Analysis of a progressive slope failure in the Xiangjiaba reservoir area,Southwest China   总被引：1，自引：0，他引：1  

Ling Xu  Fuchu Dai  Jian Chen  Javed Iqbal  Yongxin Qu 《Landslides》2014,11(1):55-66

The rehabilitation construction in the reservoir area of Xiangjiaba hydropower station in Southwest China has caused many landslides. A shallow progressive failure that occurred on the resettlement site of Xin’an Town of Pingshan County in Sichuan Province was selected as a case study. This landslide occurred in a long and gently inclined area by slope excavation under rainfall conditions. It is about 3.0 m deep with a total length of 35 m and is composed of some subfailures. Undisturbed samples were retrieved, on which the basic properties, shear strength, expansive potential, mineral compositions, and microstructures were tested and analyzed. The results show (1) the landsliding materials belong to medium expansive soil, consisting of the clay minerals of illite–smectite (I/S) and chlorite–smectite (C/S); (2) shear strength of the soil is sensitive to water, which greatly decreases once saturated; and (3) many fractures and relatively large pores are developed in the soils. Back analysis of the landslide shows that the shear strength at failure is less than the residual shear strength obtained from lab tests, indicating that some processes contributing to the slope failure could not be reflected by the shear box test. Based on the above analysis, the progressive process of the slope failure was interpreted, and it is inferred that the rainfall entered into the slope mainly through fractures and relatively large pores in the soil. It caused not only the great decrease in soil strength but also the swelling trend. The latter one would lead to growth, interaction, and coalescence of the fractures. Soon after, these fractures formed the shear planes (zones), which further decreased the resistance of the landslide. Under these favorable conditions, the slope excavation directly triggered the failure.  相似文献   

Spinels,Fe–Ti oxide minerals,apatites, and carbonates hosted in the ophiolites of Eastern Desert of Egypt: mineralogy and chemical aspects     

Abdel-Aal M. Abdel-Karim  Waheed I. Elwan  Hassan Helmy  Shymaa A. El-Shafey 《Arabian Journal of Geosciences》2014,7(2):693-709

Spinels, Fe–Ti oxide minerals, apatites, and carbonates hosted in ophiolitic serpentinites and metagabbros of Gabal Garf (southern ED) and Wadi Hammariya (central ED) of Egypt are discussed. Microscopic and electron probe studies on these minerals are made to evaluate their textural and compositional variations. Alteration of chromites led to form ferritchromite and magnetite; rutile–magnetite intergrowths and martite are common in serpentinites. Fine trillis exsolution of ilmenite–magnetite and ilmenite–hematite and intergrowth of rutile–magnetite and ilmenite–sphene are recorded. Composite intergrowth grains of titanomagnetite–ilmenite trellis lamellae are common in metagabbros. The formation of ilmenite trellis and lamellae in magnetite and titanomagnetite indicate an oxidation process due to excess of oxygen contained in titanomagnetite; trapped and external oxidizing agents. This indicates the high P _H2O and oxygen fugacity of the parental magma. The sulfides minerals include pyrrhotite, pyrite and chalcopyrite. Based on the chemical characteristics, the Fe–Ti oxide from the ophiolitic metagabbros in both areas corresponds to ilmenite. The patites from the metagabbros are identified as fluor-apatite. Carbonates are represented by dolomites in serpentinites and calcite in metagabbros. Spinel crystals in serpentinites are homogenous or zoned with unaltered cores of Al-spinel to ferritchromit and Cr-magnetite toward the altered rims. Compared to cores, the metamorphic rims are enriched in Cr# (0.87–1.00 vs. 0.83–0.86 for rims and cores, respectively) and impoverished in Mg# (0.26–0.48 vs. 0.56–0.67) due to Mg–Fe and Al (Cr)–Fe³⁺ exchange with the surrounding silicates during regional metamorphism rather than serpentinization process. The Fe–Ti oxides have been formed under temperature of ~800 °C for ilmenite. Al-spinels equilibrated below 500–550 °C, while the altered spinel rims correspond to metamorphism around 500–600 °C. Geochemical evidence of the podiform Al-spinels suggest a greenschist up to lower amphibolite facies metamorphism (at 500–600 °C), which is isofacial with the host rocks. Al-spinel cores do not appear to have re-equilibrated completely with the metamorphic spinel rims and surrounding silicates, suggesting relic magmatic composition unaffected by metamorphism. The composition of Al-spinel grains suggest an ophiolitic origin and derivation by crystallization of boninitic magma that belonging to a supra-subduction setting could form either in forearcs during an incipient stage of subduction initiation or in back-arc basins.  相似文献   

