Undisturbed Samples Research Articles

Constraints of chemical and physical properties of soil on the growth of revegetation plants on ex-nickel mining land

The chemical and physical properties of soil as a planting medium in ex-mining land reclamation areas play an important role in supporting successful revegetation. This study aims to study the properties of soils in the reclamation area of a former nickel mine which is thought to be a factor inhibiting plant growth. Undisturbed and disturbed soil samples were taken in the reclamation area and the natural environment at depths of 0-30 cm and 30-60 cm. Soil sample analysis includes pH, organic C, total N, available P and potential P reserve, cation exchange capacity (CEC), base saturation, micronutrients, texture, bulk density, permeability, and pF curve. Soil biological properties are represented by the number of mycorrhiza parameters. Several plant leaf samples were also taken for analysis of N P K Ca Mg S and micronutrient content. The results showed that the soil in the reclamation area has several anomalous properties that cause the growth of revegetation plants to be hampered, i.e. the soil pH is slightly acidic to neutral, the CEC is very low due to a positive net charge, the exchangeable Ca/Mg ratio is less than 1, the levels of elements that are potentially toxic to plants are quite high, and the distribution of soil particles is dominated by silty size. These properties are closely related to iron oxides in the soil as a result of chemical weathering of ferromagnesian minerals contained in ultramafic rocks which are the parent material of the soil.

Estimating the soil water retention curve by the HYPROP-WP4C system, HYPROP-based PCNN-PTF and inverse modeling using HYDRUS-1D

Due to the difficulty of direct field measurement, soil hydraulic properties are often obtained in laboratory settings using small undisturbed soil samples or estimated indirectly through pedotransfer functions (PTFs). The pseudo-continuous pedotransfer function (PCNN-PTF) is a neural network-based approach for estimating soil hydraulic properties. The main objective of this study was to use field soil moisture and tension data to assess soil water retention curves obtained from the HYPROP-WP4C system and the HYPROP-based PCNN-PTF. The in-situ soil water retention data were simultaneously acquired using Acclima TDT and MeterGroup MPS-6 sensors (every 30 min, May to September 2020) from 11 hybrid bermudagrass plots under different irrigation treatments in Riverside, California. We utilized extended evaporation and dewpoint methods using HYPROP-WP4C (Meter Group Inc., USA) devices to obtain lab-measured SWRCs. In addition, SWRCs were estimated from Rosetta (Schaap et al., 2001) and by inverse modeling in HYDRUS-1D utilizing in-situ moisture retention data. Although the hysteresis impacted field data, overall, there was a good agreement between the in-situ and lab water retention data for most samples, especially within the pF range of 2–3.5. The PCNN-PTF outperformed Rosetta in estimating laboratory (RMSE=0.034 cm3 cm−3 vs 0.063 cm3 cm−3) and in-situ soil moisture data (RMSE=0.048 cm3 cm−3 vs 0.082 cm3 cm−3). Inverse modeling of in-situ data also performed well in estimating the SWRC (RMSE=0.043 cm3 cm−3); however, further attention is required in dry and saturated soil conditions. We developed a simple, free, and easy-to-access tool called PC-PTF for estimating the SWRC using the PCNN-PTF model evaluated in this study. The PC-PTF can be accessed from the Verdi Water Management Group website: http://www.ucrwater.com/software-and-tools.html.

Clay mineral composition drives soil structure behavior and the associated physical properties in Brazilian Oxisols

