Marine Soil Research Articles

Dye Decolorization of Textile Dyes by Using Aspergillus fumigatus Isolated from Marine Soil

Dye Decolorization of Textile Dyes by Using Aspergillus fumigatus Isolated from Marine Soil

Spectrum-Based Logistic Regression Modeling for the Sea Bottom Soil Categorization

The present analysis of state of the art portrays that actual time series or spectrum backscattered data from a point on the sea bottom are rarely used as features for machine learning models. The paper deals with the artificial intelligence techniques used to examine CHIRP-recorded data. The data were collected using a CHIRP sub-bottom profiler to study two sand bottom sites and two sandstone bottom sites in the offshore zone of Ashqelon City (Southern Israel). The first reflection time series and spectra of all the traces from the four sites generated two training and two test sets. Two logistic regression models were trained using the training sets and evaluated for accuracy using the test sets. The examination results indicate that types of sea bottom can be quantitatively characterized by applying logistic regression models to either the backscatter time series of a frequency-modulated signal or the spectrum of that backscatter. The examination accuracy reached 90% for the time series and 94% for the spectra. The application of spectral data as features for more advanced machine learning algorithms and the advantages of their combination with other types of data have great potential for future research and the enhancement of remote marine soil classification.

Dredged marine soil stabilization using magnesia cement augmented with biochar/slag

Dredged marine soils (DMS) have poor engineering properties, which limit their usage in construction projects. This research examines the application of reactive magnesia (rMgO) containing supplementary cementitious materials (SCMs) to stabilize DMS under ambient and carbon dioxide (CO2) curing conditions. Several proprietary experimental tests were conducted to investigate the stabilized DMS. Furthermore, the carbonation-induced mineralogical, thermal, and microstructural properties change of the samples were explored. The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement (0.7–2.1 MPa) for pavement and building foundations. Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag (GGBS) altered the engineering properties and particle packing of the stabilized soils, thus influencing their performances. Biochar increased the porosity of the samples, facilitating higher CO2 uptake and improved ductility, while GGBS decreased porosity and increased the dry density of the samples, resulting in higher strength. The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples. Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration. Moreover, incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems. The biochar mixes demonstrated lower toxicity and energy consumption. Ultimately, the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO2 in soils through mineral carbonation, potentially reducing environmental pollution while meeting urbanization needs.

Unconfined compressive strength assessment of stabilized marine soil with cockle shell powder as sustainable material on subgrade pavement

Sustainable infrastructure is one of the sustainable development goals (SDGs) introduced by the United Nation. By utilizing waste materials as recycled and reused materials in construction, it offers great benefits to people, the economy and the environment for sustainable infrastructure in geotechnical project development. The low strength of marine subgrade pavement soil can be improved by chemical stabilization from abundant natural waste near the coastal area. The use of seashells such as cockle shells in powder formed can be considered a potential sustainable natural waste additive in replacing lime and cement for stabilized marine soil. Yet, its potential performance in improving geotechnical properties has not extensively been investigated. Thus, the unconfined compressive strength of stabilized marine soil with cockle shell powder (CSP) was assessed experimentally. The treated soil specimens were mixed with 2.5%, 5%, 7.5% and 10% of CSP (by dry weight of the soil sample) and prepared in the cylindrical dimension of 38 mm in diameter and 76 mm in height prior to unconfined compression test based on the optimum moisture content (OMC) obtained from the compaction test. All experiments were carried out in accordance with British Standard. The results show that the CSP can improve the strength of stabilized soil. The highest strength is 636.785 kPa for soil mixed with 10% of CSP which 157% increase compared with untreated soil. Therefore, the results of the study have shown that the addition of CSP to marine soil has improved significantly the unconfined compressive strength in soil stabilization, especially for pavement such as highways, airport runways and parking areas.

Biodegradation of low density polyethylene (LDPE) by Paenibacillus Sp. and Serratia Sp. isolated from marine soil sample

Low Density Polyethylene (LDPE) is recalcitrant and poses serious threats to our environment. The present study explored the LDPE biodegradation potential of aerobic bacteria enriched from offshore of RK beach Visakhapatnam. These isolates were specifically enriched in MSAM medium which contains LDPE as the source of carbon and energy for the growth. Six strains were isolated; among these S-6 & S-2 are the most potent strains which were attributed to the degrading ability. The phenotypic fingerprint such as Gen III biolog was used to identify the LDPE degrading S-6 as Paenibacillus sp. and S-2 as Serratia sp. respectively. Gen III Microlog, a phenotypic microarray; have been used for analysis of relative capabilities for substrate utilization of S-6 and S- 2 strains. The contact time of 72 h, temperature of 37 °C, pH of 7.1, inoculum volume 4% v/v, and weight of LDPE films 0.030 g were found to be optimal conditions for biodegradation of LDPE. Efficiency of these microbes (Paenibacillus sp. and Serratia sp) in degradation of LDPE was studied by percent weight reduction during a time period of 35 days. The Paenibacillus sps. proved to be most efficient with a weight loss of 22.46% compared to Serratia sps. with a weight loss of 9.5%. These bacterial species are capable of utilising LDPE as the sole carbon and energy source.

