Wet Clay Research Articles

Integrated use of electrical resistivity tomography and ground penetration radar for identifying subsurface sinkholes in Rufa Graben, Central Riyadh

Two-dimensional electric resistivity tomography and ground-penetrating radar (GPR) study was carried out in the eastern Rufa Graben, Riyadh area. Dipole–dipole configuration was used with a total length of 360 m and an electrode spacing of 5 m. In addition, the same number of ground-penetrating radar profiles was conducted in the same location of the electrical resistivity tomography (ERT) profiles. The goal of this study was to map and delineate the subsurface karstic features in the study area such as sinkholes, cavities, and fractured zones. The two methods showed the efficiency to detect the near-surface cavities and their distribution in the study area. The detected cavities were of different sizes. The air-filled cavities have appeared in ERT sections as anomalies that have high resistivity values while the cavities filled with wet clay were characterized with low-resistivity values. In GPR sections, the karstic features were seen by either hyperbola diffractions or uplift and discontinuity in horizontal reflection events. The results obtained from this study will contribute in solving the geotechnical problems for any expected future constructions planned to be done in the study area.

Variation in the yield of sunflower (Helianthus annuus L.) due to differing tillage systems is associated with variation in solute potential of the soil solution in a salt-affected coastal region of the Ganges Delta

Intensification of crop production in the coastal zones of the mega-deltas of Asia by dry season cropping requires timely crop establishment to mitigate the adverse effects of waterlogging, drought, salinity and poor soil structure. In the salt-affected coastal zone of the Ganges Delta, the best method of mechanized cultivation for the timely establishment of non-rice dry season crops on poorly structured, wet clay soils is unknown. Two field experiments were conducted to evaluate the effects of tillage systems with different levels of soil disturbance on the establishment, growth and yield of sunflower, and on soil physical and chemical properties. In 2016-17, five tillage treatments were tested: zero tillage (ZT), narrow strip tillage (NST), bed planting (BP), single pass shallow tillage (SPST) and double pass shallow tillage (DP); in 2017-18, four tillage types were tested: NST, wide strip tillage (WST), BP and SPST. Intensive soil disturbance (BP, DP and SPST) maintained higher soil water content in the surface soil (0–15 cm depth) than less disturbance (ZT, NST and WST) in both years. Tillage treatments had no effect on soil salinity (EC1:5) in 2016-17, but in 2017-18 BP significantly reduced the soil salinity relative to NST throughout the season. Highest yields (19 % and 10 % improvements in 2016-17 and 2017-18 respectively) were associated with tillage treatments with greatest soil disturbance, the BP and DP treatments in 2016-17, and the SPST treatment in 2017-18. These effects were mostly due to increases in soil water content and solute potential in surface soil layers. We conclude that for a wet-clay soil, heavy soil disturbance, such as with BP has the potential to increase the yield of sunflower by increasing soil water supply, decreasing soil salinity and maintaining a higher solute potential in the upper soil layers.

Improved bonding properties of rectorite clay slurry after wet/dry grinding

Rectorite/kaolin clay slurry was used as a binder for unfired high alumina bricks, and the effects of dry/wet grinding on bonding performance of rectorite/kaolin clay slurry binders were considered. The clay slurries were characterized by particle size distribution, viscosity, electrophoretic mobility, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) before and after dry/wet grinding. It indicated that the rectorite clay slurry possesses a large particle size, high viscosity and good stability. After wet grinding, the viscosity and electrophoretic mobility of retorite clay slurry are further improved, and the rectorite particles exfoliate, splitting into rectorite microsheets with a large surface area. The rectorite microsheets with an irregular fold morphology form a mechanical locking structure, and bauxite clinkers are wrapped in a rectorite microsheet network construction, helping resist external forces. The cold crushing strength (CCS) of the brick combined with rectorite clay is higher than in kaolin clay after heat treatment at 110 °C or 750 °C. And the CCS (110 °C drying) is further improved after dry/wet grinding of rectorite clay slurry, reaching 31.1 and 35.0 MPa, respectively. The refractoriness under load test showed that rectorite clay bonded bricks performed low strength at temperature above 1200 °C because of high K2O and Na2O impurities in rectorite clay raw material. So the wet ground rectorite clay slurry bonded high alumina bricks have a broad application prospect at temperature below 1200 °C.

