It has been long recognised that some of the fundamental and engineering properties of soils exhibit a certain degree of anisotropy that eventually dictates their directional geoengineering behaviours. Consideration of the importance of the volume change behaviour of soils during shrinkage and a critical review of the literature suggests scopes for further research for the development of a better understanding of the anisotropy in volume change encountered during soil shrinkage. In this paper, anisotropy in volumetric shrinkage behaviour of soil is depicted with the theory of geometry factor and shrinkage strains. A systematic investigation and analysis on the evolution of geometry factors and shrinkage strains of several geomaterial samples during evaporative dewatering is reported herein. A theoretical framework for evaluating shrinkage geometry factors of a cylindrical soil specimen undergoing volume change during progressive moisture loss is described in this paper. Furthermore, based on experimental and literature data, shrinkage geometry factors of several specimens differing in terms of gradational properties, specimen size, evaporative boundary condition and pore fluid salinity are evaluated and discussed in detail in accordance with the theoretical framework. Linkages between shrinkage process, shrinkages strains and geometry factor are also analysed to underpin the usage of geometry factor and shrinkage strains to characterise anisotropy during soil shrinkage.
Land degradation due to soil erosion is a global problem, especially on cultivated hill slopes. Economically important aromatic grasses can protect degraded hill slopes more effectively than field crops, but little information is available on their performance. This study quantifies runoff, sediment yield,enrichment ratios of soil and nutrients, and sediment-associated organic carbon and nutrients losses under three aromatic grass species: citronella(Cymbopogon nardus), lemon(Cymbopogon flexuosus), and palmarosa(Cymbopogon martini), compared with a traditional field crop, finger millet(Eleusine coracana)grown at three land slopes(4%, 8%, and 12%). It was observed that the degree of slope and type of grass both significantly influenced runoff generation. Runoff and sediment yield(SY) were significantly higher at 12% slope than at 8% and 4% slopes. Relation between rainfall and runoff were significant for all the grass species(p 0.05). Palmarosa, lemon, and citronella grass reduced the SY by 10, 54, and 60%,respectively, over finger millet. SY was also significantly related to rainfall for all the treatments(p 0.05). The threshold runoff values to produce SY were higher for aromatic grasses compared to finger millet. Enrichment of clay, silt, sand, soil organic carbon(SOC), available nitrogen(N), phosphorus(P) and potassium(K) in the sediment were not significantly different between slopes but differed significantly between aromatic grasses and finger millet. Sediment associated nutrient load varied inversely with SY mainly because of the nutrient dissolution effect of high runoff volume. Annual loss of SOC and nutrients varied from 84.7-156.8 kg ha~(-1) y~(-1) for SOC, 4.38-9.18 kg ha~(-1) y~(-1) for available N, 0.35-0.75 kg ha~(-1) y~(-1) for available P, and 2.22-5.22 kg ha~(-1) y~(-1) for available K, with the lowest values for citronella and highest for finger millet. The study found that the aromatic grasses have greater environmental conservation values than finger millet on steep degraded land. 相似文献
Besides offering significant clues towards tracking the geochemical evolution of the mantle and architectural reconstruction
of different ‘supercontinent’, geochronological and geochemical appraisal of igneous inputs are also important to bracket
the depositional time frame of any lithopackage, particularly, the unfossiliferous sedimentary successions. The present study
deals with diabasic intrusive within Mesoproterozoic Saraipalli Formation, which is an argillaceous constituent present at
the basal part of nearly 400 m thick four-tiered unmetamorphosed but deformed sedimentary succession of Singhora Group, Chhattisgarh
Supergroup, central India. The SE–NW trending intrusive comprises mainly of plagioclase and augite together with minor orthopyroxene,
biotite and opaque minerals. Though some plagioclase laths are partially sericitized, the ophitic-to-subophitic texture of
the rock is well preserved. Major and trace element geochemical data indicate that this intrusive is basalt-to-basaltic andesite
in character and of subalkaline basalt affinity. Multi-element plot shows overall LILE-enrichment and enrichment of Pb and
slight depletion of Nb and P, coupled with moderate La/Nb and Th/Nb ratios. Zr, Y and Nb ternary diagrams plot in the fields
of within plate basalt. Selected HFSE ratios indicate a non-plume source with crustal assimilation/sediment mixing. Sm–Nd
and Rb–Sr isotope data show that the intrusive has Srinitial and Ndinitial of 0.709377–0.706672 and 0.510919–0.510815, respectively. Positive εtNd [t = 1420 Ma] values (+0.3 to + 2.3) indicate depleted isotopic nature of their protolith. The calculated TDM age is 1.7–1.9 Ga. The mineral-whole rock isochron data (Sm–Nd systematics) of the intrusive implies an emplacement age of
ca. 1420 Ma. Considering synchronous terrain boundary shear zone development in Bastar craton on the southeastern part of
the Singhora basin, mafic magmatism in Eastern Ghats and large-scale basic intrusion in Sausar mobile belt, a major tectono-thermal
event around 1400 Ma is surmised that affected eastern Indian craton. Moreover, geochronology of a bedded porcellanite unit
(ca. 1500 Ma) at the base and a discordant basic intrusive (ca. 1420 Ma) allowed a unique opportunity to qualitatively offer
an upper bound of time bracket for the deposition of Saraipalli Formation, i.e., ∼80 Ma. 相似文献
Seismicity data of northeast India, recorded between 1986 and 1999 by a local network, are analysed for estimation of b-values. Based on the obtained values, viz. low (b ≤ 0.5), moderate (0.5 < b ≤ 0.7) and high (b > 0.7), the study area is classified into different seismic-domains. An assessment of stress level is also carried out in
identifying seismic-domains. Seismic activities, though mostly confined in some sectors, are presumably triggered by mutual
interaction of the Shillong Plateau, Mikir Hills, Indo-Burman Ranges and the easternmost part of the Himalayas, and the contributions