Rare Earth and High Field‐Strength Elements in the Multani Mitti Clay: A Study Using INAA     

Shahida Waheed  Naila Siddique  Yasir Faiz 《Geostandards and Geoanalytical Research》2013,37(2):197-205

Instrumental neutron activation analysis was used to determine nine rare earth elements (REE), Sc and five high field‐strength elements (HFSE) in the Multani Mitti (MM) clay. Chondrite‐normalised rare earth element patterns for the MM clay compared with those for the Post‐Archaean Australian Shale (PAAS), Upper Continental Crust (UCC) and North American Shale Composite (NASC) showed enrichment of light REEs and depletion of heavy REEs with a slight negative Eu anomaly. The Multani Mitti clay showed close resemblance to PAAS and NASC in its average REE and HFSE contents. Positive correlations between La/Ce, La/Sm, La/Yb, Zr/Hf, Th/U and Th/Ta ratios predict enrichment of LREEs, Zr and Th and depletion of HREEs. A parent source of felsic origin for the MM clay is also endorsed through the high La/Th and low Th/Sc ratios observed.  相似文献   

Influence of Icelandic Low pressure on winter precipitation variability over northern part of Indo-Pak Region     

Muhammad Jawed Iqbal  Kashif Ilyas 《Arabian Journal of Geosciences》2013,6(2):543-548

Several studies demonstrate that North Atlantic Oscillation (NAO) has dominant influence on the variability of climate over Southwest Asia. We deconstruct the NAO into its two components, the Azores High and the Icelandic Low. Regional circulations are influenced by changes not only in the pressure but also the positions of the Azores High and the Icelandic Low. The results presented in this paper exhibit that significantly great portions of interannual variance of winter precipitation over Indo-Pak Region (consists of Northeast Pakistan and Northwest India) can be explained by including the contributions of the Icelandic Low pressure in addition to ENSO and AO. This contribution also explains the physical mechanisms to establish the relationships between the COA and regional climate by examining composite maps of large-scale circulation fields using NCEP/NCAR reanalysis data.  相似文献   

A probabilistic approach for estimating return period of extreme annual rainfall in different cities of Punjab     

M. J. Iqbal  Muhammad Ali 《Arabian Journal of Geosciences》2013,6(7):2599-2606

Multi-day rainfall events are an important cause of recent severe flooding in Pakistan, and any change in the magnitude of such events may have severe impact upon urban structures such as dams, urban drainage systems, and flood. This article uses statistical distributions to define extremes of annual rainfall of different cities of Punjab (Lahore, Murree, Sialkot, and Jhelum) with given return periods. Our calculations suggest that general extreme value is the best-fitted distribution for the extreme annual rainfall of different cities of Punjab. Our calculations show that different cities of Punjab have 5 years return period for receiving more than 100 mm daily rainfall. While they have 30 years return period for receiving more than 200 mm daily rainfall. This asks for construction of new dams in Pakistan.  相似文献   

Indian record for Kepler's supernova: Evidence from Kashmir Valley     

A. Sule  A. Bandey  M. Vahia  N. Iqbal  M. Tabasum 《Astronomische Nachrichten》2011,332(6):655-657

We revisit a strange representation of the Sagittarius constellation painted on a door arch of a tomb in Kashmir. We show that it is a very strong case of a representation of Kepler's supernova (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Identification of the Phytoremediation Potential of Indian mustard Genotypes for Copper,Evaluated from a Hydroponic Experiment     

Mohd. Kafeel Ahmad Ansari  Elif Oztetik  Altaf Ahmad  Shahid Umar  Muhammad Iqbal  Gary Owens 《洁净——土壤、空气、水》2013,41(8):789-796

