RESUMEN

This study presents the findings of a comprehensive geotechnical and seismic site investigation conducted at Otuasega Town located in Bayelsa State within the Niger Delta region of Nigeria. Subsurface exploration involved advancing 10 boreholes to 30 m depth using hollow stem auger drilling. Continuous disturbed and undisturbed soil sampling was performed at 1.5 m intervals for detailed geotechnical testing. Laboratory tests on the recovered soil samples established the index properties, classification, densities and consistency limits of the stratified deposits. The subsurface profile comprised alternating layers of clay, silt and sand typical of deltaic sediments, with the clay fractions exhibiting medium to high plasticity. Shear wave velocity (Vs) profiling using Multichannel Analysis of Surface Waves (WASW) techniques categorised the site predominantly as Site Class C and D based on international standards. The Standard Penetration Test (SPT) N-values ranged from 5 to 10, indicating soft normally consolidated clay conditions typical of the Niger Delta region. Predictive empirical models developed from the field and lab data showed strong correlations for estimating key geotechnical parameters such as SPT blow count, Vs and liquefaction resistance. Ground response analyses using the Vs and SPT data indicated significant site amplification potential, with peak ground accelerations up to 1.5 times the bedrock motion. Liquefaction analysis based on the empirical SPT-based methods revealed a high potential for liquefaction in the sandy layers, especially under strong earthquake shaking. The study characterized the complex sedimentology and provided baseline information for seismic microzonation and site-specific ground response analyses to advance understanding of geohazards in this delta environment.

RESUMEN

Sandy soils cover a major portion of various natural and managed ecosystems. Soil health plays a key role in achieving sustainable development goals 2, 3,11, 12, 13 and 15. The engineering properties of soil are crucial in determining the stability and safety of structures. The increasing microplastic contamination in the soil ecosystem creates a need to study the effect of terrestrial microplastic contamination on the strength and stability of soil and therefore on the index properties and engineering properties of the soil. The present paper investigates, the effects of varying concentrations (2 %,4 %,6 % (w/w)) of Low-density polyethylene (LDPE), Polyvinyl chloride (PVC), and High-density polyethylene (HDPE) microplastics on the index properties and engineering properties of sandy soil for varying observation days. The moisture content, specific gravity, shear strength, compaction characteristics and permeability are found to be significantly altered by changing the concentrations of microplastics but, insignificant changes are observed with respect to observation days. The shear strength value of non-contaminated sandy soil is 1.74 kg/cm2 which reduces after 5th observation days as 0.85 kg/cm2, 0.90 kg/cm2, and 0.91 kg/cm2 for 2 %, 4 %, and 6 % LDPE microplastic contamination respectively. Similar trends are observed for PVC and HDPE microplastic contamination. It is also observed that although the shear strength value decreases, the cohesion value increases for the microplastics-contaminated sandy soil. The coefficient of permeability for non-contaminated sample is 0.0004 m/s which reduces for 2 % LDPE microplastic contamination to 0.000319 m/s, for 4 % to 0.000217 m/s, and 6 % to 0.000208 m/s respectively. Similar trends of are observed for the PVC and HDPE microplastic contamination. The soil strength and structural stability are affected due to alterations in soil index and engineering properties. The paper provides detailed experimental evidence of the impact of microplastic pollution on index properties and engineering properties of sandy soil.

RESUMEN

Soil health is one of the prominent features of the Sustainable Development Goals (SDGs). The SDGs seek to achieve the target of 75% healthy soils by 2030. On the contrary, the growing accumulation of microplastic contamination in soil environments is an issue of worldwide concern. The effect of a variety of microplastic accumulation on soil index and engineering properties is still unclear. Clayey soil is very important in geotechnical engineering because of its complex behaviour. This study investigates the effects of a variety of microplastics such as Low-Density Polyethylene (LDPE), Polyvinyl Chloride (PVC), and High-Density Polyethylene (HDPE) in environmental relevant concentrations (2%,4%,6% w/w) on index and engineering properties of clayey soil with respect to a number of observation days. In the present study, the non-contaminated soil treated as a control. The detailed experimentation revealed a significant change in the liquid limit, plastic limit, and shear strength values of clayey soil with an increasing percentage of microplastic contamination, whereas minute changes are recorded with respect to the number of observation days, this may be due to inert nature of microplastic. The shear strength is one of the critical engineering properties of soil that determines the strength and stability of the soil. The shear strength value of 0.94 kg/cm2 for control decreased to 0.76 kg/cm2 and 0.73 kg/cm2 and 0.85 kg/cm2 for the addition of 2%, 4%, and 6% respectively of LDPE microplastic contamination, similarly, for PVC microplastic contamination of 2%, 4% the shear strength decreases to 0.77 kg/cm2, 0.85 kg/cm2 respectively, the HDPE microplastic contamination of 2%, 4%, and 6% results in shear strength decrease to 0.52 kg/cm2, 0.53 kg/cm2 and 0.65 kg/cm2.The altered values of shear strength along with other index and engineering properties of soil due to microplastic contamination may lead to instability in structures or may increase the chances of harmful natural threats such as landslides. The present study provides evidence of significant changes in the index and engineering properties and therefore the stability of the soil which is the major contribution of the study.

