Monitoring of micromorphological changes in a virgin Solonetz under regional changes in hydrology and climate (Northern Caspian Lowland, Russia)

2018 ◽  
Vol 8 ◽  
Author(s):  
Marina Lebedeva ◽  
Maria Konyushkova ◽  
Sergey Khokhlov
Keyword(s):  
Water Table ◽  
Soil Mass ◽  
Published Data ◽  
Research Station ◽  
Silty Clay ◽  
Clear Trend ◽  
Thin Sections ◽  
Caspian Lowland ◽  
Humus Accumulation ◽  
Upper Boundary

Over the past 40 years, a clear trend towards an increasing humidity and a rising groundwater table has been observed in the south-eastern semidesert part of European Russia. According to the published data, two clear periods of climate are distinguished: 1950s-1970s and 1970s-2000s. The thin sections of a Solonetz sampled in different periods of time (1950s, 1960s, 1970s, 1982, 2002 and 2013) at the Dzhanybek research station were studied micromorphologically to observe how these natural changes influenced soil pedofeatures. A comparison of thin sections showed no significant changes in soil properties between 1950s and 1982, when the hydrological (ground water table) and climatic parameters remained relatively stable. However, between 1982 and 2013, due to a significant increase in climatic moisture and rising groundwater, the following changes in soil microfeatures took place: the activation of humus accumulation and biogenic structuring, the eluviation of the silty clay-humus matter, the development of solodic features, gleyization of the soil mass, and the accumulation of opaque black organic grains about 2-3 µm formed in the topsoil due to the long stagnation during the springtime after snow melting. The water table rise leads to the consequent rise of the upper boundary of the accumulation of gypsum and carbonates.

scholarly journals Intraspecific Latitudinal Variation in Nest Orientation Among Ground-Nesting Passerines: A Study Using Published Data

The Condor ◽  
2007 ◽  
Vol 109 (2) ◽  
pp. 441-446 ◽  
Author(s):  
Niall H.K. Burton
Keyword(s):  
Early Morning ◽  
Published Data ◽  
Nest Entrance ◽  
Clear Trend ◽  
European Species ◽  
Statistical Comparison ◽  
Species Comparisons ◽  
Nest Microclimate ◽  
The Relationship ◽  
Ground Nesting

Abstract The relationship between nest entrance orientation and latitude among ground-nesting passerines was reviewed using published information. Data were collated for seven North American and European species. Pooling within-species comparisons, there was a clear trend from a preference for north-facing nests at lower latitudes to eastward- or southward-facing nests farther north. Orientations differed significantly in eight of 12 cases for which statistical comparison was possible, means differing in the expected direction in six of these cases. These results highlight how the influence of solar radiation on nest microclimate typically delineates preferred nest orientation in these species, i.e., at lower latitudes, the need for shade results in a preference for northward orientations; at mid latitudes, eastward orientations predominate, reflecting a probable balance between the benefits of warmth in the early morning and shade in the afternoon; while at high latitudes, nests may be oriented southward to gain warmth throughout the day.

Evaluation on Features of Soft Foundation Engineering and Bearing Layer of Pile in Jiaxing City

2011 ◽  
Vol 90-93 ◽  
pp. 217-221
Author(s):  
Jin Long Zhou ◽  
Qiao Li ◽  
Wei Zhong Cai
Keyword(s):  
Soil Mass ◽  
Shallow Foundation ◽  
Silty Clay ◽  
Foundation Engineering ◽  
Foundation Soil ◽  
Cone Tip Resistance ◽  
Soft Foundation ◽  
Tip Resistance ◽  
Bearing Layer

Through the investigation into composition of major shallow foundation soil mass and the correlation of mechanical indicators in this study, the regression equation of mechanical indicators of the features of local foundation soil mass and the data of in situ testing was obtained. Based on massive quantities of exploration materials, this study analyzed engineering features, distribution status, and the feasibility of silty clay to be used as the bearing layer of the pile in Layer ④2 . The analytical results showed that the silty clay with the uniform depth of over 3.5m and the cone tip resistance in static sounding of over 400MPa could be used as bearing layer of the pile. This study could provide the reference for the accurate understanding of the engineering features of soil mass, and the design and evaluation of foundation in Jiaxing City.

