Silt Clay Research Articles

The Effect of Varying Compaction Levels on Soil Dynamic Properties and the Growth of Canola (Brassica napus L.)

Extremely low field emergence rates for canola are primarily attributed to soil compaction from field traffic during and after planting. This study aimed to determine the critical compaction level for canola emergence across different soil types. A laboratory experiment was conducted using sandy loam, silt clay, and clay soils, compacted to five levels (zero to four) using Proctor hammer drops after sowing canola (Brassica napus L.). The lab results were validated through two years of field experiments in sandy loam, applying four compaction levels (zero to three) using a tractor. Soil properties (bulk density and surface resistance) and canola growth parameters (plant emergence rate, count, height, and above-ground biomass) were measured. Zero compaction resulted in lower bulk density and surface resistance across all soil types. Laboratory results showed maximum emergence rates of 95% for sandy loam, 100% for silt clay, and 60% for clay, while field emergence rates were 63% and 87.59% in the first and second years, respectively, both at zero compaction. Recommendations include light or no compaction for sandy loam, and zero compaction for silt clay, while clay soil did not achieve the 80% emergence target at any compaction level. These results can assist agricultural producers in optimizing their seeding equipment setup and managing field traffic for canola production.

A Method for Determining Yield Stress of Unsaturated Soils from Lateral Pressure

Abstract Predicting the stress–strain behavior of unsaturated soils is essential for determining yield stress. This paper explores a new method for determining the yield stress of unsaturated soils from the lateral pressure curve. A series of earth pressure at rest (K0) ondometer tests were conducted on unsaturated Yangqin silt clay. Lateral stress was obtained under different saturations and compactness. The relationship curves between lateral and vertical net stress were drawn for each condition. An obvious turning point was observed in the curve, which can be used to determine the yield stress. The oedometer tests were conducted, and the Casagrande and the bilogarithmic methods were used for comparison purposes. The difference between the proposed and traditional methods was less than 17 %. The initial saturation and compactness influence on the yield stress was discussed. The yield stress increased with the decrease in saturation and increases in compactness, which is consistent with that of the classic method. The test results and comparison prove the rationality of the proposed method. No coordinate transformation is required in the proposed method, which is more convenient for data processing. It can be used to determine the yield stress of unsaturated soils from another perspective.

Vegetation restoration changed the soil aggregate stability and aggregate carbon stabilization pathway according to δ13C signatures

Vegetation restoration can increase soil organic carbon (SOC) sequestration through the physical protection of soil aggregates. However, the soil aggregate stability and C flow pathway associated with long-term plantation restoration have not yet been fully characterized. Here, we conducted a study on Robinia pseudoacacia plantations at different recovery stages, studied the distribution and stability of aggregates, analysed the aggregate-associated organic carbon (OC) content and δ13C value, and quantified the aggregate C flow pathway. The results revealed that vegetation restoration increased the proportion of large macroaggregates (LMAs) and decreased the proportion of small macroaggregates (SMAs), with no changes observed in the proportion of microaggregates (MIAs) or silt + clay (SC) at 0–20 cm. The indices of aggregate stability, namely, the mean weight diameter (MWD), geometric mean diameter (GMD) and structural stability index (SSI), increased under vegetation restoration at 0–20 cm, with maximum values of 3.83 mm, 2.88 mm, and 2.00 %, respectively, at 35 years of age (35Y). The OC content of the LMAs increased from 10.96 to 21.64 g kg−1 and from 7.27 to 10.05 g kg−1 in the 0–20 cm and 20–40 cm layers, respectively. LMAs and SMAs had the greatest contributions to SOC accumulation in the 0–20 cm and 20–40 cm layers, respectively. The δ13C value increased with decreasing aggregate size. The C flow pathway was from macroaggregates to MIAs or SC. Compared with abandoned farmland, vegetation restoration decreased the aggregate C flow intensity in the 0–20 cm layer. The soil aggregate stability and aggregate-associated OC content decreased with increasing soil depth, but the soil δ13C value exhibited the opposite trend. Vegetation restoration regulated soil aggregate stability by influencing the fine root biomass (FRB) and SOC content. In summary, our analysis offers a valuable reference for the controlling effect of aggregation on C stability influenced by vegetation restoration.

