Silty Clay Research Articles

Experimental Investigation on the Critical Dynamic Stress of Frozen Silty Clay Under Different Temperature and Moisture Conditions

In this paper, a comprehensive series of dynamic triaxial tests were conducted to delve into the influence of temperature and moisture content on the behavior of frozen silty clay. Upon scrutinizing the experimental outcomes under prolonged reciprocal cyclic loading, insights were gained into how varying temperatures and moisture contents impact the cumulative permanent strain (CPS) and critical dynamic stress (CDS) of frozen clay. The results show that the variation curves of CPS with the number of cyclic loadings show significant changes at different temperatures and moisture contents. Additionally, based on the assessment of vertical CPS recorded at the 100th and 1000th loading iterations, criteria for assessing the plastic stability and plastic creep threshold of frozen silty clay were devised. Consequently, an analysis was conducted to delineate the correlation between the variation in vertical cumulative strains and the dynamic stresses applied within the frozen clay, resulting in the formulation of a series of correlation curves. The relationship between the changes in CDS affected by different temperatures and water contents were analyzed. The CDS under the plastic stability and plastic creep limits showed a slowly increasing trend with decreasing temperatures and a slowly decreasing trend with increasing water contents.

Geoelectrical Investigation of the Groundwater Potential in Eti-Osa, Lagos State, Nigeria

An electrical resistivity survey was conducted in Eti-Osa, Lagos State, Nigeria, to characterize the subsurface lithologic units, delineate the underlying aquifer, and assess groundwater potential. The study utilized an ABEM SAS 1000 terrameter for the data acquisition. Eight vertical electrical soundings were carried out using the Schlumberger electrode configuration. Data interpretation, both qualitative and quantitative, was presented through tables, charts, and sections. The interpreted geoelectric models revealed three to five layers with varying lithologies, including topsoil, sand, silty sand, sandy clay, silty clay, and clay. The first geoelectric layer, with resistivity values ranging from 8 Ωm to 320 Ωm, is relatively thin, with a thickness between 0.4 m and 3 m. The second layer exhibits thicknesses of 1.3 m to 15 m and resistivity variation between 1.5 Ωm to 185 Ωm. The third layer varies in thickness from 1 m to 36 m, with varying resistivity between 9 Ωm to 335 Ωm. The fourth geoelectric layer has a thickness range of 5 m to 20 m and resistivity values between 1.6 Ωm and 193 Ωm. The basement resistivity ranges from 3 Ωm to 361 Ωm. The study identified the sand layers, particularly at VES points 1, 2, 3, and 8, as the most promising for groundwater extraction. In contrast, VES points 4 and 5 are less favorable, and points 6 and 7 may yield lower-quality water. It is recommended that boreholes be drilled to depths greater than 20 meters at VES sites 1, 2, 3, and 8 for optimal water quantity and quality. However, sites 3 and 8 may be at risk of contamination due to shallower depths.