Soil aggregation controls several physical, chemical, and biological processes. Soil organic matter (SOM) and its stabilizing agents are regarded as the most important factors driving formation and stabilization of soil aggregates. However, aggregate stability in highly weathered soils may also be related to clay mineral composition and soil chemical properties. This study aims to evaluate the processes controlling soil aggregate stability and to understand the influence of soil chemical and clay mineral composition on the structural stability of highly weathered soils. Four Brazilian Oxisols were investigated: (P1) Xanthic Kandiustox, (P2) Rhodic Haplustox, (P3) Anionic Acrustox, and (P4) Typic Hapludox. Undisturbed and disturbed soil samples were collected from the Bw horizon under a native forest. Soil structural stability was evaluated using a variety of techniques and indices, including mean weight diameter (MWD) by hydraulic stress, mechanically-dispersible clay (MDC) by turbidimetry, tensile strength (TS) by crushing aggregates, and soil structural stability index (SSI) taking into account soil organic carbon (SOC). In general, P1 exhibited the highest MDC content (3.05 ± 0.54, Nephelometric Turbidity Unit, NTU/g L‐−1), while P4 had the highest MWD (10.26 ± 0.24 mm) and the highest TS (80.42 ± 18.54 kPa) within the 8–4 mm aggregate size class. The TS for the 4–2 mm and 2–1 mm aggregate size classes was found to be equal for P2 and P4, with values ranging from 158.17 ± 24.70 kPa to 148.04 ± 38.50 kPa in the 4–2 mm class, and from 459.51 ± 189 kPa to 328.35 ± 78.22 kPa in the 2–1 mm one. The SSI was found to be inadequate for evaluating the structural stability of the Oxisols. In general, SOC was found to be the main stabilizing agent of larger aggregates, while clay mineral composition determined the stability of smaller aggregates. Goethite associated with gibbsite was more effective in increasing the structural stability of P2 and P4. Furthermore, kaolinites with low crystallinity, which are found in clayey Oxisols, resulted in a high specific surface area, particularly in Rhodic Haplustox and Typic Hapludox soils, which promoted more interactions with other clay minerals (e.g., goethite and gibbsite) and SOC, thereby increasing the tensile strength in these Oxisols. In fact, the formation and stabilization of aggregates in highly weathered soils depends on several factors, but the influence of clay mineral composition stands out as the most pronounced.

Compilation of Consolidation Properties Data of Champlain Sea Clay from Ottawa Region

Estimation of consolidation settlements in fine-grained soils due to various civil infrastructure loads is traditionally based on results derived from consolidation tests performed on undisturbed soil samples, combined with the data of other soil properties. In many geotechnical engineering applications, consolidation settlements are also estimated using empirical consolidation parameters derived from basic soil properties. This approach relies on correlations from the literature to bypass the time-consuming and expensive sampling techniques, laboratory testing, and other associated expenses. However, these correlations may not provide reasonable consolidation settlement estimations as these correlations are typically developed without considering the influence of stress history, geology, salinity of pore water, gradation, soil fabric, and chemical properties of the soils. This is especially true for Champlain Sea clay deposits from Eastern Ontario region of Canada that are typically with heterogeneous site conditions and exhibit spatial variability of soil properties. In this paper, data from the published literature and industrial and government reports on sensitive Champlain Sea clays were gathered for the Ottawa region. The data collection and clean-up methodology towards enhancing the reliability of the gathered data is comprehensively discussed. The summarized data from this study can be used with a greater degree of confidence towards developing reliable correlations in the estimation of consolidation settlements in geotechnical engineering practice.

Soil hydro-physical variables and crop residues determinate runoff, soil loss, and glyphosate and AMPA concentration in the aqueous phase under simulated rainfall events.

