Evaluating Soil Water Matric Pressure and Sorptivity Relationship as Affected by some Properties of a Clay Soil

Sorptivity (S) is the fundamental variable controlling the early infiltration process. Besides soil properties, soil initial water content (θi) and/or matric pressure (hi) are key factors determining extent of S. Assessment of interrelationship among S, hi and soil properties can provide a considerable insight into understanding the behaviour of dry soils to rainfall or irrigation water. This study was conducted to evaluate relationship between S and some selected soil parametric and morphometric properties within a range of hi. Sixteen undisturbed soil samples (5 cm id, 5 cm length) were taken from the topsoil (0-15 cm) of a paddy soil with clay texture. Sorptivity was measured with a mini-disc infiltrometer (MDI) on the samples equilibrated at h, ranging from -20 to -1500 kPa. A parameter (η), representing the relationship between S and hi, was introduced. Correlation analysis was conducted between η and selected soil morphometric and parametric properties. Soil structure and clay content appeared the most important soil attributes influencing S-hi relation between -200 and -1500 kPa. The results provided a fundamental understanding on S-hi-soil properties interrelations in a clay soil. The methodology developed in this study can be used to evaluate S-hi relationship across different soils and scales.

The application of vapour equilibrium technique to control suction to study the shrinkage and water retention of compacted Claystone-Bentonite mixtures

Understanding soil shrinkage and retaining water is essential for learning more about the possibility of cracking of liner. Moreover, the factors that influence it are also important to know to improve the material tested as hazardous waste liners. The vapour equilibrium technique is widely used to control suction of compacted soils experiencing drying-wetting phenomena. It is considered to be inexpensive, simple, and has the ability to adequately control the suction applied to soil samples. This paper, therefore, describes its application in studying the shrinkage and water retention in compacted claystone-bentonite mixtures. This involved using five saturated salt solutions including potassium sulphate (K2SO4), potassium chloride (KCl), sodium chloride (NaCl), potassium carbonate (K2CO3), and magnesium chloride (MgCl2.6H2O). The sample was allowed to be in equilibrium with the relative humidity salt solution and a calliper was used to measure the dimensions every day up to when this was achieved. The results showed the bentonite in the mixture affects the amount of shrinkage and water retention while the sample’s initial moisture content was also found to be very influential on the magnitude of the primary and residual shrinkage. Moreover, the sample’s ability to hold water was almost the same without differentiating the initial water content at a total suction of more than 41084.91 kPa.

Shear strength characteristics of Jerash expansive soil

The results of the direct shear test on Jerash expansive soil show the effect of the initial water content on the cohesion (c) and on the angel of internal friction ( ) [shear strength parameters].it show that, as the initial water increase, the cohesion (c) of Jerash expansive soil also increase up to the shrinkage limit, after that increase of water even small amount, decrease the cohesion of the soil. On the other hand, the results of direct shear test show also that as the water content increase, the angle of internal friction ( )remain unchanged up to shrinkage limit , any increase of water cause a large decrease on the angle of internal friction of Jerash expansive soil.

Factors affecting the swelling pressure for Jerash expansive soil

In this study for factors effecting the swelling pressure of jerash expansive soils were investigated in this study, effect of initial dry density and effect of initial water content on the jerash expansive soil were investigated.It show that as the initial dry density decrease from 1.85 gm/cm3 to1.25 gm/cm3 , the swelling pressure also decrease are from 3.1 to 0.25gm/cm2 also it show that as the initial water content increase from 0%to 15% , the swelling pressure of jerash expansive soil decrease from 2.65 gm/cm2 to 1.35 gm/cm2 .

Mixed formulation for an easy and robust numerical computation of sorptivity

Sorptivity is one of the most important parameters for the quantification of water infiltration into soils. Parlange (1975) proposed a specific formulation to derive sorptivity as a function of the soil water retention and hydraulic conductivity functions, as well as initial and final soil water contents. However, this formulation requires the integration of a function involving the hydraulic diffusivity, which may be undefined or present numerical difficulties that cause numerical misestimations. In this study, we propose a mixed formulation that scales sorptivity and splits the integrals into two parts: the first term involves the scaled degree of saturation while the second involves the scaled water pressure head. The new mixed formulation is shown to be robust and well-suited to any type of hydraulic functions - even with infinite hydraulic diffusivity or positive air-entry water pressure heads - and any boundary condition, including infinite initial water pressure head, h → −∞.