Vertical variations in planar lamination of marine shale: Elucidating hydrodynamic changes during the Ordovician–Silurian transition on the Upper Yangtze Block

The hydrodynamics and their evolution on the Upper Yangtze Block during the Ordovician–Silurian transition period remain unclear. The present study is an assessment of how regional and global events may have influenced the hydrodynamic evolution based on a planar lamination investigation of the shales from the Upper Yangtze Block. Analyses of large thin sections and argon-ion polished thin sections using field emission-scanning electron microscopy (FE-SEM) showed that there are four types of planar lamination, namely, silty graded planar lamination (SGPL), silt–clay graded planar lamination (SCGPL), silt–clay interlaminated planar lamination (SCIPL), and paper-like planar lamination (PPL). SGPL is formed by turbidity current with a flow speed less than 15 cm/s. SCGPL is formed by turbidity currents with a flow speed less than 15 cm/s for normal grading type and 15–25 cm/s for alternating grading type. SCIPL has a continuum of sparsely spaced type, closely spaced type, and alternating type, which is formed by bottom current with an increasing flow speed from 15 to 25 cm/s to above 25 cm/s. PPL can be divided into normal grading and composite grading types. The former is formed by vertical settling, while the latter is formed by bottom current with a flow speed of 5–15 cm/s. Vertically, types of planar lamination varied from SGPL to PPL and then SCIPL manifesting the waxing and waning of flow speed with a positive excursion at graptolite biozone Metabolograptus extraordinarius (WF4) and a negative excursion at graptolite biozone Persculptograptuspersculptus (LM1). The sudden decrease in flow speed across Linxiang and graptolite biozone Paraorthograptuspacificus (WF3) and the subsequent progressive increase from graptolite biozone Akidograptus ascensus (LM2) to graptolite biozone Demirastrites triangulatus (LM6) and to graptolite biozone Stimulograptus sedgwickii (LM8) during deposition of the Ordovician–Silurian transition succession on the Upper Yangtze Block were linked to the bulge uplift, the rapid subsidence, and the relaxation controlled by the Kwangsian orogeny. In contrast, the positive excursion at WF4 and the negative excursion at LM1 were strongly controlled by the Hirnantian Glaciation and global warming, respectively.

Statistical characteristics of aquitard hydraulic conductivity, specific storage and porosity

Aquitard hydraulic conductivity (K), specific storage (Ss) and porosity (ϕ) are critical to the modeling of flow and mass and heat transport in groundwater systems, yet comprehensive insights into their statistical characteristics remain limited. This study compiles 456 K values from 47 studies, 202 Ss values from 49 studies and 239 ϕ values from 18 studies, followed by rigorous statistical analysis of aquitard K, Ss and ϕ with dependence on the features of test method, lithology and burial depth. Additionally, the interrelationships among K, Ss and ϕ are analyzed. A predictive model for aquitard K and Ss is developed utilizing the random forest (RF) approach. The statistical findings unearth that laboratory experiments tend to yield lower K while higher Ss, particularly when burial depths are less than 50 m. Clay, silt clay, and glacial till exhibit comparable K values, in contrast to significantly lower K values observed in shale formations. Aquitard K, Ss, and ϕ exhibit depth-decaying characteristics. Between two adjacent depth intervals, 0 ∼ 50 m, 50 ∼ 150 m and >150 m, there is nearly an order of magnitude difference in either K or Ss. Aquitard K tends to increase with ϕ when ϕ is below 0.25 and decreases vice versa. This phenomenon is probably attributed to the significant amount of immobile-bound water adhering to clayey particles within the aquitard with a high ϕ value, which reduces the pore space available for water flow. Elastic Ss, which indicates recoverable aquitard groundwater depletion, is about one order of magnitude lower than inelastic Ss, which indicates permanent aquitard groundwater depletion, implying that the majority of groundwater depletion from aquitards under long-term groundwater exploitation is non-recoverable. The RF-based predictive model indicates that ϕ is a highly important feature for predicting K and outperforms lithology, test method and burial depth in predicting Ss. The statistical findings of this study present a valuable basis for aquitard hydraulic parameters.

