Geotechnical Properties Research Articles

On the mechanical behaviour of a coral silt from the South China Sea

During land reclamation on the reef islands, large amounts of silt-sized coral soils were created by segregation and degradation. The accumulation of silt-sized coral soils is fairy uncommon while the research on the geotechnical properties of the coral silt is very limited. In this study, a systematic experimental investigation on the mechanical behaviour of a coral silt obtained from a reclaimed reef island in the South China Sea has been performed, with comparisons to the coral sand collected from the same area. Similar to the coral sand, the coral silt particles also exhibit irregular particle shape and intra-particle pore due to their nature origin. According to the limiting water contents, the coral silt is classified as a low-plasticity clayey silt. Under one-dimensional compression, the coral silt exhibits a much quicker convergence compared to coral sand. Prior to convergence, the compressibility of coral silt is higher. After yielding, the compressibility of coral sand becomes higher due to significant particle breakage. The loose coral silt subjected to undrained shearing at low confining pressures exhibits obvious strain softening behaviour, indicating static liquefaction or flow failure. The peak and critical state friction angles of coral silt are lower than those of coral sand but much higher than those of the other terrigenous clayey silts. A curved critical state line with well-defined horizontal asymptote in the deviatoric stress – mean effective stress plane is identified for coral silt, again indicating higher potential to static liquefaction.

Excavated material from shield tunnelling – Part 1: Geotechnical properties and environmental classification in Germany

Excavated material from shield tunnelling – Part 1: Geotechnical properties and environmental classification in Germany

Effects of nano-clay on the geotechnical properties of gypseous soil

Abstract Gypseous soils suffer from sudden settlement when subjected to water flow due to dissolving of gypsum salts, so all structures constructed on gypseous soil undergo significant deformations due to the soil’s ability to collapse. Around the world, specifically in the arid and semi-arid regions gypseous soils are mostly found also, and can be found in the west desert of Iraq and even in the southern regions, amounting about between 30 and 35% of the country’s total area. There are several techniques to improve the geotechnical properties of collapsible soils, but one of the most recent techniques is using the nano technology. Five different proportions of nano-clay (NC) were incorporated into a gypseous soil containing 80% gypsum in order to enhance its chemical and geotechnical characteristics (1, 2, 3, 4, and 5%). The tests findings (chemical, physical, and mechanical tests) demonstrated that the addition of nano-clay to gypseous soil has a significant impact on the geotechnical properties of soil where it leads to decrease the gypsum content of soil, pH value, maximium dry density, specific gravity, and collapse index. On the other hand, the utilized of nano clay material causes to increase shear strength parameters (c and φ), optimum water content and liquid limit. Adding 4% of nano-clay results in a significant decrease of 53% in the collapse index and an increase of 311% in soil cohesion and 30% in the angle of internal friction.

Geochemical Evaluation of Itakpe Iron Ore Mine Tailings, Itakpe, Nigeria

The study focus on the characterisation of the tailings attributes with a view to understanding the geotechnical properties, leaching potential and possible major oxides. The samples were composited into five. The composited samples were subjected to both physical and chemical tests. The physical tests include particle size distribution, specific gravity, density, residual humidity and Atterberg limits. The chemical tests include pH, organic matter, and Energy Dispersive X-Ray Fluorescence Spectrometry (ED-XRFS). Mineralogical analyses were also carried out on the composited samples using the Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDX). The results from the physical tests show that the tailings are mostly fine-medium sands, having high specific gravity and bulk density, with low residual humidity. The chemical analyses show that the tailings are weakly acidic and neutral with low organic matter. The energy dispersive x-ray fluorescence spectroscopy analysis of the samples shows that they contain high concentrations of Fe2O3, SiO2, and other trace compounds. The Fe2O3 of the samples ranged from 15.03 to 20.12% and SiO2 ranged from 57.26 to 60.10%. SEM micrographs obtained revealed the interlocking nature of the minerals constituting the ore matrix. EDX analysis of the regions within the ore matrix revealed the presence of Si, Fe, Al, K, Ca, Nb, Y, Ag, Zn, Mg, Cl, P, S, Na, Ti, Zr; such that silicon and iron are the major elemental constituents of the ore matrix while other elements exists in trace form.

