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721.
M. Ahmad M. K. Ansari Rajesh Singh L. K. Sharma T. N. Singh 《Geotechnical and Geological Engineering》2017,35(2):827-842
Weathering and durability are the key factors of the rock in the suitability and usefulness of different construction materials, building materials and engineering structures. A single test never predicts the entire factor for suitability of rock stone and aggregate in different uses. Thus, variety of physical, mechanical and chemical tests and indices of rocks are widely used to estimate and evaluate the rocks for the suitability of the required purpose. In all the cases, knowledge of durability and weathering properties are the most important along with the strength of the rock. Micropetrographic index and rock durability indicators (dynamic and static) are the one of the best methods to evaluate the rock for weathering and durability. To estimate these indices, variety of tests are performed such as petrographic examination test, point load index, sulfate soundness test, water absorption test, modified aggregate impact value test and test for specific gravity. Slake durability index and impact strength index tests were also performed for correlation with static and dynamic rock durability indicators due to its application and usefulness in the durability and strength of the rock materials. Micropetrographic index was obtained by petrographic examination test and correlated with all the physical and mechanical properties used for find out the durability indicators. The present study is to express the usefulness of these three indices in the classification of weathering and durability classes and estimation of durability indices by slake durability index, impact strength index and micropetrographic index. 相似文献
722.
Majid Dehghani Bahram Saghafian Firoozeh Rivaz Ahmad Khodadadi 《Arabian Journal of Geosciences》2017,10(12):266
In this study, application of a class of stochastic dynamic models and a class of artificial intelligence model is reported for the forecasting of real-time hydrological droughts in the Black River basin in the USA. For this purpose, the Standardized Hydrological Drought Index (SHDI) was adopted in different time scales to represent the hydrological drought index. Six probability distribution functions (PDF) were fitted to the discharge time series to obtain the best fit for SHDI calculation. Then, a dynamic linear spatio-temporal model (DLSTM) and artificial neural network (ANN) were used to forecast SHDI. Although results indicated that both models were able to forecast SHDI in different time scales, the DLSTM was far superior in longer lead times. The DLSTM could forecast SHDI up to 6 months ahead while ANN was only capable of forecasting SHDI up to 2 months ahead appropriately. For short lead times (1–6 months), the DLSTM has performed nearly perfect in test phase and CE oscillates between 0.97 and 0.86 while for ANN modeling, CE is between 0.72 and 0.07. However, the performance of DLSTM and ANN reduced considerably in medium lead times (7–12 months). Overall, the DLSTM is a powerful tool for appropriately forecasting SHDI at short time scales; a major advantage required for drought early warning systems. 相似文献
723.
Mehdi Veiskarami Mir Ahmad Lashteh Neshaei Mehran Karimpour Fard Tina Pourramezan 《Marine Georesources & Geotechnology》2017,35(1):42-51
Marine structures which cover a wide range of offshore and onshore structures are often subjected to different external and internal forces against which a proper design should be performed. Among many, breakwaters constructed over a relatively loose agglomerate of granular soils are much prone to deep seated failure extended beneath the foundation. This type of failure has been given less attention in conventional design approaches. Stability analysis of such failures is the main subject of this research which includes both the static and the seismic stability of breakwaters over granular marine soils. As the subsoil strata in sea beds often comprise loose sand deposits, it is more convenient to assume a rather small angle of dilation, at least at failure, which certainly reduces the potential to resist geotechnical instabilities. The method of stress characteristics along with slight modifications to handle this issue has been used to assess the overall stability of breakwaters against deep seated failures. Investigations revealed that while even under static condition, there is certain potential of failure, under seismic condition, the risk is quite very high. A series of design charts are also developed presenting the factor of stability as a measure of safety against such failure. 相似文献
724.
Michael Fuchs Adnan A. Awan Sardar S. Akhtar Ijaz Ahmad Simon Sadiq Asif Razzak Naghmah Haider 《山地科学学报》2017,14(5):948-963
In the frame of landslide susceptibility assessment, a spectral library was created to support the identification of materials confined to a particular region using remote sensing images. This library, called Pakistan spectral library (pklib) version 0.1, contains the analysis data of sixty rock samples taken in the Balakot region in Northern Pakistan. The spectral library is implemented as SQLite database. Structure and naming are inspired by the convention system of the ASTER Spectral Library. Usability, application and benefit of the pklib were evaluated and depicted taking two approaches, the multivariate and the spectral based. The spectral information were used to create indices. The indices were applied to Landsat and ASTER data to support the spatial delineation of outcropping rock sequences in stratigraphic formations. The application of the indices introduced in this paper helps to identify spots where specific lithological characteristics occur. Especially in areas with sparse or missing detailed geological mapping, the spectral discrimination via remote sensing data can speed up the survey. The library can be used not only to support the improvement of factor maps for landslide susceptibility analysis, but also to provide a geoscientific basis to further analyze the lithological spot in numerous regions in the Hindu Kush. 相似文献
725.
The Asmari Formation consists of shallow marine sedimentary rocks deposited on ramp setting .Lar-ger benthic foraminifera collected from Asmri Formation are dominated by hyaline and porcelanouse forms , in-cluding Amphistegina, Nummulites, Archaias, Astrotrillina, Miogypsinella, Miogypsinoides, Lepidocyclina, Operculina, Spiroclypeous and Miliolids.The presence of Nummulites cf.vascus in the lower part of the forma-tion allows the age to be determined as Rupelian .The occurrence of Borelis pygmae is an index taxon of the Ru-pelian-Chattian and indicates Early Chattian of SBZ 21-22 in the study section .The first appearance of Mio-gypsinella akadagensis shows Late Chattian ( SBZ 23) and defines the upper boundary of the SBZ 21-22.The new data are the first evidences showing that the shallow marine Asmari Formation is attributed to Oligocene (Rupelian-Chattian) age for this region. 相似文献