Arching effect in fine sand due to base yielding

2010 ◽  
Vol 47 (3) ◽  
pp. 366-374 ◽  
Author(s):  
Jamshid Sadrekarimi ◽  
Alireza Abbasnejad
Keyword(s):  
Relative Density ◽  
Experimental Work ◽  
Fine Sand ◽  
Soil Mass ◽  
Flow Process ◽  
Flow Phenomenon ◽  
Dense Sand ◽  
Arching Effect ◽  
Different Diameters ◽  
Upper Boundary

This paper presents results of an experimental work on the arching effect in loose and dense sand. The apparatus comprises concentric circular trapdoors with different diameters that can yield downward while stresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole mass of soil deforms elastically. However, after a specified displacement that depends on the trapdoor diameter and soil relative density, the soil mass behaves plastically. This behavior, which is due to flow phenomenon, continues until the stress applied onto the trapdoor decreases to a minimum value. Then the stress carried by the trapdoor shows an ascending trend. This indicates the gradual separation of the yielding mass from the whole soil body. Finally, the flow process creates a stable arch of sand. This process is called the arching mechanism. Depending on the trapdoor diameter, there is a critical relative density at and beyond which the test leads to the formation of a stable arch. The results are also compared with Terzaghi’s theory and the assumption of an upper boundary solution is discussed.

The 1994 landslide at Sainte-Monique, Quebec: geotechnical investigation and application of progressive failure analysis

2015 ◽  
Vol 52 (4) ◽  
pp. 490-504 ◽  
Author(s):  
A. Locat ◽  
S. Leroueil ◽  
A. Fortin ◽  
D. Demers ◽  
H.P. Jostad
Keyword(s):  
Shear Strength ◽  
Failure Analysis ◽  
Progressive Failure ◽  
High Sensitivity ◽  
Failure Surface ◽  
Soil Mass ◽  
Silty Clay ◽  
High Plasticity ◽  
Geotechnical Investigation ◽  
Progressive Failure Analysis

In 1994, a landslide occurred in the municipality of Sainte-Monique, Quebec. The debris of the landslide had graben and host shapes, typical of spreads in sensitive clays. The geotechnical investigation shows that the soil involved is a firm to stiff, sensitive, nearly normally consolidated grey silty clay of high plasticity. This soil exhibits a high sensitivity and a high brittleness during shear and is therefore susceptible to progressive failure. Traditional stability analysis cannot explain this landslide. This gives the opportunity to examine the applicability of progressive failure analysis to this spread. Using the finite elements method, it is demonstrated that the initiation and observed extent of the failure surface are explained by a soil having high brittleness during shear and a large-deformation shear strength close to the remoulded shear strength of the soil. The dislocation of the soil mass can also be explained by the active failure occurring in the soil mass above the failure surface during or shortly after failure propagation. It is therefore numerically demonstrated that progressive failure explains the initiation and the extent of the failure surface of this spread.

EFFECT OF SOIL WATER STATUS AND STRENGTH ON TRAFFICABILITY

1979 ◽  
Vol 59 (3) ◽  
pp. 313-324 ◽  
Author(s):  
C. L. PAUL ◽  
J. DE VRIES
Keyword(s):  
Soil Water ◽  
Water Table ◽  
Structural Damage ◽  
Water Status ◽  
Water Table Depth ◽  
Silty Clay ◽  
Clay Loam ◽  
Silty Clay Loam ◽  
Soil Water Tension ◽  
Farm Vehicles

