into the rock matrix. The SRM samples were submitted to uniaxial loading, and the complete stress–strain behaviour of each specimen was recorded. This approach provided a way to determine the complex constitutive behaviour of large‐scale rock mass samples. This is often difficult or not possible to achieve in the laboratory. The numerical experiments suggested that higher post‐peak modulus values were obtained for smaller samples and lower values for larger sample sizes. Furthermore, the observed deviation of the recorded post‐peak modulus values decreased with sample size. The ratio of residual strength of rock mass samples per uniaxial compressive strength intact increases moderately with sample size. Consequently, for the investigated massive sulphide rock mass, the pre‐peak and post‐peak representative elemental volume size was found to be the same (7 × 7 × 14 m). Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
35.
Material transfer in underground mines often relies on ore and waste pass systems. In mines where ore pass systems transcend multiple production levels, finger raises are used to funnel material into the system. Empirical evidence, from several mines, suggests that the use of finger raises often results in damage in the immediate vicinity of finger raise-ore pass junctions. Of particular concern is damage on the ore pass walls as a result of impact loads generated by material flowing through the fingers on to the ore pass walls. The severity of damage is directly related to the rock mass quality of the excavation walls, material properties of transiting ore and the ore pass-finger raise configuration. This paper examines the influence of different configurations aiming to develop strategies to minimize ore pass wall damage. To these purposes the Particle Flow Code was employed to undertake a series of numerical experiments. This involved dumping a batch of rock fragments, represented by a uniform distribution of disc-shaped particles, into a finger raise and allowed to flow into an ore pass. It has been clearly demonstrated that higher impact loads were generated when the angle of intersection between ore pass and finger raise was 140° to 145°. This configuration results in the most damage. The results of these numerical experiments were collaborated by observations at an underground mine in Canada.  相似文献   
36.
To increase soil productivity, ameliorate nutrient scarcity, and reduce metal toxicity in highly weathered acidic soils usually requires fertilizer and lime application. Effects of three biochars on soil acidity, Olsen-phosphorus (P), phosphatase activities, and heavy metal availability were investigated to test potential of these biochars as soil amendments in highly weathered acidic soils. Incubation experiments were conducted for 6 weeks with three acidic soils: Alfisol, Ultisol, and Oxisol. Three biochars were derived from chicken manure (CMB), pig manure (PMB), and peat moss (PB) at 400 °C and applied at 1 or 2% (wt/wt). The addition of the three biochars increased Olsen-P in the three acidic soils in the following order: CMB?>?PMB?>?PB. Application of 2% CMB increased Olsen-P contents by 2.41-, 7.4-, and 1.78-fold in the Ultisol, Oxisol, and Alfisol compared with controls, respectively. Moreover, CMB increased the soil pH, electrical conductivity (EC), cation exchange capacity (CEC), and alkaline phosphatase activity, but reduced exchangeable acidity, acid phosphatase activity, and the availability of heavy metals—more effectively than PMB and PB. Addition of CMB increased soil pH by 0.90, 0.90, and 0.92 units for the Alfisol, Ultisol, and Oxisol, respectively, correspondingly followed by 0.80, 0.84, and 0.87 units for PMB and 0.15, 0.28, and 0.25 for PM. Changes in EC, CEC, and exchangeable acidity followed the same order for the three soils: CMB?>?PMB?>?PB. The results suggested that the magnitude of changes in soil properties and Olsen-P contents depended on biochar type and application rate. Application of CMB increased nutrient availability and reduced the availability of heavy metals more than other amendments. Due to higher pH, EC, and CEC, and greater concentrations of carbon, nitrogen, and exchangeable calcium and potassium, incorporation of CMB should be a better cost-effective method to correct soil acidity and improve fertility and Olsen-P contents in Ultisols and Oxisols from tropical and subtropical regions of the world.  相似文献   
37.
The present study deals with removal of 4-chloro-2-nitrophenol (4C2NP) as a model contaminant from pharmaceutical and pesticide industries using titanium dioxide nanoparticles as an adsorbent. 4C2NP is recalcitrant and persistent toward biodegradation and its generation in aqueous environment during formulation, distribution and field application of pesticides is often unavoidable. Batch experiments were carried out to investigate the effect of contact time, nano-titanium dioxide dosage, initial pH, initial 4C2NP concentration and temperature on adsorption efficiency. The results showed that the adsorption capacity was increased with increasing 4C2NP concentration and temperature. Optimum conditions for 4C2NP adsorption were found to be initial pH????2, nano-titanium dioxide dosage????0.01?g/250?mL and equilibrium time????1?h. Titanium dioxide nanoparticles recorded a maximum capacity of 86.3?mg/g at optimal conditions. The linear correlation coefficients of Langmuir, Freundlich and Temkin isotherms were obtained. The results revealed that the Freundlich isotherm fitted the experimental data better than the other isotherm models.  相似文献   
38.
All the conventional techniques for the analysis of slope stability ranging from simple kinematic analysis using stereonets, to the various widely used limit equilibrium methods, to sophisticated numerical methods belong to a category that are generally known as the analytic approaches and thus are only able to consider a limited number of affecting factors and then solve the problem in details. In contrast, the systems approaches not only can examine the problem in its totality with a complete list of the components, but also can take the interactions between the factors into account. This paper presents a complete application of a well-known systems technique named the Interaction Matrix (IM) in ranking the instability potential of rock slopes of the Khosh-Yeylagh Main Road, Iran as the case study of the research. For this purpose, 15 stations have been selected and a relatively comprehensive database containing the fieldwork information has been constructed. Following the IM technique, the most important factors relating to the general environment and to the rock mass characteristics have been considered. Their reciprocal causes and effects have been analyzed in order to weight each parameter according to its degree of interactivity in the system. Then, the slope instability index has been calculated which refers to the inherent potential instability of each slope of the examined region. The final instability ranking has been presented for the investigated slopes in Khosh-Yeylagh Main Road based on a simple classification. The main aim of the study is to extend the use of systems approach and specifically the IM technique in slope stability analysis. Also, this research shows the importance of consideration of an approximately complete set of key parameters affecting the stability of rock slopes.  相似文献   
39.
Applications of NTNU/SINTEF Drillability Indices in Hard Rock Tunneling   总被引:1,自引:1,他引:0  
Drillability indices, i.e., the Drilling Rate Index? (DRI), Bit Wear Index? (BWI), Cutter Life Index? (CLI), and Vickers Hardness Number Rock (VHNR), are indirect measures of rock drillability. These indices are recognized as providing practical characterization of rock properties used in the Norwegian University of Science and Technology (NTNU) time and cost prediction models available for hard rock tunneling and surface excavation. The tests form the foundation of various hard rock equipment capacity and performance prediction methods. In this paper, application of the tests for tunnel boring machine (TBM) and drill and blast (D&B) tunneling is investigated and the impact of the indices on excavation time and costs is presented.  相似文献   
40.
Journal of Geographical Systems - Despite all distortions and incompleteness present in Sketch maps, they can be used for different purposes such as collecting and searching spatial data and...  相似文献   
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