Vertical Shrinkage Research Articles

Analysis of rainfall infiltration effects on the stability of pyroclastic soil veneer affected by vertical drying shrinkage fractures

The paper presents a preliminary, simplified evaluation of the effects of rainfall infiltration on the stability of slopes in layered pyroclastic soils affected by shrinkage vertical fractures. The analysis has been developed with a special reference to a stratigraphic sequence obtained by an in situ survey at Pizzo d’Alvano (Southern Italy). The analysis of rainfall infiltration is performed using an original dual-permeability model. Results show how fractures strongly condition infiltration depending on rainfall intensity. Prolonged low-intensity rainfall may lead to a higher saturation of the surface soil layer than short, intense rainfall when water may flow quickly through fractures into the underlying more permeable soil layers. Calculated distributions of pore pressure are used for the slope stability analysis using the infinite slope approach. Variations of the safety factor as a consequence of infiltration show that prolonged rainfall can induce a more relevant decrease in the safety factor than intense precipitations.

Swell and shrinkage strain prediction models for expansive clays

A comprehensive laboratory investigation was conducted to study volume change behaviors of five different types of expansive clayey soils sampled from various regions in Texas, USA. The laboratory test results, which were presented in an earlier paper, are analyzed here to evaluate existing correlations that can be used to predict swell and shrink-related displacements in these soils. The test database is also used to develop newer and practical models for predicting volume change-related soil properties. Models developed here used soil plasticity and compaction properties as independent variables. Newer models, that rely on seasonal compaction moisture content variations in the subsoils, were introduced to estimate both volumetric and vertical swell and shrinkage strains expected under civil infrastructure. The developed correlations, along with the existing models, were then used to predict vertical soil swell movements of four case studies where swell-induced soil movements were monitored. This comparison analysis showed that the model dependency on the volume change test procedural information and moisture content variation due to seasonal changes will lead to better prediction of swell movements in subsoils. Future research directions and recommendations are provided on implementation of the developed models in a realistic estimation of swell movements of infrastructure construction projects.

A simplified model on vertical density profile and shrinkage ratio of virgin and charred medium density fibreboard

ABSTRACTThis work is part of a wider scope of research on developing comprehensive pyrolysis model for medium density fibreboard (MDF) in fires. A simplified model is developed to predict the vertical density profile of virgin MDF. The model shows that vertical density profile can be reproduced using a second order conic curve. Several sets of experimental data are used to validate the model with promising results that are presented. Further investigation shows that the density difference between surface and core densities tends to maintain constant within a range of 300 to 450 kg/m3. Moreover, the model can predict the mean density with an error less than 30 kg/m3. Typical MDF panels were experimentally charred using thermogravimetric analysis and cone calorimetry to investigate the shrinkage and density of char. The actual char density is measured as 330 kg/m3 with a uniform density distribution along the char layer thickness. A model is developed to predict the shrinkage ratios. The restraining effect caused by surface deformation will lead to different vertical and horizontal shrinkage ratios. The volume reductions at vertical and horizontal directions are experimentally measured as 40% and 20% for the two tested MDF panels, which is comparable with the model predictions. Copyright © 2013 John Wiley & Sons, Ltd.

Satellite‐Based Radar Interferometry to Estimate Large‐Scale Soil Water Depletion from Clay Shrinkage: Possibilities and Limitations

Satellite‐based radar interferometry is a technique capable of measuring small surface elevation changes at large scales and with a high resolution. In vadose zone hydrology, it has been recognized for a long time that surface elevation changes due to swell and shrinkage of clayey soils can serve as an estimate for soil water storage change. Therefore, satellite‐based radar interferometry can potentially offer an alternative methodology to estimate soil water storage change at field or regional scales. This paper introduces principles of satellite‐based radar interferometry and identifies limitations and potential applications of the technique to measure surface elevation changes from clay shrinkage. In situ measurements were performed and a linear relation between soil water storage depletion and layer shrinkage was obtained. Data from the TerraSAR‐X satellite over the measurement area were analyzed to identify the most favorable conditions for radar interferometry to measure vertical shrinkage. High‐quality phase observations over clayey areas in polders with limited vegetation can be explained from differences in land use and soil type. Signal noise over sparsely vegetated agricultural fields was successfully reduced by multilooking over agricultural fields at the cost of spatial resolution. Good resemblance between in situ measured shrinkage and differential phase change was found in a test period. Based on this study, we expect that radar interferometric processing of data from the future satellite mission Sentinel‐1 can play a crucial role in providing much‐needed observations of vadose zone processes at the field scale and beyond.

