Piotr Osinski

Slope failures due to erosion effect are a well-established cause of civil engineering structure disasters. Streams passing at the toe of a slope are a severe threat to geotechnical safety, especially in urbanized areas. To increase global safety, a retaining wall is usually proposed to limit the risk of failure. However, such works could also bring the high danger of a landslide during the construction works if not managed properly. The paper aims at investigating the collapse cause of residential buildings located at the edge of the slope at northwest part of Vietnam, where engineering works were performed to prevent failure due to soil erosion at the toe of the slope. During the retaining wall construction works, the applied excavation method caused significant vibrations and additional dynamic loads that could have affected the bearing capacity of the building foundations. Another cause of failure is associated with heavy precipitation recorded at the site just before the excavation works down the slope. The paper consists of numerical analyses allowing simulation of possible scenarios, including the effect of changing groundwater conditions using the meteorological data collected from the nearby monitoring weather station. The computations were performed using geotechnical software to reflect the in-situ conditions, and the entire process of earthworks performed at the site was carefully analyzed. The numerical analyses involved computations performed for a reinforced slope where a retaining wall was proposed to assure geotechnical safety of the remaining infrastructure after the failure.

Vertical low-permeability barriers are widely used to improve the stability and seepage resistance of flood embankments. The present study evaluates three barrier technologies—vibrating beam slurry walls (VBSWs), deep soil mixing (DSM), and low-pressure grout injection (LPG)—through a series of consolidated drained triaxial tests and permeability coefficient tests on soil samples collected from the sites where different barrier installation technologies were used. All three barrier installation methods produced substantial improvements in both mechanical and hydraulic performance: the effective angle of internal friction (φ′) increased by 3–6° in samples with a plasticity index near 3.5%, and coefficients of permeability dropped from 10⁻⁸–10⁻⁷ m/s in untreated soils to below 10⁻⁹ m/s in treated specimens. The key finding of the study is that the barrier performance varies by the technology and the soil type. According to the result, DSM is the most effective technology used in clay-rich soils (φ′ increased up to 4°); LPG achieved the lowest permeability (7 × 10⁻¹¹ m/s) in granular soils; and VBSWs balanced strength and impermeability, most effective in silty sands. Flow-pump tests further demonstrated that treated soils required much longer to stabilize under a constant flow rate and could sustain higher hydraulic gradients before reaching equilibrium. These findings show the importance of matching barrier technology to soil plasticity and liquidity characteristics and highlight saturation as essential for reliable laboratory evaluation. The results provide a scientific basis for selecting and designing vertical barriers in flood-preventing infrastructure, offering performance benchmarks for improving hydraulic and geotechnical structures.

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.

This study investigated properties of soft Bangkok clay stabilized with ordinary Portland cement (OPC) and various polymers. Variables included initial water content (1.0LL, 1.5LL, and 2.0LL; LL = liquid limit), polymer type (polyvinyl alcohol (PVA), polyethylene glycol (PEG), and polyvinylpyrrolidone (PVP), polymer concentration (1%, 3%, 5% and 7%), and curing time. The unconfined compressive strength (UCS), consolidation, permeability, and microstructure were analyzed. UCS decreased with increasing water content due to delayed polymer bonding; however, at 1.0LL, polymers effectively bonded clay particles, resulting in higher UCS. A 3% polymer concentration yielded the highest UCS, while 5–7% led to non-homogeneous structures and reduced UCS. The UCS of the sample with PEG outperformed those with PVA and PVP. At 1.0LL and 3% polymer, 28-day UCS values were 1.20 MPa (PEG), 1.12 MPa (PVA), and 1.04 MPa (PVP), all exceeding the Department of Highways’ standard 1.0 MPa. Higher polymer concentrations decreased void ratios and permeability by forming hydrogel layers and thin films, increasing soil density. SEM/EDS analysis confirmed 3% polymers formed uniform films enhancing soil bonding, while 7% resulted in thicker, irregular films, reducing UCS. These findings suggest that polymers could be a promising alternative to OPC in environmentally friendly deep mixing applications. Doi: 10.28991/CEJ-2025-011-04-022 Full Text: PDF

In seismic tunnel lining design, most existing studies have focused on circular and box‐type tunnels, while the response of subrectangular tunnel linings under seismic loading, especially in imperfect soil‐lining conditions, remains underexplored. The present paper aims to address this gap by investigating the behavior of subrectangular tunnel lining subjected to seismic loadings in full‐slip condition using a novel calculation approach based on the hyperstatic reaction method (HRM). The innovation of this study is the introduction of a new quasi‐static loading scheme to characterize the soil‐lining interaction for subrectangular tunnels. New relationships between loading parameters, soil Young's modulus, tunnel lining thickness, tunnel dimension, and maximum horizontal acceleration are established through the back analysis of HRM and finite difference method (FDM) calculations. These relationships are then verified by considering different input parameters affecting subrectangular tunnel behavior under full‐slip conditions. Numerical results indicate that the maximum incremental internal forces computed by the new HRM model are in excellent agreement with those from FDM. Meanwhile, the computational efficiency of HRM is far better than FDM due to 1D meshing and simpler boundary conditions. Therefore, the new HRM model offers an effective alternative to FDM for the preliminary design of the subrectangular tunnels subjected to seismic loading in full‐slip conditions.