ANALISIS SENYAWA FITOKIMIA DAUN Moringa oleifera DARI KAWASAN GEOTERMAL ACEH BESAR SEBAGAI KANDIDAT ANTIINFLAMASI

Indonesia is home to a diversity of herbal plants, particularly in Aceh. Moringa oleifera is traditional medicinal plant utilized by locals in the geothermal area Aceh Besar, recognized for its anti-inflammatory properties. However, the bioactive compounds in M. oleifera leaves sourced from Ie Seum have not been documented, making it challenging to explain the roles of the compounds scientifically to anti-inflammatory factors. This research aimed to identify the phytochemical compounds in the ethanol extract of M. oleifera leaves (referred to as EDM) and analyze the physicochemical characteristics of the soil in the geothermal area. This study used a qualitative design to identify EDM compounds with GC-MS and soil physicochemistry. The identification of EDM compounds is conducted through gas chromatography with mass spectrometry (GC-MS). The physicochemical properties of the soil are assessed by examining its texture, pH, organic carbon content, total nitrogen, exchangeable cations, and phosphorus. Sample collection on topsoil (0-20 cm) with an area of ​​100cmx100cm on one land where M. oleifera plants grow in Ie Seum area in September 2024. A soil sample of 500g was using several methods, namely the hydrometermethod, pH meter, Walkey and Black, ammonium acetate 1M pH 7, Kjeldahl, KCl 1N, Bray 1, HCl 25%, and DTPA extraction. The soil test result showed classified as silty clay. The results GC-MS indicated the presence 11 metabolites, including linolenic acid, phytol, 9,12,15-octadecatrienoic acid ethyl ester, hexadecanoic acid, neophytadiene, gamma-tocopherol, vitamin E, squalene, icosane, and beta-pinene. EDM from the Ie Seum contains compounds that are beneficial in anti-inflammatory.

3D modeling and identification of post-dredging sediment layer types using hydroacoustic instruments

Abstract Sedimentation in harbor areas is a serious problem because it can interfere with ship navigation activities due to silting depth. Overcoming the siltation problem requires dredging to transport most sediment on the bottom of the water. In 2023, dredging was carried out to overcome the siltation problem, where the dredged layer was a soft layer and a small part of the hard layer. This research focuses on identifying the type of bottom sediment layer in PT Gresik Jasatama after dredging, modeling the sub-bottom layer and its depth and in addition, analyzing the difference in depth before and after dredging and interpreting the Side Scan Sonar image. The method used is an acoustic method, which consists of various instruments used to perform the analysis. The sub-bottom Profiler uses the acoustic wave reflection principle to determine the sediment layer type. Multibeam Echosounder is used to analyze the difference in bathymetry depth in 2021 and 2023 while analyzing the type of layer based on the digitation of the Sub-bottom Profiler. An echo-logger is used to analyze the difference in depth generated by low and high frequencies. Side Scan Sonar is used to provide a visual appearance of the shape of the seabed or objects on the seabed, and Backscatter MBES is used to analyze the type of sediment at the bottom of the water. Overlay between the difference data of Echologger, Sub-bottom Profiler, and bathymetry in 2023, a hard layer in the study area indicates dredging. In addition, the bathymetry measurement in the research area in 2021 was 1-8 meters, while in 2023, it was 7-12 meters, and the depth difference between the two depths was 4 meters. Side Scan Sonar interpretation shows the hard layer and soft layer by the borehole retrieval point, and the results of the water bottom characteristics show sediments in the form of gravel, gravel silty sand, clay, and sandy clay.

Identification of Types and Thickness Layers of Seabed Sediments

Abstract The sea toll program is one of the developments in the water sector that has a major influence on the areas it passes through. The sea highway acts as sea transportation that is carried out regularly and connects various ports in the territory of Indonesia. With the sea highway, there will be increased activity in the port area which will certainly increase the risk of shipping safety. This encourages periodic mapping and identification to reduce shipping risks that can occur. One of the activities to conduct mapping and identification is by hydrographic survey. There are many acoustic instruments that can be used for mapping the bottom of the water, in this study a sub-bottom profiler and side scan sonar were used. From the results of the study, the depth in the Berlian Terminal dock pool area ranges from 3.1 to 13 meters. The average thickness of the sediment layer from each survey lane is 1.01 m, 0.93 m, 1.41 m, 1.20 m, 1.37 m, 1.86 m, 1.15 m. The results of side scan sonar processing of the seafloor image interpretation produced several features consisting of pitted seafloor, ship grounding, and dredged areas. The distribution of sediment types was successfully classified into three classes consisting of silty clay, silty loam, and silty sand. This result is supported by sediment sampling which shows that the majority of sediment types in the study area was silty.