An artificial neural network system for predicting the deformation of steel plate in triangle induction heating process

This paper presents the development of an artificial neural network (ANN) model to predict the positions and sizes of induction triangle heating based on laminated plate theory combined with Finite Element Method (FEM) solutions. The vertical displacements and transverse shrinkage of nodes on the plate are used as inputs to the network and the position of the heating triangles on the plate, heated surface, and size of the heating triangles are the outputs of the models. The developed feed-forward ANN with 242-100-72 arrangement is capable of estimating all necessary conditions for the induction triangle heating process. The training patterns of the neural network are obtained using an analytical solution derived from the plate laminate theory to predict the plate deformations in the induction heating process. The developed neural network model is tested to demonstrate its feasibility for determining the heating positions on the surface of a flat steel plate in the triangle induction heating process for forming a desired shape.

Shrink–swell behavior of soil across a Vertisol catena

Summary An accurate estimate of the degree of soil cracking is important in partitioning rainfall into soil infiltration and runoff in watersheds with clay soils that shrink and swell. Usually in the application of surface hydrology models, cracking is considered to be predicted by assuming equidimensional shrinkage and a 1:3 ratio of change in soil profile thickness to depth of water loss. Our objective was to use in situ measurements of soil profile subsidence with loss of water in an apparently uniform Vertisol to determine: (1) whether or not the soil profile subsidence followed the 1:3 ratio of change in thickness to depth of water loss and (2) how the ratio of subsidence to water loss varies with the Coefficient of Linear Extensibility (COLE). The research was conducted on a catena of Houston Black and Heiden clays. Vertical soil shrinkage and swelling along with soil water content were measured at the summit, shoulder, backslope, and footslope positions of the catena. Change in soil water content along with spatial variability in COLE were the primary drivers of temporal and spatial variability of shrinkage and swelling on the catena. The rate that soil shrank or swelled with change in the amount of water stored in the soil was related to COLE, which was negatively correlated with carbonate content of the soil. Shrinkage of the soil profile with water lost was less than the commonly used 1:3 ratio. Our data supported using COLE to predict the degree to which the ratio is less than 1:3. Incorporating COLE values into a hydrology model to simulate soil shrinkage with water loss is a useful approach because COLE values have been measured for soils with shrink–swell potential and that data is available in USDA NRCS Soil Survey databases.

Investigation on the plastic shrinkage of cementitious materials under drying conditions: mechanism and theoretical model

The plastic shrinkage behaviours of fresh paste under drying conditions were investigated for several typical cementitious materials, including cement, silica fume, fly ash and calcium carbonate powder. For all four kinds of slurries, pore water under pressure (PWP) at different depths, shrinkage both in the vertical and horizontal directions, and water evaporation were measured simultaneously. Preliminary experimental investigations show an obvious anisotropic character of the plastic shrinkage behaviour in the vertical and horizontal directions and strong dependence on the PWP development. At the beginning of exposure, no PWP is generated, the total shrinkage is fully displayed by vertical displacement, and the responsible mechanism for plastic shrinkage is water evaporation. Once PWP arises, the investigated pastes exhibit vertical expansion and horizontal shrinkage; the responsible mechanism is the capillary tension in pore fluid. Based on the experimental observations, a two-phase theoretical model is proposed, which builds a quantitative relationship between water evaporation and vertical shrinkage before PWP is generated, as well as between PWP and horizontal shrinkage after PWP arises.

Graft Shrinkage and Survival Rate of Implants After Sinus Floor Elevation Using a Nanocrystalline Hydroxyapatite Embedded in Silica Gel Matrix

The aims of this study were (1) to evaluate the vertical shrinkage percentage of nanocrystalline hydroxyapatite embedded in silica gel used for maxillary sinus floor elevation (SFE) and (2) to determine the survival rate of the implants 1 year after placement in the healed grafted sinuses. Eleven maxillary sinuses were augmented in eight patients with NanoBone. After a healing period averaging 14.42 months, 19 implants were placed and followed up with clinical and radiographic evaluation. Panoramic radiographs were taken immediately after SFE and at 12 months after grafting. Measurements of changes in height were made by a computerized measuring technique using an image editing software. The mean graft height shrinkage percentage at 12 months after surgery was 8.84% (±5.32). One implant was lost before loading. All the 18 remaining osseointegrated implants received the prosthetic rehabilitation and were controlled after 3 months of functional loading. The implant survival rate at the 1-year interval was 94.74%. A 100% NanoBone alloplastic graft used in lateral SFE procedures presented limited height shrinkage. Implants placed in these grafted sinuses showed survival rates similar to those found in published data. These results should be interpreted cautiously considering the study's reduced sample size.