Solar Powered Soil Condition Activated Irrigation System with Automated Bird Repellant

Irrigation plays a very important role in agriculture. Not all geographical regions utilize irrigation which is an important activity that is expensive. For the regions where irrigation is used, it commonly amounts to significant energy consumption. Traditional methods of farming are time-consuming and can only be efficient on a small scale. This project was implemented to make irrigation progressively inventive, easy to use, more efficient and cheaper than the current irrigation system and to solve traditional farming problems like an attack on crops by bird thereby increasing agricultural productivity. This system incorporates a soil moisture sensor to guarantee the application of water to soil adequately. It uses a PIR sensor and a buzzer to solve the problem of attack on crops by birds. This project is powered by a solar panel which is one of the cheapest form of renewable energy and environmentally friendly. The main objective of this project is to upturn the agricultural productivity of the nation by automating the irrigation process. Bird attacks on farmlands are also responsible for destroying a vast amount of crops. One of the traditional problems of agriculture is that farmers frequently neglect to water their plants; it can be as a result of inattentiveness or because of the fact that the farmers are far from home. The utilization of the soil moisture sensor limits the human presence. The microcontroller utilizes the real-time readings of the sensors and automates the irrigation and bird repellent process. From the results, it was observed that the irrigation time was higher in totally dry clay compared to partially wet clay and wet clay respectively. For clay, the irrigation time is in order of magnitude dry clay > partial wet clay > wet clay of the irrigation other soil samples. For the loamy soil, the dry soil was higher. It follows the same trend as the clay in magnitude. It can be found in sandy soil that the wet sample was higher than the totally dry and partially wet sandy soil in terms irrigation time

Acoustic guided wave techniques for detecting corrosion damage of electrical grounding rods

Determining the integrity of grounding electrodes is challenging and there is need to augment expensive and time consuming excavation based methods. In this work pulse-echo methods based on acoustic guided waves were tested on model ground rods with machined model corrosion pits. The generation and propagation of the guided acoustic waves in the model grounding rods using different types of acoustic wave emitters and sensors was studied. The existence of three principle wave modes, longitudinal, flexural and torsional modes, was experimentally observed. The experimentally obtained group velocities versus frequency are consistent with numerical simulations. The principal longitudinal mode at low frequencies has been identified as the best candidate for damage detection on the grounding rods. The pulse-echo signals from the simulated corrosion pits are well correlated with the positions and cross-sectional areas of the pits. Wet-clay wrapping of the rods was used to simulate the influence of soil on the wave propagation. In the wet clay wrapped rods pulse-echo signals from the simulated corrosion pits are well correlated with the positions and cross-sectional areas of the pits, despite the significant attenuation of the echo signals. Acoustic pulse-echo methods based on acoustic guided waves have potential practical application for detecting corrosion-damage of the grounding rods.

Dynamic model for convective heating of a wet brick during energy characterisation of domestic electric ovens

Electric ovens usually represent a low-efficiency category among household appliances, influencing the overall environmental impact of buildings. The energy class of such devices is determined through a test procedure defined by the EN 60350 European standard, where a wet clay brick is heated under set conditions and accurate control of the air temperature during the test is required, which marks the importance of efficient control strategies. In this work a control-oriented dynamic model was devised to predict the transient thermal behaviour of the oven during energy consumption tests carried out in forced-convective mode, including the heat and mass transfer occurring between the wet brick and the cavity air. Model parameters were determined through an optimisation procedure based on experimental data. Comparisons with other sets of experimental data also allowed to validate the predictive capability of the model. The model predicts well the temperature of the cavity air, the Pt500 probe used as a temperature feedback and the core temperature of the brick with deviations lower than 10% after the heating phase of the cavity. The brick heating time and water loss are also captured by the model, with deviations lower than 6% for the former and 9% for the latter.

Wet clay adhesion to antistick coatings: effects of binder type and surface roughness

The handling of sticky raw material can cause problems during operation of process equipment in the cement production industry. These handling problems are generally observed when raw material (e.g., wet clay) sticks to machine walls and causes blockage of outlets. This leads to frequent production shutdowns and expensive cleaning operations. In this work, the effects of surface material and process parameters on the friction forces between wet clay and surface were investigated. Various surface materials and clay impact speeds were investigated. The results demonstrate that not only the equipment surface material but also the surface roughness influences the observed frictional behavior. The ranking of the materials in terms of effective static friction coefficients fell in two groups with equal performance within the group: (1) Two Teflon-based coatings (Accofal 2G54 and Accolan LB), polished AISI 304 stainless steel, Matrox lining, and a polyurethane-based coating (best performing surfaces), (2) Mild steel, a silicone-based coating, and AISI 304 stainless steel (worst performing surfaces). However, the friction coefficients of the two groups only varied by a factor of two, suggesting that adhesion of wet clay to surfaces is difficult to avoid by the use of coatings.