Sedimentary dynamics and depositional model for mud accumulation in deep lake basins: A case study in the Upper Triassic Chang-7 Member, Ordos Basin, northern China

Shales in deep lake basins have become the main focus of continental shale oil and gas exploration. In order to highlight the sedimentary dynamics of mud deposition in deep lake basins, a combination of core observation, thin section examination, X-ray diffraction, and QEMSCAN (quantitative evaluation of minerals by scanning electron microscopy) was used to analyze the depositional characteristics of mudrocks in the Chang-7 Member from the Yanchang Formation (Upper Triassic) in Ordos Basin, and to establish a depositional model for mud accumulation in deep lake basins. This study recognizes four mudrock lithofacies in the Chang-7 Member: (1) the laminated silt-bearing mudstone, which generally develops a binary composition of “silt–clay” or a ternary composition of “silt–clay–organic matter”; (2) the graded mudstone, mainly composed of dark gray and gray-black mudstone sandwiched by silt-bearing mudstone; (3) the massive mudstone, internally showing a uniform distribution of quartz, clay, and carbonate minerals, with also a small amount of organic detritus; and (4) the laminated shale, which is generally composed of clay laminae, and organic laminae of the former two. Sediment supply, topographic slope, and flood intensity combine to control the evolution of gravity flows and the transport and deposition of the mudrock in the Chang-7 Member. The influence of orogeny provides terrain gradient, water depth, abundant sediments at source areas, and triggering mechanism for the formation of gravity flows. Floods triggered by wetting events provide the impetus for sediment transport. Mud deposition in the Chang-7 Member was mainly related to the transport and sedimentation of mud by hyperpycnal flows and rapid sedimentation by buoyant plume flocculation. A comprehensive evolutionary model for shale accumulation in the deep lake basin is established by integrating various triggering mechanisms and mud transport sedimentary processes.

Time-dependent regulation of soil aggregates on fertilizer N retention and the influence of straw mulching

Fertilizer nitrogen (N) turnover is highly controlled by soil aggregation. However, the functions of the various aggregates that regulate long-term fertilizer N retention under conservation management remain unexplored. In this study, 15N-labeled fertilizer was initially applied in situ to investigate the effects of maize straw mulching on fertilizer N allocation in soil aggregates at a decadal scale. The topsoil was fractionated into macroaggregate, microaggregate, and silt-clay (SC) fractions. Macroaggregate was further divided into particulate organic matter (POM) and mineral-associated organic matter (MAOM). A higher enrichment factor of fertilizer N than of soil total N in macroaggregate indicated that the fertilizer N was more apt to incorporation into macroaggregate. The fertilizer N in the bulk soil declined gradually to 84.0% by the 13th year. Temporally, the reduction proportion of fertilizer N in the SC fraction was the largest before 5th years, whereas macroaggregate was the main reactive spot for fertilizer N transformation from 9 to 13 years. Therefore, the function of aggregates was time-dependent in controlling fertilizer N retention and turnover via the release of previously entrapped fertilizer N, but encapsulated the subsequently applied N (i.e., unlabeled fertilizer), whereas mineral adsorption contributed to the long-term stabilization of fertilizer N. Compared with fertilization alone, straw mulching improved aggregates stability, favored the initial fertilizer N retention in macroaggregate by enriching fertilizer N in POM, and reduced the proportion of N loss in MAOM after 9 years. These finding indicate that the improvement in fertilizer N stability related to straw decomposition was sequentially attributed to the enhancement of aggregate encapsulation and persistent interaction with soil minerals. Therefore, this study provides new insights into the functional heterogeneity of soil aggregates at different time stages and the intricate interplay between carbon availability-controlled fertilizer N retention and the improvement in soil aggregation.