Fabrication of carbon nanostructures using photo-nanoimprint lithography and pyrolysis

High-throughput synthesis of carbon nanostructures with reproducible shape and dimensions, at desired locations, has been a key challenge for further exploring carbon nanostructures as functional units in various nanodevices. In this work, carbon structures with dimensions from the 50 nano- to micrometer level have been fabricated by carbonizing a photo-nanoimprint lithography patterned resist polymer (AR-UL-01) at high temperature under inert atmosphere. The resulting carbon nanostructures showed significant vertical shrinkage but minimal loss in the lateral direction. Thermal behavior studies of the resist polymer in the pyrolysis cycle indicated gaseous evolution of various byproducts before the formation of solid carbon. Microstructure, elemental composition and resistivity characterization of the nanostructures produced by this process has shown that the carbon derived from a pyrolyzed nanoimprint resist is very similar to the pyrolyzed photoresist carbon from an SU-8 negative-tone photoresist. This simple approach is valuable as a wafer-level carbon nano-patterning technique.

Coking theory: Formation and heating of coke cake and pyrolysis of gaseous products

The shrinkage of the charge and the formation of coke cake are described on the basis of theoretical research and industrial experiments. Shrinkage begins when the coal batch is introduced, and therefore rewards careful scrutiny. With changes in coke-battery design—in particular, increases in height—the vertical shrinkage of the coke cake changes, along with the heating of the cake’s upper section and the pyrolysis of the gaseous coking products. In this context, the distance fallen by the combustion products from the fuel gas is calculated.

Experimental characterization of shrinkage and desiccation cracking in thin clay layer

Knowledge of shrinkage mechanism and the accompanied cracking behavior is helpful for better understanding the hydraulic and mechanical performance of clay soil under atmosphere condition. Initially saturated thin clay layers were prepared and subjected to air drying in this investigation. Water evaporation, volume shrinkage, surface crack initiation and propagation processes were monitored during the whole drying period. With application of image processing technique, the geometric or morphological characteristics of crack patterns were quantitatively described. Results show that the water in the clay layer evaporated at a near constant rate and then it began to decline when the water content was close to the air entry value. The clay layer volume shrinkage was contributed completely by vertical subsidence before desiccation crack initiation, and the measured final vertical shrinkage strain was several times higher than the lateral shrinkage strain. In addition, it was found that most of the cracks and volume shrinkage occurred during the constant rate of evaporation period while the specimen was still saturated. Crack initiation and propagation generally took place in three stages and terminated at the shrinkage limit. During the process of crack propagation, the crack intersections reached a stable value first and were followed by crack length and crack width.

Simulation aided testing of hydro-mechanical processes on clay

This paper presents a study focused on the hydro-mechanical behaviour of a plastic clay under partially saturated conditions. Clay remoulded samples were dried using vapour transfer under one-dimensional conditions. Samples underwent an important vertical shrinkage on drying, which progressed along more than one week. To study the time evolution of this phenomenon, simulation aided techniques were used to analyse the progression of suction at local scale and to determine the time required to equilibrate homogeneously the sample. In this case the fully coupled thermo-hydro- mechanical finite element code Code_Bright (1) was used to analyse this process. The simulation adequately followed the evolution of sample shrinkage measured experimentally. The determination of the suction equalisation time also agreed with the experimental information.