Monitoring of the nano-structure response of natural clay under mechanical perturbation using small angle X-ray scattering and digital image correlation

This paper introduces a new experimental method to monitor the evolving intra-particle, nanometre-scale response during hydro-mechanical tests on undisturbed wet clay samples using small angle X-ray scattering (SAXS). The method uses a newly developed miniature plane-strain one-dimensional compression cell that facilitates simultaneous full-field surface displacement measurements using digital image correlation and SAXS measurements. The 60–120 s acquisition times offered by SAXS at synchrotron facilities are beneficial to study time-dependent mechanisms in clays. The experimental results presented indicate that, for the natural sensitive clay tested in this work, no significant structural changes occur at the intra-particle scale during loading, even when large strains are measured at the macro-scale. In addition, changes that are observed at this scale occur after the end of perturbation, i.e. the creation of new intra-particle structures. Further information is obtained on the orientation evolution of the fabric by the comparative analysis of the individual mineral component response.

Nanocomposites from Clay, Cellulose Nanofibrils, and Epoxy with Improved Moisture Stability for Coatings and Semistructural Applications

A new type of high reinforcement content clay–cellulose–thermoset nanocomposite is proposed, where epoxy precursors diffuse into a wet porous clay–nanocellulose mat, followed by curing. The processing concept was scaled to >200 μm thickness composites, the mechanical properties were high for nanocomposites, and the materials showed better tensile properties at 90% RH compared with typical nanocellulose materials. The nanostructure and phase distributions were studied using transmission electron microscopy; Young’s modulus, yield strength, ultimate strength, and ductility were determined as well as moisture sorption, fire retardancy, and oxygen barrier properties. Clay and cellulose contents were varied as well as the epoxy content. Epoxy had favorable effects on moisture stability and also improved reinforcement effects at low reinforcement content. A more homogeneous nano- and mesoscale epoxy distribution is still required for further property improvements. The materials constitute a new type of three-ph...

Microwave drying of wet clay with intermittent heating

In this article, we study an alternative process for the conservative drying of wet clay based on combined microwave heating and convective drying. The study is founded on an experimental analysis of the processes that control drying of porous matter in presence of temperature gradients. We show and discuss that process control cannot be reliably based on temperature alone because mass transfer phenomena associated with microwave heating dictate drying kinetics. Essentially, the occurrence of pressure build up and liquid expulsion, dominating mass transfer if microwave heating is uncontrolled or with high power, vitally depend on the moisture content of the clay. As a consequence, the deterioration of clay is problematic if internal evaporation rates are high, thus at the start of drying when also the moisture content is high. Following this, we propose intermittent microwave heating in combination with convective drying periods with the aim to reduce overall drying time (compared to conventional convective drying) and to improve product quality by reduced material shrinkage. Drying experiments indicate that the overall drying time reduction and product quality depend on the frequency and duration of the two subsequent periods of intermittent heating and convective drying. The observations can be explained with the evolution of the pore-scale distribution of liquid and vapor during drying.

Experimental Modeling of Methane Hydrate Formation and Decomposition in Wet Heavy Clays in Arctic Regions

Experimental studies on clay sample saturation by methane hydrates proved that clay particles play an important role in the hydrate accumulation and decomposition processes in sediments. Depending on water content, the same clay mineral can serve as inhibitor, neutral component and promoter of hydrate formation. Wet clay is a good mineral surface for hydrate formation, but clays represent the worst media for hydrate accumulation and existence. Nevertheless, there are many observations of hydrate presence in clay-containing sediments, especially offshore. Experimental modelling of metastable hydrate decomposition in sediment samples recovered from permafrost in “Yamal crater” in the Russian Arctic has shown that metastable hydrates located in frozen, salted clays can generate huge volumes of gas, even with a negligible (tenth and hundredth of a degree) temperature rise.

Establishment and finite element analysis of soil load-sinkage model

The research of load-sinkage characteristic between soil and vehicle is focused by many scholars in vehicle terramechanics field all the time. The classical models of load-sinkage characteristic between soil and loading plate were established based on a large amount of in-situ tests, but it’s sometimes difficult to conduct the in-situ experiments. So the finite element method was used to analyze the load-sinkage characteristic relationship between soil and loading plate based on the triaxial compression experiment date. The finite element calculation result shows that the simulation load-sinkage curve is very close to the curve fitted by classical model. According to the simulation date, a new model, double-exponential equation, to describe the load-sinkage characteristic of soil was proposed, and the R2 ≥ 0.99. The new model was verified by fitting the measured date of wet clay and have a better accuracy compared with other models which is bekker, LSA and Kacigin-Guskeo model.

