Shear Parameters Research Articles

Shear, Consolidation Characteristics and Carbon Footprint Analysis of Clayey Soil Blended with Calcium Lignosulphonate and Granite Sand for Earthen Dam Application

Soil is a composite material of great interest to civil engineers. When the quality of such composite soils is poor, ground improvement techniques must be adopted to withstand the design load of superstructure. Existing soil stabilizers include lime and cement; however, their environmental safety and sustainable use during stabilization have been receiving increasing attention in recent years. This study investigated the use of granite sand (GS) and calcium lignosulphonate (CLS) as sustainable stabilizers that could be blended with clayey soils. The considered dosages of GS were 30%, 40% and 50%, and those of the CLS were 0.25%, 0.5%, 1% and 1.5%. Direct shear and consolidation tests were performed on the GS–CLS blended soil samples that were cured for 7 and 14 days. The amended stabilizers improved the shear parameters and consolidation characteristics at an optimum dosage of 30% GS and 0.5% CLS. Maximum improvements of 84% and 163% were observed in the cohesion and angles of internal friction, respectively. A significant change was also observed in the consolidation characteristics, making them practically applicable. The soil hydraulic conductivity was reduced by 14%, and the coefficient of consolidation increased by 203% for 30% GS and 05% CLS. Carbon footprint analyses were performed on the soil composition that would be best-suited for a typical homogenous earthen dam section. The results showed that the use of GS and CLS together reduced the carbon emissions by 6.57 and 7.7 times, compared to traditional stabilizers, such as cement and lime.

HOLISMOKES

Modeling of strong gravitational lenses is a necessity for further applications in astrophysics and cosmology. With the large number of detections in current and upcoming surveys, such as the Rubin Legacy Survey of Space and Time (LSST), it is pertinent to investigate automated and fast analysis techniques beyond the traditional and time-consuming Markov chain Monte Carlo sampling methods. Building upon our (simple) convolutional neural network (CNN), we present here another CNN, specifically a residual neural network (ResNet), that predicts the five mass parameters of a singular isothermal ellipsoid (SIE) profile (lens center x and y, ellipticity ex and ey, Einstein radius θE) and the external shear (γext, 1, γext, 2) from ground-based imaging data. In contrast to our previous CNN, this ResNet further predicts the 1σ uncertainty for each parameter. To train our network, we use our improved pipeline to simulate lens images using real images of galaxies from the Hyper Suprime-Cam Survey (HSC) and from the Hubble Ultra Deep Field as lens galaxies and background sources, respectively. We find very good recoveries overall for the SIE parameters, especially for the lens center in comparison to our previous CNN, while significant differences remain in predicting the external shear. From our multiple tests, it appears that most likely the low ground-based image resolution is the limiting factor in predicting the external shear. Given the run time of milli-seconds per system, our network is perfectly suited to quickly predict the next appearing image and time delays of lensed transients. Therefore, we use the network-predicted mass model to estimate these quantities and compare to those values obtained from our simulations. Unfortunately, the achieved precision allows only a first-order estimate of time delays on real lens systems and requires further refinement through follow-up modeling. Nonetheless, our ResNet is able to predict the SIE and shear parameter values in fractions of a second on a single CPU, meaning that we are able to efficiently process the huge amount of galaxy-scale lenses expected in the near future.

On the use of asymptotically motivated gauge functions to obtain convergent series solutions to nonlinear ODEs

AbstractWe examine the power series solutions of two classical nonlinear ordinary differential equations of fluid mechanics that are mathematically related by their large-distance asymptotic behaviours in semi-infinite domains. The first problem is that of the ‘Sakiadis’ boundary layer over a moving flat wall, for which no exact analytic solution has been put forward. The second problem is that of a static air–liquid meniscus with surface tension that intersects a flat wall at a given contact angle and limits to a flat pool away from the wall. For the latter problem, the exact analytic solution—given as distance from the wall as a function of meniscus height—has long been known (Batchelor, G. K. (1967) An Introduction to Fluid Dynamics, chapter 1: The physical properties of fluids. Cambridge). Here, we provide an explicit solution as meniscus height versus distance from the wall to elucidate structural similarities to the Sakiadis boundary layer. Although power series solutions are readily obtainable to the governing nonlinear ordinary differential equations, we show that—in both problems—the series diverge due to non-physical complex or negative real-valued singularities. In both cases, these singularities can be moved by expanding in exponential gauge functions motivated by their respective large distance asymptotic behaviours to enable series convergence over their full semi-infinite domains. For the Sakiadis problem, this not only provides a convergent Taylor series (and conjectured exact) solution to the ODE, but also a means to evaluate the wall shear parameter (and other properties) to within any desired precision. Although the nature of nonlinear ODEs precludes general conclusions, our results indicate that asymptotic behaviours can be useful when proposing variable transformations to overcome power series divergence.

Structural variations of endothelial cell monolayer under startup shear conditions

We study the response of an endothelial cell monolayer lining the bottom surface of a cartesian Couette geometry in variations of critical shearing parameters that affect the fluid environment, such as the gap distance between the upper moving and the bottom stationary plates and the velocity of the moving plate. Specifically, we propose an in silico rheometric emulation based on startup shear experiments in a representative two-dimensional domain of the monolayer that accounts for the interaction of the blood plasma and the deformable multilayer poroelastic endothelial cells. We present quantitative predictions for the shear and normal stresses on each cell compartment (membrane, cytoplasm, and nucleus) and their structural changes. We show that the variation of the Wall Shear Stress (WSS) along the cell membrane is considered significant and strongly dependent on the shape of the cell, while membrane thinning is more prominent at the locus of high WSS in the range of physiological velocities. However, under extreme velocities, wall thinning prevails at the locus of flow stagnation.

Shear layers in two-stage compound channels investigated with LS-PIV

Flow experiments are conducted in a two-stage compound open-channel, with varying intensity of the velocity difference between the main channel (deep part) and the floodplain (shallower part), using a large-scale free surface PIV technique (LS-PIV). For all investigated flows, a shear layer develops at the interface between main channel and floodplain, characterised by a peak of turbulent shear stress. Yet, two different kinds of shear layer could be identified. The first kind is characterised by the presence of large-scale quasi-periodic structures of Kelvin-Helmholtz type which are growing in downstream direction, whereas the second kind is characterised by smaller-scale vortical structures without quasi-periodicity and which do not grow in downstream direction. The shear parameter lambda =(U_2-U_1)/(U_2+U_1), where U_1 and U_2 are defined as the velocities outside the shear layer, is identified as a key parameter to distinguish between these two types of shear layers, supporting a result from Proust et al. (Water Resour Res 53: 3387–3406, 2017). A physical interpretation of the lambda-criterion is proposed, based on the inhibiting effect of ambient turbulence (the turbulence level outside the shear layer) on the emergence of Kelvin-Helmholtz structures. Accordingly, the threshold value of lambda, above which large-scale structures can develop, is dependent on the level of the ambient turbulence. Despite their very different behaviours, the two types of shear layer have the same efficiency to generate turbulent shear stress for a given velocity difference across the shear layer, except for lambda-values close to the threshold value.

A review on the thermo-hydro-mechanical response of soil–structure interface for energy geostructures applications

Energy geostructures have been identified as a cost-effective mitigating strategy for the adverse impact of climate change. Operation of energy geostructures results in temperature fluctuation and subsequent water migration, particularly at the soil–structure interface, determining the shear response of soil and soil–structure interface. This state-of-the-art paper brings together experimental data from direct shear tests carried out on the soil–structure interface from several laboratory investigations, presenting a comprehensive review to gain a thorough understanding of the interface response in different thermo-hydro-mechanical states, which is critical in the analysis and design of energy geostructures. First, the evolution of shear strength parameters, i.e., adhesion and friction angle, with matric suction and temperature, are investigated. Then, a more detailed analysis of the impact of matric suction and temperature on the shear strength of the soil–structure interface is provided. Furthermore, a comprehensive discussion is provided in this section on the role of the most recent stress history in determining the non-isothermal shear strength of an interface. Data on the effect of matric suction and temperature on shear parameters of the corresponding fundamental soil is reviewed as a reference to the interface behaviour throughout the study, revealing potential underlying mechanisms. In general, a higher matric suction results in higher shear strength of the interface, whereas non-isothermal variations in adhesion and friction angle may lead to a higher or lower shear strength of a saturated interface.

Investigation of intralayer and interlayer shear properties of stabilized rammed earth by direct shear tests

Rammed earth construction has attracted a lot of attention because of its unique advantages of energy saving, environmental protection, low cost, easy access to materials, and suitability for living. Due to the special layered segmental ramming process, the distribution of rammed earth is superimposed, which makes the rammed earth walls have many weak horizontal interfaces. The failure mode of many post-earthquake rammed earth buildings is mainly in the form of shear failure, and the slip failure at the interface of adjacent rammed layers is particularly serious. There is a lack of research on the cracking and slip phenomena between rammed earth layers and the shear parameters between and within rammed earth layers. In this study, the interlayer and intralayer shear behavior of rammed earth were compared in four aspects: failure phenomenon, shear stress-displacement curve, cohesion and internal friction angle, and shear modulus, using normal stress, additive type, and additive content as variables. The causes of slip failure easily occurring at the interlayer interface were investigated. The interlayer interface and intra-layer shear failure laws of unstabilized and stabilized rammed earth were explored. The compressive strength was used to predict the interlayer shear strength. The shear resistance parameters of unstabilized and stabilized rammed earth were determined to provide data for future measures to enhance the optimization of the interlayer interface. The results showed that the interlayer failure of rammed earth was mainly caused by the lack of cohesion of the soil at the interlayer interface, and the interlayer cohesion was 24%-45% of the intra-layer cohesion. The interlayer interface shear strength was about 35%-84% of the intra-layer shear strength.

Buckling of Coated Functionally Graded Spherical Nanoshells Rested on Orthotropic Elastic Medium

Coated functionally graded materials (FGMs) are used in several industrial structures such as turbine blades, cutting tools, and aircraft engines. Given the need for analytical and numerical analysis of these complex structures, a mathematical model of tricoated FG structures is presented for the first time in this paper. The objective of this work was to analyze analytically the buckling problem of unidirectional (1D), bidirectional (2D), and tridirectional (3D) coated FG spherical nanoshells resting on an orthotropic elastic foundation subjected to biaxial loads. Based on the generalized field of displacement, a 2D higher-order shear deformation theory was proposed by reducing the number of displacement variables from five to four variables for specific geometry cases. The nonlocal strain gradient theory was employed to capture the size-dependent and microstructure effects. The equilibrium equations were performed by applying the principle of the virtual work, and the obtained differential equations were solved by applying the Galerkin technique to cover all possible boundary conditions. The proposed elastic foundation was defined based on three parameters: one spring constant and two shear parameters referring to the orthotropy directions. A detailed parametric analysis was carried out to highlight the impact of various schemes of coated FGMs, gradient material distribution, length scale parameter (nonlocal), material scale parameter (gradient), geometry of the nanoshell, and variation in the orthotropic elastic foundation on the critical buckling loads.

Effect of particle size distribution on shear strength of soil

Soil grain size distribution has a significant impact on the mechanical properties of geotechnical materials. This study presents a laboratory investigation into the effects of fine content and grading factors on shear parameters. A series of shear tests and triaxial tests on sandy soils were performed for this aim. Finally, the outcomes of both strategies were compared and assessed. It was discovered that altering the grain size distribution results in changing the values of shearing parameters. Furthermore, the outcomes of different laboratory tests are not the same.

Experimental assessment of diagonal shear parameters of dry stacked block masonry built with self-interlocking compressed earth blocks

Experimental assessment of diagonal shear parameters of dry stacked block masonry built with self-interlocking compressed earth blocks

Strouhal number for boundary shear flow past a circular cylinder in the subcritical flow regime

Strouhal number (St) is an essential dimensionless quantity for characterizing the vortex-shedding frequency of the flow past a cylinder. In this study, the Strouhal number for a near-wall circular cylinder fully immersed in a boundary shear flow in the subcritical flow regime was experimentally investigated in a water flume. The velocity fluctuations and flow fields of the lee-wake were systematically measured with an Acoustic Doppler Velocimeter (ADV) and an upward-illumination Particle Image Velocimetry (PIV) system, respectively. Based on dimensional analyses, a non-dimensional shear parameter (K) is introduced to characterize the shear flow. An explicit expression between K and e/D is obtained on the basis of the boundary theory and verified with the flume measurements. Spectral analysis of wake velocities indicates that the multi-peaks can be identified as the cylinder gets closer to the wall. The PIV measurements indicate that the multi-peaks spectra are predominantly induced by the intense interactions between the lower shear layer and wall boundary layer. By fitting the experimental results, empirical relationships for the variations of St with K or e/D are finally established for the subcritical flow regime.