Trafficability tests with typical farm vehicles were carried out on three lowland fields at various degrees of wetness. Structural damage after the first and third passes was assessed in terms of bulk density, aeration porosity, pore-size distribution and rut depth. These indices could not be used per se as criteria for trafficable conditions because of lack of information concerning their relationship to plant growth. Instead, a trafficability criterion oriented toward traction efficiency was established by determining for each soil the relationship between its strength (assessed with a cone penetrometer) and traction efficiency measured by wheelslip. A critical value of strength for trafficability was inferred from this relationship. This was then used to obtain soil water tension limits for trafficability from known relations between tension and strength. Soil strength was found to be linearly dependent upon water table depth in spring when evapotranspiration was small and when the water table depth was less than 80 cm. Consideration of these relationships led to the establishment of critical water table limits for trafficability. These were 53, 45, and 60 cm for Lumbum muck, Hallart silty clay loam (SiCL) (grassland), and Hallart silty clay loam (cultivated), respectively.

scholarly journals Micromorphological features of soils of semidesertic solonetzic complexes under different herbaceous communities with the participation of fodder plant Kochia prostrata (Caspian lowland)

2020 ◽  
pp. 83-116
Author(s):  
Oxana Plotnikova ◽  
Marina Lebedeva ◽  
E. B. Varlamov ◽  
Yu. D. Nukhimovskaya ◽  
E. V. Shuyskaya
Keyword(s):  
Salt Content ◽  
Morphological Properties ◽  
The North ◽  
Herbaceous Communities ◽  
Wide Range ◽  
Caspian Lowland ◽  
Exchangeable Magnesium ◽  
Humus Accumulation ◽  
Maximum Penetration ◽  
Pedogenic Processes

The aim of the study was to research the relationship of chemical and micromorphological properties of soils with the growth of Kochia prostrata. The objects of study were the soils on natural pastures of the North-Western part of the Caspian lowland. It was laid 4 soil pits (soils – light solonetz, solonetzic chestnut) with the maximum penetration depth of the main mass of roots of the studied plants. K. prostratais a very plastic forage species that can grow on soils with a wide range of morphological properties, different salt content and their chemical composition. It is revealed that on the background of almost the same content of humus and high content of exchangeable magnesium micromorphological features represent the different degree of manifestation of primary pedogenic processes – humus accumulation, leaching of soluble salts, gypsum accumulation, carbonate enrichment, solonetzization. Despite the different content of exchangeable sodium, in all soils there are fresh clay or humus-clay illuvial coatings, indicating the manifestation of the modern eluvial-illuvial redistribution of fine matter (lessivage or illimerization).

scholarly journals Calibration of DRAINMOD for prediction of water table depths and drain discharges under waterlogged Vertisols of Maharashtra, India

2019 ◽  
Vol 11 (3) ◽  
pp. 724-731
Author(s):  
Shrimant Rathod ◽  
Sudhir Dahiwalkar ◽  
Sunil Gorantiwar ◽  
Mukund Shinde
Keyword(s):  
Water Table ◽  
Agricultural Research ◽  
Drainage System ◽  
Subsurface Drainage ◽  
Design Parameters ◽  
Design System ◽  
Research Station ◽  
Drain Spacing ◽  
Drainage Design ◽  
Rainy Days

An estimation of optimal design parameters of subsurface drainage system through monitoring of water table depths and drain discharges are expensive in terms of time and money. The simulation modeling is an effective tool for estimation of drainage design parameters at less cost and short time. In view to this, calibration of DRAINMOD model for prediction of water table depths and drain discharges were conducted by installing subsurface drainage system with 40 m drain spacing and 1.0 m drain depth at Agricultural Research Station, Kasbe Digraj, Dist. Sangli (Maharashtra) during 2012-13 to 2013-14. The field data on water table depth and drain discharge were used for calibration of DRAINMOD model. The input data files on climatic, soil, crop and drainage design system parameters were attached to DRAINMOD model and calibrated successfully. It is found that both observed and simulated water table depths and drain discharges showed a fluctuating trend and predicted both water table depths and drain discharges closely with the observed values during frequent rainy days and following the rainy days. The DRAINMOD model reliably predicted water table depths with a goodness of fit (R2 = 0.97), MAE (12.23 cm), RMSE (15.49 cm) and CRM (0.05); drain discharges with R2 of  0.93, MAE of 0.095 mm day-1, RMSE of 0.1876 mm day-1and CRM of 0.04. Thus, the calibrated DRAINMOD model can be used to simulate the water table depths and drain discharges in semi-arid climatic conditions of Maharashtra and in turn to estimate and evaluate drain spacing and depth.