Soil structural degradation and water erosion processes were observed even in no-tillage schemes in the Pampas region. Within these conservation systems, agrochemical application per hectare is one of the highest globally. Thus, this entails a serious risk of water contamination. The objectives of this study were to (1) test the hypothesis that the hydrological dynamics and sediment concentration related to surface runoff were conditioned by soil structure regardless of the presence of maize (Zea mays L.) crop residue and (2) assess the incidence of maize crop residue on glyphosate and aminomethylphosphonic acid (AMPA) concentration in runoff. The soil under study corresponded to Arroyo Dulce Series (Typic Argiudoll silty loam soil). Rain simulations were performed in the laboratory on undisturbed soil samples. Total runoff and infiltration rate were similar between treatments with C(+) and without C(-) maize crop residues (C(+) 1381.40mL and 14.27mm h-1, C(-): 1529.70mL and 21.67mm h-1). The C(-) treatments showed a higher sediment concentration than C(+) (1.58 and 0.42g 100mL-1, respectively). Glyphosate and AMPA average values in runoff were 15.9 and 33.9µg L-1. High variability of the hydro-physical properties and occurrence of soil structure, particularly platy ones, were detected. The hydrological variables were conditioned mainly by the occurrence of platy structures regardless of crop residue presence. Glyphosate concentration was increased in the first runoff event by the presence of corn residues, while AMPA concentrations were higher in the second runoff event in both residue treatments. In this study, maize residue on the soil surface protected the soil from sediment detachment but did not change runoff or infiltration. Thus, the implementation of agricultural management practices that promote vegetative residue cover has shown positive results to erosion.

Variations in pore structures and permeabilities of ion adsorption rare earth ores during simulated in-situ leaching: Effect of newly formed clay particles and their swelling

In-situ leaching is essential for mining rare earth elements (REEs) from ion-adsorption rare earth (RE) ores. The efficiency of RE mining is dependent on the permeabilities of ion-adsorption RE ores, and the permeabilities are controlled by their pore structures. However, the current understanding of the pore structures and permeabilities of the RE ores during leaching is limited, particularly their dynamic variations, the controlling roles of different pore structure parameters on the permeability, the roles of the influencing factors and the mechanisms causing the variations. To investigate the above-mentioned issues, we conducted an experimental study of simulated in-situ leaching on undisturbed ion-adsorption RE ore samples under different conditions via constant waterhead permeability tests. The leaching conditions included leaching time, concentration and waterhead of the (NH4)2SO4 solution. Three-dimensional (3-D) pore structures of the RE ores before, during, and after leaching were constructed via X-ray computed tomography, and their pore structure parameters were measured using 3-D image computation. It was observed that the dynamic variations in both the pore structure parameters and permeability coefficients of the RE ores occurred in three distinct stages: rapid reduction, less rapid reduction, and little reduction. The experimental results also revealed that the permeability coefficients of the RE ores were primarily dependent on the average coordination number among the seven pore structure parameters examined, and that the pore throats larger than 30 μm in diameter served as the most effective seepage channels within the RE ores. The waterhead of the leaching solution had a stronger influence on the variations in pore structures and permeabilities compared to that of the concentration. Analysis of the particle/aggregate size distribution and mineralogical compositions of the RE ores before and after leaching indicated that the decreases in the pore structure parameters and permeabilities were largely attributed to clogging of the pore throats and pores by migrated and newly formed clays, as well as swelling of the latter. The newly formed clays were the products of the decomposition of K-feldspar and mica resulting from chemical reactions with the leaching solution. The clays from the two sources occurred in disaggregated and aggregated forms. The results of this study provide an important reference for the mining of RE ores via leaching.

How does soil water retention change over time? A three‐year field study under several production systems

AbstractAgricultural practices and meteorological conditions affect soil structure and soil hydraulic properties. However, their temporal evolution is rarely studied, and even less in the field. Thus, their dynamics are rarely taken into account in models, often leading to inconsistent results and poor decision making. In this study, the temporal evolution of water retention properties and soil structure was monitored over a 3‐year period under several contrasting production systems. Soil Water Retention Curves (SWRCs) obtained directly in the field (with soil water content and potential sensors) were compared with theoretical SWRCs predicted by pedotransfer functions (PTFs) and laboratory SWRCs measured on undisturbed samples. Bulk densities were measured every 2 months. Results indicate a high degree of variability in SWRCs over time and between production systems. The results suggest that variations in the soil water retention behaviour can be induced by crop differentiation, weed control, crop residue management, compaction during harvest, or the introduction of temporary grassland. Contrasting climatic conditions between 2021 (water excess), 2022 (severe drought) and 2023 (intermediate) provided a unique opportunity to study the resilience of the crop systems to extreme climatic conditions. Different soil drying dynamics were observed and some agricultural practices were identified as influencing the soil water retention behaviour for at least 2 years. Comparison of SWRCs showed that the theoretical curves obtained from PTFs are not a good representation of the field SWRCs, especially for less conventional agricultural practices. The laboratory curves are closer with similar trends. However, these SWRCs are not optimal for investigating the temporal evolution of water retention properties. This research also shows that agricultural practices and crops can be levers for contributing to greater food resilience against future climatic conditions. Therefore, to assess the relevance of production systems for tomorrow's needs, studies should focus on the impact of multi‐cropping systems on water retention dynamics in the field.