Development and field test of Red mud-Fly Ash Geopolymer pile (RFP)

Red mud is an industrial solid waste obtained from the extraction of alumina from bauxite. In order to study the resource utilization of red mud and improve its comprehensive utilization rate, based on the principle of geological polymers, red mud based geological polymers are prepared using raw materials such as red mud, fly ash, blast furnace slag powder, sand, stone, and alkaline solution as pile materials. Through lab experiments, the ratio of red mud and fly ash geopolymer mixtures that can be used for underwater injection and pumping has been obtained; Through on-site experiments, the complete construction process and the bearing characteristics of red mud-fly ash geopolymer piles (RFP) was studied. Environmental impact assessments were conducted by monitoring the changes in water quality around the RFP. The research results laid the foundation for the engineering application of RFP piles. It was found that: (1) At a liquid-solid ratio of 0.55, the geopolymer mixture of red mud: fly ash: sand: crushed stone: GGBS=(1:2:2:4.94:0.1) has good workability. The geopolymer with this mix ratio can meet the performance requirements of pumping and underwater perfusion, the slump can be controlled between 220-225mm, and the strength after 28 days of room temperature curing is 13.9MPa. (2) Developed a complete set of construction techniques for RFP, including drying, grinding and sieving of red mud, preparation of alkaline activator solution, sequence of material mixing, and related processes for pile drilling, placement of conduits, and conduit method grouting. (3) The load test results show that in a silty clay foundation, the ultimate vertical compressive bearing capacity of a single RFP with a pile length of 10.0 meters and a pile diameter of 520mm is 753kN. When the pile spacing is 1.5m, the bearing capacity of single-pile composite foundation is 240kPa. The Q-S curve and the stress distribution curve of the pile indicate that its load transfer characteristics are consistent with those of ordinary concrete piles. The results of the core sampling test on the pile body show that the core sample taken from the 10m pile is relatively complete, the rate of core recovery reaches over 99%,it shows that the pile body is intact. The compressive strength experiment shows that the strength of core samples at different depths is above 10MPa,and up to 19.5MPa. (4) The continuous water quality monitoring results for 5 months indicate that the implementation of RFP has not cause significant adverse effects on the quality of surrounding water bodies.

SPECIFICS OF LATE HOLOCENE SEDIMENTATION IN THE CHUKCHI SEA INFERRED FROM GRAIN SIZE AND MINERALOGICAL ANALYSES OF BOTTOM SEDIMENTS

The aim of this work is to elucidate the specifics of recent sedimentation in the Chukchi Sea, based on the study of the material composition of Late Holocene bottom sediments. Analytical methods included grain size and mineralogical analyses. The results of 210Pb and 137Cs dating were used. The sediments are clayey silt and silty clay containing sand admixture and single gravel grains and pebble. The content of coarse-grained material increases slightly in the upper parts of the studied sections. This is probably due to the greater contribution of ice rafting to the recent Chukchi Sea sedimentation as a result of climate warming. The ultrafine- and fine-grained (0.25–0.05 mm) sandy material is dominated by light-fraction minerals. Volcanic glass was discovered in the sediments sampled in the southern and central areas of the Chukchi Sea. It might have been transported from the volcanoes of Alaska, the Aleutian Islands, and the Kamchatka Peninsula through the Bering Strait by the Pacific currents directed from south to north. The sediments collected in the southern, central, and northern areas of the Chukchi Sea differ in grain size and mineral composition. This is probably due to their remoteness from the coastline and provenance areas and is also caused by different rates of sedimentation.