The Practice and Development of T-Bar Penetrometer Tests in Offshore Engineering Investigation: A Comprehensive Review

In recent years, the development of marine hydrocarbon resources has led to an increased demand for research on the marine soil bearing capacity and cyclic loading effect in marine engineering design. Because of the difficulties and high costs involved in obtaining high-quality soil samples from offshore sites, in situ testing techniques have become the preferred method of determining design parameters in offshore geotechnical engineering projects. This paper provides a review of the current state of marine penetrometer deployment technology used in offshore engineering investigations and presents a summary of the T-bar penetrometer test for measuring marine soft clay. The existing literature research on penetration mechanisms, numerical simulations, laboratory experiments, and field tests of the T-bar penetrometer in the field of marine geotechnical engineering are analyzed. Finally, the potential difficulties, challenges, and prospects of the T-bar penetrometer tests are discussed.

Load-Settlement Characteristics of Stone Column Reinforced Soft Marine Clay Deposit: Combined Field and Numerical Studies

Foundations supporting infrastructure built on soft and compressible marine soil are unlikely to sustain due to possibility of undrained shear failure or excessive settlement of the supporting soil. This necessitates the importance of implementing an adequate ground improvement strategy. Among different techniques, soft soil reinforcing by the installation of stone columns is one of the most successful methods in terms of long-term stability of foundations. To investigate the load-settlement characteristics of such reinforced soil, a group of closely spaced stone columns was constructed at a location along the eastern coast of Australia. The site geology revealed thick layers of soft, compressible marine clay deposit. These stone columns were loaded by constructing earthen embankment and the resulting load-settlement characteristics were measured by an array of sensors. A two-dimensional plane strain analysis was performed using finite element modeling simulations. Comparison of numerical results with the field data demonstrated accuracy of the numerical model. Additional studies were carried out to investigate the efficiency of the model. This paper integrates the new findings from the full-scale field study and advanced numerical simulations while drawing pertinent conclusions.

A study on utilization of landfill mined soil like fraction for sustainable reduction in swelling and cracking potential for expansive and marine soils

Landfill mined soil like fraction (LMSF) is derived from mining of legacy landfill waste after removal of larger fraction such as construction debris, clothes, plastics and other recyclables, and accounts for significant proportion of the total legacy landfill waste. LMSF has found applications as landfill cover material; however, owing to its large quantity in many cities, there is a need to explore more applications for its utilization. In this context the present study explores the role of LMSF (filler replacement) with/without ultrafine slag, US (primary admixture) and lime, L (activator) in controlling the shrinkage and cracking of marine and expansive soils during drying. The ratio of the area of crack and shrinkage to total area of specimen, defined as crack and shrinkage intensity factor (CSIF), has been utilized for quantification of the cracking and shrinkage characteristics of soils with/without stabilization. Further, the effect of soil stabilization on the swelling potential (viz., free swell index and swelling pressure) has been evaluated for the soils. In the present study, complete crack mitigation for expansive soil has been achieved for the combination: 40%LMSF (<425 μm) + 50% expansive soil + 8%US + 2%L, while for the marine soil it has been achieved for combination: 40% LMSF (<425 μm/<2 mm) + 50% marine soil + 8.5%US + 1.5%L. The study findings are useful in the context of utilizing LMSF with sustainable admixtures for reducing cracking and swelling potential of soils for various infrastructure applications such as natural and stabilized slopes, embankment, canal bed and ponds.

Numerical study on coupled modelling of artificial freezing marine soil

A theoretical model is proposed to investigate the coupling of the hydro-ice-salt-crystalline-thermal-mechanical of the artificial frozen marine soil in coastal areas. The influence of non-convective and thermal permeability in the fields of salt, pressure, thermal, and water, the compressibility of solid particles, as well as solute potential and ice resistance coefficients in convective flux are comprehensively considered based on the mass, energy, and momentum conservation equations. The proposed coupling model is solved using the COMSOL Multiphysics software. The accuracy of the proposed theoretical model is verified by the model test results in the literature. The parametric studies are conducted to investigate the effects of the key parameters on the freezing process. It is found that the salt desorption of the frozen marine soil cannot be ignored. The effect of salt desorption in the frozen area is strong which makes the adsorbed salt content in the unfrozen area greater than that in the frozen area. The change in salt mass fraction has a great influence on the overall frost heave, salt heave and water freezing. With the increase of overburden, the soil is compressed and the desorption effect is enhanced in the frozen area.