Application of hybrid modeling to predict California bearing ratio of soil

California Bearing Ratio (CBR) is used to assess bearing capacity, deformation characteristics of roadbed soil, and base layer material in pavement structure. In general, CBR is often determined by laboratory or in-situ tests. However, it is time- and cost-consuming to conduct this experiment because this test requires cumbersome equipment such as a compressor. In this study, two Artificial Intelligence models are developed, including a simple model (Decision Tree Regression, DT) and a hybrid model (AdaBoost - Decision Tree, AB-DT). Using 214 data samples from Van Don - Mong Cai expressway, Vietnam, 10 input variables of the model were considered namely particle composition (content of gravel (X1), coarse sand (X2), fine sand (X3), silt clay (X4), organic (X5)), Atterberg limits (Liquid limit (X6), Plastic limit (X7), Plastic index (X8)), and compaction curve (optimum water content (X9) and maximum dry density (X10)). The developed models were evaluated by using a variety of statistical indicators, including coefficient of determination (R2­­), Root mean square error (RMSE), and Mean absolute error (MAE). The results show that AB-DT model has higher accuracy than the DT model. Moreover, the SHAP value analysis shows that the variable X10 influences the CBR value the most. Thus, it implies that applying the AB-DT model to effectively predict the CBR of the roadbed soil saves time and money for experiments.

Geophysical methods reveal the soil architecture and subsurface stratigraphic heterogeneities across land-lake interfaces along Lake Erie

PurposeThe land-lake interface is a unique zone where terrestrial and aquatic ecosystems meet, forming part of the Earth’s most geochemically and biologically active zones. The unique characteristics of this interface are yet to be properly understood due to the inherently high spatiotemporal variability of subsurface properties, which are difficult to capture with the traditional soil sampling methods. Geophysical methods offer non-invasive techniques to capture variabilities in soil properties at a high resolution across various spatiotemporal scales.MethodsWe combined electromagnetic induction (EMI), electrical resistivity tomography (ERT), and ground penetrating radar (GPR) with data from soil cores and in situ sensors to investigate hydrostratigraphic heterogeneities across land-lake interfaces along the western basin of Lake Erie.ResultsEMI revealed high spatial heterogeneities in ECa distribution across the land-lake interfaces, with higher values in the wetland and transition zones compared to the upland zone. Soil ECa maps matched soil maps from a public database with the hydric soil units delineated as high conductivity zones (ECa > 40 mS/m). ERT and GPR showed vertical variation in soil properties with clear stratigraphic boundaries, and correlation of ERT profiles with lithologs from piezometers revealed the stratigraphic units of silt–clay and till sequence down to 3.5 m depth which are consistent with the surficial geology of the study area.ConclusionsThese results validate the use of multiple geophysical methods for extrapolating soil properties and mapping stratigraphic structures at land-lake interfaces, thereby providing the missing information required to improve the earth system model (ESM) of coastal interfaces.

Deciphering silver nanoparticles perturbation effects and risks for soil enzymes worldwide: Insights from machine learning and soil property integration