Cation exchange capacity- An alternative method to investigate the geological barrier for landfills?

Clays and clay minerals are ideal raw materials for geological barriers and landfill liners because of their low-hydraulic permeabilities, their swelling properties and adsorption capacities. The geological barrier is a supplementary barrier beneath the body of the landfill, intended to protect the environment from uncontrolled leachate from the waste material. An Austrian standard defines the process for site exploration and the required laboratory tests and parameters for the analysis of the geological barrier. The most important laboratory tests besides grain size analysis are the Atterberg limits and the determination of the clay mineralogy using X-ray diffraction. However, the analysis of the cation exchange capacity (CEC) is not included in the list of laboratory tests. CEC is a numerical value that describes the physical properties of clays, such as the diffusion of charged and uncharged molecules and the cation retention. Hence, the objective of this study is to clarify whether the determination of the CEC using the Cu-trien method represents a possible alternative to currently used laboratory tests.For this purpose, three samples (loess, sand and clay) from two landfill sites owned and operated by Zöchling GmbH as well as six mixtures of these samples with varying compositions were examined for their mineralogical, chemical and geotechnical properties. The samples consisted of varying amounts of quartz, feldspar, calcite, dolomite and the clay minerals smectite, illite, kaolinite, vermiculite and chlorite. The results showed that the bulk clay mineralogy correlates well with the Atterberg liquid limit (R2 = 0.73) and the CEC (R2 = 0.88) and furthermore, the results of the two methods – Atterberg liquid limit and CEC- even correlated better (R2 = 0.95).This demonstrates that the CEC can be an alternative to the Atterberg liquid limit and/or the analysis of the mineralogical composition of the material. Advantages of the CEC are rapidness, its good reproducibility and cost-efficiency of the analyses compared to the other two methods. Based on the results of this study, a partial substitution of the currently used laboratory tests is considered feasible and CEC could at least be used for fast and efficient screening.

Assessing the Improvement of Geotechnical Properties of Clayey Soil Using a Substrate Cement Mortar Material, from Ilgin, Konya City, Turkey

The increase in needs and the decrease in places with good, usable foundation soil have made the construction of engineering structures on problematic soils mandatory. Problematic soils generally do not have sufficient bearing capacity and soil strength, which may create an environment prone to high settlement or liquefaction. To investigate potential ways to enhance the compaction, undesirable or problematic plasticity, and soil’s strength characteristics, various geotechnical tests have been carried out on clayey soils and their mixtures treated with a Substrate Cement Mortar (0, 4, 8, and 12% by weight). These tests involved Atterberg limits, dry density, compaction, and shear strength. The obtained results show that the addition of substrate cement materials increased the dry density of soil treated with SCM, which can significantly enhance the soil properties. Meanwhile, adding SCM decreased the soil's plasticity limits. Furthermore, adding 12% Substrate Cement Mortar resulted in the lowest optimum moisture content and the maximum dry unit weight. Soil treated with 12% also exhibits maximum cohesion and shear strength. This research led to the conclusion that the utilization of Substrate Cement Mortar additive is an inexpensive product and has significantly improved the soil’s geotechnical parameters.