KAJIAN STUDI GEOTEKNIK KLASIFIKASI TANAH PERMUKAAN UNTUK PERENCANAAN PEMBANGUNAN DIKAWASAN UNIVERSITAS SAMUDRA

Soil classification is a science that aims to study ways to differentiate soil properties and divide soil into classes based on general characteristics. The aim of this research is to determine the physical properties of the land surface and determine the classification of surface land in the Samudra University area to be mapped based on soil type using ArcGis. 38 undisturbed soil samples were taken using a hand drill and 38 soil samples were tested in the laboratory to determine the physical properties of the soil and to map research results for surface soil types using Arcgis with the kriging interpolation method. From the test results, the lowest water content was at point 35 with a value of 4 55% and the highest was at point 5 with a value of 62 64%. The lowest liquid limit was at point 1 with a value of 15 65% and the highest was at point 13 with a value of 47 99% and the lowest plasticity index was at point 5 with a value of 5 70% and the highest at point 3 with a value of 26 93% while the lowest filter analysis was at points 10 and 12 with a value of 0% and the highest was at point 5 with a value of 40 74%. From the research results, it was concluded that the soil types in the Ocean University area received 7 classification groups based on AASHTO with the most dominant group being group A.2-6 with 19 points.

Hydraulic Properties Within the Complete Moisture Range of Hydric Soil on the Tibetan Plateau

AbstractThe Tibetan Plateau is well‐known for its expansive wetland environments. Hydric soils, a fundamental component of these environments, exhibit diverse hydraulic characteristics attributable to their varied botanical and mineralogical composition and their inherent porous structures. Nonetheless, research on the hydraulic properties of such soils in Tibet remains notably underrepresented relative to European and Canadian regions. Consequently, in this study, we evaluate the effectiveness of different unsaturated hydraulic schemes in equilibrium and examine the parameter uncertainty of 14 undisturbed samples collected from four soligenous wetlands. The findings suggest that both the van Genuchten and Kosugi functions, when integrated with the Peters‐Iden‐Durner (PDI) model, yield a nearly consistent fit to experimental observations and demonstrate strong identifiability of parameters. This indicates that the PDI model can accurately characterize hydraulic properties across the complete moisture range of hydric soils. Analysis of samples with a low clay content and no sphagnum suggests that the intertwined, twisted, and hollow residues of herbaceous vascular tissues do not create a distinct, independent macro‐pore system. Therefore, the unimodal scheme integrating the PDI model is adequate. However, for samples that exhibit nonmonotonicity of the first‐order derivative of the retention curve, such as uncompacted samples containing sphagnum or samples rich in clay, the integration of the PDI model into the bimodal scheme boosts accuracy while having almost negligible impact on identifiability. The varied observed hydraulic properties of only 14 samples underscore the necessity for extensive hydric‐soil sampling and hydraulic analysis across the expansive and varied wetland landscapes on the Tibetan Plateau.

