Based on the results of dynamic probing (DP), time-domain reflectometry (TDR/MUX/MPTS), resistivity cone penetration tests (RCPT), Marchetti dilatometer tests (DMT), and seismic dilatometer tests (SDMT), it is possible to develop a relationship to calculate the relative density (D_r) and degree of saturation (S_r) of selected sandy soils. Compiled databases from documented research points for selected sandy soils were used to construct and develop direct correlations between the measured pressures p₀ and p₁ from DMT and shear wave velocity (V_s) from SDMT, along with pore water pressures (u₀) and atmospheric pressure (Pa). The results allowed us to make a preliminary prediction when evaluating the parameters. Further, they allowed limiting the use of an additional device, especially in the case of multilayer heavy preconsolidated subsoils. Moreover, soil physical and mechanical characteristics (temperature, humidity, pressure, swelling, salinity) measured from TDR/MUX/MPTS (laboratory/field-operated meter for simultaneous measurements of soil moisture, matric potential, temperature, and salinity—bulk electrical conductivity) were assessed. The main achievement of this paper is the original proposal of using a new nomogram chart to determine the relative density and degree of saturation based on DMT and SDMT tests.

The stability and mechanical properties of municipal solid waste (MSW) deposits in closed landfills are critical for safe land reclamation and infrastructure development. This study employs Cone Penetration Testing (CPT) to evaluate the geotechnical parameters of aged waste at three closed landfill sites in central Poland. Key parameters, including shear strength, internal friction angle, density, and liquidity index, were assessed to determine slope stability and bearing capacity for future redevelopment. Due to the heterogeneous nature of MSW, CPT results were analyzed in conjunction with empirical correlations and nomograms to improve accuracy, so the parameters can be used for future numerical modeling and proposing new computational approaches for landfill body elastic and mechanical behavior predictions. The findings indicate significant variability in landfill waste mechanical properties, influenced by waste composition, decomposition stage, and compaction history. The study highlights CPT’s reliable detremination of geotechnical parameters for landfill restoration projects, particularly for infrastructure, creating the potential for green energy and sustainable development. The results contribute to improving engineering practices in landfill restoration and ensuring the long-term stability of post-closure land use. This study also contributes to obtaining reliable results on anthropogenic waste material mechanical parameters at both the material point and at the overall structural scale, benefiting future computational methods and modeling approaches for analyzing structural and geotechnical safety of such complex and demanding structures as landfills.

The permeability of soil is an important factor controlling the flow of water through the subsoil. The article presents the results of studies of hydraulic parameters for overconsolidated clays using in situ tests. Using the excess pore pressure normalization technique, both in the case of monotonic and dilatory dissipation tests, and the time at which 50% dissipation of excess pore water pressure takes place, as well as taking into account the rigidity index of the analyzed soil, it was possible to estimate the permeability and consolidation coefficients for the analyzed clays. Based on these studies, simple relationships between the permeability coefficient and the soil behavior-type index are proposed. Proposed formulas may be applied for overconsolidated cohesive soils with soil behavior-type index values within the range of 2.05–3.30 and described in Robertson’s chart as overconsolidated silty clays, clays and heavily overconsolidated and cemented fine-grained soils. Although our proposal of determining flow parameters has been calibrated only for two analyzed cases, its utility for wider use in other overconsolidated fine-grained soils may also be taken into account.

There is a growing global trend toward reducing the consumption of natural resources and newly produced construction materials by replacing them with secondary raw materials. Concrete derived from construction and demolition waste can be recycled multiple times and is considered environmentally sustainable. This study evaluates the feasibility of reinforcing weak subsoil using crushed recycled concrete. Concrete obtained from the demolition of residential buildings was crushed under laboratory conditions to produce material with grain sizes corresponding to sands, and mixtures were subsequently prepared containing up to 30% fine fraction. The case study focuses on circular wind turbine foundations supported by symmetrically arranged columns made of four different materials, located beneath the foundation slab. The analyzed subsoil is characterized by strong stratification, low bearing capacity, and high compressibility. The calculation results indicate that the bearing capacity conditions for all foundations were met within similar ranges of the safety factor for the given loads, both for low- and high-power turbines. However, foundation deformations increased with turbine size and bending moments, and were nearly twice as large for recycled aggregates compared to recycled concrete. Numerical simulations demonstrate that recycled aggregate without fine fraction, as well as with fine fraction, and recycled concrete can provide load-bearing performance comparable to conventional concrete under low loading conditions, while offering significant environmental benefits.

Overseeing the relative density of soils in all types of earth structures during both construction and operation is crucial to ensure that these structures attain the necessary density and strength. Especially in linear structures that extend over significant lengths, geotechnical investigations should include planning tests that allow for determining the maximum number of geotechnical parameters, such as cone penetration tests (CPTU) or Marchetti dilatometer tests (DMT). The article presents the in situ tests aimed at assessing the relative density of sandy soils. Empirical formulas available in the literature for determining the relative density D _r from DMT gave inconsistent results compared to those obtained from dynamic soundings, especially in the near-surface zone, where high K _D readings significantly overestimate relative density values. Assuming the results of DPL probe tests as reference values, a formula for the compaction index based on DMT soundings has been proposed. In contrast to the formulas commonly used in the literature, the proposed formula for the relative density depends not only on the horizontal stress index K _D , but also on the dilatometer modulus E _D .