Sandy Silt Research Articles

New Approach for Developing Correlation of NSPT and Shear-Wave Velocity (Vs): Bantul Case Study

DOI:10.17014/ijog.9.3.395-413Predictions of ground motion levels that, under certain conditions, may cause liquefaction require a sufficient knowledge of the underlying soil characteristics. The utilization of the seismic refraction method applies measurements of the subsurface shear-wave velocities (Vs) as a representation of the properties of stiffness and soil amplification. This study, carried out in Bantul, Yogyakarta Province, Indonesia, is conducted to determine the relationship between Standard Penetration Test N values (NSPT) and Vs by using data from eighty-eight drill sites and twenty-nine seismic reflection investigations with the statistical method, namely the Statistical Gradation Approach. The new equations, developed from a power regression analysis, are applied to all soil and eight soil types: silty sand, sand, gravelly sand, clay, silt, sandy clay, clay sand, and sandy silt. The equations, proposed to predict Vs, show a strong relationship between NSPT and Vs values, which applied to other regions with the shear-wave velocity of <300 m/sec, shallow groundwater depth, and dominant sandy soil.

KAJIAN POTENSI LONGSOR LERENG GALIAN CURAM DI KELURAHAN KALUMATA KOTA TERNATE MENGGUNAKAN GEOLISTRIK

The study of the potential for landslides on steep excavation slopes in Kalumata Village, Ternate City using geoelectricity is important to do. The location of the sirtu mining excavation which tends to be steep and close to residential areas is urgent to know the type of lithology so as to facilitate recommendations for handling to be carried out. The purpose of this study was to determine the lithological composition of the material from tracks 1, 2, and 3 along the steep excavation slope using the geoelectric resistivity Sclumberger configuration method. In addition, knowing the potential for landslides that will occur if there is no handling of steep slopes. This research is a quantitative type of field research. The research location is in the formation of lahar deposits (Gtla) and pyroclastic debris (pr) deposits. Trajectory 1 dominant lithology is 17.52 m of sand, andesite rock as an interlude and on the bedrock it is characterized by large resistivity (3241 m) while the top layer is clay type overburden. The 2 lithological paths consist of overburden, sand (7.82 m), silt (10.5 m), and andesite bedrock (resistivity 2811 m). The lithology of track 3 consists of overburden, andesite, sand (16.9 m), and andesite bedrock (4575 m). Lithology that tends to landslide in the field is overburden filled with sedimentary material in the form of clay, silt, and sandy silt (resistivity 1.5-114 m). Sand lithology with a resistivity of 479-855 m is very susceptible to landslides. Another factor causing landslides is the slope of the excavation which tends to be steep (> 60o). Keywords: Kalumata Village, Sclumberger configuration, lithology, landslide, sand

Reduction of dynamic shear modulus of saturated marine sandy silt under complex stress conditions

Investigating the dynamic characteristics of seabed soil under complex vibrations or cyclic loads such as waves and earthquakes is important for analyzing the dynamic response and stability of the foundations of marine geotechnical structures. This paper presents an experimental investigation on the dynamic shear modulus (G) of saturated marine sandy silt subjected to various initial consolidation conditions and cyclic loading patterns. The initial consolidation condition is characterized by the initial effective mean principal stress P 0 ' and the stress ratio of anisotropic consolidation R 0 (= σ 1/σ 3), and the cyclic loading pattern is described quantitatively by the ellipse ratio of elliptical stress path (δ) and the orientation angle of major principal stress of linear stress path (α 0). A remarkable finding is that the maximum dynamic shear modulus G max and G/G max–γz θ curve is affected significantly by the initial consolidation condition (P 0′ or R 0) but is insensitive to changes in the cyclic loading pattern (δ and α 0). G max increases with increasing P 0′ or R 0, and the nonlinearity of the G/G max–γz θ curve decreases with increasing P 0′ or R 0. The control parameters G max and reference torsional shear strain γ r of the modified hyperbolic model usually known as the KZS model are related linearly to the synthesizing initial consolidation state parameters (P 0′/P a)(R 0)0.5 and (P 0′/P a)0.5 R 0, respectively. A wide-strain-range G evaluation method with comprehensive consideration of the initial consolidation condition and the cyclic loading pattern was established, and the applicability of the proposed method was verified.

Iodine biofortification of bean (Phaseolus vulgaris L.) and pea (Pisum sativum L.) plants cultivated in three different soils.