Effect of Geotextile Encasement on the Shear Strength Behavior of Stone Column-Treated Wet Clays

The behavior of clay beds treated with ordinary and geosynthetic-encased stone columns under vertical loads is wisely well known. Since soil movements occurring in the field conditions may cause shear deformations in the stone columns, investigating the shear behavior of clay beds treated with stone columns is necessary. Also, a wide range of clays on the ground are wet (unsaturated) or dry in place, so this paper aims to experimentally investigate the shear strength parameters of untreated and treated wet clays by ordinary and encased stone columns by performing a series of large direct shear tests. For this purpose, the effect of some variables such as tensile stiffness and length of the encasement, frictional angle and size of column’s aggregates, diameter, number and arrangement of stone columns on shear strength parameters of such soils under various normal pressures are evaluated. The obtained results show a significant improvement in the shear strength behavior of the wet clay treated by stone columns due to geotextile encasement, but the rate of this improvement depends on physical and strength properties of stone columns and encasement.

Modelling optimisation of vehicle velocity for wheeled construction vehicles traversing in off-road terrain

This paper presents the results of an investigation into the effect of terrain conditions on vehicle velocity at each given vehicle speed selection in wet clay and sand terrain beds. Wheeled vehicles face mobility challenges when traversing in deformable terrain resulting in reduced velocity. This experimental modelling-based investigation was carried out using a modified and instrumented wheeled mobility scooter named MOBILITY SF-3713. This vehicle was run on non-deformable pavement in order to obtain reference results. It was then run on wet sand and clay terrain test beds under controlled laboratory conditions. Results from this experiment indicated that terrain type, applied load and tyre inflation pressure all have significant effects on velocity, influenced by tyre rutting in deformable terrain. The results suggest that reliable prediction of this relationship can assist earth moving and deformable haulage road engineers in making economic operational decisions that affect the velocity of wheeled plant.

Modelling optimisation of vehicle velocity for wheeled construction vehicles traversing in off-road terrain

This paper presents the results of an investigation into the effect of terrain conditions on vehicle velocity at each given vehicle speed selection in wet clay and sand terrain beds. Wheeled vehicles face mobility challenges when traversing in deformable terrain resulting in reduced velocity. This experimental modelling-based investigation was carried out using a modified and instrumented wheeled mobility scooter named MOBILITY SF-3713. This vehicle was run on non-deformable pavement in order to obtain reference results. It was then run on wet sand and clay terrain test beds under controlled laboratory conditions. Results from this experiment indicated that terrain type, applied load and tyre inflation pressure all have significant effects on velocity, influenced by tyre rutting in deformable terrain. The results suggest that reliable prediction of this relationship can assist earth moving and deformable haulage road engineers in making economic operational decisions that affect the velocity of wheeled plant.

Three-dimensional fault geometries and interactions within experimental models of multiphase extension

ABSTRACT We use experimental (analog) models to examine the three-dimensional (3-D) fault geometries and interactions that develop during two phases of noncoaxial extension. In the models, a homogeneous layer of wet clay undergoes two phases of extension whose directions differ by 45°. The resulting fault pattern varies significantly with depth. At shallow levels, second-phase normal faults accommodate most second-phase extension. At depth, both second-phase normal faults and reactivated, first-phase faults with oblique slip accommodate most second-phase extension. A variety of interactions occurs between first-phase and second-phase faults. One interaction involves the upward propagation of second-phase faults from tips of reactivated, blind, first-phase faults. These hybrid faults have deep segments that strike subperpendicular to the first-phase extension direction and shallow segments whose strike varies with depth, becoming increasingly subperpendicular to the second-phase extension direction at shallow levels. A second interaction involves the nucleation of second-phase normal faults on the surfaces of reactivated, first-phase faults. These splay faults propagate upward and laterally from their nucleation sites into the hanging walls of the first-phase faults. As they propagate, they commonly encounter and link with different first-phase faults. The resulting composite faults have zigzag geometries in both map and cross-sectional views. A third interaction involves either the termination of second-phase antithetic normal faults against or near first-phase faults or the offset of first-phase faults by second-phase antithetic normal faults. The 3-D fault patterns and interactions within our models closely resemble those within the Taranaki basin of offshore New Zealand and Milne Point on Alaska’s North Slope.