Curing process of silsesquioxane in self-organized diblock copolymer template

In the case that a self-organized diblock copolymer pattern is applied as an etching mask, one of the polymer components is required to have a high etching durability similar to that of silicon oxide. One suitable material for the purpose is a mixture of polystyrene-b-polyethyleneoxide (PS-PEO) and silsesquioxane (SSQ). After phase separation, the SSQ component is located only in PEO phase. By the following post-treatment, the polymer component was removed and residual cured SSQ structure was formed that could be available as etching mask. In this study, the authors investigated post-treatment process of SSQ in the mixed component system, comparing thermal treatment and oxygen plasma treatment. A significant difference was observed in the vertical shrinkage of the film thickness formed on a Si wafer. The plasma-treated film shrank to 72% of the baked film. By the examination of behavior of PS phase and PEO phase during post-treatment, respectively, it was found that the difference was caused by the curing behavior of SSQ in PEO. In the case of plasma treatment, the polymer component was removed before SSQ curing. As a consequence, plasma treatment gives voidless structure. Using the template as etching mask, 16nm pitch pattern was transferred to Si wafer.

Polymeric microsieves via phase separation microfabrication: Process and design optimization

Phase separation microfabrication (PSμF) is a fabrication method that allows the preparation of membranes having micropattern surface topologies. PSμF has been successfully used for manufacturing polymeric microsieves. The technique benefits from the vertical shrinkage of polymer solutions to ensure perforation by the pillars on the mold. The horizontal shrinkage causes deformation of some pores and increased peeling forces. This can lead to rupture of molds as well as inoperable microsieves. The effect of several parameters of mold design as well as peeling orientation is addressed. A peeling device equipped with a force transducer is used to measure the force required for peeling in each case. Peeling forces decrease with lower pillar densities, the use of alternative geometries for the pillars (i.e. not round pillars) and the use of alternative pillar placing (i.e. not square pitch).

Crystallization of sputtered-deposited and ion implanted amorphous Ge2Sb2Te5 thin films

X-ray diffraction and transmission electron microscopy have been utilized to measure the ion irradiation-induced modification in amorphous Ge2Sb2Te5 thin films. The isothermal crystallization of sputtered-deposited and Sb+ ion irradiated amorphous samples has been studied, focusing on the evolution of the microstructure during the initial stage of the transformation. In both samples, the amorphous to crystal transition occurs through the nucleation of face centered cubic (fcc) crystal domains at the film surface. A fast bidimensional growth of the crystalline nuclei in the sputtered-deposited films occurs by the generation of transrotational grains. The lattice parameter decreases as the crystalline fraction increases above 80%, and it approaches the fcc bulk value at the end of the transformation. Ion irradiation produces a densification of the deposited amorphous film (∼4% vertical shrinkage measured by atomic force microscopy) and an enhancement of the crystallization rate. Even in the irradiated amorphous, the nucleation occurs at the film surface and proceeds by the growth of the grains through the thickness of the layer although the density of the transrotational grains is strongly reduced with respect to the unirradiated amorphous. A link between the ion beam induced densification and the reduction of transrotational grains is proposed.

SPRAY CHARACTERISTICS OF ARTIFICIAL AEROSOL CLOUDS IN A LOW-SPEED ICING WIND TUNNEL

This article investigates liquid water content (LWC) and its uniformity in supercooled aerosol clouds produced in a low-speed horizontal icing wind tunnel used for simulating atmospheric icing. The dependence of LWC obtained at mid-height of the tunnel test section on thermodynamic parameters of the air stream and on dynamic parameters applied to the nozzle system is determined empirically for two types of nozzles. The investigation reveals that LWC increases with air velocity, reaches a maximum at a low airspeed (below 30 m/s), and decreases as was observed at high airspeeds used for modeling aircraft icing (up to 160 m/s) only after passing this maximum. This complex behavior is explained by the concurrence of two processes: the vertical separation of droplets of different size due to the effect of gravity, and the vertical and transverse shrinkage of the aerosol cloud co-occurring with its streamwise expansion.

Physical origin of residual thermal stresses in a multilayer ceramic capacitor

The physical origin of the residual stresses developed in the ceramic layer of the active region in a multilayer ceramic capacitor was numerically investigated. The compressive in-plane stress components σ11 and σ22 originate without regard to the presence of the margins but rather from the difference in in-plane thermal shrinkage between ceramic and metal electrode. The out-of-plane stress component σ33 physically originates mainly through the presence of the housing margin; the presence of the lateral margin is a minor source: the more ceramic-rich margins hinder the apparent vertical shrinkage of the active region to yield tensile σ33.

