scholarly journals The behaviour of near‐surface soils through ultrasonic near‐surface inundation testing

2019 ◽  
Vol 17 (4) ◽  
pp. 331-344 ◽  
Author(s):  
Oliver‐Denzil S. Taylor ◽  
Amy L. Cunningham ◽  
Robert E. Walker ◽  
Mihan H. McKenna ◽  
Kathryn E. Martin ◽  
...  
Keyword(s):  
Geoderma ◽  
2004 ◽  
Vol 119 (1-2) ◽  
pp. 113-120 ◽  
Author(s):  
Tait Chirenje ◽  
L.Q. Ma ◽  
M. Reeves ◽  
M. Szulczewski

Geophysics ◽  
2004 ◽  
Vol 69 (2) ◽  
pp. 460-465 ◽  
Author(s):  
Rob Long ◽  
Thomas Vogt ◽  
Mike Lowe ◽  
Peter Cawley

A technique is presented that uses a circular ultrasonic waveguide to measure the bulk shear (S‐wave) and longitudinal (P‐wave) velocities of unconsolidated media, with particular application to near‐surface soils. The technique requires measuring the attenuation characteristics of the fundamental longitudinal mode that propagates along an embedded bar, from which the acoustic properties of the surrounding medium are inferred. The principles behind the technique are discussed, and the results of an experimental laboratory validation are presented, followed by details of in‐situ soil property measurements obtained at various sites in urban areas of the United Kingdom.


2019 ◽  
Vol 48 (4) ◽  
pp. 921-930 ◽  
Author(s):  
Henry Wilson ◽  
Jane Elliott ◽  
Merrin Macrae ◽  
Aaron Glenn

2020 ◽  
Author(s):  
Oxana Sadovskaya ◽  
Vladimir Sadovskii ◽  
Evgenii Efimov

<p>We developed a computational technology for numerical modeling of wave fields generated by seismic sources in blocky-layered geological media, and applied it to the analysis of efficiency of the electromagnetic pulse source of new generation "Yenisei", created recently by international geotechnical company "Geotech Seismic Services". To describe wave processes, we worked out new mathematical models of the dynamics of elastic, viscoelastic and elastic-plastic media, of porous and granular materials taking into account the increase in stiffness of such materials as pores collapse, [1]. Algorithms of numerical implementation of governing equations were realized for the cluster-type supercomputers, based on the method of two-cyclic splitting with respect to spatial variables. The conducted computational experiments have demonstrated that the proposed technology allows reproducing the system of waves near the region of excitation of seismic oscillations in 3D setting with a high degree of details and accuracy, [2]. We analysed frequencies and amplitudes of waves generated in the near-surface soils, and showed that our computational results are in a good agreement with seismic parameters of a real electromagnetic pulse source. We studied seismic efficiency of the pulse source as the ratio of the energy passing through the reflecting surface in the depth of layered massif to the energy of pulse effect on the surface. Besides, the energy of surface waves, which is obviously useless for the excitation of reflected waves, was estimated. To compare the energy efficiency of pulse sources with seismic sources of periodic action (vibrators), the problem of cyclic loading through the platform was solved numerically by the same method and the same geometric scheme. The seismic efficiency of vibrator was calculated by the maximum value of the energy fluxes during large time interval. Judging by computations, the pulse seismic sources are not inferior to the sources of vibratory type by seismic efficiency in the range of low frequencies. However, it is necessary to take into account that they differ sharply by the level of expended energy, because the energy of a pulse source, needed for generation of incident wave of a given amplitude, is many times lower than the energy of a vibrator.</p><p>The reported study was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project No. 18-41-242001: "Analysis of wavy seismic fields generated by the electromagnetic pulse source "Yenisei" in heterogeneous soil massifs during geological exploration in the conditions of northern regions of Eastern Siberia".</p><p>References</p><ol><li>Sadovskaya O., Sadovskii V. Mathematical Modeling in Mechanics of Granular Materials. Ser.: Advanced Structured Materials, vol. 21. Springer, Heidelberg – New York – Dordrecht – London, 2012. 390 p.</li> <li>Sadovskii V.M., Sadovskaya O.V., Efimov E.A. Analysis of seismic waves exited in near-surface soils by means of the electromagnetic pulse source "Yenisei". Materials Physics and Mechanics. 2019. V. 42, No. 5. P. 544–557.</li> </ol>


Author(s):  
Larry D. Hinzman ◽  
Kevin C. Petrone

Hydrological processes exert strong control over biological and climatic processes in every ecosystem. They are particularly important in the boreal zone, where the average annual temperatures of the air and soil are relatively near the phase-change temperature of water (Chapter 4). Boreal hydrology is strongly controlled by processes related to freezing and thawing, particularly the presence or absence of permafrost. Flow in watersheds underlain by extensive permafrost is limited to the near-surface active layer and to small springs that connect the surface with the subpermafrost groundwater. Ice-rich permafrost, near the soil surface, impedes infiltration, resulting in soils that vary in moisture content from wet to saturated. Interior Alaska has a continental climate with relatively low precipitation (Chapter 4). Soils are typically aeolian or alluvial (Chapter 3). Consequently, in the absence of permafrost, infiltration is relatively high, yielding dry surface soils. In this way, discontinuous permafrost distribution magnifies the differences in soil moisture that might normally occur along topographic gradients. Hydrological processes in the boreal forest are unique due to highly organic soils with a porous organic mat on the surface, short thaw season, and warm summer and cold winter temperatures. The surface organic layer tends to be much thicker on north-facing slopes and in valley bottoms than on south-facing slopes and ridges, reflecting primarily the distribution of permafrost. Soils are cooler and wetter above permafrost, which retards decomposition, resulting in organic matter accumulation (Chapter 15). The markedly different material properties of the soil layers also influence hydrology. The highly porous near-surface soils allow rapid infiltration and, on hillsides, downslope drainage. The organic layer also has a relatively low thermal conductivity, resulting in slow thaw below thick organic layers. The thick organic layer limits the depth of thaw each summer to about 50–100 cm above permafrost (i.e., the active layer). As the active layer thaws, the hydraulic properties change. For example, the moisture-holding capacity increases, and additional subsurface layers become available for lateral flow. The mosaic of Alaskan vegetation depends not only on disturbance history (Chapter 7) but also on hydrology (Chapter 6).


2012 ◽  
Vol 16 (4) ◽  
pp. 455-467 ◽  
Author(s):  
Mohammed A. Rasheed ◽  
M. Lakshmi ◽  
M. S. Kalpana ◽  
P. L. S. Rao ◽  
D. J. Patil ◽  
...  

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