U-Pb zircon geochronology of dropstones and IRD in the Amundsen Sea, applied to the question of bedrock provenance and Miocene-Pliocene ice sheet extent in West Antarctica

2021 ◽  
Author(s):  
Christine Siddoway ◽  
Stuart Thomson ◽  
Sidney Hemming ◽  
Hannah Buchband ◽  
Cade Quigley ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Detrital Zircons ◽  
East Antarctica ◽  
Published Data ◽  
Silty Clay ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Early Pliocene ◽  
West Antarctic ◽  
The Antarctic

<p>IODP Expedition 379 to the Amundsen Sea continental rise recovered latest Miocene-Holocene sediments from two sites on a drift in water depths >3900m. Sediments are dominated by clay and silty clay with coarser-grained intervals and ice-rafted detritus (IRD) (Gohl et al. 2021, doi:10.14379/iodp.proc.379.2021). Cobble-sized dropstones appear as fall-in, in cores recovered from sediments >5.3 Ma.  We consider that abundant IRD and the sparse dropstones melted out of icebergs formed due to Antarctic ice-sheet calving events. We are using petrological and age characteristics of the clasts from the Exp379 sites to fingerprint their bedrock provenance. The results may aid in reconstruction of past changes in icesheet extent and extend knowledge of subglacial bedrock.</p><p>Mapped onshore geology shows pronounced distinctions in bedrock age between tectonic provinces of West or East Antarctica (e.g. Cox et al. 2020, doi:10.21420/7SH7-6K05; Jordan et al. 2020, doi.org/10.1038/s43017-019-0013-6). This allows us to use geochronology and thermochronology of rock clasts and minerals for tracing their provenance, and ascertain whether IRD deposited at IODP379 drillsites originated from proximal or distal Antarctic sources. We here report zircon and apatite U-Pb dates from four sand samples and five dropstones taken from latest Miocene, early Pliocene, and Plio-Pleistocene-boundary sediments. Additional Hf isotope data, and apatite fission track and <sup>40</sup>Ar/<sup>39</sup>Ar Kfeldspar ages for some of the same samples help to strengthen provenance interpretations.</p><p>The study revealed three distinct zircon age populations at ca. 100, 175, and 250 Ma. Using Kolmogorov-Smirnov (K-S) statistical tests to compare our new igneous and detrital zircon (DZ) U-Pb results with previously published data, we found strong similarities to West Antarctic bedrock, but low correspondence to prospective sources in East Antarctica, implying a role for icebergs calved from the West Antarctic Ice Sheet (WAIS). The ~100 Ma age resembles plutonic ages from Marie Byrd Land and islands in Pine Island Bay.  The ~250 and 175 Ma populations match published mineral dates from shelf sediments in the eastern Amundsen Sea Embayment as well as granite ages from the Antarctic Peninsula and the Ellsworth-Whitmore Mountains (EWM). The different derivation of coarse sediment sources requires changes in iceberg origin through the latest Miocene, early Pliocene, and Plio/Pleistocene, likely the result of changes in WAIS extent.</p><p>One unique dropstone recovered from Exp379 Site U1533B is green quartz arenite, which yielded mostly 500-625 Ma detrital zircons. In visual appearance and dominant U-Pb age population, it resembles a sandstone dropstone recovered from Exp382 Site U1536 in the Scotia Sea (Hemming et al. 2020, https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Paper/357276). K-S tests yield high values (P ≥ 0.6), suggesting a common provenance for both dropstones recovered from late Miocene to Pliocene sediments, despite the 3270 km distance separating the sites. Comparisons to published data, in progress, narrow the group of potential on-land sources to exposures in the EWM or isolated ranges at far south latitudes in the Antarctic interior.  If both dropstones originated from the same source area, they could signify dramatic shifts in the WAIS grounding line position, and the possibility of the periodic opening of a seaway connecting the Amundsen and Weddell Seas.</p>