An important challenge for mankind today is to find a plant-based source of iodine, instead of table salt, which would provide the recommended daily dosage of iodine. The aim of this work was to study the accumulation of iodine and the physiochemical changes in bean (Phaseolus vulgaris L.) and pea (Pisum sativum L.) irrigated with iodine-containing water. Applying iodine at concentration of 0.5 mg L-1 resulted 51, 18, and 35% decrement in biomass of bean fruit, while in pea fruit, a 13% reduction and a 3 and 2% increment were observed when the plants were cultivated in sand, sandy silt, and silt, respectively. The highest iodine concentrations in the bean and pea fruits were detected in plants cultivated in silt soil with concentration of 0.5 mg I- L-1 and amounted to 1.6 and 0.4 mg kg-1, respectively. In presence of iodine at concentration of 0.5 mg L-1, the concentration of magnesium, phosphorous, manganese and iron increased in the bean fruit, while in the case of pea, at iodine concentration above 0.1 mg L-1 the uptake of these nutrients were hampered. Based on these facts, the iodized bean can be recommended as a possible food source to enhance the iodine intake.

Improved Lumped-Parameter and Numerical Modeling of Unsaturated Water Flow and Stable Water Isotopes.

Characterizing unsaturated water flow in the subsurface is a requirement for understanding effects of droughts on agricultural production or impacts of climate change on groundwater recharge. By employing an improved lumped-parameter model (LPM) approach that mimics variable flow we have interpreted stable water isotope data (δ18 O and δ2 H), taken over 3 years at a lysimeter site located in Germany. Lysimeter soil cores were characterized by sandy gravel (Ly1) and clayey sandy silt (Ly2), and both lysimeters were vegetated with maize. Results were compared with numerical simulation of unsaturated flow and stable water isotope transport using HYDRUS-1D. In addition, both approaches were extended by the consideration of preferential flow paths. Application of the extended LPM, and thus varying flow and transport parameters, substantially improved the description of stable water isotope observations in lysimeter seepage water. In general, findings obtained from the extended LPM were in good agreement to numerical modeling results. However, observations were more difficult to describe mathematically for Ly2, where the periodicity of seasonal stable water isotope fluctuation in seepage water was not fully met by numerical modeling. Furthermore, an extra isotopic upshift improved simulations for Ly2, probably controlled by stable water isotope exchange processes between mobile soil water and quasi-immobile water within stagnant zones. Finally, although LPM requires less input data compared with numerical models, both approaches achieve comparable decision-support integrity. The extended LPM approach can thus be a powerful tool for soil and groundwater management approaches.

Consecutive Application Effects of Washed Rice Water on Plant Growth, Soil Chemical Properties, Nutrient Leaching, and Soil Bacterial Population on Three Different Soil Textures over Three Planting Cycles

The benefits of washed rice water (WRW) as a plant fertilizer, particularly over a consecutive application period, are not well studied. An experiment was therefore carried out to determine: the continuous effects of applying unfermented (F0) and 3-day fermented (F3) WRW on the: (1) soil chemical properties, soil bacterial count, and the growth and plant nutrient content of a test crop, choy sum (Brassica chinensis var. parachinensis), grown on three contrasting soil textures (sandy clay loam, clay, and silt loam); (2) nutrient leaching losses from these three soils due to the continuous application of WRW; (3) crops’ improvement in water use, if any, in terms of its water productivity (WP) and water use efficiency (WUE); and (4) the relationship between soil bacterial count and plant growth parameters. The effects of F0 and F3 were compared with conventional NPK fertilizer and a control (only tap water; CON). Two factors, treatments and soil types, were used factorially in a randomized complete block design for three consecutive planting cycles. Results showed that NPK and F3 produced a significantly (p < 0.01) higher plant growth in terms of fresh and dry leaf weights and total leaf area by 5 to 61%, compared to that obtained in the other treatments. Furthermore, plants receiving either NPK or F3 had a significantly higher plant nutrient content (P, K, Ca, Mg, and Cu) in the third planting cycle. Clay soil treated with F3, NPK, and F0 had significantly higher NH4+, P, Ca, Mg, Zn, and B, by 19 to 152% relative to the other soils, irrespective of treatments. Soil nutrient leaching losses of P, K, Ca, Mg, Cu, Zn, and B decreased with successive planting cycles for all treatments. However, soils treated with either F3 or F0 experienced higher leaching of NH4+ and NO3− by 37 to 259% and 13 to 34%, respectively, relative to the NPK and CON. Plants treated with either NPK or F3 also had higher WP by 21 to 42% than the other treatments. For all the treatments, plants’ WUE increased with successive planting cycles; however, there was no significant difference between the treatments. F3 stimulated a significantly higher growth and yield of choy sum due to its nutrient and bacterial contents, and the continuous increase in plant growth with successive planting cycles indicated the carryover effects of the treatments, particularly by F3.