Effect of Openings in Shear wall on Seismic Behaviour of RC Buildings

Shear walls along the exterior perimeter of buildings increase the efficiency of buildings to resist seismic forces. In some conditions, the locations of shear walls are very critical because of the demand of architectural openings like doors and windows in the exterior face of the buildings. The literature has revealed that stiffness and seismic response of the structure is affected by the size of openings and location of openings in shear walls. This paper demonstrates effect of static and dynamic actions on 15 storey RC building having shear walls with openings. 32 building models have been prepared in commercial software STAAD for various inline and staggered openings in shear walls. Seismic coefficient method and Response spectrum method are used for seismic analysis. The analysis is carried out for the seismic zones III and IV for hard and medium soil conditions. The paper compares the response of these building models having shear wall with and without openings on parameters of time period, base shear, storey displacement, storey drifts and surface stress distribution. Uniform stress distribution was observed in shear wall with staggered opening as compared to inline openings.

Probabilistic assessment of induced seismicity at the Alberta No. 1 geothermal project site

Alberta No. 1 (ABNo1) is a geothermal project targeting deep carbonate, conglomerates, and sandstone formations in a potential production and injection zone for geothermal energy exploitation within the Municipal District of Greenview south of Grande Prairie, Alberta, Canada. In geothermal systems without a steam fraction (typically systems under 170 °C), rapid widespread pore pressure changes and slow temperature changes have led to increased deviatoric stresses, resulting in induced seismicity. A concern for the ABNo1 Geothermal Project is that anthropogenic seismicity from oil, gas, and well field fluid injection has created felt events in Alberta. Thus, at the beginning of this type of project, it is prudent to review the potential for induced seismicity. In this study, a geomechanical study of the Leduc and Granite Wash Formations, two potential geothermal fluid exploitation zones, has been undertaken based on borehole geophysics and regional injection-induced earthquake data. Determining subsurface properties such as state of stress, pore pressure, and fault properties, however, poses uncertainties in the absence of actual data from the target formations. Geomechanical analysis results (with associated uncertainties) are used to assess the potential for injection-induced earthquakes. A Monte Carlo probability analysis is employed to estimate the likelihood of slippage of the known faults close to the ABNo1 Geothermal Project. A cumulative distribution function of the critical pore pressure on each fault is derived from the local tectonic stress state and Mohr–Coulomb shear parameter analyses. The resultant probabilistic fault stability maps can serve as a baseline for future fluid injection projects in the region including wastewater disposal, hydraulic fracture stimulation, CO2 sequestration, as well as geothermal energy extraction.

Flow velocity evolution through a floating rigid cylinder array under unidirectional flow

Floating canopies with unanchored roots are often distributed in streams and wetlands, which alters the evolution of the flow velocity inside the canopy interiors. Based on the flow continuity equation and layer-averaged momentum equations, an analytical model was proposed to predict the velocity evolution through floating canopies under unidirectional flow. Laboratory experiments showed that the velocity evolution within the canopy interior was impacted by the mean channel velocity, canopy density and ratio of the height of the free flow region below the floating canopy to the flow depth. Inside a floating canopy, the flow adjustment distance, XD, was defined as the distance from the canopy leading edge to the position at which the velocity decreased to a constant value. A new estimator of XD was proposed and validated for floating canopies. The shear parameter (C = 0.076 ± 0.025) was determined and used to characterize the vertical momentum exchange between the in-canopy and below-canopy flows. The velocities of the proposed model predicted using the new estimator (XD) and shear parameter (C) were in good agreement with fourteen groups of measurements from different sources. The vegetation rigidity and flexibility had a weak influence on the flow velocity evolution inside the floating canopy. This indicated that the proposed model was capable of accurately predicting the velocity evolution through floating canopies of vegetation. In addition, the proposed model can be applied to predict the velocity evolution inside the root zones of floating vegetation islands (FVIs). Compared to that of the drag of the root zones, the influence of the drag of the floating island on the velocity evolution inside the root zones was negligible.

Creation of solitons and density cavities by lower hybrid waves

Formation of Korteweg-de Vries (KdV) solitons by nonlinear lower hybrid waves (LHWs) is not possible in usual electron ion plasma because a dispersive term does not have a suitable form. It is pointed out that the dispersion characteristics of electrostatic LHWs are modified in the presence of field-aligned shear flow to produce KdV solitons with negative electrostatic potential as it has been observed by satellites in the upper ionosphere. Plasma density decreases within the solitary structures. The parallel electron velocity shear ve0=ve0(x)ẑ also gives rise to unstable waves in the intermediate frequency range in linear limit whereas the ambient magnetic field B0=B0ẑ is assumed to be constant. The instability and structure size depend upon the electron parallel velocity shear parameter Se=1Ωedve0(x)dx (where Ωe is the electron gyrofrequency) and the propagation direction with respect to the ambient magnetic field B0. The theoretical model is applied to the upper ionosphere, and the estimated width of the structures turns out to be of the order of 70 m, which is closer to the observations.

A computer-assisted proof of dynamo growth in the stretch-fold-shear map

The Stretch-Fold-Shear (SFS) operator is a functional linear operator acting on complex-valued functions of a real variable x on some domain containing in It arises from a stylized model in kinematic dynamo theory where magnetic field growth corresponds to an eigenvalue of modulus greater than 1. When the shear parameter α is zero, the spectrum of can be determined exactly, and the eigenfunctions corresponding to non-zero eigenvalues are related to the Bernoulli polynomials. The spectrum for has not been rigorously determined although the spectrum has been approximated numerically. In this paper, a computer-assisted proof is presented to provide rigorous bounds on the leading eigenvalue for , showing inter alia that has an eigenvalue of modulus greater than 1 for all α satisfying , thereby partially confirming an outstanding conjecture on the SFS operator.

Revised mixing coefficient scaling for sheared stably stratified turbulence

We revisit and extend the turbulent Froude number ( $Fr_k$ ) scaling for the mixing coefficient ( $\varGamma$ ) introduced by Garanaik & Venayagamoorthy (GV) (J. Fluid Mech., vol. 867, 2019, pp. 323–333) by directly incorporating the effects of mean shear through the non-dimensional shear parameter $S_{\ast } = S k/\epsilon _k$ . For flows where the effects of mean shear are stronger than the background vertical stratification, we find $\varGamma \sim Fr_k^{-2} S_\ast ^{-1}$ for weakly stratified sheared turbulence and $\varGamma \sim Fr_k^{-1}S_\ast ^{-1}$ for moderately stratified sheared turbulence. The scaling procedure is inconclusive for strongly stratified sheared turbulence, but using two independent datasets of homogeneous, sheared, stably stratified turbulence, we empirically observe $\varGamma \sim Fr_k^{-0.5} S_\ast ^{-1}$ . Our revised scaling better collapses both datasets compared with the original GV scaling, and we note that the moderately stratified sheared regime is extremely narrow (or maybe even non-existent). We also apply our scaling to the time-varying open channel simulations of Issaev et al. (J. Fluid Mech., vol. 935, 2022) and observe $\varGamma \sim Fr_k^{-2}S_\ast ^{-1}$ for weakly stratified sheared turbulence, but we observe deviations from our revised scaling for moderate and strong stratifications due to time-varying mean shear and vertical transport. Finally, we apply our revised scaling to field measurements of Conry, Kit & Fernando (Environ. Fluid Mech., vol. 20, 2020, pp. 1177–1197) and observe $\varGamma \sim Fr_k^{-2} S_\ast ^{-1}$ . We emphasize that our revised scaling is applicable only for stably stratified, vertically sheared turbulence with weak spatio-temporal variations of the mean shear and stratification, and we expect different scaling to apply when additional effects such as depth-varying radiative heating/cooling are present or when the orientation of the mean shear relative to the gravity vector is modified (e.g. horizontal shear).

