The Shear Behavior of Bedding Planes of Weakness Between Two Different Rock Types with High Strength Difference   总被引：4，自引：2，他引：2  

A. H. Ghazvinian  A. Taghichian  Mahmoud Hashemi  S. A. Mar’ashi 《Rock Mechanics and Rock Engineering》2010,43(1):69-87

In this article, the shear behavior of discontinuities caused by bedding planes of weakness between two different rock types with high strength difference is investigated. The effect of roughness and compressive strength of joint wall in such discontinuities are studied. The designed profiles consist of two regular and three irregular artificial joints molded by three types of plaster mortars with different uniaxial compressive strengths. Firstly, it is demonstrated that the shear behavior of discontinuities with different joint wall compressive strengths (JCS) is different from rock joints with identical wall compressive strengths by showing that Barton’s empirical criterion is not appropriate for the former discontinuities. After that, some correlation equations are proposed between the joint roughness coefficient (JRC) parameter and some surface statistical/fractal parameters, and the normal stress range of Barton’s strength criterion is also modified to be used for such discontinuities. Then, a new empirical criterion is proposed for these discontinuities in such a way that a rational function is used instead of JRC log₁₀(JCS/σ _n) as i ₀(σ _c/σ _n)^a/[b + (σ _c/σ _n) ^a ] by satisfying the peak dilation angle boundary conditions under zero and very high normal stress (physical infinite normal stress causing zero peak dilation angle). The proposed criterion has three surface parameters: i ₀, a, and b. The reason for separation of i ₀ from JRC is indicated and the method of its calculation is mentioned based on the literature. The two remaining coefficients (a and b) are discussed in detail and it is shown that a shows a power-law relationship with b, introducing the coefficient c through b = c ^a . Then, it is expressed that a is directly related to discontinuity surface topography. Finally, it is shown that the coefficient c has higher values in irregular profiles in comparison with regular profiles and is dominated by intensity of peak dilation angle reduction (majorly related to the surface irregularity and minorly related to roughness). The coefficient c is to be determined by performing regression analysis on experimental data.  相似文献   

Impact and analysis of geotechnical processes on earthfill dam breaching   总被引：2，自引：2，他引：0  

Mahmoud Al-Riffai  Ioan Nistor 《Natural Hazards》2010,55(1):15-27

For over three decades, emergency planners have used numerical models to predict breaching in earthfill dams due to extreme events such as overtopping. However, current models neglect the role of the unsaturated zone present within the downstream face of an earthfill dam. This leads to an incorrect estimation of the time and space evolution of the breaching process, as such models often oversimplify governing geotechnical aspects such as the presence of the unsaturated soil medium in the vicinity of the breach channel. The stress state in the soil due to matric suction acts as a stabilizing force for the breaching mechanism and influences the erosion of the breach channel, especially during the initial phases of the breaching. The side-slope failure mechanism observed along the breach channel is also influenced by the negative pore-water-pressures in the soil. Based on a comprehensive experimental research program carried out in the Hydraulics Laboratory at the University of Ottawa, Canada, several new concepts are proposed to incorporate geotechnical factors and techniques which must be considered during the construction of earthfill dam models for laboratory testing. Two main findings emerged from this experimental work. First, the installation of a drainage mattress at the downstream toe of the dam depressed the phreatic surface through the earthfill dam body, which caused a lag in the breaching process due to the infiltration and reduced erosion occurring in the breach channel. Second, it is essential to control compaction during the construction of the earthfill dam model, since this significantly influences the erosion, as well as the side-slope failures which occur in the breach channel. Future studies are under way by the authors with the purpose of scaling of parameters such as the matric suction and soil erodibility.  相似文献   

Shear strength characteristics of sand-mixed with granular rubber   总被引：1，自引：0，他引：1  

Mahmoud Ghazavi 《Geotechnical and Geological Engineering》2004,22(3):401-416

Waste materials such as waste tires, rubbers, and plastic materials are normally produced in every society, entering the environment and causing serious problems. These problems may be somehow reduced by finding applications for them in engineering, for example, as lightweight materials for backfill in geotechnical projects. To this aim, this paper demonstrates how shear strength characteristics of sand mixed with various percentages of waste garden hose grains are altered. A relatively, uniform sand has been mixed with waste hose grains in loose and slightly compacted states. Waste hose grains were prepared with special popular machinery in a local area. Various sand-rubber mixtures having 0%, 10%, 15%, 20%, 50%, 70%, and 100% waste hose particles by weight were chosen. The rubber grains were distributed in the sand such that uniform mixtures are obtained. In order to compare the shear strength of different sand-rubber samples, two compaction states were considered. The results show that the influencing parameters on shear strength characteristics of sand-rubber mixtures are normal stress, mixture unit weight, and rubber content. With the selected waste hose particles, compaction states, and rubber contents, the initial friction angle φ₁ does not change significantly. However, an apparent cohesion appears in the mixtures. From environmental point of view and due to lightweight material for the sand-waste hose particles, it may be useful to use such materials in corresponding geotechnical projects. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Silver and silver-bearing minerals at the Um Samiuki volcanogenic massive sulphide deposit, Eastern Desert, Egypt     