Asunto(s)

Plásticos , Contaminantes del Suelo , Polietileno , Suelo/química , Microplásticos , Cloruro de Polivinilo , Arcilla , Contaminantes del Suelo/análisis

RESUMEN

Significant research investigations on the characteristics of unexplored clay deposits are being conducted in light of the growing need for clay in the ceramic industry and the variable chemistry of clays. Parallel to this, the generation of waste materials like fly ash, ferrochrome slag, and silica fume is also increasing, responsible for environmental degradation. This paper aims to study the mineralogical properties of pure clays (one specimen from Siberia and five specimens from different locations in Turkey), and the effect of mentioned waste materials on the index properties of clays obtained. This study is divided into two phases, wherein in the first phase, the pure clay specimens are analyzed against mineralogical properties (i.e., chemical composition, thermal analysis, and particle size distribution). While in the second phase, index properties of pure clay specimens and clay specimens modified with 0-50% fly ash, ferrochrome slag, and silica fume are analyzed. The results reveal that the clay specimens from Turkey (USCS classification: CL) are fit for the ceramic industry and bricks production, and incorporation of waste materials can further improve their index properties. It is also observed that incorporation of 10-30% fly ash and ferrochrome slag have higher efficiency in reducing the plasticity index of clays studied as compared to the addition of silica fume.

RESUMEN

Most of the damaging geo-hazards recorded in modern history are caused by soil swelling or expansion. Therefore, proper evaluation of a soil's capacity to swell is very crucial for the achievement of a secure and safe ground for civil infrastructures and related land developments which are founded on the soil. In order to simulate as well as estimate the heave that can occur under field conditions, laboratory one-dimensional oedometer vertical swell-strain testing are most frequently used. Hence, in this brief, one-dimensional swelling tests adopted to measure soil swelling on laboratory-engineered and natural soils covering various regions on the globe are reported. The testing standards and procedures followed in the measurement of one-dimensional swelling are those enumerated in the American Standards for Testing of Materials (ASTM) DDD698, and American Association of State Highways Transport Officials (AASHTO). Slight modifications to the measurement procedures (such as the use of different surcharge loading and custom-made consolidation rings) reflecting special laboratory testing conditions and for the purposes of comparisons, are also reported. Corresponding soil properties characterising the dataset includes moisture content, void ratio, specific gravity, unit weight, liquid limit, plastic limit, plasticity index, clay content, silt content, maximum dry unit weight, optimum moisture content, and soil activity index, all of which are known to bear either direct or indirect influences on soil. Determination of the state of compaction of the soils where applicable, are carried out based on the American Standards for Testing of Materials (ASTM) DDD698, Turkish Standards (TS), American Association of State Highways Transport Officials (AASHTO)and a combination of both standard and modified efforts. A total of 395 data samples on soil swelling potential are reported. With regards to the corresponding soil properties, a total of 219 data records of soil specific gravity, 321 data records of initial moisture content, 163 data records of void ratio, 273 data records of dry unit weight, 347 data records of liquid limit, 347 data records of plastic limit, 395 data records of plasticity index, 209 data records of activity index, 339 data records of clay content, 174 data records of silt content, 246 data records of optimum moisture content, 228 data records of maximum dry density and 347 data records of Unified Soil Classification System (USCS) are presented. Finally, the dataset of one-dimensional soil swelling described herein are intended to aid geotechnical engineers and researchers who are involved in statistical correlation studies, data analytics, and machine learning predictions using soft computing methods mostly aimed at evaluating soil expansion especially during the preliminary phases of soil investigation and foundation design.