Probabilistic approach to the stability analysis of caisson foundations under combined loading in spatially variable soil

Caisson foundations are increasingly used in offshore engineering and are usually subjected to combined vertical-horizontal-moment (VHM) loading caused by self-weight, wind, waves, and currents. The bearing capacities of foundations under combined loading are represented by the VHM failure envelopes. In the literatures, failure envelopes for caisson foundations were usually established using a deterministic model of soil properties, ignoring the actual uncertainty and spatial variability of marine soil. The present study focuses on the investigation of the bearing capacities for caissons in spatially variable undrained soil under both uniaxial loading and VHM combined loading. Random finite element method combined with Kriging metamodeling technique and Monte Carlo simulation was applied to evaluate the uniaxial bearing capacities and to define the probabilistic VHM failure envelopes. The soil's undrained shear strength was considered to be increasing with depth, while its coefficient of variation was depth-independent. The effects of the coefficient of variation and scale of fluctuation of undrained shear strength on the uniaxial bearing capacity, on both size and shape of VHM failure envelopes for caisson foundations were discussed. It is shown that spatial variability of soil not only causes a change in the size of the failure envelope but also affects its shape when compared with the deterministic case. Therefore, it is necessary to consider the spatial variability of soil when designing caisson foundations and the present results provide some guidance for the design.

Numerical and experimental modeling of wave-induced forces on submarine pipeline buried in the soil of different engineering properties

In the present paper, the wave-induced forces on the submarine pipeline buried in porous soil having different properties are studied. The mathematical problem is solved using the higher-order boundary element method, and the numerical results are validated with experimental results obtained through rigorous model tests. Four different types of Kuwaiti marine soil: Al-Khiran, Al-Koot, Sabiya, and Shuaiba are considered in the present study. The effect of burial depth of the submarine pipeline in the soil seabed, incident wave period and wave height, and hydraulic conductivity of the soils on the wave forces acting on the submarine pipeline is analyzed in a detailed manner. The study reveals that for moderate burial depth of the pipeline in the soil bed, the wave force acting on the submarine pipeline can be reduced up to 50% for soil having less hydraulic conductivity. The measured wave forces and numerical predictions are matching well for a wide range of wave, soil and structural parameters.

Analysis of the relationship between the resistivity and shear zone volume in fine-grained marine soil under loads based on the resistivity triaxial experiments

Analysis of the relationship between the resistivity and shear zone volume in fine-grained marine soil under loads based on the resistivity triaxial experiments

Critical Dynamic Stress and Cumulative Plastic Deformation of Calcareous Sand Filler Based on Shakedown Theory

Calcareous sand is a special marine soil rich in calcium carbonate minerals, characterized by brittle particles. It is, therefore, widely used as a filling material in the construction of islands and reefs. In this study, a series of cyclic tri-axial tests were conducted on calcareous sand taken from a reef in the South China Sea under different confining pressures and cyclic stress ratio (CSR). Then, applying the shakedown theory, the cumulative deformation of calcareous sand under a long-term cyclic load of aircraft was evaluated. Results showed that with the increase in the effective confining pressure, the stress–strain curves of calcareous sand showed a change from the strain-softening to the strain-hardening state; the volumetric strain of calcareous sand showed a change from shear shrinkage and then shear expansion to continuous shear shrinkage. Calcareous sand showed three different response behaviors under cyclic load: plastic shakedown, plastic creep and incremental plastic failure. With the plastic strain rate as the defining index, this study determined the critical CSR of calcareous sand under different shakedown response statuses and found them to increase with the effective confining pressure. The empirical formula for critical stress was established based on the fitting analysis of critical CSR under different confining pressures, taking the confining pressure as the variable. At the early stage of the cyclic load, calcareous sand samples were under compression. When the resilient modulus grew rapidly and the number of loading cycles continued to increase, the particles of calcareous sand samples were crushed, causing the fine particles to fill the voids among coarse particles, further compacting the samples and increasing the resilient modulus of calcareous sand samples. Hardin’s breakage potential model was adopted to quantitatively describe the particle breakage of calcareous sand samples before and after tests. The results indicated that calcareous sand samples produced obvious particle breakage when the CSR was small. As the CSR increased, the extent of the breakage of the sample particles first increased and thereafter stabilized. This study provides a theoretical reference for the assessment of the dynamic stability of calcareous sand subgrade subjected to traffic loads.