from deep-seated fractures cannot be ignored. The results resemble the seismic character of a foreland setting adjacent to
a convergent margin. The b-values estimated for 240 square grids of dimension 0.6° × 0.6° over five seismic domains indicate wide variation. An analysis
of cumulative seismic moment release (MO) in different layers also indicates an anomaly in reference to the total seismic-energy budget of the five zones. The lower
b-value and higher MO recorded at relatively lower depth (~30 km) towards the southwest of the study area might be associated with upward bulging
of a strong lithosphere. The bulging is perhaps regionally compensated by the downward flexing of the descending Indian lithosphere
beneath the Upper Assam area; features unequivocally observed in any foreland setup. Towards the north and east of the study
area, random variations of in both b-value and MO along the converging zone suggest a varied tectonic environment with active interaction between the tectonic elements in
these areas. 相似文献
Intensive agriculture by indiscriminate use of agrochemicals, sewage water, and polluted drain water has posed a serious threat to groundwater quality in some peri-urban areas of Delhi like Najafgarh block. The objective of the study was to determine the groundwater quality and to map their spatial variation in terms of suitability for irrigation and drinking purpose. Ordinary kriging method was used for preparation of thematic maps of groundwater quality parameters such as electrical conductivity, sodium adsorption ratio, bicarbonate, magnesium/calcium ratio, total dissolved solids, chloride, nitrate and hardness. Exponential semivariogram model was best fitted for all quality parameters except chloride and hardness, where spherical model fitted best. Pollution level was highest at south and south-eastern part of the study area. Better quality groundwater may be expected at the northern and western part. High salinity was due to high chloride concentration in the groundwater. Nitrate pollution level was found to be very alarming and need immediate interventions. High dissolved solids and hardness made the groundwater unsuitable for drinking. There were negligible sodium and bicarbonate hazard in the study area. The groundwater quality index was devised to analyse the combined impact of different quality parameters on irrigation and drinking purposes. The irrigation water quality index and drinking water quality index distribution maps delineated an area of 47.29 and 6.54 km2 suitable for irrigation and drinking, respectively. These safe zones were found as a small strip along the northern boundary and a very small pocket at the western side of the study area. 相似文献
The concept of oscillatory Universe appears to be realistic and buried in the dynamic dark energy equation of state. We explore its evolutionary history under the framework of general relativity. We observe that oscillations do not go unnoticed with such an equation of state and that their effects persist later on in cosmic evolution. The ‘classical’ general relativity seems to retain the past history of oscillatory Universe in the form of increasing scale factor as the classical thermodynamics retains this history in the form of increasing cosmological entropy. 相似文献
Secondary aerosol formation was studied at Allahabad in the Indo-Gangetic region during a field campaign called Land Campaign-II
in December 2004 (northern winter). Regional source locations of the ionic species in PM10 were identified by using Potential Source Contribution Function (PSCF analysis). On an average, the concentration of water
soluble inorganic ions (sum of anions and cations) was 63.2 μgm−3. Amongst the water soluble ions, average NO3− concentration was the highest (25.0 μgm−3) followed by SO42− (15.8 μgm−3) and NH4+ (13.8 μgm−3) concentrations. These species, contributed 87% of the total mass of water soluble species, indicating that most of the water
soluble PM10 was composed of NH4NO3 and (NH4)2SO4/NH4HSO4 or (NH4)3H(SO4)2 particles. Further, the concentrations of SO42−, NO3−, and NH4+ aerosols increased at high relative humidity levels up to the deliquescence point (∼63% RH) for salts of these species suggesting
that high humidity levels favor the conversion and partitioning of gaseous SO2, NOx, and NH3 to their aerosol phase. Additionally, lowering of ambient temperature as the winter progressed also resulted in an increase
of NO3− and NH4+ concentrations, probably due to the semi volatile nature of ammonium nitrate. PSCF analysis identified regions along the
Indo-Gangetic Plain (IGP) including Northern and Central Uttar Pradesh, Punjab, Haryana, Northern Pakistan, and parts of Rajasthan
as source regions of airborne nitrate. Similar source regions, along with Northeastern Madhya Pradesh were identified for
sulfate. 相似文献
We perform Large eddy simulations of turbulent compressible convection in stellar-type convection zones by solving the Naviér-Stokes
equations in three dimensions. We estimate the extent of penetration into the stable layer above a stellar-type convection
zone by varying the rotation rate (Ω), the inclination of the rotation vector (θ) and the relative stability (S) of the upper stable layer The computational domain is a rectangular box in an f-plane configuration and is divided into two regions of unstable and stable stratification with the stable layer placed above
the convectively unstable layer. Several models have been computed and the penetration distance into the stable layer above
the convection zone is estimated by determining the position where time averaged kinetic energy flux has the first zero in
the upper stable layer. The vertical grid spacing in all the model is non-uniform, and is less in the upper region so that
the flows are better resolved in the region of interest. We find that the penetration distance increases as the rotation rate
increases for the case when the rotation vector is aligned with the vertical axis. However, with the increase in the stability
of the upper stable layer, the upward penetration distance decreases. Since we are not able to afford computations with finer
resolution for all the models, we compute a number of models to see the effect of increased resolution on the upward penetration.
In addition, we estimate the upper limit on the upward convective penetration from stellar convective cores. 相似文献