Research on the optimization of proportions for synchronous grouting material in composite muck during shield tunneling

To tackle the challenge of onsite resource reuse of composite muck, which relies on a shield tunneling section in the case of Nanjing Metro Line 7, this paper examines the effects of component substitution and varying proportions of factors on slurry properties through laboratory tests and multiobjective modeling. From a practical application perspective, the potential of using composite muck as a synchronous grouting material for shield tunneling was explored. In reference to the common mixed strata encountered in shield tunneling construction in the Nanjing area, a general slurry mixing ratio suitable for various mixed strata conditions was derived. The research results indicate the following optimized mixing ratios for the composite muck slurry: a water-to-binder (cement + fly ash) ratio of 0.76, a cement-to-fly ash ratio of 0.53, a binder-to-soil (silty clay + silty fine sand + river sand) ratio of 0.67, a clay (i.e., silty clay)-to-sand (i.e., silty fine sand + river sand) ratio of 0.4, and a substitution ratio (i.e., silty fine sand/silty fine sand + river sand) of 0.2. This slurry is feasible for practical applications and can reduce construction costs by 38.13%. The obtained general mixing ratio for the composite muck slurry, suitable for various mixed stratigraphic conditions, essentially meets onsite construction requirements (the bleeding rate is controlled within a low range of 1.1–3.1%, and the maximum compressive strength reaches up to 6.76 MPa at 28 days), with reasonable costs. It streamlines construction by eliminating the need for onsite screening of muck, allowing for the direct onsite reuse of composite muck in shield tunneling.

Experimental investigation on bearing capacity of rock-socketed bored piles in silty clay stratum in beach areas

In this study, six rock-socketed bored piles were tested in the field to investigate the bearing characteristics of rock-socketed bored piles in silty clay formations in coastal areas, and the model piles were simulated and optimized using the finite element (FE) method. The results showed that the lateral resistance of the piles in the clay layer is less than 50 kPa, and the lateral resistance of the rock-embedded portion is within 136.2−166.4 kPa. Compared with increasing the rock-embedded depth, increasing the diameter of the test piles can improve their vertical bearing capacity more effectively. The average horizontal critical load (Hcr) increased by 84.54 %, and the average horizontal ultimate load (Hu) increased by 50.3 % for the 800 mm diameter piles compared to the 600 mm diameter piles. Also, at the end of the test, the 600 mm diameter test piles showed severe damage at 6−9.5 D below the mud surface and were more susceptible to instability damage than the 800 mm diameter test piles. In soft clay strata, the 'm' values converged rapidly with increasing horizontal displacement and stabilized when the displacement exceeded 10 mm. The FE simulations confirmed that the horizontal displacement of the pile mainly occurs at 4 m depth below the mud surface, and the displacement of the test pile can be effectively reduced by reinforcing the soil around the pile. The silt at the bottom of the pile is one of the critical factors causing the uneven settlement of the test pile, severely affecting the vertical bearing capacity of the pile foundation.

Additional sources of salinity and heavy metals from plant residues of peaty horizons in the Po River lowland (Italy)

The Po River lowland (Italy) is suffering of soil and surface water salinization due to seepage of saline groundwater into drainage canals of agricultural lands. The main drivers are paleo-saline porewaters trapped in peaty and silty clay lenses, deposited in back barrier and lagoonal environments. To study this phenomenon, a 2-ha tile drained agricultural field, experiencing dramatic crop yield decrease in the last years, was selected. The field is located in a reclaimed area at approximately 3 m below sea level in the Ferrara province, 24 km from the Adriatic Sea. To delineate the salinity gradients, 10 high resolution vertical profiles of soil cores were collected with a manual auger corer and analysed in laboratory for EC, pH, grain size, organic matter content, major ions and trace elements. The composition of porewater's leaching fraction (LF) was gained via deionized water batch extraction with solid liquid ratio 1:5, while the plant available water (PAW) was obtained via microwave hot water extraction in three selected profiles. Linear correlation matrix, principal components analysis (PCA), LF and PAW depth profiles were employed to gain insights on the salinity sources. Stratigraphical cores were almost homogeneous with the most permeable layers constituted by peats. An average porewater salinity of 8.2 g/L with a downward increasing trend was found, with slight acidic pH and very high content of organic matter. PCA highlighted the strong connection among some trace elements (like As, Cd, Cr, Li, Pb, Se), NH4+ and the saline peaty horizons. The PAW salinity was up to two times the LF, highlighting that peaty aquitards are the major saline source in these reclaimed lands. A new salinizing mechanism was then postulated, since plant tissue fragments can store much more salts than the mineral fraction and can act as a long-term source of diffusion driven salinization, so far neglected.

Controlled soil monolith experiment for studying the effects of waterlogging on redox processes

Climate change induced mild and rainy winters may expose soils to more frequent and prolonged waterlogging in boreal regions. Resulting oxygen depletion induces reductive dissolution of iron (Fe) oxides further altering the stability of Fe-associated organic matter. Thus far, the impact of waterlogging on the coupled cycling of Fe and carbon (C) in upland arable soils remains unknown. We constructed a monolithic experimental system with 32 soil profiles (l = 63 cm, d = 15.2 cm) collected from two agricultural fields (silty clay, sandy loam) to study the effects of off-season waterlogging, overwintering cover crop and soil type on soil redox potential (Eh), Fe solubility, and movement of C and nitrogen (N) within the soil–plant-atmosphere continuum. Soil moisture, temperature, electrical conductivity, and Eh were continuously monitored, and soil pore water samples were collected at three soil depths. Here, we assess the systems suitability for studying coupled Fe and C dynamics in boreal climate, and investigate the treatment impacts on soil Eh, pH, reductive Fe dissolution and N concentration in pore water. Waterlogging led to reducing conditions in both soils down to 30 cm depth at the soil temperature (+4 to 12 °C) matching those of spring and autumn in southern Finland. The declining Eh and the slightly rising Fe concentration in porewater (max ∼ 10 µmol l−1) suggest that reductive dissolution of Fe could proceed even during mild winters if the duration of waterlogging exceeds 1–2 weeks. The study demonstrated that cover crops may accelerate the drop in soil Eh by removing bioavailable N, and hence controlling the availability of alternative electron acceptors (nitrate) in the soil. Thus, the simultaneous effects of cover crops on C inputs, and on N and water dynamics, all influencing redox reactions, emphasize the importance of incorporating vegetation into studies exploring the impacts of waterlogging on coupled dynamics of Fe and C.

Triaxial tests and numerical simulations on frozen silty clays under different stress paths and minor principal stresses

To investigate the mechanical characteristics of frozen silty clay under complex stress paths, using the true triaxial instrument for permafrost, tests were carried out under triaxial compressive and plane strain stress states using the true triaxial instrument for permafrost to analyze deformation characteristics and strength evolution law under different stress paths and minor principal stresses (σ 3) and establish strength criterion under plane strain conditions. PFC3D numerical simulation results were compared to test results and meso-crack evolution law was discussed. The results showed that stress-strain curves were characterized by strain hardening. Destructive strength showed a gradual increase with the increase of σ 3 and the values obtained from plane strain tests were higher than those of triaxial compression tests. Volume strains basically showed shear shrinkage characteristics and all σ 3 directions were expansion deformation. Strength at damage under plane strain state was approximated based on generalized Mises and Lade-Duncan plane strain strength criterion using generalized plane strain strength criterion. Stress-strain curves obtained from numerical simulation tests in PFC3D basically agreed well with those obtained from indoor test results. The number of tensile and shear cracks in the developed numerical model under various stress paths were increased with generalized shear strain.

Utilization of cement deep mixing pile for soft soil foundation: a malaysian case study

Cement deep mixing piles, as representatives of deep mixing technology, are mature and widely applied. However, effective application cases of cement deep mixing piles are relatively scarce in countries like Malaysia in Southeast Asia. In this paper, the application of cement deep mixing pile reinforcement in Malaysia is presented. Solidifying material was selected for deep mixing piles based on the soil conditions using unconfined compressive strength (UCS) tests. The relationship between the strength of deep mixing piles on-site and soil properties (type, organic matter content, and ion content) was analyzed. And a quality evaluation of the deep mixing piles in the project is conducted based on Kolmogorov-Smirnov (K-S) tests and relevant standards. Results show that fly ash cement is suitable as a solidifying agent for acidic soil layers containing organic matter in the local area. The strength of piles is significantly related to the soil condition. The UCS of cement mixing piles in silty clay and peat soils is smaller than clay. The overall correlation between organic matter content in the soil and UCS is negative, particularly when the organic matter content ranges from 10% to 14%, resulting in a significant drop in UCS. The bilateral significance probability is greater than 0.05 in K-S test, indicating that the UCS results in the projectconform to a normal distribution. Additionally, the evaluation of the overall quality of the mixing piles aligns with the requirements in the Japanese standard “Manual of Deep Mixing Construction Technology for Harbors and Airports” and the Chinese standard “Technical Code for Building Foundation Detection”.

Investigation on possibility of mangrove regeneration: a case study from Indian Sundarbans.

Mangroves serve as biotic fences of estuarine belts consisting of salt-tolerant plants that grow in intertidal zones and can be regenerated naturally as well as artificially. Mangrove regeneration refers to the process of restoring or rebuilding mangrove ecosystems that have been already degraded, damaged, or lost from their native place through the monitoring of geomorphological, taxonomical, pedological, and ecological aspects. The primary objective of this study was based on the remote sensing application through several important health monitoring indices over the minute part of Indian Sundarbans to prove the possibility of mangrove regeneration. Change detection analysis in the indices proves that there was possible growth and development in mangrove colonization over the same. The secondary objective is to comprehend the association of field-related study with the remotely sensed data on species diversity assessment over the same where the native species are Avicennia marina (Peyara Bain), Avicennia officinalis (Jat Bain), Avicennia alba (Kalo Bain), Aegialitis rotundifolia (Tora), Acanthus ilicifolius (Horgoj Kanta), Bruguiera gymnorrhiza (Kankra), Ceriops tagal (Goran), and Aegiceras corniculatum (Khalisi). The latter objective is associated with the tertiary one that unveils the correlation between several physico-chemical properties of soil samples taken from the field with the species accommodation.Textural classes are grouped between clay and silty clay that helps to get the foundation of hard wood-basedspecies (Avicennia type) specifically with the salinity ranges between 200 ppt (Site 2) and 633 ppt (Site 1)approximately which presents that the zone is highly saline zone as specifically Avicennia species can sustain highsalinity. Importance Value Index (IVI) and species diversity indices have been run to support whether the zone is diversified or not.Equilibrium between deforestation and regeneration through mangrove plantation has to be attained in the nearfuture as deforestation for the livelihood purposes exists, so this newly born island locally named Dorabagdamangrove patch, upper part (Gopalganj) of Kaikhali village, would be the best experimental study site on mangroveregeneration.

Risk for nitrogen leaching after application of solid manure in autumn differs between manure types

Manure application performed in autumn requires regulation due to the risk of nitrogen (N) leaching during winter. On the other hand, application of manure in spring can pose some practical problems depending on the risk for N immobilization and the difficulty in ploughing heavy clay soils during this time of year. The risk for leaching is likely to differ between different soil texture and manure characteristics. In this study, we sought to estimate the risk for nitrogen leaching depending on the carbon/nitrogen ratio (C/N) of the manure, time for manure application, and soil type. We combined 3-year lysimeter experiments with 2-year field plot experiments and laboratory soil incubations and compared results with those from an empirical model. We compared effects of manure application on two soils (silty clay and loamy sand) and solid manures with different representing C/N ratios. In incubations, only manure with a C/N-ratio below 14 contributed with significant amounts of leachable N during the first months after application. In the lysimeter study, N leaching was unaffected by the timing of the application of the manure with C/N-ratio 18. However, regarding manure with C/N-ratio 10, N leaching was elevated with 10–15 kg N per ha after manure application in October compared to November and March on both soil types. The mineral N analyses from soil profiles in the field experiments showed a similar pattern, however, the increase was higher on the loamy sand compared to the silty clay. The ammonia emissions did not differ between manure types, but were on average 24% of applied NH4-N after application in October when air temperature was on average 12°C compared to only 3% of applied NH4-N in November and March when air temperature was on average 5°C. Similar to lysimeter results, the modelled N leaching was higher the earlier the manure application occurred in autumn. However, the model also predicted increased leaching for the manure with a high C/N-ratio, and a smaller effect on leaching on clay soil. Considering this, the model calculations overestimated the leaching effects from manure with a high C/N-ratio and underestimated the leaching effects on clay soil.

Aging Dynamics of Polyvinyl Chloride Microplastics in Three Soils with Different Properties.

Microplastic (MP) contamination in soil has been of great concern, but the dynamic aging process and potential pathways of MPs in natural soil systems remain poorly understood. Herein, poly(vinyl chloride) microplastics (5% w/w) were weathered for 12 months in sandy soil, silty clay, and silt loam. The results showed that the continuous increase of C═O and O-H groups (rate constant, k = 0.080-0.424 m-1) with time was observed on the surface of MPs aging in sandy soil due to the leading role of •OH induced by light irradiation. In the loam soil, the abundant coating of aluminosilicates and iron oxides on the MP surface by the formation of mineral-hydroxyl groups inhibited the generation of the C═O group (k < 0.165 m-1). The k of the characteristic bond C-Cl during the first 9 months was 9.51 and 1.93 times higher in clay compared to that in sandy and loam soil, respectively, revealing that dechlorination triggered the first step of the aging process for MPs in clay owing to the participation of degrading bacteria (Phenylobacterium and Caulobacteraceae). The results provide important insights into the aging dynamics of MPs in environmentally realistic circumstance, which account for understanding the different aging processes of MPs in different soils.

Assessment of selective quartz flotation in phosphate beneficiation: A waste-to-product solution for tailings valorization

Silicate minerals, primarily quartz and clays, are frequently encountered as impurities in sedimentary phosphate ores. If not effectively removed, these gangue minerals can undermine the entire phosphate value chain. In this study, the challenge of selectively recovering silicates from a sedimentary carbonaceous siliceous phosphate ore was successfully addressed, enabling the recovery of an enriched phosphate concentrate as the main product, along with a high-purity quartz concentrate as a valuable by-product. This approach aligns with circular economy principles, promoting integrated waste management. The effective flotation of quartz was investigated using various amine-based collectors, including fatty alkyl amines, ether amines, diamines, quaternary ammonium salts, alkanolamines, and Gemini amines. Preliminary tests yielded unsatisfactory results, characterized by a lack of selectivity and substantial apatite losses. Consequently, this study identified the detrimental impact of dissolved ionic species on the adsorption of collector molecules onto quartz surfaces, which hindered effective flotation. To mitigate this issue, an acid-washing and water substitution process was implemented, resulting in significant improvements in flotation efficiency. The integration of response surface methodology (RSM) and automated mineralogical characterization enabled a comprehensive analysis and optimization of the flotation process. A systematic evaluation of operating parameters enabled the effective removal of most silicate impurities from the phosphate ore. This approach resulted in the recovery of high-purity silicate concentrates (greater than 80% SiO2), suitable for various industrial applications. Furthermore, the optimized flotation process reduced the silicate content in the final phosphate concentrate from 18.83% to below 2%.