Evaluation of the Laboratory Degradation Performance of a Straw Drainage Board

Plastic drainage boards are installed into the foundation as vertical drainage channels in vacuum preloading projects. After construction, numerous plastic drainage boards are left in the foundation, causing not only white pollution but also potential groundwater contamination. Straw was utilized to produce degradable drainage boards in this study, and the feasibility of straw drainage boards was confirmed by laboratory degradation tests. The results revealed that Zhuhai’s soft marine soil is rich in degrading bacteria such as Bacteroidota and Firmicutes, which have adverse effects on the performance of the straw drainage board. The straw drainage board was deteriorated by bacteria in the foundation, and the discharge capacity and tensile strength dropped with time, with the discharge capacity degradation relationship as qw(t) = qw0(1 − 3.83 × 10−6t2). The discharge capacity and tensile strength of straw drainage boards are lower than those of plastic drainage boards, but they all meet the engineering requirements. Straw drainage boards can replace plastic drainage boards in vacuum preloading reinforcement projects, which not only solves the problem of environmental pollution but also expands the comprehensive utilization of straw resources in a new way.

Suppression of Streptococcosis and Modulation of the Gut Bacteriome in Nile Tilapia (Oreochromis niloticus) by the Marine Sediment Bacteria Bacillus haynesii and Advenella mimigardefordensis.

Streptococcosis is one of the major threats to Nile tilapia (Oreochromis niloticus) in most regions of the world. Recently, Enterococcus faecalis has been widely reported to be involved in streptococcosis in O. niloticus in Asia and Africa. This study aimed to isolate beneficial marine bacteria to evaluate their effects on growth, hematological parameters, nonspecific immunity, the gut bacteriome, and streptococcosis prevention efficacy in O. niloticus. A total of 36 marine soil bacteria were isolated, and in vitro screening was conducted to determine their antibacterial activities against fish pathogens. Two antagonistic bacteria were identified based on 16S rRNA gene sequencing, Bacillus haynesii CD223 and Advenella mimigardefordensis SM421. These bacteria were incorporated into fish feed and fed to O. niloticus for 90 days. The application of these strains via incorporation into fish feed significantly promoted growth, improved hematological parameters and immunoglobulin M (IgM) levels, modulated the gut bacteriome by reducing the load of pathogenic Enterococcus spp., and developed disease prevention efficacy in O. niloticus. Furthermore, in vivo assays revealed that the inclusion of extracellular products (ECPs) (at 250 μg mL-1) of CD223 and SM421 with feed significantly enhanced the rate of survival (100%) of O. niloticus from streptococcosis compared to the controls (only 30%). The ECPs of these bacteria also prevented 90 to 100% of fish from developing streptococcosis. These strains could be promising for safe use in O. niloticus farming to prevent and control the emergence of streptococcosis caused by E. faecalis. IMPORTANCE Nile tilapia (Oreochromis niloticus) is one of the most economically important cultured fish species throughout the world. Streptococcosis is a significant threat to global Nile tilapia farming. Enterococcus faecalis has recently emerged as an important pathogen of streptococcosis in Asia and Africa. The application of antibiotics and probiotics and vaccination are the major ways to combat streptococcosis. However, the extensive use of antibiotics leads to the development of antibiotic resistance in pathogenic as well as environmental bacteria, which is a great threat to public health. There is no study on preventing streptococcosis caused by E. faecalis using beneficial bacteria. For the first time, the present study demonstrated that two marine bacteria, Bacillus haynesii strain CD223 and Advenella mimigardefordensis strain SM421, have great potential for controlling streptococcosis in Nile tilapia. These bacteria also enhanced the growth, improved hematological parameters and IgM levels, and positively modulated the gut bacteriome of Nile tilapia.

Coupling effect of roughness and normal pressure on mechanical characteristics and failure mode of deep-sea sediment interface

Revealing the failure mechanism at the soil–structure interface is an important prerequisite for foundations bearing capacity analysis. In deep-sea structures, due to the special sedimentary conditions and extremely low permeability coefficient of marine soil, obviously, the undrained behavior at the interface is becoming more complex and needs due attention. The objective of this study is to investigate the coupling effects of roughness and normal pressure on the interface mechanical characteristics and failure mode from the perspective of the pore pressure index through improved interface triaxial apparatus. The obtained results revealed that increased surface roughness makes it difficult for the soil particles in the grooves to climb along the structure surface and consequently the failure surface shifts from the interface to the soil. The confining pressure strongly influences the failure mode and critical roughness; Based on the response of two factors to the interface, a new piecewise Mohr-Coulomb failure criterion is established to reveal the real interface mechanical parameters, accordingly two new concepts are proposed and analyzed: transition roughness and critical normal stress; Furthermore, the relationship between the critical roughness and confining pressure is determined by the interface shear resistance equation considering the coupling effect; Finally, the interface failure mechanism and failure modes related to the confining pressure and surface roughness are revealed and distinguished. The dominant effect of effective interface friction parameters on the failure modes is evaluated for various surface roughness ranges.