Chemical, mineralogical and geotechnical properties of volcanic ash of Tajogaite (La Palma, Canary Islands, Spain)

Volcanic eruption at La Palma island (Tajogaite, 2021) has produced tons of volcanic ash as natural sediments spread all around the island covering existing crops, roads, embankments, buildings, etc., by that way producing damage to environment. For the rehabilitation and reconstruction of island, and its application to adjacent areas, it is practical and economical to employ these volcanic ashes as construction material being encountered in abundant volume, and by that way could be considered as a resource material instead as a waste material, reducing necessary volume of landfills for its deposition. This paper defines the investigation of chemical, mineralogical and geotechnical properties of these deposited materials for its possible reuse by that way providing solution for its recovery. These young volcanic ashes are studied in its fresh natural state, prior to consolidation and cementation has taken place for its chemical, mineralogical and geotechnical characterization. Volcanic ash of Tajogaite is of a poorly graded sandy nature having difficulties for its compaction, having low improvement of relative density by the application of standard compaction methods. Mineralogy analysis indicates it is rich in silica, iron, calcium and alumina oxide, although being necessary the addition of mineral additives for its alkali-activation. Geotechnical characteristics of different samples vary depending on the sampling site, being resistance parameters determined by direct shear test (friction angle 30° to 34°) and deformational properties defined by one-dimensional consolidation test considered low values as of loose sand materials (deformation modulus range from 20 to 40 MPa).

Mineralogy and Geotechnical Properties of Fine-Grained Sediments from Swali Community

Mineralogy and Geotechnical Properties of Fine-Grained Sediments from Swali Community

Soil Resistivity Assessment and Correlation on Geotechnical Properties of Backfill Soils for Substation Grounding System in Thailand

Soil Resistivity Assessment and Correlation on Geotechnical Properties of Backfill Soils for Substation Grounding System in Thailand

Engineering Evaluation of Laterite Derived from Sedimentary Rock for Use as Subgrade and Sub-Base Materials

Geotechnical assessment of lateritic soils obtained from along the Ojota and Shagamu ends of the Lagos–Ibadan expressway was conducted to evaluate their suitability for use as sub-grade and sub-base materials. Laboratory tests, including moisture content, specific gravity, particle size distribution, fabric/plasticity, compaction, and California Bearing Ratio (CBR), were performed on eight (8) soil samples following British Standards (BS) 1377 methods for soil testing. The lateritic soils were classified as clayey sand, silty clay, and silty to clayey sand. They exhibited moderate plasticity and semi-pervious characteristics, suggesting suitability for use as sub-grade materials. Samples 3, 5, 7, and 8 were identified as more suitable for road construction materials, while Samples 1, 2, 4, and 6 showed susceptibility to seasonal volume changes due to high clay content. These samples would require minor soil stabilization to mitigate the effects of their active clay contents. Adequate drainage systems were recommended to prevent water accumulation, soil volume changes, loss of load-bearing capacity, and potential material failure beneath road pavements. The geotechnical properties of the lateritic soils from the tropical area of Ojota–Shagamu differed significantly from those of other lateritic soils found in southwestern Nigeria.

Geotechnical Stability Analysis of the Tiga Dam, Nigeria on the Assessment of Downstream Soil Properties, Erosion Risk, and Seasonal Expansion

The Tiga Dam, a primary hydraulic structure in northern Nigeria, is subjected to intense hydrological stress during the rainy season, posing potential risks to its structural integrity. This study investigates the geotechnical properties and stability of the Tiga Dam in Kano State, Nigeria. Twelve soil samples from the downstream area were analyzed for specific gravity, grain size distribution, Atterberg limits, compaction parameters, permeability, and shear strength. The dam’s stability was assessed using Plaxis 2D under various reservoir conditions. Soil erodibility was evaluated using the Revised Universal Soil Loss Equation (RUSLE), and a linear regression model with noise was developed to predict soil expansion rates. The results showed heterogeneous soil properties, with specific gravity ranging from 2.11 to 2.63 and permeability from 3.40 × 10−9 to 1.49 × 10−7 m/s. Stability analysis revealed factors of safety of 1.322, 1.006, 1.002, and 1.147 for high reservoir, rapid drawdown, slow drawdown, and low reservoir conditions, respectively. The RUSLE K factor ranged from 0.055 to 0.145, indicating low to moderate soil erodibility. The expansion rate model demonstrated high accuracy (R2 = 0.989) in predicting seasonal and long-term soil expansion trends, with peak rates increasing from 16.94 mm/month in 2010–2013 to 19.45 mm/month in 2017–2020. This comprehensive analysis provides crucial insights into the Tiga Dam’s geotechnical behavior, highlighting potential vulnerabilities and the need for targeted management strategies to ensure long-term stability and safety.