Ibrahim M. Shalaby  Eugen Stumpfl  Hassan M. Helmy  Mahmoud M. El Mahallawi  Omar A. Kamel 《Mineralium Deposita》2004,39(5-6):608-621

The Um Samiuki Zn–Cu–Pb–Ag mineralisation, south Eastern Desert, Egypt is hosted by felsic volcanic rocks which form part of the 712-Ma-old, east-west-trending Shadli Volcanic Belt. Two major occurrences of massive sulphides are present at the top of rhyolitic breccia in the Western and Eastern mine areas. In each occurrence, a bornite-bearing zone is overlain by a pyrite-chalcopyrite-bearing zone and underlain by a disseminated, Cu-depleted zone. In the massive sulphide ore, sphalerite, chalcopyrite, pyrite, galena, bornite and tetrahedrite–tennantite are major minerals, whereas arsenopyrite, pyrrhotite, molybdenite and magnetite are accessory phases. Covellite and digenite are common secondary minerals. Bornite, tetrahedrite–tennantite and covellite contain high amounts of silver (averages of 1.97, 1.39 and 1.82 wt% respectively). Based on mineralogical balance calculations, bornite and covellite accommodate 80% of silver in the Um Samiuki deposit. Ag was incorporated in the crystal structure of the early-crystallised copper sulphides and sulphosalts and silver minerals. The temperature, sequential precipitation of the fluids and the structure of the crystallising phases control the distribution of silver. Post-depositional deformation and metamorphic processes caused liberation, remobilisation and redeposition of silver within the massive sulphides.Editorial handling: D. Lentz  相似文献   

GPS constraints on Africa (Nubia) and Arabia plate motions   总被引：16，自引：0，他引：16  

S. McClusky  R. Reilinger  S. Mahmoud  D. Ben Sari  A. Tealeb 《Geophysical Journal International》2003,155(1):126-138

  相似文献   

Worth of head data in well-capture zone design: deterministic and stochastic analysis     

Mahmoud I. Bakr  Adrian P. Butler 《Journal of Hydrology》2004,290(3-4):202-216

In this study, we examine the effects of conditioning spatially variable transmissivity fields using head and/or transmissivity measurements on well-capture zones. In order to address the challenge posed by conditioning a flow model with spatially varying parameters, an innovative inverse algorithm, the Representers method, is employed. The method explicitly considers this spatial variability.

A number of uniform measurement grids with different densities are used to condition transmissivity fields using the Representers method. Deterministic and stochastic analysis of well-capture zones are then examined. The deterministic study focuses on comparison between reference well-capture zones and their estimated mean conditioned on head data. It shows that model performance due to head conditioning on well-capture zone estimation is related to pumping rate. At moderate pumping rates transmissivity observations are more crucial to identify effects arising from small-scale variations in pore water velocity. However, with more aggressive pumping these effects are reduced, consequently model performance, through incorporating head observations, markedly improves. In the stochastic study, the effect of conditioning using head and/or transmissivity data on well-capture zone uncertainty is examined. The Representers method is coupled with the Monte Carlo method to propagate uncertainty in transmissivity fields to well-capture zones. For the scenario studied, the results showed that a combination of 48 head and transmissivity data could reduce the area of uncertainty (95% confidence interval) in well-capture zone location by over 50%, compared to a 40% reduction using either head or transmissivity data. This performance was comparable to that obtained through calibrating on three and a half times the number of head observations alone.  相似文献   

Effect of the damping and excitation on the identification of the hydrodynamic parameters for an underwater robotic vehicle     

Ayman B. Mahfouz  Mahmoud R. Haddara 《Ocean Engineering》2003,30(8):589-1025

The main objective of this work is to investigate the effects of the damping level as well as different excitation forms on the overall prediction of the hydrodynamic parameters in the equations describing the coupled heave and pitch motions for an Underwater Robotic Vehicle (URV) sailing near the sea surface in random waves. The response of an underwater vehicle heaving and pitching in random waves having wide-band and narrow-band spectra are generated. The RDLRNNT technique is used to identify the hydrodynamic parameters in the equations. The technique is based on a combination of a multiple linear regression algorithm and a neural networks technique. The combination of the classical parametric identification techniques and the neural networks technique provides robust results and does not require a large amount of computer time. The identification technique would be particularly useful in identifying the parameters for both moderately and lightly damped motions under the action of unknown excitations effected by a realistic sea. It is shown that the developed technique produces reliable results for the parameters in the equations describing the coupled heave and pitch motions for a URV.  相似文献   

Estimating of water erosion in semiarid regions using RUSLE equation under GIS environment   总被引：1，自引：0，他引：1  

Omar Djoukbala  Mohamed Mazour  Mahmoud Hasbaia  Oussama Benselama 《Environmental Earth Sciences》2018,77(9):345

Water erosion is one of the main forms of land degradation in Algeria, with a serious repercussion on agricultural productivity. The purpose of this study is to estimate the soil loss of Wadi El-Ham watershed in the center of Algeria, this study aims also to evaluate the effectiveness and reliability of the use of the Revised Universal Soil Loss Equation (RUSLE) under a Geographic Information System in this field. The RUSLE model involves the main factors of erosion phenomena, namely, rain aggressiveness, soil erodibility, topographic factor, land cover index and the anti-erosive practices factor. Using this approach, the specific erosion in Wadi El-Ham watershed is estimated as 5.7 (t/ha/yr) in the entire watershed area. This result is compared to the measured suspended sediment at the Rocade-Sud gauging station situated outlet the watershed. These data consist of 1293 instantaneous measures of the water discharge and the suspended sediment concentration recorded during 21 years. Through this comparison, the used approach of RUSLE under GIS estimates the soil loss in Wadi El-Ham in Hodna region of Algeria with an error of 7.5%. Consequently, the results obtained in cartographic format make it possible to target the areas requiring priority action for a larger scale analysis to find appropriate solutions to combat erosion and to protect the natural environment.  相似文献   

Mineralogy and geochemistry studies on the Nusab El Balgum granitic batches,South Western Desert,Egypt     

Soliman Abu Elatta A. Mahmoud  Anthony E. Williams-Jones 《Arabian Journal of Geosciences》2018,11(18):556

Igneous rocks of Nusab El Balgum are formed as an elongated complex mass covering an area of about 4 km?×?12.5 km (50 km²), in the NNE-SSW direction of the Tarfawi-Qena-South Sinai trend, which is a branch of the Trans-African shear zone at the intersection with the Kalabsha fault, which is a branch from Guinean-Nubian lineaments. The continuous reactivation of these two major weakness zones from the late Triassic to recent times has created many generations of the magma batches. The exposed granitic rocks of these batches at Nusab El Balgum were represented by the fresh peralkaline granite (youngest) and hydrothermally altered granites (oldest). The fresh peralkaline granite takes the form of a small stock composed essentially of perthites, quartz, sodic pyroxenes, amphiboles (secondary), and rare albite according to the proportion of presence, respectively. The accessory minerals are zircon, bastnaesite-(Ce), columbite-(Fe), magnetite, barite, and sphalerite. The geochemical study indicated that this granite is peralkaline, ferroan, A-type (specifically belongs to the A1-subgroup), anorogeny, emplaced in a within-plate, and crystallized at relatively shallow depth from the alkali basaltic magma similar to the OIBs. Furthermore, it is enriched in the HFSE (e.g., Th, U, Nb, REE, and Zr). The hydrothermally altered granites are formed as an incomplete ring shape and a small stock. They were formed during the late Cretaceous age and were altered due to the hydrothermal solutions from the continuous reactivation affected weakness zones and the new magmatic batches. The hydrothermally altered granites are extremely rich in HFSE found in the accessory minerals such as zircon (different in shape, size, and contains inclusions of bastnaesite and columbite), columbite-(Fe&Mn), rare gittinsite, pyrochlore minerals (ceriopyrochlore and plumbopyrochlore) carlosbarbosaite, changbaiite, bastnaesite-(Ce), monazite-(Ce), stetindite, cerianite-(Ce), thorite, and uranothorite. These rocks were subjected to many highly superimposed hydrothermal alteration types, including propylitic, sericitic, potassic, silicification, argillic, and Fe-Mn oxy-hydroxides. The hydrothermal solutions with low temperatures and containing F^1? and CO₃^2?, PO₄^3? and H₂O caused redistribution; transportation and redeposition of the HFSE in these rocks, in addition to the clay minerals and K-metasomatism, were formed. The relations between the silicification index (SI?=?SiO₂/(SiO₂ + Al₂O₃) and Zr, Nb, Th, U, LREE, and HREE are positive but they become negative with the K-metasomatism.  相似文献   

Mapping Oolitic Iron Ore Deposits in the Ashumaysi Formation,Western Saudi Arabia,Using Different Remote Sensing Techniques Applied to Landsat 7 Enhanced Thematic Mapper Plus Data (ETM+)     

Habes A. Ghrefat  Abdullah A. Al Zahrani  Mahmoud A. Galmed 《Journal of the Indian Society of Remote Sensing》2018,46(9):1399-1411

Mapping the surficial extent of oolitic iron ore deposits hosted in the Oligo–Miocene sedimentary rocks of the Ashumaysi Formation, western Saudi Arabia, was carried out using Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data. Ore samples were collected from four various locations in the study area, and were studied in the laboratory using the GER 3700 Spectroradiometer (0.4–2.5 µm) and X-ray diffraction (XRD). Principal component analysis (PCA), minimum noise fraction (MNF), and minimum distance classification were used and assessed to map mineralization zones in the study area. Good correspondences were observed between the results obtained from the above mentioned techniques, spectral reflectance analyses, and XRD. The confusion matrix results revealed that mapping of iron ores using MNF is better and more accurate than using PCA. Good matching was also observed between the spectral reflectance curves of the collected samples and the corresponding pixels from Landsat 7 ETM+. The results demonstrated the usefulness of the image processing and interpretation of Landsat 7 ETM+ data for the detection and delineation iron ore deposits in arid and semi-arid areas.  相似文献