Experimental and Finite Element-Based Investigation on Lateral Behaviors of a Novel Hybrid Monopile

A monopile is the most conventional structure foundation for offshore wind turbines (OWTs) in the world. However, the Korean offshore wind industry has mostly been using the jacket type of foundation. The main reason for the current situation in Korea is that most of the marine soil consists of weak layers of sand and clay. Thus, the monopile foundation depth has to be deep enough to satisfy the intended serviceability design requirement of the monopile and the rotation limit at the seabed; a conventional monopile design concept alone might be insufficient in Korean offshore conditions, or otherwise could be very expensive, e.g., resulting in a rock socket installation at the tip of the monopile. The main objective of this paper is to introduce a novel hybrid monopile that is composed of a monopile and a supplemental support with three buckets, followed by assessing the lateral resistance of the hybrid system through physical experiments and finite element (FE) simulations. Namely, 1/64.5 small-scaled monopile and hybrid physical models with a monopile diameter of 7 m for a 5.5 MW OWT were loaded monotonically. The results show that the hybrid monopile improves the lateral bearing capacity regarding the initial lateral stiffness and ultimate load. The FE analyses of the corresponding physical models were also implemented to support the results from the physical model test. The numerical results, such as the structural member forces and soil deformation, were analyzed in detail. Additionally, a case study using FE analysis was conducted for the 5.5 MW OWT hybrid monopile support installed in a representative Korean weak soil area. The results show that the hybrid monopile foundation has a larger lateral resistance and stiffness than the monopile.

Experimental investigation on the thixotropic effect on the mechanical recovery characteristics of clay–structure interface

The mechanical characteristics of the soil–structure interface have a crucial impact on the bearing capacity of offshore foundations. The thixotropy-induced strength recovery of remolded soils has a significant effect on the increase in the stability of the foundation. To explore the effects of thixotropy on the recovery characteristics of the soil–structure interfacial shear strength, a self-designed interfacial mechanical characteristic apparatus is designed in this study to perform a series of soil–structure interface tests on clays from the South China Sea and offshore Dalian, respectively. The relationship between the recovery of undrained shear strength and the change of interfacial shear strength is analyzed by the index of shear-resistant coarseness. And the effect mechanism of thixotropy on interfacial shear strength is discussed from the microscopic view. The test results indicated that the rate of increase of the soil–structure interfacial shear strength is higher than that of the undrained shear strength. The particle size index of the soil was found to significantly influence the strength recovery characteristics of the soil–structure interface. A higher clay content will accelerate the development of the interfacial shear strength. This article provides a deep insight into the thixotropic effect on the mechanical properties of the marine soil–structure interface.

Failure-Mechanism and Design Techniques of Offshore Wind Turbine Pile Foundation: Review and Research Directions

Wind energy is one of the most sustainable and renewable resources for power generation. Offshore wind turbines (OWTs) derive significant wind energy compared to onshore installations. One of the greatest challenges encountered by installing the OWTs is the adequate design of their foundation in relatively soft and compressible marine soil. In most cases, the OWTs are supported by a single pile, termed as ‘monopile foundation’. Apart from the usual loads from the superstructure, these piles are subjected to complex loading conditions under static and cyclic modes in the axial, lateral, and torsional directions due to the primary actions of the wave, wind, and current. To incorporate an appropriate design methodology, understanding the failure mechanisms of such piles is of the utmost necessity. This review paper aims to focus on the progressive development in the analysis of failure mechanisms and design practice relevant to the monopile foundations for OWTs by theoretical and experimental studies conducted globally. An extensive literature survey has been carried out to study the gradual progress on offshore pile-soil interaction, failure mechanisms, and design techniques of OWT supporting monopile foundations. Based on the studies, a brief overview of the various aspects of analysis and design has been carried out, and the relevant conclusions are drawn therefrom.

Antibacterial, antibiofilm and antioxidant activity of secondary metabolites of antagonistic bacterial strain Bacillus endophyticus PK2 isolated from marine soil

Antibacterial, antibiofilm and antioxidant activity of secondary metabolites of antagonistic bacterial strain Bacillus endophyticus PK2 isolated from marine soil