ANALISIS GEOTEKNIK DAN KESTABILAN LERENG TOWER SUTT PT. PLN (Studi kasus: TW. 203 Pembangunan T/L 150 KV GI KAMBANG – GI TAPAN)

Slope instability is caused by several lithological and structural factors, slope geometry, relative relief, ground water, as well as changes in use and land cover. Mountainous areas, development and expansion of infrastructure networks can inadvertently cause natural slope shifts, thereby negatively impacting the stability of the excavated slope. Analysis of the geotechnical properties of soil and rock is important for understanding and predicting the possibility of landslides at certain locations. Geotechnical analysis is needed to carry out slope stability analysis which is carried out using GEO5 software. Construction of T/L 150 KV GI Kambang – GI Tapan, Tower TW. 203 with a tower structure at the top of the slope. Based on these conditions, a comprehensive study is needed to analyze the stability of natural slopes due to tower loads. Soil Type, Parameters c' and ?' (Drained), Parameters Cu and ? (Undrained) and soil properties index are based on CPT test results. The Bishop, Spencer, Janbu and Morgenstern-Price methods on natural slopes, tower loads, Natural with Tower+Pile Loads, Natural Slopes with Tower+Pile Loads, Earthquake Loads produce a safe condition against failure in Short-Term (Construction) and Long-Term conditions. Term (Operational). Analysis of the Fellenius method on natural slopes and tower loads in Short-Term (Construction) and Long-Term (Operational) conditions shows unsafe conditions. The safety factors resulting from the Bishop, Spencer, Janbu and Morgenstern-Price methods do not show significant differences in values.

A study of the effects of early diagenesis on the geotechnical properties of carbonate sediments (North West Shelf, Australia)

Carbonate sediments are often regarded as problematic in geotechnical engineering due to the high variability of their properties. Understanding and quantifying this variability will become increasingly critical in the years ahead, notably with respect to upcoming developments in offshore renewable energy, for which limited in-situ data are typically available to characterise large areas. Here, six intervals from the North West Shelf of Australia, each composed of similar carbonate grains but accumulated in different environments, are investigated to better understand how the post-depositional cementation, alteration and dissolution of sediments, known as diagenesis, impact their geotechnical properties. Intervals are primarily affected by mineralogy-driven meteoric diagenesis, comprising in-situ dissolution of metastable grains and subsequent precipitation of cement that occurred when the shelf was exposed during lower sea-levels, and by marine diagenesis. In both cases, increased diagenesis results in a higher cement-to-solid ratio and compressive strength. However, while marine diagenesis is associated with a reduction in void ratio, this is not initially observed with mineralogy-driven meteoric diagenesis. Additionally, for a similar cement-to-solid ratio, microcrystalline cement results in higher compressive strength than sparite cement. The data further reveal that the level of meteoric cementation and the compressive strength increase as a function of the duration of exposure and of the regional climate, along with a reduction of the specific gravity related to the replacement of aragonite by calcite. However, increased meteoric diagenesis also leads to the formation of macro-scale heterogeneities such as calcrete layers and karsts that can affect the holistic geotechnical behaviour of such deposits.