scholarly journals Localized surface-ice weakness on a glacial ice runway

1996 ◽  
Vol 42 (142) ◽  
pp. 426-439 ◽  
Author(s):  
R. M. Lang ◽  
George L. Blaisdell
Keyword(s):  
Ice Cores ◽  
Published Data ◽  
Compression Tests ◽  
Ice Shelf ◽  
Thin Sections ◽  
Glacial Ice ◽  
Ross Ice Shelf ◽  
Flight Operations ◽  
Frequent Failure ◽  
Surface Ice

AbstractFollowing construction of a glacial ice runway on the Ross Ice Shelf, Antarctica, and prior to flight operations, the runway was proof-rolled. The proof exercise was designed to simulate typical heavy aircraft. Initial testing produced numerous brittle surface failures in the runway ice. Thin sections of ice cores taken from the failed areas showed large crystals (сaxis vertical) of clear, blue ice with long, vertical bubbles, indicative of ice formed directly from meltwater. Uniaxial unconfined compression tests on core samples were used to compare runway ice strength with published data for polycrystalline laboratory ice. Since the frequent failure of surface ice had not been expected, it was critical to understand the formation and mechanical properties of the weak ice to prevent its occurrence in the future and to strengthen the existing problem areas. We discuss the likely scenarios for development of weak ice on the airstrip and the physical properties of this type of ice. Also, the procedure used to repair successfully the runway surface is described, which culminated in test flights, followed by full flight operations.

scholarly journals Water table effects on measured and simulated fluxes in weighing lysimeters for differently-textured soils

2015 ◽  
Vol 63 (1) ◽  
pp. 82-92 ◽  
Author(s):  
Martin Wegehenkel ◽  
Horst H. Gerke
Keyword(s):  
Water Balance ◽  
Soil Water ◽  
Water Table ◽  
Sandy Soil ◽  
Water Storage ◽  
Soil Water Balance ◽  
Soil Water Storage ◽  
Silty Clay ◽  
Bottom Boundary ◽  
Soil Hydraulic

Abstract Weighing lysimeters can be used for studying the soil water balance and to analyse evapotranspiration (ET). However, not clear was the impact of the bottom boundary condition on lysimeter results and soil water movement. The objective was to analyse bottom boundary effects on the soil water balance. This analysis was carried out for lysimeters filled with fine- and coarse-textured soil monoliths by comparing simulated and measured data for lysimeters with a higher and a lower water table. The eight weighable lysimeters had a 1 m2 grass-covered surface and a depth of 1.5 m. The lysimeters contained four intact monoliths extracted from a sandy soil and four from a soil with a silty-clay texture. For two lysimeters of each soil, constant water tables were imposed at 135 cm and 210 cm depths. Evapotranspiration, change in soil water storage, and groundwater recharge were simulated for a 3-year period (1996 to 1998) using the Hydrus-1D software. Input data consisted of measured weather data and crop model-based simulated evaporation and transpiration. Snow cover and heat transport were simulated based on measured soil temperatures. Soil hydraulic parameter sets were estimated (i) from soil core data and (ii) based on texture data using ROSETTA pedotransfer approach. Simulated and measured outflow rates from the sandy soil matched for both parameter sets. For the sand lysimeters with the higher water table, only fast peak flow events observed on May 4, 1996 were not simulated adequately mainly because of differences between simulated and measured soil water storage caused by ET-induced soil water storage depletion. For the silty-clay soil, the simulations using the soil hydraulic parameters from retention data (i) were matching the lysimeter data except for the observed peak flows on May, 4, 1996, which here probably resulted from preferential flow. The higher water table at the lysimeter bottom resulted in higher drainage in comparison with the lysimeters with the lower water table. This increase was smaller for the finer-textured soil as compared to the coarser soil.

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