Field evaluation of tractor-operated seeder for sowing mat type paddy nursery

Mat-type nursery having uniform growth is a prerequisite for mechanized paddy transplanting. Generally, this type of nursery is sown manually in the open field or in trays. It requires several simultaneous operations and hence is laborious and time-consuming. The performance of tractor-operated mat-type nursery seeder was evaluated at the Research Farm of Punjab Agricultural University, Ludhiana, Punjab during 2019–20 with an objective to obtain the finest speed of operation to get the uniform seed and soil spread. Study was carried out on three different types of soil (sandy loam, loam and silt loam) for three different forward speeds (1.7, 2.2 and 2.7 km/h). Results have shown that the soil type had a non-significant effect on the performance of the machine, whereas forward speed had significant (P<0.05) effect. In overall, with an increase in forward speed of the machine, there was a reduction in uniformity for both seed and soil spread. The best results were obtained at a forward speed of 1.7 km/h with the overall seed spread of 90.93%, overall soil mat thickness 99.70%, fuel consumption 4.36 l/h and effective field capacity 0.092 ha/h. Therefore, the developed tractor-operated seeder can be operated on sandy loam to silt loam soils with a forward speed of 1.7 km/h with 59.5% saving in cost and 62.6% saving in labour for sowing mat type nursery as compared to manual method with MS frames.

Heavy vibratory plate compaction of silty sand: A field study

Heavy vibratory plate compaction is an efficient technique for improvement of granular soils. However, its practical application is limited by insufficient knowledge about the compaction process and the optimum procedure of execution. In this study, compaction tests were conducted in the field with a 40.5-ton heavy vibratory plate compactor. The site consisted of partially saturated, overconsolidated medium-dense silty sand and sandy silt. Such conditions can generally be characterized as difficult for vibratory compaction. The objective of the tests was to study the compaction depth and the influence of treatment layout, duration of compaction, and vibration frequency. In-situ measurements conducted before, during and after treatment included static cone penetration tests, flat dilatometer, and heavy dynamic probing. The in-situ tests showed a statistically significant compaction after treatment. The main conclusions highlight the importance of a sufficient centrifugal force of the vibratory hammer to cause disconnection between the plate and the soil. Other important parameters are the vibration frequency and the duration of treatment, which can be optimized by field monitoring. Full coverage of the ground surface is required for compaction of the entire soil volume. It was also found that the compaction depth corresponds to the side length of the plate, in line with previous studies.

Erosion and runoff reduction potential of vetiver grass for hill slopes: A physical model study

Severe erosion is caused by intense rainfall in tropical regions. The erodible soil of steep hill slopes, accompanied by destruction of vegetation due to human interventions results in accelerated erosion. A sustainable and cost-effective solution such as vetiver grass (Chrysopogon zizanioides) is, thus, required to control the erosion process. In the current study, 6 small-scale glass models: 1 bare and 5 with vetiver grass, having a slope angle of 37° have been constructed. One year after planting, artificial rainfall of extremely high intensity was applied to all 6 small models and the role of vetiver canopy and roots in erosion and runoff control was observed. To see the effect of soil texture, one among these 5 models was made with silty sand and others contained sandy silt. The results demonstrated that, for sandy silt, the inclusion of vetiver reduced the soil loss by 94%–97%, and soil detachment rates were lowered by 95%. The average runoff also was reduced by 21%. The canopy cover showed a positive impact on reducing both quantities. An increase in average root diameter from 1.6 to 2.5 mm increases the soil loss due to its negative impact on added cohesion. The added cohesion showed a linearly negative correlation with soil loss. A composite system of vetiver and jute geotextile was most effective in erosion reduction among 4 vegetated models with sandy silt. Under same vetiver planting layout, the grass covered model of silty sand yielded 84% lower erosion and 62.5% lower runoff than the grass covered one with sandy silt. