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21.
Debasis Sen Gupta 《Journal of Earth System Science》1995,104(3):407-417
Recrystallized grain size was measured from quartzite mylonite specimens collected from parts of Singhbhum shear zone in eastern
India. The specimens were collected along five traverses (Mushabani, Pathargora, Surda, Rakha and Jadugoda) across the elongation
of the shear zone. The sheared quartzites range from protomylonite through mylonite to ultramylonite. The microstructural
studies of the specimens reflect that dynamic recrystallization was the main deformation process. Estimation of flow stresses
were derived from these specimens using empirical equations relating to flow stress and recrystallized grain size. The calculated
stresses range from 12–28 MPa (Mercieret al 1977), 23–49 MPa (Twiss 1977), 20–68 MPa (Christie and Ord 1980), considering all the traverses. The results show that these
values can only be used semiquantitatively. 相似文献
22.
In Korea most of the old mine workings were worked with room and pillar method or sublevel caving method and today they possess
great possibility of surface subsidence especially for shallow depth mines. In most of the cases, mine roadways, rooms and
pillars are irregular in shape and information about the local geology is uncertain. For these reasons, it is difficult to
standardize the estimating method of subsidence especially sinkhole type over abandoned mine area. This paper describes the
application procedure for the fuzzy reasoning techniques to analyze the possibility of sinkhole occurrences over abandoned
mines. This technique is implemented in software which can simplify the analysis procedure and present the possibility of
sinkhole subsidence without having precise information about local geological/mining conditions. This technique has been applied
to forecast sinkhole possibilities at Bonghwa site where a massive sinkhole has already been occurred. 相似文献
23.
Ratkin V. V. Eliseeva O. A. Pandian M. S. Orekhov A. A. Mohapatra M. Vishnu Priya S. K. 《Geology of Ore Deposits》2018,60(8):672-684
Geology of Ore Deposits - A special investigation of fluid inclusions and geochemical and isotopic studies of their typomorphic features were carried out for danburite and datolite from skarn... 相似文献
24.
U. C. Mohanty Krishna K. Osuri A. Routray M. Mohapatra Sujata Pattanayak 《Marine Geodesy》2013,36(4):294-314
An attempt is made to delineate the relative performances and credentials of GFS, FNL, and NCMRWF global analyses/forecast products as initial and boundary conditions (IBCs) to the WRF-ARW model in the simulation of four Bay of Bengal tropical cyclones (TCs). The results suggest that FNL could simulate horizontal advection of vorticity maxima at 850 hPa; hence, the tracks are more realistic with least errors as compared to GFS and NCMRWF. The mean landfall errors for 24-, 48-, and 72-hour forecasts are 73, 41, and 72 km, respectively. The TC intensity is well captured by NCMRWF IBCs, as it could predict 850 hPa vorticity maxima. The 24-hour accumulated rainfall is well simulated with FNL, and equitable threat score is more than 0.2 up to 100 mm with minimum bias. 相似文献
25.
Construction of a 16-m deep, 55-m wide, almost square, underground structure through 8-m of soft soils and 8-m of sandstone and siltstone led to the development of widespread settlements. The affected area extended to distances of over 200 m from the perimeter of the structure. The floor slab of the underground structure was not designed for water pressure. Thus, operation of the structure requires continuous pumping of seepage water collected at a sump located at the lowermost elevation within the structure. Subsurface investigation and monitoring data obtained over 5.75-year period following the construction of the structure indicated that the settlement resulted from consolidation of soft soils due to depressurization of an aquifer within the underlying bedrock caused by continuous dewatering needed for the operation of the structure. An analytical study was undertaken to project the long term settlement. A simple analytical model could be used to simulate the complex hydrogeological problem reasonably. The details of hydrogeologic setting, subsurface investigation and monitoring activities, and the analytical model for projecting long-term settlements are presented in this paper. 相似文献
26.
27.
S. Mohapatra 《地球物理与天体物理流体动力学》2013,107(5):347-374
Scattering of oblique incident waves by small bottom undulation in a two-layer fluid, where the upper layer has a thin ice-cover while the lower one has the undulation, is investigated within the framework of linearized water wave theory. The ice-cover is being modeled as an elastic plate of very small thickness. There exist two modes of time-harmonic waves–one with lower wave number propagating along the ice-cover (ice-cover mode) and the other with higher wave number along the interface (interfacial mode). A perturbation analysis is employed to solve the corresponding boundary value problem governed by modified Helmholtz equation and thereby evaluating the reflection and transmission coefficients approximately up to first order for both modes. A patch of sinusoidal ripples, having two different wave numbers over two consecutive stretches, is considered as an example and the related coefficients are determined. It is observed that when the wave is incident on the ice-cover surface we always find energy transfer to the interface, but for interfacial incident waves there are parameter ranges for which no energy transfer to the ice-cover surface is possible. Also it is observed that for small angles of incidence, the reflected energy is more as compared to the other angles of incidence. These results are demonstrated in graphical form. From the derived results, the solutions for problems with free surface can be obtained as particular cases. 相似文献
28.
Outcrop of wad, about 3–5 m thick, associated with low to medium-grade manganese ore deposits in Iron Ore Group (IOG), is present in large quantum in Bonai-Keonjhar belt, Orissa. It is often inter-bedded with volcanic ash layers. Wad is powdery, fine grained, black to blackish-brown in colour, very soft, readily soils the fingers and its hardness on the Mohs’ hardness scale is 1–3. The wad zone is capped by a thin lateritic zone and overlies manganese ore beds of variable thickness in Dalki, Guruda and Dubna mines. Wad constitutes two mineral phases, viz. manganese oxides (δ-MnO2, manganite, romanechite with minor pyrolusite) and iron oxides (goethite/limonite and hematite) with minor clay and free quartz. Mixed limonite-clay and cryptomelane-limonite are commonly observed. Under microscope the ore appears oolitic, pisolitic, elipsoidal to globular in shape having small detritus of quartz, pyrolusite / romanechite and hematite at the core. The ore contains around 23% Mn and 28% Fe with ～7% of combined alumina and silica. Wad might have developed in a swampy region due to slow chemical precipitation of Fe-Mn-Co enriched fluid, nucleating over quartz/hematite grains. Influence of a marine environment is indicated from δ-MnO2 phase. Remnants of some microfossils, like algal filament, bacteria, foraminifera and diatomite are observed in wad sample under SEM. These microorganisms might have been responsible for the oxidation of dissolved Mn2+ and Fe2+ precipitates. These findings suggest biochemogenic origin of wad in Bonai-Keonjhar belt of Orissa. 相似文献
29.
A. J. Litta U. C. Mohanty S. Kiran Prasad M. Mohapatra Ajit Tyagi S. C. Sahu 《Natural Hazards》2012,61(3):1219-1242
A severe thunderstorm produced a tornado (F3 on the Fujita-Pearson scale), which affected Rajkanika block of Kendrapara district
of Orissa in the afternoon of March 31, 2009. The devastation caused by the tornado consumed 15 lives and left several injured
with huge loss of property. The meteorological conditions that led to this tornado have been analyzed. An attempt is also
made to simulate this rare event using Non-hydrostatic Mesoscale Model (NMM) core of the Weather Research and Forecasting
(WRF) system with a spatial resolution of 4 km for a period of 24 h, starting at 0000 UTC of March 31, 2009. The atmospheric
settings resulted from synoptic, surface, upper air, satellite and radar echo studies were favorable for the occurrence of
a severe thunderstorm activity over Rajkanika. The model-simulated meteorological parameters are consistent with each other,
and all are in good agreement with the observation in terms of the region of occurrence of the intense convective activity.
The model has well captured the vertical motion. The core of the strongest winds is shown to be very close to the site of
actual occurrence of the event. The wind speed is not in good agreement with the observation as it has shown the strongest
wind of only 20 ms−1, against the estimated wind speed of 70 ms−1. The spatial distributions as well as intensity of rainfall rates are in good agreement with the observation as model simulated
35.4 mm against the observed rainfall of 41 mm over Chandbali. The results of these analyses demonstrated the capability of
high-resolution WRF–NMM model in simulation of severe thunderstorm events. 相似文献
30.
M. Mohapatra G. S. Mandal B. K. Bandyopadhyay Ajit Tyagi U. C. Mohanty 《Natural Hazards》2012,63(3):1601-1620
Hazards associated with tropical cyclones are long-duration rotatory high-velocity winds, very heavy rain and storm tide. India has a coastline of about 7,516?km of which 5,400?km is along the mainland. The entire coast is affected by cyclones with varying frequency and intensity. The India Meteorological Department (IMD) is the nodal government agency that provides weather services related to cyclones in India. However, IMD has not identified cyclone-prone districts following any specific definition though the districts for which cyclone warnings are issued have been identified. On the other hand, for the purpose of better cyclone disaster management in the country, it is necessary to define cyclone proneness and identify cyclone-prone coastal districts. It is also necessary to decide degree of hazard proneness of a district by considering cyclone parameters so that mitigation measures are prioritised. In this context, an attempt has been made to prepare a list of cyclone hazard prone districts by adopting hazard criteria. Out of 96 districts under consideration, 12, 45, 31 and 08 districts are in very high, high, moderate and low categories of proneness, respectively. In general, the coastal districts of West Bengal, Orissa, Andhra Pradesh and Tamil Nadu are more prone and are in the high to very high category. The cyclone hazard proneness factor is very high for the districts of Nellore, East Godawari, and Krishna in Andhra Pradesh; Yanam in Puducherry; Balasore, Bhadrak, Kendrapara and Jagatsinghpur in Orissa; and South and North 24 Parganas, Medinipur and Kolkata in West Bengal. The results give a realistic picture of degree of cyclone hazard proneness of districts, as they represent the frequency and intensity of land falling cyclones along with all other hazards like rainfall, wind and storm surge. The categorisation of districts with degree of proneness also tallies with observed pictures. Therefore, this classification of coastal districts based on hazard may be considered for all the required purposes including coastal zone management and planning. However, the vulnerability of the place has not been taken into consideration. Therefore, composite cyclone risk of a district, which is the product of hazard and vulnerability, needs to be assessed separately through detailed study. 相似文献