Globally extensive research into how silver nanoparticles (AgNPs) affect enzyme activity in soils with differing properties has been limited by cost-prohibitive sampling. In this study, customized machine learning (ML) was used to extract data patterns from complex research, with a hit rate of Random Forest > Multiple Imputation by Chained Equations > Decision Tree > K-Nearest Neighbors. Results showed that soil properties played a pivotal role in determining AgNPs’ effect on soil enzymes, with the order being pH > organic matter (OM) > soil texture ≈ cation exchange capacity (CEC). Notably, soil enzyme activity was more sensitive to AgNPs in acidic soil (pH < 5.5), while elevated OM content (>1.9 %) attenuated AgNPs toxicity. Compared to soil acidification, reducing soil OM content is more detrimental in exacerbating AgNPs’ toxicity and it emerged that clay particles were deemed effective in curbing their toxicity. Meanwhile sand particles played a very different role, and a sandy soil sample at > 40 % of the water holding capacity (WHC), amplified the toxicity of AgNPs. Perturbation mapping of how soil texture alters enzyme activity under AgNPs exposure was generated, where soils with sand (45–65 %), silt (< 22 %), and clay (35–55 %) exhibited even higher probability of positive effects of AgNPs. The average calculation results indicate the sandy clay loam (75.6 %), clay (74.8 %), silt clay (65.8 %), and sandy clay (55.9 %) texture soil demonstrate less AgNPs inhibition effect. The results herein advance the prediction of the effect of AgNPs on soil enzymes globally and determine the soil types that are more sensitive to AgNPs worldwide.

Construction of Buildings in Soft Clay Deposits: A Case Study in a Public School in Florianópolis/SC, Brazil

The gradual increase in the risks of constructions without structural planning in hillside areas characterizes the expansion of urbanization in Brazil. In this process of territorial occupation, constructions on soft clay soils represent significant structural hazards. This study aimed to evaluate structural instabilities in a public school in Florianópolis (SC, Brazil), using integrated geology, geotechnics, and geophysics data. This is a case study in an area characterized by the urbanization process of the West Side of the Costeira do Pirajubaé Massif. Geologically, the study area is composed of granitic rocks, soft clay deposits, and colluvial soils, in an environment of the upper third to the middle of the slope. For data analysis, geophysical, geotechnical, and geological methods were used. In the results, it was identified upstream colluvium, evidenced by the wide variety of soils (sandy, yellowish silt clay, of medium consistency), as well as gray clay deposits, ranging from very soft to hard, with distinct characteristics of the residual soils of the granitoid downstream, which are normally medium consistency brown to yellowish clays, expected for the B horizon. The results indicate a potential slip surface, which corresponds to a layer of soft clay deposits. Thus, it can be concluded that the observed instabilities, characterized by footing displacement, cracks, and subsidence demonstrate subsoil fragilities related to human interventions and the insufficiency of the drainage system, even when existing.

Enhancing Soil Aggregation and Organic Carbon Retention in Greenhouse Vegetable Production through Reductive Soil Disinfestation with Straw and Fertiliser: A Comprehensive Study

In greenhouse vegetable production, reductive soil disinfestation (RSD) effectively mitigates soil-borne diseases, yet its impact on the dynamics of soil organic carbon (SOC) has not been adequately examined. This study investigated the distribution of soil aggregates and the organic carbon retention mechanism following intensive RSD treatment. Greenhouse experiments, including control (CK), wheat straw (RSD), and wheat straw with chemical fertilizer (RSD + NP) treatments, indicated augmentation in the formation of macro-aggregates (&gt;2 mm and 0.25–2 mm) under RSD, particularly in the RSD + NP treatment. Silty clay particles transform into macro- and micro-aggregates. Fourier infrared spectroscopy highlighted the augmentation of carbon-containing functional groups in SOC, with aliphatic carbon accumulating in macro-aggregates and aromatic carbon in silt clay. Laboratory culture experiments employing different C/N ratios (RSD1 with wheat straw, RSD2 with kiwifruit branches) underscored the beneficial impact of low C/N ratio organic matter on coarse and fine macro-aggregate content, mean weight diameter, geometric mean diameter, and reduced silt clay. Low C/N ratios enhance SOC retention in large aggregates, while high ratios stabilise micro-aggregate carbon. This research underscores the severe degradation in continuous greenhouse cropping systems and emphasises RSD’s dual benefits—disease prevention and improved SOC retention. Implementing RSD requires careful consideration of organic material choices, specifically their C/N ratios, as a pivotal factor influencing SOC dynamics.