The effectiveness of 10 Indian mustard (Brassica juncea L.) genotypes (viz. Agrani, BTO, Kranti, Pusa Bahar, Pusa Basant, Pusa Bold, Pusa Jai Kisan, Vaibhav, Vardhan, and Varuna) were evaluated for their potential to phytoremediate copper from contaminated waters under laboratory controlled conditions. The genotypes were grown for 20 days in aqueous solutions containing various concentrations of copper sulfate (0–50 µM) in a hydroponic chamber. Throughout plant development, changes in growth variables, biomass accumulation, and total Cu content were evaluated. The results suggested that Indian mustard cv. Pusa Jai Kisan possesses the best capacities of Cu sequestration and tolerance amongst all the genotypes studied. Thus, Pusa Jai Kisan has the greatest potential to become a viable candidate in the development of practical phytoremediation technologies for Cu contaminated sites.  相似文献   

Assessment of Heavy Metal Contamination in Soil and Groundwater at Leather Industrial Area of Kasur,Pakistan   总被引：1，自引：0，他引：1       下载免费PDF全文

Muhammad Afzal  Ghulam Shabir  Samina Iqbal  Tanveer Mustafa  Qaiser Mahmood Khan  Zafar Mahmood Khalid 《洁净——土壤、空气、水》2014,42(8):1133-1139

  相似文献   

Adaptive state estimation of groundwater contaminant boundary input flux in a 2-dimensional aquifer     

Muhammad Malik Nauman  Murtuza Mehdi  Asif Iqbal  Muhammad Saifullah Abu Bakar  Brahim Aissa  Dk Nur Afiqah Jalwati Puteri  Amer Farhan Rafique 《地下水科学与工程》2019,(4):373-382

In many circumstances involving heat and mass transfer issues,it is considered impractical to measure the input flux and the resulting state distribution in the domain.Therefore,the need to develop techniques to provide solutions for such problems and estimate the inverse mass flux becomes imperative.Adaptive state estimator(ASE)is increasingly becoming a popular inverse estimation technique which resolves inverse problems by incorporating the semi-Markovian concept into a Bayesian estimation technique,thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters.The ASE is particularly designed for a system that encompasses independent unknowns and/or random switching of input and measurement biases.The present study describes the scheme to estimate the groundwater input contaminant flux and its transient distribution in a conjectural two-dimensional aquifer by means of ASE,which in particular is because of its unique ability to efficiently handle the process noise giving an estimation of keeping the relative error range within 10%in 2-dimensional problems.Numerical simulation results show that the proposed estimator presents decent estimation performance for both smoothly and abruptly varying input flux scenarios.Results also show that ASE enjoys a better estimation performance than its competitor,Recursive Least Square Estimator(RLSE)due to its larger error tolerance in greater process noise regimes.ASE's inherent deficiency of being slower than the RLSE,resulting from the complexity of algorithm,was also noticed.The chosen input scenarios are tested to calculate the effect of input area and both estimators show improved results with an increase in input flux area especially as sensors are moved closer to the assumed input location.  相似文献   

Quaternary fossil coral communities in uplifted strata along the Balochistan coast of Pakistan: understanding modern coral decline in the Arabian Sea     

Amjad Ali  Pirzada Jamal A. Siddiqui  Kate Bromfield  Athar Ali Khan  Pervaiz Iqbal 《Arabian Journal of Geosciences》2017,10(23):520

Uplifted reefs due to being important palaeoclimate archives and a rich source of information on past physical and geochemical changes globally have become the centre of marine research. The uplifted fossil Quaternary coral communities of Jiwani and Gwadar are perfect places to study the palaeoclimatic and geological changes that have shaped the Balochistan coast. Studies on the palaeodiversity of corals along the Makran coast of Pakistan are lacking. In the present study, the samples collected using line intercept method from four uplifted sites (Balochistan coast: one at Gwadar and three at Jiwani) were analysed. The relative distribution and diversity of scleractinian fossil corals was determined, and the factors responsible for coral decline along Pakistan coast were compared with modern coral distribution and diversity. A total of 48 fossil coral species were recorded in nine families and 22 genera. High coral diversity was recorded in the uplifted landward sites of Jiwani and Gwadar headland. Terraces close to the shore at Jiwani had lower diversity. The corals seem to be Quaternary: most likely Pleistocene to Holocene. The modern fauna lacks many species recorded in the fossil community, thus suggesting a faunal turnover in diversity and redistribution of coral fauna which may be linked with past geological events and increasing anthropogenic pressure.  相似文献