RELIABILITY OF GUELPH PERMEAMETER FOR DETERMINING THE LINERS HYDRAULIC CONDUCTIVITY

The aim of this study is to evaluate whether the Guelph permeameter can be effectively used as a quick and reliable instrument to measure the hydraulic conductivity of compacted mineral liners. The investigation was carried out on two distinct areas of the final capping of a municipal solid waste landfill in Italy. On the first test site, hydraulic conductivity tests were performed using the Guelph permeameter, assessing reliability and repeatability of test results. On the second one, many undisturbed soil samples were taken and tested in the laboratory using a modified oedometric apparatus as a falling-head permeameter. Further hydraulic conductivity tests with Guelph permeameter were also performed in the holes made by soil sampling. The campaign was integrated with in situ density tests using the calibrated sand method, to check the uniformity of the compaction degree of liners. A final comparison between hydraulic conductivity obtained in situ and in the laboratory was proposed and critically analysed. The experiments performed on the two test sites with the Guelph permeameter and their statistical processing demonstrate that the instrument is not only economical and easy to use, but also reliable if used with appropriate precautions.

Estimation of Consolidation and Settlement Characteristics of Madhupur Clay Formation from Dhaka City and Adjacent Area (Savar), Bangladesh

Pleistocene Madhupur Clay covers mostly the investigated region including Dhaka and the surrounding area (Savar). Without knowing the consolidation characteristics and settlement of this Clay, it is difficult for any construction sites to build infrastructure. In Bangladesh, the research on this parameter is limited hence for better understanding the consolidation and settlement behavior of Madhupur Clay samples in this area, a detail investigation is carried out by conducting one dimensional consolidation test. The undisturbed samples, Pleistocene Madhupur Clay and the fill materials which are also partly composed of the Madhupur Clay, are collected from 2.4 m to 4.11 m depths of many distinct points. The compression index Cc and coefficient of compressibility, av of the samples are range from 0.073 to 0.23 and from 0.059 to 0.14m2/mn respectively. The values recommend that both types of specimens are medium plastic clay. The Madhupur Clay are stiff consolidated clay and slightly compressible in nature whereas the Madhupur Clay fill samples are less stiff over consolidated and moderately compressible in nature. Fill samples are settled more with time and are not suitable for Shallow foundation of light or heavy infrastructure. However, the Madhupur Clay samples are only appropriate for light infrastructure foundation. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 27-39

Carbon leaching from peat soils of the north of Western Siberia under different hydrological conditions

Frozen peat soils in the north of Western Siberia are vulnerable to the on-going climate changes. The increase in temperature which affects the permafrost thaw returns the huge carbon stocks to the global element cycle. Its export in the form of dissolved organic matter from peatlands is determined by a number of factors, among which hydrological conditions are the least studied. The influence of hydrological regimes on carbon export from oligotrophic peat soils in discontinuous permafrost zone was investigated in laboratory conditions. The model column experiment allowed estimating the carbon yield from undisturbed (monolithic) peat samples of different degrees of decomposition. Three types of mesocosms were considered: undisturbed samples of the TO horizon, as well as the TO horizon with underlying material of different texture (sand and loam). The concentration of dissolved organic carbon in the lysimetric waters of a fibric peat does not differ for the “precipitation” and “snowmelt” simulating modes, and in the “stagnation” mode it is 1.4 times less. Sapric peat lysimetric waters show no differences under simulating hydrological regimes. The total export of organic carbon for three successive extractions for fibric peat is 32% higher than for sapric peat. An increase in carbon in the sandy material after three cycles of the experiment was revealed, the loamy material did not show significant differences. The carbon adsorption by mineral soil layers of the study area can be a protective mechanism that prevents increased runoff from the soils.