Effect of Adding Chelated Zinc and Vermicompost on Some Indicators of Maize Growth

A field experiment was conducted for the fall season 2022 to grow a crop of yellow corn, zea mzys, class F1, in the Kala Agriculture field of the University of Babylon, in silt clay. The study included an investigation of the effect of adding chelated zinc and Vermicompost and the interaction between them on the growth indicators of maize, Where it included three levels of chelated zinc fertilizer (0, 5, 10) kg.H-1 and symbolized by symbols (Zn0, Zn1, Zn2) respectively for the first factor, while the second factor was the addition of Vermicompost with three levels (0, 10, 20) ton.H-1 and symbolized by the symbols (F0, F1, F2), respectively, and thus the number of transactions became 9 by 3 replications, so the number of experimental units became 27 experimental units. The experiment was carried out according to the RCBD random sectors design. The addition of chelated zinc to the Zn2 treatment gave the highest increase in the vegetative growth characteristics of plant height, chlorophyll index, leaf area, and dry weight of the vegetative total, as the values reached 189.60 cm, 53.92 Spad unit, 56.53 dm2, and 4.86 tons H-1 for each respectively. The addition of Vermicompost to treatment F2 gave the highest increase in vegetative growth indicators for each of the plant height 186.39 cm, chlorophyll index 50.75 spad unit, leaf area 52.87 dm2, and dry weight of the vegetative total 4.88 tons H-1. The dual interaction of chelated zinc and Vermicompost for Zn2F2 treatment gave the highest increase in the growth indicators of yellow corn represented by plant height, chlorophyll index, leaf area, shoot dry weight.

Model of Soil Particles to Investigate Shear Stress and Deformation in Silt Loam and Silt Clay Soil Using Finite Element Method

Model of Soil Particles to Investigate Shear Stress and Deformation in Silt Loam and Silt Clay Soil Using Finite Element Method

Estimation of fine sediment stocks in gravel bed rivers including the sand fraction

ABSTRACTFine sediment stored in the gravel bed is an important component of river systems. Current field protocols usually allow evaluation of the silt–clay fraction of fine sediment stocks only and neglect the sand fraction. This study proposes a new protocol to quantify fine sediment stocks, including the sand fraction inside the gravel bed matrix. Fine sediment stocks were sampled within patches of 0.30 m × 0.30 m on the dry gravel bed surface, separating the surface layer and the subsurface layer. The grain‐size distribution of the samples was obtained by field sieving (10 mm, 2 mm, 500 μm and 100 μm) over a bucket, using a known volume of water. The mass of the fraction below 100 μm was measured based on the concentration within the bucket. The local stocks were then integrated over the whole river reach by assigning local stocks to facies, in which fine sediment stocks were assumed to be homogeneously distributed. The methodology was applied to a 1 km long reach of the River Galabre (Southern French Alps), characterized by significant fine sediment stocks and upstream sediment input. Results from local measurements show a large amount of sand in both surface and subsurface layers. The quantity of sand can reach up to three times the quantity of silt–clay. An estimation of porosity showed that fine material may play an important role in structuring the bed, since porosity increases with increasing fine sediment content. The potential fine sediment stock that can be resuspended due to channel migration is found to be of the same order of magnitude as the sediment budget estimated from the measured flux in the upstream hydrometric station of the studied reach.