Mathematical Model for Estimation of Shear Parameters of Alluvial Soils of Kamrup Metro District (Assam, India) from Index Properties

ABSTRACT Projects related to Geotechnical Engineering require thorough ground study to know the soil behaviour thus making it necessary to determine the strength and stability parameters of soil. The soils of Assam are primarily of four types viz., Alluvial (old and new), Piedmont, Hill and Lateritic soils with the alluvium abundantly available in the state. The most important soil parameters are the shear strength parameters, namely, cohesion (c) and angle of internal friction (Φ) which can be obtained using triaxial tests with different drainage conditions. But one triaxial test may take weeks to complete and are very expensive. Moreover, for large projects it is practically preposterous to conduct large number of triaxial tests. Hence, an alternate way is to develop a relation between different parameters which enable us to determine others. The main objective of this study is establishing prediction models that allow the shear parameters to be predicted from soil index properties. For this, three prediction models are developed by combining various soil parameters viz., Liquid Limit (LL), Plastic Limit (PL), Specific Gravity (G) and Optimum Moisture Content (OMC) using Multivariate Regression Analysis (MRA) and Artificial Neural Network (ANN). The results show better performance for ANN than MRA.

Shallow mixing layers over hydraulically smooth bottom in a tilted open channel

Shallow mixing layers (SMLs) behind a splitter plate were studied in a tilted rectangular open-channel flume for a range of flow depths and the initial shear parameter ${\lambda = (U_{2}-U_{1})/(U_{2}+U_{1})}$ , where $U_1$ and $U_2$ are streamwise velocities of the slow and fast streams, respectively. The main focus of the study is on (i) key parameters controlling the time-averaged SMLs; and (ii) the emergence and spatial development of Kelvin–Helmholtz coherent structures (KHCSs) and large- and very-large-scale motions (LSMs and VLSMs) and associated turbulence statistics. The time-averaged flow features of the SMLs are mostly controlled by bed-friction length scale $h/c_f$ and shear parameter $\lambda$ as well as by time-averaged spanwise velocities $V$ and momentum fluxes $UV$ , where $h$ and $c_f$ are flow depth and bed-friction coefficient, respectively. For all studied cases, the effect of shear layer turbulence on the SML growth is comparatively weak, as the fluxes $UV$ dominate over the spanwise turbulent fluxes. Initially, the emergence of KHCSs and their length scales largely depend on $\lambda$ . The KHCSs cannot form if ${\lambda \lessapprox 0.3}$ and the turbulence behind the splitter plate resembles that of free mixing layers. Further downstream, shear layer turbulence becomes dependent on the bed-friction number $S = c_f \delta _v /(4 h \lambda )$ , where $\delta _v$ is vorticity thickness. When $S \gtrapprox 0.01$ , the KHCSs are longitudinally stretched and the scaled transverse turbulent fluxes decrease with increasing $S$ . The presence and streamwise development of LSMs/VLSMs away from the splitter plate depends on the $\lambda$ -value, particularly when $\lambda > 0.3$ , resembling LSMs/VLSMs in conventional open-channel flows when $\lambda$ is small.

Maximum height estimation for mine waste dumps

Waste dumps are widely used to discharge stripped mine wastes in open pit mining methods. As mining progresses, the height of the waste dumps will increase gradually, which may induce sliding failure once the height exceeds a critical value. Therefore, estimation of the maximum dumping height is crucial to the life-cycle use of a waste dump. However, published information about the maximum height of mine waste dumps are extremely rare. In this study, the maximum dumping height is estimated based on the strength-reduction technique by numerical simulations. The influences of dump geometry and properties on the maximum height are investigated. The results show that the maximum dump height decreases as the dump slope inclination angle a or the unit weight of dump materials y increases, but decreases when the shear parameters of dump materials (cohesion c and internal friction angle 9) increase. The maximum height starts to increase with the ground inclination p when shear failure occurs at the interface between the dump and the base. Furthermore the effects of the dump width B, Young's modulus E, and Poisson's ratio u of dump materials on the maximum height are almost insignificant. Good agreement was found between numerical results available in the literature and those obtained in this study.