Analisis Perubahan Volume pada Timbunan Tanah Lempung Berdasarkan Nilai Batas Susut (SNI 3422:2008)

Sedimentation has continuously resulted in siltation of the port of Pelabuhan Perikanan Samudera (PPS) Lampulo located in Kuta Alam District, Banda Aceh City. The dredged soil collected outside the port area visually indicates clay soil. In addition to the low bearing capacity and high plasticity, the effect of water on clay is high swelling and shrinkage. One of the prominent behaviors that cause major damage to structures built on clay is associated with volume decrease i.e., shrinkage in saturated compressible clay soil when water get evaporated. Shrinkage in clay will result in volume changes. The purpose of this research is to calculate the volume changes in mound of clay soil based on shrinkage limit values using SNI 3422:2008. The soil sample used is an undisturbed sample (UDS) originating from the dredging area of the port of PPS Lampulo. The test consists of water content, specific gravity, liquid limit, plastic limit, shrinkage limit and grain size distribution using the SNI method. Based on the results of the index properties test, according to AASHTO the soil sample belongs to group A-7-5 which means it is a clay soil with a GI value greater than 20, so it is considered poor as a subgrade soil. According to USCS, the soil belongs to the CH classification, which means clay soil with high plasticity, so it has a large potential for expansion and shrinkage. Based on SNI 3422:2008, the average shrinkage limit (SL) is 21.21%, the average shrinkage ratio (R) is 2.27% and the average linear shrinkage (LS) is 9.65%. With an average volume change (VC) value of 35.59%, the shrinkage volume of soil embankment of the dredging area of the port of PPS Lampulo is 32,438.85 m3 compared to its initial volume (91,145.97 m3). Therefore, the shrinkage limit is an important parameter for calculating the volume shrinkage in mound of soil due to the soil type is clay with high plasticity.

Impact of roots on the shear strength of root-reinforced soil on slopes

Abstract Tropical countries generally receive high rainfall throughout the year causing high runoff, wet soils and erosion. Undulating terrain from continuing erosion and frequent occurrences of landslides are the features of topographic evolution under such hydrological conditions. Vegetation is the only natural supporting factor that mitigates both erosion and landslides. It contributes to controlling soil erosion and strengthening of the soil by forming a mesh of roots at the surface. The objective of this study is to quantify soil strength on slopes when there is a presence of roots. Undisturbed samples were taken from two different depths of soil. The exact depth and distance varied slightly to avoid large roots and large gravel particles present in the natural environment. Immediately after sampling, the triaxial tests were performed under unconsolidated and undrained conditions. Subsequently, the tested samples were crushed carefully, to manually recover all roots and to classify the soil. From this study, it was observed that the presence of root fibres within the soil matrix has enhanced the soil strength through a binding action in the fibre-soil composite. The correlation between root content and shear strength is prominent near the surface and becomes less obvious in deeper soil layers when the root concentration becomes more sparsely distributed.

Utilizing undisturbed soil sampling approach to predict elastic modulus of cohesive soils: a Gaussian process regression model

Utilizing undisturbed soil sampling approach to predict elastic modulus of cohesive soils: a Gaussian process regression model

Assessing the impact of sample size and geology on earthen embankment design and construction

This technical paper investigates the influence of sample size and geologic characteristics on the geotechnical design of levee embankments. Sample quality plays a vital role in quantifying engineering properties for levee embankment projects, and numerous studies have highlighted the impact of sample disturbance on such engineering properties. Despite this evidence, conventional tube and piston samplers of different diameters continue to be widely used, potentially leading to underestimation of shear strength. The paper focuses on comparing 7.6 cm and 12.7 cm diameter undisturbed Shelby tube samples and CPT data collected from three levee sites in the Greater New Orleans Area, Louisiana, USA, which encompass diverse geologic histories. The study aims to assess the effect of industry used samples size and geology on levee construction costs. The findings provide valuable insights into optimizing sample collection methods and improving geotechnical design for earthen embankments.