Monitoring the Water Quality of the Tigris River and Producing Maps to Determine the Locations of Turbidity in the Water for the Year 2022 in Baghdad Governorate

Abstract Interest has recently increased in the sustainable development of the natural resources of the land cover, including the water resources stored in natural catchments such as lakes and marshes and flowing from the sources to the rivers, and in increasing human activities from cultivating and fertilizing the land, to establishing factories and throwing industrial waste into rivers to throwing bore water in addition to Clay silt as a result of weathering and erosion of the soil. The purpose of the study is to monitor and determine the quality of the Tigris River water from turbidity, industrial waste and the rest of the materials that pollute the Tigris River. The section of the Tigris River passing through the city of Baghdad was selected as a sample for the study, and the data were used. Remote sensing techniques in the investigation of the polluted area in the Tigris River in Baghdad. The Landsat 8 (OLI) image of Baghdad was used as the best sensor to measure the spectral reflectivity of land features, including water, with a spatial resolution of 30 m on October 18, 2020. The Arc GIS v10.8 application software package was used to process the image data and measure the normalized turbidity index using the green band (3) and the red band (4). Turbidity was calculated using Normalized Difference Turbidity Index (NDTI), and then classified based on the high and low values of (NDTI). The results indicated that three categories of water quality succeeded in assessing and mapping the turbidity of the water that pollutes the Tigris River. The study is worthwhile. I can be deal with the rest of the pollutants using remote sensing data as the best technology and results at the fastest costs.

Identification of interbedded gas hydrate and free gas using amplitude versus offset forward modelling

AbstractThe complex contacts between gas hydrate and free gas have been confirmed by gas hydrate pilot production in the Pearl River Mouth Basin, South China Sea. The laminated clay silt reservoirs have high amplitude reflections which may be filled with different saturations of gas hydrates, free gas and the coexistence between gas hydrate and free gas. To distinguish the variations of amplitude reflections caused by different reservoirs properties below the bottom simulating reflection, we combine the forward modelling, pre‐stack gathers with different incident angles and well log analysis to conduct the seismic responses. A number of geological models are established with variable saturations and different interfaces between gas hydrate and free gas. First, we analyse the seismic and well log responses at Sites W11, W01 and W17 near the production test area. Then, we perform the forward modelling to quantify the differences among seismic reflections with different saturations, thickness, incident angles and strata dips in free gas‐ or gas hydrate‐bearing geological models. We extract the seismic amplitudes along the bottom simulating reflection and other layers to compare with the amplitudes generated from forward modelling. The results indicate that the inclined intervals below the bottom simulating reflection have high amplitude, continuous reflection and polarity reversal which may be caused by thin gas reservoir and the interlayered gas hydrate and free gas with different saturations. The top interfaces of the gas hydrate‐ and free gas‐bearing layers show typical Class III amplitude versus offset and exhibit high amplitude reflections at seismic data with near, mid and far‐incident angles, which are easy to distinguish. Seismic response of far‐incident angle can be used to identify the coexistence of gas hydrate and free gas.

Effects of the Properties of Fines on the Pore Water Pressure Generation Characteristics of Sand–Silt–Clay Mixtures during Cyclic Loading

To investigate the effects of the properties of plastic fines on the pore water pressure generation characteristics of fine-grained soils during cyclic loadings, we used 29 sets of test data from the literature and prepared another 21 reconstituted specimens with different types of fines and fine contents (FCs) for cyclic triaxial testing. Two types of undisturbed soil specimens and three types of reconstituted soil specimens were also included for testing. The results indicated that under cyclic loading, the pore water pressure (PWP) ratios of clean sands increased slowly, stagnated, then finally accelerated until initial liquefaction, whereas those of the plastic soils containing fines with a plastic index (PI) value of &gt;5 increased sharply in the initial stage. In addition, the cyclic stress ratio of specimens containing mudstone (PI = 12.4) and kaolinite (PI = 32.0) fines increased by 1.5–3.0 times more than non-plastic fines if the cyclic number chosen was 100. The range of the upper and lower limits of the PWP curves of the specimens with an FC of 30% were smaller that of the limits of the PWP curves of the specimens with an FC of 15%. The above results were further analyzed using a mathematical model. This paper systematically uses both the literature and laboratory test data to demonstrate that plastic fines and non-plastic fines have significantly different effects on water pressure generation under cyclic loading conditions, and a mathematical model also demonstrated the same trends. These findings are able to clarify previous unclear arguments. Thus, the model results developed in this study could also provide the field of engineering with a complete advanced calculation, requiring analysis only via software.