Mechanical Properties of Frozen Glacial Tills due to Short Periods of Thawing

Due to the warming climate, glacier retreat has left massive glacial tills in steep gullies; ice in the soil is prone to change phase resulting in the decrease of the ice strength and bonding of soil particles; collapse of thawing tills can lead to debris flows with disastrous consequences for geotechnical infrastructures. To improve our understanding of the mechanics of thawing glacial tills, we conducted unconsolidated–undrained direct shear tests on glacial tills from Tianmo gully on the southeastern Tibetan Plateau. Control specimens were not subjected to freeze–thaw action. A total of 648 specimens with three different dry densities, three initial water contents, and 18 thawing times were tested. Peak shear strength, peak stress to displacement ratio (0.857), and cohesion were the highest in frozen specimens. After a thawing time of 0.25 h, there was a marked decline in shear strength; maximum friction was 2.58, which was far below the value of cohesive strength. For thawing times of 0.25–4 h, peak strength varied little with thawing time, but cohesion decreased and internal friction angle increased with increasing thawing time. Our results indicate that thawing of the solid ice in the till during the initial phase of till thawing is the key control of peak till strength; the effect of ice on cohesion is greater during the initial phase of thawing and in loose tills. Moreover, frequent sediment recharge of gullies may be explained by the decrease of cohesion with increasing thawing time caused by short-term destruction of ice bonding.

Desiccation-resurrection linked antioxidant machinery of a moss species Campylopus flexuosus (Hedw.) Bird.

Dehydration and rejuvenation during rehydration is the salient feature of certain plants which can withstand drought. The present study was undertaken to justify the tolerance capacity of Campylopus flexuosus, the moss of the Ponmudi belts of Thiruvananthapuram, against dehydration followed by rehydration. Fresh leafy plants of C. flexuosus were hydrated, afterwards dried, and rehydrated under in vitro environment. In the course of loss of water from cells, the relative water content of desiccated thallus was reduced after 4 h with intense inward curling. Upon rehydration, the RWC was regained 85% of its initial water content within hours. The rehydrated thallus showed the normal morphology. Photosynthetic parameters like chlorophyll b (1.01 to 1.56 μg g –1 ), and total carotenoid (0.251 to 0.514 μg g –1 ) increased remarkably in the desiccated state. Superoxide radical (O2 _) content increased (11.4 nmol/g FW), resulting in an oxidative burst during desiccation. Consequently, antioxidant enzymes such as catalase (0.369 U mg protein −1), superoxide dismutase ( 2.68 to 6.02 Units mg−1), peroxidase ( 0.12 μmol min−1 g−1 protein) and glutathione reductase ( 312 Units mg−1 protein) activities were up-regulated in the desiccated thallus to ameliorate oxidative damage. Increased malondialdehyde (1.08 nmol g−1 FW) content during desiccation substantiates membrane damage and loss of its integrity. During desiccation, the osmolytes sucrose and proline (27.6 and 2.57 μmol/g FW respectively) were enhanced to maintain cell structure integrity. After rehydration, biochemical and morphological properties were maintained similar to hydrated conditions. Thus, the study reflects the unique adaptations of the moss to tide over desiccation tolerance.

A Study of Dispersed, Thermally Activated Limestone from Ukraine for the Safe Liming of Water Using ANN Models

Liming surface water is a fairly popular method of increasing the pH values and decreasing the concentration of phosphates and heavy metals. According to the Environmental Protection Agency (EPA) recommendations, the increase of water pH should not exceed 1.5. If surface water is the source of water supply, liming is a process that reduces water contamination. This should prevent the creation of an additional load for the water treatment plants in urban settlements. This article is an interdisciplinary research study aiming to (1) determine and compare the doses of new dispersed, thermally activated limestone and natural limestone, (2) find the relation between dose value and initial water parameters (pH, Eh and total mineralization), and (3) create an artificial neural network (ANN) model to predict changes in water pH values according to EPA recommendations. Recommended doses were obtained from experimental studies, and those of dispersed, thermally activated limestone were lower than the doses of natural limestone. Neural networks were used to predict the changes in water pH values when adding different doses of limestone with different initial water parameters using the ANN model. Four ANN models with different activation functions and loss function optimizers were tested. The best results were obtained for the network with the ReLU activation function for hidden layers of neurons and Adam’s loss function optimizer (MAPE = 14.1%; R2 = 0.847). Further comparison of the results of the loss function and the results of calculating the quality metric for the training and validation dataset has shown that the created ANN can be used to solve the set research issue.

Modification of basic hydrology formulation based on an approach of the rational method at field measurement

The rational method was a simple technique for estimating the design discharge of a small watershed and can be used in a probabilistic approach. The main parameter in the rational method formula was the C coefficient. The rational method was the primary method for determining the peak discharge from surface runoff flow. At the end of the dry season and the beginning of the rainy season, it placed an automatic water level recorder and automatic rain gauges for the initial water level. This field research aimed to correct a simple hydrological formulation with field measurements and build a numerical rainfall modelling based on rainfall simulation, infiltration, land use, and flow parameters according to the relationship model of precipitation. The hypothesis in this study, the basic formulation of hydrology, is simple: it requires experience to fit the theoretical hydrological formula so simply (simplicity). The theory needs to be simplified because it is an experience of field necessary to explain.