Impacts of riverbed aggradation on groundwater regime in a lowland area

Abstract In this study, the influence of riverbed silting on the groundwater regime in a lowland area was investigated. The study area is situated at the Rye Island (Žitný Ostrov) in Slovakia, along the Gabčíkovo – Topoľníky canal, which is part of the drainage-irrigation canal system constructed in this locality. The Rye Island is an area with very low slope (0.25 10–4) and good climatic conditions for aquatic vegetation, therefore the canals are influenced by intensive silting processes. The spatial and temporal patterns of surface water – groundwater exchange are significantly influenced by the thickness of riverbed sediments and their permeability. The aim of this study was to evaluate the thickness and hydraulic conductivity of bed sediments in the Gabčíkovo – Topoľníky canal and to examine their influence on the groundwater – surface water interaction in the area. The hydraulic conductivity of the sediments was assessed from undisturbed samples by the falling head method. The obtained data were used for numerical simulations of groundwater heads by the TRIWACO model for different drainage and infiltration resistance conditions in the area of interest. The results of this study can support the planning of canal maintenance.

A preliminary investigation on the mechanical behaviour of a stiff Italian clay in the context of hydrogen storage

The large-scale use of renewable energy sources is closely linked to the ability to store excess energy generated during periods of overproduction for use when demand is at a peak. Storing green energy is therefore a key component in the move towards a carbon-neutral economy. Underground hydrogen storage in depleted oil and gas reservoirs may provide an efficient long-term solution. Cyclic injection and production of hydrogen alter the chemo-hydro-mechanical conditions of the reservoir and caprocks, and possible geomechanical consequences of such alterations must be preliminarily assessed for safe storage operations. This study aims at exploring the possible effects of cyclic mechanical loads, such as those that might be induced by hydrogen storage and production, on the mechanical behaviour of a clayey caprock. A series of triaxial tests, both monotonic and cyclic, were carried out on undisturbed samples of a stiff Italian clay cored from a caprock formation overlying a hydrocarbon reservoir. The results show that the material response is characterized by the distinctive stress-strain behaviour of stiff clays, with a rather high fragility, which was found to be highly dependent on the loading strain rate. During laboratory experiments conducted at frequencies larger than in situ ones, cyclic loading under stress control causes a gradual degradation of the material structure leading to the formation of a clear shear band followed by a reduction in shear strength. Eventually, failure occurs as the peak shear strength approaches the applied load. The progressive destructuration also implies a reduction in P- and S-wave propagation velocities and a significant change in the signal shape, which is therefore a promising parameter for monitoring the material degradation process.

Experimental study of the dynamic characteristics of deep silty clay in Shanghai

To investigate the dynamic properties of deep silty clay, a comprehensive set of cyclic triaxial and resonant column tests were performed on undisturbed samples of silty clay containing sand from depths reaching 54.5 m in Shanghai. This study aimed to characterize the influence of confining pressure on the stress–strain behavior, pore water pressure, and dynamic modulus of the soil. The present findings revealed that the confining pressure, which is correlated with the depth of burial, significantly influenced the soil deformation. Moreover, elevated confining pressures resulted in increased stress within the hysteresis loops, a higher initial shear modulus, and a diminished ratio of excess pore water pressure. Based on the empirical data, a refined model was formulated for the shear modulus and damping ratio as functions of the shear strain for deep silty clay in Shanghai. These insights are intended to offer a robust reference point, facilitating calibration and guiding subsequent investigations into structures situated in the deep subterranean environments of Shanghai.

Non-Linear Multivariate Analysis with Artificial Neural Network in Estimating Compression Index for Cohesive Soils of Northern Jakarta Coast

This study presents a novel application of artificial neural network (ANN) to develop a model for predicting compression index (Cc) of cohesive soils from their index properties. The model was trained using data from 347 undisturbed samples on a variety of cohesive soils from Northern Jakarta. It takes up to three variables as inputs: specific gravity (Gs), liquid limit (LL), and plastic limit (PL). The model was tested on a separate dataset of 117 samples and found to have a strong capability to predict Cc values when compared to some reference correlations. The ANN model has demonstrated good performance for each set by producing overall error of 29.6%, compared to 38.1% and 30.5% for the empirical formulas. This study shows that the application of ANN offers an essential advancement in this area, helping to overcome the limitation of conventional statistical correlation.