Experimental study on the deformation behavior of soils under one-dimensional unloading

Soils are usually subjected to one-dimensional unloading due to the excavation, groundwater recharge, and other activities. This paper investigates the deformation behavior of soils under one-dimensional unloading. A series of oedometer tests with loading–unloading cycles were conducted on silty sand, silt, silty clay, and muddy silty clay samples extracted from southern Jiangsu, China. The influence of effective vertical stress before unloading on rebound deformation of soils was investigated. Test results show that the unloading deformation of soils increases nonlinearly with the increasing unloading ratio. When the unloading ratio reaches 0.8, only 30% of the total rebound deformation occurs. The rebound ratio increases with the increasing effective vertical stress before unloading. A power function was proposed to describe the relationship between one-dimensional unloading modulus and unloading ratio with two parameters named initial one-dimensional unloading modulus and decrease rate of the one-dimensional unloading modulus. The initial unloading modulus increased linearly with the increase of effective vertical stress before unloading, and a power function could be used to describe the relationship between the decrease rate and effective vertical stress. Formulas were also proposed to predict the initial unloading modulus and decrease rate of the one-dimensional unloading modulus based on piezocone test measurements.

Impact of broiler litter and swine liquid manure on nutrient loss in runoff from three consecutive one acre-inch rainfall events

Manure is an important source of plant nutrients and organic matter that can benefit soil health over time. However, indiscriminate use of manure can lead to environmental problems including eutrophication of water bodies caused by nutrient runoff during precipitation events. There is a need to understand the effect of manure source and application rate on nitrogen (N) and phosphorus (P) forms and their losses during runoff events. In this study, we assessed the impact of application rate of broiler litter (BL) and swine liquid manure (SLM) on runoff volume, soil, N, and P losses using a rainfall simulator and three consecutive 2.45 cm rainfall events. Surface Decatur silty clay loam (0–0.06 m) was collected and packed in trays (0.55 x 0.30 × 0.06 m3). Manure was surface-applied to the soil at equivalent P rates ranging from 62 to 249 kg ha−1 for BL and 5–18 kg ha−1 for SLM, respectively. Rainfall events took place 7, 14, and 21 d after manure application. Results indicated that the runoff volume decreased at the highest manure application rate compared to the lowest manure application rate. The total suspended solids (TSS) loss was lower in control compared to BL and SLM treatments. The loss of nitrate-N (NO3-N) dissolved reactive P (DRP) and dissolved organic P (DOP) in runoff water was maximum at the highest application rates for both the BL and SLM with respect to control. Mehlich 3 extractable P (M3P) and water soluble P (WSP) increased with increasing P application rates for both manure types in soils following post rainfall simulation study. An increase in M3P and WSP, along with a decrease in soil P storage capacity following post-rainfall simulation for higher P application rates, indicates caution should be taken for considering the manure application rate to prevent environmental nutrient loss during runoff events.

Numerical simulation study on the force of overwintering foundation support structure of unsaturated seasonal permafrost under indoor experiments.

When analysing the effect of negative temperature on overwintering pit constructions of unsaturated soil, using the mechanical parameter of saturated soil at room temperature leads to an inaccuracy in the research findings. The strength parameters are obtained through indoor experiments. The foundation pit model is created using FLAC3D numerical simulation software based on the indoor experimental data. The influence of different parameters on the stress and deformation of the overwintering deep foundation pit supporting structure is analysed. The numerical simulation results obtained are compared with the actual monitoring data. According to research, the matric suction of the silty clay in its natural state in the Changchun area is 70 kPa. As the temperature decreases, the total cohesion of the unsaturated soil increases, and the internal friction angle tends to decrease. The numerical simulation results are consistent with the actual monitoring data changes. With the excavation, the horizontal displacement of the supporting structure increases first and then decreases, reaching the maximum displacement at two-thirds of the foundation pit. Compared with room temperature, the deformation of the supporting structure is larger under a negative temperature condition. The deformation of the supporting structure simulated by the actual temperature mechanical parameters is larger than that under the condition of normal temperature mechanical parameters. The frost-heaving force increases with the overall excavation, and a surge occurs at the bottom of the pit. The frost-heaving force changes most significantly under the condition of freezing at -20°C for 30 days.