Development of lightweight structural concrete with artificial aggregate manufactured from local clay and solid waste materials

The partial replacement of conventional natural coarse aggregate (NCA) with artificial light weight aggregate (LWA) manufactured from local clay and solid waste to develop a lightweight aggregate concrete (LWAC) for the structural use was studied in this paper. Red clay and Savar clay were used individually with solid wastes like rice husk ash (RHA) and waste glass to produce LWA. The suitability of raw materials and LWA was evaluated by investigating various properties. The mechanical, thermal and durability properties of manufactured LWAC were explored. The results of physical, chemical, thermal and geotechnical properties revealed that Red clay is better than Savar clay for the preparation of LWA. All the physical and mechanical properties of LWA prepared from Red clay are suitable for the preparation of LWAC compared to Savar clay. The test results demonstrated that the concrete manufactured by replacing 30 % of NCA with LWA produced a concrete of lightweight properties. The compressive strength of LWAC for 7 and 28 days was observed as 28 and 48 MPa, respectively. The results of modulus of elasticity, splitting tensile strength, flexural deformation, and creep test of LWAC revealed that these mechanical properties meet the requirements for the structural concrete. The RCP test proves that chlorine permeability of LWAC is comparable with NCA. It was observed that the superior performance of LWAC can be achieved only when the optimized mix designed is followed strictly. The suitability of the replacement of natural aggregate by LWA may be helpful for Bangladesh due to the scarcity of natural coarse aggregate and reusability of solid waste materials.

Microcrystalline Cellulose-A Green Alternative to Conventional Soil Stabilizers.

Biopolymers are polymers of natural origin and are environmentally friendly, carbon neutral and less energy-intense additives that can be used for various geotechnical applications. Biopolymers like xanthan gum, carrageenan, chitosan, agar, gellan gum and gelatin have shown potential for improving subgrade strength, erosion resistance, and as canal liners and in slope stabilization. But minimal research has been carried out on cellulose-based biopolymers, particularly microcrystalline cellulose (MCC), for their application in geotechnical and geo-environmental engineering. In this study, the effect of MCC on select geotechnical properties of kaolin, a weak, highly compressible clay soil, like its liquid and plastic limits, compaction behavior, deformation behavior, unconfined compression strength (UCS) and aging, was investigated. MCC was used in dosages of 0.5, 1.0, 1.5 and 2% of the dry weight of the soil, and the dry mixing method was adopted for sample preparation. The results show that the liquid limit increased marginally by 11% but the plasticity index was nearly 74% higher than that of untreated kaolin. MCC rendered the treated soil stiffer, which is reflected in the deformation modulus, which increased with both dosage and age of the treated sample. The UCS of kaolin increased with dosage and curing period. The maximum UCS was observed for a dosage of 2% MCC at a 90-day curing period. The increase in stiffness and strength of the treated kaolin with aging points out that MCC can be a potential soil stabilizer.

Investigating the Potential of Water Treatment Sludge for Improvement of the Geotechnical Properties of Gypseous Soil

Investigating the Potential of Water Treatment Sludge for Improvement of the Geotechnical Properties of Gypseous Soil

A Novel Technosol Formulation for Sustainable Landfill Top Covers Using Non-Hazardous Wastes

This study explores the potential of non-hazardous wastes for crafting an engineered soil-like material (Technosol) suitable for landfill capping applications. Three distinct materials—waste foundry sand (WFS), washing aggregate sludge (WAS), and composted biosolids (CBS)—were strategically combined to develop this innovative Technosol. The formulation process involved a comprehensive analysis of their physical–chemical properties, mineral composition, leachate quality, and a series of geotechnical assessments to ensure compliance with landfill top cover construction standards. The blend 90WFS/10WAS showed optimal geotechnical properties for constructing a protective layer, including maximum dry density (1.77 g cm−3), void ratio (0.4), CBR index (23.2), cohesive strength (40 kPa), internal friction (ϕ = 30°), and permeability coefficient (k = 1.48 × 10−6 cm s−1). Further enhancement was achieved by adding 10% CBS, resulting in the development of a functional organo-mineral topsoil horizon (81WFS/9WAS/10CBS). Importantly, leachate analysis confirmed the negligible environmental footprint of this Technosol. Moreover, a pot-based experiment with Brassica juncea planting validated its capacity to support plant growth and establish a vegetative cover on the landfill surface.

