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The paper presents the results of laboratory tests of plastic limit wP and liquid limit wL of Eemian gyttja characterized by different organic matter content Iom and calcium carbonate content CaCO3. Comparison of the liquid limit wL determined with the use of the Casagrande apparatus wLC and a cone penetrometer with cones having apex angles of 60° wL60 and 30° wL30 is shown. Based on statistical analysis of the test results, single- and two-factor empirical relationships for evaluating the plastic limit wP and liquid limit wL of Eemian gyttja depending on the organic matter content Iom and/or calcium carbonate content CaCO3 are presented in this study.

In general, the current performance evaluation of the Mamak Dam falls into the "fairly good" category, even in the aftermath of the earthquake event with a magnitude of 6.5 Mw in 2018. However, the presence of leakage on the downstream slope has become an issue that requires attention. This study analyses seepage using GeoStudio and Slide Rocscience software. The seepage rates obtained from instrument readings exceed those calculated by GeoStudio and Slide Rocscience software. All of the obtained seepage rate results do not surpass the maximum allowable seepage rate requirements. The most critical gradients are from flood water level cases in Saddle Dam-1 and Saddle Dam-2. They reached values of 0.35 and 0.34, which fall below the maximum hydraulic gradient. [ABSTRACT FROM AUTHOR]

The paper presents the results of tests performed in a Torsional Shear Hollow Cylinder Apparatus on undisturbed cohesive soils. The tests were performed on lightly overconsolidated clay (Cl) and sandy silty clay (sasiCl). The main objective of the tests was to determine the undrained shear strength at different angles of rotation of the principal stress directions. The results of laboratory tests allow assessing the influence of rotation of the principal stress directions on the value of undrained shear strength that should be used during designing structure foundations

The estimation of optical density (OD) with viable cells is challenging for engineering purposes. In this study, the OD conversion based on previous study was used. The inhibited and retarded behavior of the microbially induced carbonate precipitation (MICP) process was examined. The experimental results showed that high Ca2+ drastically influences the inhibited and retarded behavior on MICP processes. The analysis showed that the inhibition and retardation effects occurred when the Ca2+/OD loading rate exceeded 8.46 M. The critical value was equal to the proportional constant for obtaining carbonate precipitation rate (CPR) from OD. Due to this, the blending design of materials became possible, with no risk of inhibition. In conclusion, the inhibition and retardation of the MICP process are governed by the Ca2+ load and the linear standard line (LSL), which may be attributed to the capacity or tolerance of viable cells, i.e., CPR/OD = 8.46 M or Ca2+/OD = 8.46 M. [ABSTRACT FROM AUTHOR]

In engineering practice, due to the high compressibility and very low shear strength of organic soils, it is difficult to construct an embankment on organic subsoil. High variability and significant change in geotechnical parameters cause difficulties in predicting the behavior of organic soils under embankment loading. The aim of the paper was to develop empirical relationships used in the preliminary design for evaluating the settlement and undrained shear strength of organic subsoil loaded by embankment based on data obtained from four test sites. Statistical multiple regression models were developed for evaluating the settlement in time and undrained shear strength in time individually for peat and gyttja. Neural networks to predict the settlement and undrained shear strength in time for peat and gyttja simultaneously as double-layer subsoils as well as a separate neural network for peat and a separate neural network for gyttja as single-layer subsoils were also developed. The vertical stress, thickness, water content, initial undrained shear strength of peat and gyttja, and time were used as the independent variables. Artificial neural networks are characterized by greater prediction accuracy than statistical multiple regression models. Multiple regression models predict dependent variables with maximum relative errors of about 35% to about 60%, and neural networks predict output variables with maximum relative errors of about 25% to about 30%. [ABSTRACT FROM AUTHOR]

Soil parameters in agricultural areas play an important role in the migration of nitrogen compounds to groundwater. Nitrogen loss from subsoil depends on soil permeability, organic content, and soil saturation. Our study evaluates the parameters controlling the migration of nitrogen compounds through selected fine and sandy soils that may affect the quality of groundwater in agricultural areas. The results of this study indicate that denitrification processes that substantially affect ammonium (NH+ 4) and nitrate (NO3-) concentrations take place in fine soils. These processes decrease the flow of nitrogen into groundwater and are indicated by the production of a gashouse phase, a decrease in hydraulic conductivity, and a nitrogen compound concentration in the filtrate that is lower than the maximum concentration. Column tests have shown that the dominant transport process for silt loam and sand samples was advection, and the dominant transport process for loam was dispersion. Moreover, the velocities of NH+ 4 ion transport were lower than the velocities of water flow by approximately seven and five times for loam and sand, respectively. The estimated values of the retardation factor and dynamic sorption capacity for NO3 - were lower than those for NH+ 4 ions. Finally, groundwater located below the silt loam and loam soil layers can effectively be protected against the infiltration of nitrogen compounds from agricultural sources. [ABSTRACT FROM AUTHOR]