Evolution of AC conductivity of wet illitic clay during drying

The evolution of the AC electrical conductivity during drying as well as the relationship between sample volume and moisture of green illite samples were investigated. The samples were prepared from illitic clay (80 mass % illite, 4 mass % montmorillonite, 12 mass % quartz and 4 mass % of orthoclase) and distilled water with initial moisture content 36 mass % and were freely dried in air. Conductivity was measured by the volt-ampere method with AC power supply of 5 V in the frequency range from 50 Hz to 10 kHz. The AC conductivity steeply increased with increasing moisture, up to 15 mass %. At higher values of the moisture, the AC conductivity was high and almost constant. The volume of samples increased with increasing moisture when the moisture was higher than 8 mass %. Below this value, the dimensions of samples do not significantly change. The dependence of the relative volume change on moisture is presented in a form of the Bigot’s curve.

THE SINKHOLE

5 8 Y T H E S I N K H O L E D E V I N J O H N S T O N Unclenched and half asleep – bloodstream tinged with melatonin, the hormonal expression of darkness – I lie still, listening to a soft persistent tapping at the baseboard, the little sounds that demand nothing, ordain nothing, explain nothing . . . A mouse worries a curl of wire. The house settles a hair’s breadth, ground giving way far below in a bed of porous limestone. And through the stone, a cavern meanders for a mile or so to Uhrig’s Cave, a dank saloon strung with lights, where the chorus sings, We sail the ocean blue. A stream of cold air, redolent of soil, leads on through a mushroom farm to swimming pools of wet clay, penates of brick, and bones of prehistoric peccaries. The entrances have long been lost in basements, behind furnaces, or sealed with highway rubble. These birdless regions now permit no tra≈c with the surface but for the secret course of water and low tones of a gallon jug. 5 9 R I see my mother’s ghost among the dead, sitting in silence near the blood. Not once has she glanced this way or spoken: does she not recognize her son? Thick drops beat against the glass. The ceiling plaster ticks, a sound as soft as a struck match or shutter click. As my head begins to settle, days flash behind my lids without sound – Lampyridae, the cold and shining ones. ...

Use of Clay Dispersed in Water for Decreasing Soil Water Repellency

AbstractIn this study, we examined the efficiency of a kaolinite clayey soil to mitigate water repellency of a sandy soil with olive trees. The treatment was applied to the soil zone below the tree canopy, which displayed the highest degree of water repellency [average water drop penetration time (WDPT) value = 820 s]. Both dry (incorporated onto the top soil) and wet clay applications (after dispersion in irrigation water) were examined in a replicated experiment, with control trees being used for comparison. The application rate of the clayey soil was maintained in both cases (wet and dry mode) equal to 1 kg m−2, while the effect of subsequent wetting and drying cycles on the treatment performance was evaluated. The results of the study verify that clay application was effective to mitigate soil water repellency. Dry supplementation displayed low efficiency (26% reduction of the air‐dry WDPT compared with the control soil) within the first week of application. The efficiency of the dry‐clay treatment increased to 76% after applying three subsequent wetting and drying cycles. In comparison with the dry mode, the wet clay was efficient immediately after application (74% reduction of the WDPT), indicating that the limiting step in the overall process was clay dispersion. Based on the findings of this study, it was proposed that wet clay application is of interest for controlling soil water repellency in agricultural land. Copyright © 2016 John Wiley & Sons, Ltd.

Simulation of a solar-ice system for heating applications. System validation with one-year of monitoring data

In the present paper a dynamic system simulation for a combined solar thermal and heat pump system including an ice storage is presented. The simulated system was validated with one-year measurements from a pilot plant situated in Rapperswil-Jona, Switzerland. The system is installed in an old kindergarten with a yearly heating demand of around 35MWh and a high temperature hydronic heat distribution system (radiators). The pilot plant is composed of 50m2 of covered and 14m2 of uncovered collectors, both with selective coating; a heat pump of 17kW, a sensible storage of 3.5m3 and an ice storage of 75m3. The monitored yearly system performance factor was 4.6.The system simulation was compared to measurements at monthly and yearly bases for global variables of interest such as system performance factor, energy flows between the collectors, ice storage, heat pump and combi-storage. The yearly difference in system performance (SPFSHP+) was found to be within the uncertainty range. After the system was validated, a sensitivity analysis was conducted. The most sensitive parameter was found to be the variation of ground properties between two extremes, i.e. from wet clay to dry sand where differences up to 4% were found in the yearly SPFSHP+.Results from annual simulations with Meteonorm weather data were compared with results from simulations using measured weather data for the climate of Zurich. The average of the results of 13 years with real data showed an increase of SPFSHP+ of 24% compared to the results obtained with Meteonorm data.