The undrained shear strength of organic soils can be evaluated based on measurements obtained from the dilatometer test using single- and multi-factor empirical correlations presented in the literature. However, the empirical methods may sometimes show relatively high values of maximum relative error. Therefore, a method for evaluating the undrained shear strength of organic soils using artificial neural networks based on data obtained from a dilatometer test and organic soil properties is presented in this study. The presented neural network, with an architecture of 5-4-1, predicts the normalized undrained shear strength based on five independent variables: the normalized net value of a corrected first pressure reading (p_o − u_o)/σ′_v, the normalized net value of a corrected second pressure reading (p₁ − u_o)/σ′_v, the organic content I_om, the void ratio e, and the stress history indictor (oc or nc). The neural model presented in this study provided a more reliable prediction of the undrained shear strength in comparison to the empirical methods, with a maximum relative error of ±10%.

A fast reduction of a reservoir level may result in instability of an earth dam caused by the high pore water pressures that remain relatively high in the embankment. Moreover, the dissipation of the accumulated pore water pressures is highly dependent on the permeability of the materials used for the embankment and the storage characteristics of the reservoir. Therefore, in the design of embankment dams, the stability analysis under rapid drawdown loading conditions is an important design case. In this study, the influence of different permeability rates on dam stability under different cases of rapid drawdownwas investigated using the finite element method in SEEP/W and SLOPE/W of the GeoStudio with a case of the Lugoda dam in Ndembera catchment, Tanzania. The modeling process considers the time-dependent hydraulic conditions and the transient flow conditions using different water levels during rapid drawdown for evaluation of the factor of safety. From the 1m per day drawdown rate; the lowest minimum factor of safety value (0.90) was obtained from the 10 -7 m/s material permeability of the upstream zone of the dam. It means that, at a drawdown rate of 1m per day, there is a potential for failure of the embankment if the hydraulic conductivity value will be somewhere below 10 -6 m/s.

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 (NH₄⁺) 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 NH₄⁺ 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 NH₄+ 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.

This paper presents a method describing the application of artificial neural networks to evaluate the change in undrained shear strength in cohesive soils due to principal stress rotation. For analysis, the results of torsional shear hollow cylinder (TSHC) tests were used. An artificial neural network with an architecture of 7–6–1 was able to predict the real value of normalized undrained shear strength, τ_fu/σ’_v, based on soil type, over-consolidation ratio (OCR), plasticity index, I_P, and the angle of principal stress rotation, α, with an average relative error of around ±3%, and a single maximum value of relative error around 6%.

Influence of the rotation of principal stress directions on undrained shear strength. The paper presents the results of research on natural cohesive soil carried out in the Hollow Cylinder Apparatus (HCA). The main goal of this study was to determine the values of undrained shear strength at different angle of the rotation of principal stress directions. The research were carried out with anisotropic consolidation and shearing in undrained conditions (CAU) on cohesive soil with overconsolidation ratio (OCR) equals 4 and plasticity index (Ip) about 77%. The results of laboratory tests allow to assess the influence of the rotation of principal stress directions on undrained shear strength

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.