Susceptibility to Liquefaction of Iron Ore Tailings in Upstream Dams Considering Drainage Conditions Based on Seismic Piezocone Tests

One of the critical challenges facing the mining sector is related to the prevention and mitigation of catastrophic incidents associated with its tailing dams. As mining tailings are very heterogeneous and field characterization is expensive and complex, geotechnical properties of these materials are largely unknown. The seismic cone penetration test (SCPTu) provides a field approach to estimate a large array of geotechnical information, including the liquefaction potential of tailing dams. Yet, the exploration of strain softening behaviors in geomaterials under undrained loading, utilizing the state parameter (ψ) inferred from SCPTu tests initially applied to soft soils, has been often used for mining tailings. This study is concerned with the implementation of a tailing classification system which uses the ratio between the small strain shear modulus and the cone tip resistance (G0/qt). A series of laboratory tests was executed, and three different methodologies were adopted to assess the effects of (partial) drainage conditions based on 531.26 m of SCPTu measurements conducted at three different upstream iron ore tailing dams in Brazil. Furthermore, the G0/qt ratio is integrated with ψ to assess the liquefaction tendencies of the investigated materials. The findings reveal the heterogeneous nature of the tailings, wherein indications of partial drainage are discernible across numerous records. Liquefaction analyses demonstrate that the tailings exhibit a contractive behavior in over 94% of the SCPTu data, confirming their susceptibility to flow liquefaction. Our findings are relevant for site characterization within iron ore tailing dams and other mining sites with similar geotechnical attributes.

Seismic site effects in Lisbon: the role of complex geological and morphological conditions

Lisbon’s historical seismicity, socioeconomic importance and population density contribute to a moderate to high seismic risk. The geological setting of the city includes cases of inclined layers, interbedding sedimentary rock layers in soil deposits, sand and clay layers in the same geological unit, leading to cases of shear wave velocity inversion and a large scatter of geotechnical properties within each geological unit. The morphological setting of the city is characterised by the existence of several hills and relatively shallow, stream-carved valleys filled with alluvial deposits. The seismic site effects in Lisbon were assessed through numerical simulation using the linear equivalent method and adopting the two types of seismic action defined in the Portuguese National Annex of Eurocode 8: (i) one-dimensional subsoil models covering the city, at sites where borehole data and geophysical data were available; (ii) two-dimensional subsoil models along three cross-sections representative of the geological settings and morphology. The distribution of amplification factors in the city revealed a pattern related to ground characteristics that impact seismic soil response, such as the presence of high-thickness cover deposits, significant shear-wave variations, alluvial valleys, a crest or significant slope variations and inclined layers. The 2D/1D spectral ratio highlighted the areas were 2D seismic effects are more important. The soil factor determined in the numerical analyses was consistently greater than the soil factor values indicated in Eurocode 8.

Analysis of geotechnical properties in soil, reclaimed asphalt pavement (RAP) and Portland cement mixtures for use as pavement layers

A study is presented of mixes of fine soil and reclaimed asphalt pavement in the contents of 20, 30 and 50% with and without the addition of 5% Portland cement. The experimental program involved a battery of tests which found that the addition of up to 50% RAP alters the granulometry, increases the maximum dry density, bearing capacity and permeability, reduces plasticity, optimum moisture and expansion. The addition of 5% cement caused strong granulometric changes with an increase in the bearing capacity, reduced expansion and permeability. The compressive strength was below the required, but with considerable tensile strength and durability. Plasticity was presented as the greatest impediment to the use of mixes in view of the requirements of technical standards. However, it was found that the RAP is promising in improving soil properties and as a material to be applied in paving.