Anisotropy, cracking, and shrinkage of vertisol samples Experimental study and shrinkage modeling

Measuring and modelling the soil shrinkage curve (ShC) has generated increased interest, but uncertainty in shrinkage curve parameters has not been documented, and the most recent models have not been compared. This study was performed on 11 core samples collected in the same horizon of a vertisol. The objectives of the study were to (i) characterize the anisotropy of soil samples shrinkage by comparison of vertical, horizontal and volume shrinkage, (ii) analyse the impact of shrinkage anisotropy on fitted shrinkage parameters, (iii) determine uncertainty in shrinkage parameters, and (iv) compare the plasma pore volume as modelled by the clay-paste model (CP) to the plasma pore volume as estimated with the soil shrinkage XP model. The coefficients of variation of the different ShC parameters were smaller than 12% and 3% for water contents and volumes, respectively. Cracking led us to exclude some vertical ShC for XP model fitting, as the ShC departed strongly from the S-Shape model. The vertical geometry factor was smaller than 3 and the horizontal geometry factor was larger than 3 in average. The geometry factor values were changing with water content; they deviated widely from 3 at water saturation, but remained constant and close to 3 in between air entry (AE) and maximum swelling (MS). Cracking and anisotropy had no impact on the XP fitted shrinkage parameters. They were not significantly different between one-dimensional (1-D) and volume measurements. The results of our study suggest that parameters from 1-D shrinkage might be adequate to describe three-dimensional shrinkage. The XP plasma pore volumes at shrinkage limit (SL) were in the range of mercury porosimetry values, the average fitted plasma volume was only 1.7% larger than the median measured value. Direct calibration of CP model from independently measured parameters gave water contents at SL and AE one order of magnitude smaller and two times larger than the fitted values, respectively. But when the AE point water content was set equal in the CP and the XP model, the two modelled plasma ShC were almost identical, with differences depending only on the small difference between fitted and measured plasma volume at SL. Thus, the CP model could be used instead of XP-plasma model to describe the plasma ShC, provided that AE points were identical. This is, however, contradictory with the proposed independent calibration method. The present results are encouraging regarding ShC determination and the comparability of shrinkage modelling approaches. Further comparison of the models requires additional experimental information on the soil plasma shrinkage, especially on MS point.

Quantification of soil shrinkage in 2D by digital image processing of soil surface

Knowledge of soil shrinkage behavior is needed to improve the understanding and prediction of changes of unsaturated hydraulic properties in non-rigid soils. The heterogeneity and interaction of horizontal and vertical soil shrinkages that produce soil cracks and associated soil subsidence require additional quantification. Vertical shrinkage can be calculated easily by soil height with vernier caliper. However, a quantitative and feasible measurement of horizontal shrinkage has not been developed yet because of the complicated and irregular geometry of soil cracks. This paper introduces a new method to measure soil cracks non-destructively and continuously by digital image analysis. Using Adobe Photoshop and Windows Scion 4.02 image processing, the proposed procedure accurately identifies changes as small as 1.0 mm 2 and shows differences even when areas of soil cracks were increased by as little as 1%. Various geometry factor values indicated soil shrinkage in the two dimensions was anisotropic during the whole drying. During initial dehydration from saturation, only subsidence shrinkage could be identified. With the further dehydration, the soil cracks developed and increased in size. These results suggest that the heterogeneity of soil shrinkage in 2D should be taken into account when modeling the total soil shrinkage behavior and associated unsaturated hydraulic properties.

Effect of rapid thermal annealing on the properties of GaNAs thin films grown by molecular beam epitaxy

High-resolution X-ray diffraction (HRXRD) and micro-Raman scattering probe have been used to study the effect of post-growth thermal annealing on GaNAs thin films grown on (0 0 1) GaAs substrates by solid-source molecular beam epitaxy assisted with a nitrogen radio-frequency plasma source. X-ray reciprocal space mapping shows slightly in-plane strain relaxation after annealing, however, the vertical lattice constant measured by HRXRD from the (0 0 4) atoms planes shows a shrinkage, which is contrary to both the relaxation of tensile strain and the decreasing of nitrogen due to out-diffusion. The ratio of Raman intensity between the nitrogen-localized vibration mode and the GaAs-like LO is found to increase as a function of annealing temperature, which provides evidence for the increase of substitutional N As atoms at elevated temperatures. The anneal-induced vertical lattice shrinkage can be explained in term of the redistribution of nitrogen bonding configurations among the substitutional N As, interstitial N–N, and the N–As complex.