Random Characteristics of Hydraulic Gradient through Three-Dimensional Multilayer Embankment

The distribution characteristics of hydraulic gradient in embankment are closely related to seepage failure. Seepage failures such as flowing soil and piping will lead to serious damage and even the overall failure of embankment. The hydraulic conductivity has strong spatial variability, which changes the distribution of hydraulic gradient in embankment and increases the difficulty for predicting the embankment seepage instability. In this study, the distribution of soil hydraulic conductivity in a section of Shijiu Lake embankment was obtained by the permeability test. Based on Local Average Subdivision technique, a three-dimensional multilayer random field of embankment hydraulic conductivity was generated. Then, the mean and standard deviation of overflow point height and hydraulic gradient were calculated by the Monte Carlo method, which combined the generated three-dimensional random model and the deterministic analysis method of seepage field. Finally, the coefficient of variation (COV) of hydraulic conductivity (0.1, 0.3, 0.5, 0.7, 1.0, 2.0, and 3.0), the fluctuation scale in vertical direction (3 m) and the fluctuation scale in horizontal plane (3 m, 6 m, 12 m, 24 m, 36 m, and 48 m) were selected respectively for analyzing the random characteristics of embankment overflow point height and hydraulic gradient under the influence of different COV and fluctuation scale of embankment soil hydraulic conductivity.

Using Inverse Modeling by HYDRUS-1D to Predict Some Soil Hydraulic Parameters from Soil Water Evaporation

The objective of this research was to assess the use of unsaturated water flow in terms of soil water evaporation, which was determined by evaluating some soil hydraulic parameters in different soil textures. The results show that the predicted values of these parameters, which were obtained through inverse modeling with the HYDRUS-1D software and depend on the change of the volumetric water content, exhibited a significant agreement with the measured values from laboratory or field simulation data for soil water evaporation at 5. 10. 20. and 45 days of measurement. At the same time, inverse simulation was conducted on soil hydraulic parameters obtained from a 5-day laboratory soil evaporation period to predict field infiltration values and water retention curve, which showed a significant agreement with measured values for all soil textures.

Effect of domestic greywater reuse for irrigation on soil physical and chemical characteristics and tomatoes growth.

This study aimed at determining the effect of laundry greywater on the growth of tomatoes and physical and chemical properties of a sandy loam Perrox in the Eastern province of Rwanda, Kayonza district, Mwiri sector. The experimental design consisted of plots planted with tomatoes (Lepersicon Esculantum) in a randomized complete block design with three replications and four treatments. Treatment 1: Tomatoes irrigated with pure greywater; Treatment 2: Tomatoes irrigated with a mixture of tap water and greywater at 1:1 ratio; Treatment 3: Alternation of greywater and tap water in a consecutive manner; and Treatment 4: only tap water serving as a control. Results showed that the following soil chemical parameters were significantly increased with greywater application: pH, EC, Av P, Na and SAR. Conversely, soil concentration in Mg and Ca significantly decreased with increase in greywater application. With the exception of soil bulk density, other measured physical properties such as soil hydraulic conductivity, aggregate stability and porosity were significantly reduced with greywater application. The highest values for soil hydraulic conductivity, aggregate stability and porosity were found for soil irrigated with tap water which ranged between 1.01 to 2.1 times higher than that of greywater, mixed or alternated with tap water. The alternate application of greywater and tap water did not affect significantly the stem height and weight of tomatoes. We concluded that the absence of positive growth effect of application of greywater was due to low concentration in essential plant nutrients in greywater, and induced adverse effects on soil chemical, physical, and biological properties. However, alternate application of the greywater and tap water preserved approximately the same soil physico-chemical characteristics as with application of tap water. Thus, among the irrigation treatments involving greywater, the latter should be considered as the most environmentally friendly. We propose combination of greywater with various forms of composts as the one of the most promising investigations on the reuse of greywater in irrigation.

Estimation of Stagnosol Hydraulic Properties and Water Flow Using Uni- and Bimodal Porosity Models in Erosion-Affected Hillslope Vineyard Soils

Erosion has been reported as one of the top degradation processes that negatively affect agricultural soils. The study objective was to identify hydropedological factors controlling soil water dynamics in erosion-affected hillslope vineyard soils. The hydropedological study was conducted at identically-managed Jastrebarsko (location I), and Jazbina (II) and (III) sites with Stagnosol soils. Soil Hydraulic Properties (SHP) were estimated on intact soil cores using Evaporation and WP4C methods; soil hydraulic functions were fitted using HYPROP-FIT software. For Apg and Bg/Btg horizons, uni- and bimodal soil hydraulic models could be well fitted to data; although, the bimodal model performed better in particular cases where data indicated non-uniform pore size distribution. With these SHP estimations, a one-year (2020) water flow scenario was simulated using HYDRUS-1D to compare water balance results obtained with uni- and bimodal hydraulic functions. Simulation results revealed relatively similar flux distribution at each hillslope position between the water balance components infiltration, surface runoff, and drainage. However, at the bottom profile at Jastrebarsko, bimodality of the hydraulic functions led to increased drainage. Soil water storage was reduced, and the vertical movement increased due to modified soil water retention curve shapes. Adequate parameterization of SHP is required to capture the hydropedological response of heterogenous erosion-affected soil systems.

Effect of the dewatering on the surrounding terrains during the construction of Metrostation 9-III of the Sofia Metropoliten

The international practice often faces significant settlements of terrains and structures due to dewatering. This study presents of the dewatering impact during the construction of Metrostation 9-III from the Sofia Metropoliten on the surrounding terrains and buildings. The subsidences are quantified for specific values of the soil deformation modulus and varying values of the soil hydraulic conductivity.