Afforestation Influences Soil Aggregate Stability by Regulating Aggregate Transformation in Karst Rocky Desertification Areas

Surface vegetation has a substantial impact on soil aggregate stability, which is an important indicator of soil quality. However, there is still limited research on the response of soil aggregate stability indicators and the organic carbon, total nitrogen, and total phosphorus content in soil aggregates for different vegetation patterns in rocky desertification fragile ecological areas. Therefore, in order to study the effects of different vegetation restoration models on soil aggregate stability and aggregate related nutrient content and their promoting relationships in the karst rocky desertification areas in southwest China, soil samples under three artificial restoration vegetation measures (Juglans regia L.-Rosa roxburghii Tratt., Rosa roxburghii Tratt.-Lolium perenne L., Juglans regia L.-Lolium perenne L.) were collected in 0–10 cm and 10–20 cm soil, and the traditional farmland (Zea mays L.) was used as the control, combined with dry and wet sieving experiments for the research and analysis. The results showed that there were significant differences in the distribution of aggregates and soil nutrients among the four types of plots. Compared with traditional agricultural land, artificial afforestation increased the content of soil large macroaggregates (LMAs) and decreased the proportion of microaggregates (MIAs) and silt+clay (SCA), which enhanced the soil aggregate stability and reduced the soil fragmentation and erodibility. The afforestation restoration increased the content of soil aggregate-related SOC, TN, and TP, and increased with the decrease in the aggregate particle size. Research has found that soil aggregate stability indicators are significantly influenced by the particle size distribution of soil aggregates. In the positive succession process of vegetation types, soil nutrient accumulation is controlled by changes in the soil aggregate particle size, which affects the soil aggregate stability and reduces soil erodibility, thereby protecting the soil nutrient loss. The composite management of forest and irrigation in degraded ecological areas has certain reference and indicative significance for ecological restoration in rocky desertification areas.

Exploration of Secondary Deposit to Determine Manganese Ore Body

Manganese ore is one of the most critical mineral commodities and irreplaceable in steelmaking. With the high demand for manganese ore, exploration to find manganese ore deposits is essential before large investments in mine development. The purpose of this study is to determine the content of secondary manganese through exploration in Ladang Sungai Terah Gua Musang with an area of 40.5 hectares. The area is located near the Permian -dominated zone which can be observed during plutonic igneous granites in the southwest and in the presence of phyllite, slate and shale with subordinate sandstone and schist. The significant secondary mineral found is manganese oxide or pyrolusite. The exploration method is by excavating the trial pit (TP) and bore hole (BH) drilling. The location of TP and BH are determined from anomalies data and outcrop and boulders presence at site. Results that obtained from the thirteen TP sampling showed that the deepest TPs are excavated at 4.0 meter depth and the shallowest depth was at 3.6 meter depth. The thickest manganese ore was at 0.4 meter for TP 06. The highest-grade manganese was 54.3% at 3.8 meter depth of TP 01 located at north-west from BH1. The BH soil which obtained at 12.0 meter depth with silt clay and the presence of sand gravel. The BH soil was taken and homogenised prior testing in order to get representative result. The XRF analysis shown that the manganese ore was found at 55.90 % and second highest mineral was silica oxide which was 21.74 % followed by aluminium at 14.32 %. The calculation of manganese ore reserves was estimated at 157,545 tonnes of which the lifespan of manganese mining operations was estimated at only 10.375 months. Even the quality was high but it still not reaching the ore body It can be concluded that this area is not economical for commercial production of manganese ore and by pursuing this area will surely contribute to business risks, negatively impacting on potential profitability. Mining revenue calculated from estimated ore reserved in this area is not expected to cover costs such as the exploration working capital, property acquisition costs, mine development costs including development drilling and infrastructure development such as roads, utilities, plant and equipment costs which include mining equipment, mill and processing equipment and building, structure and many more.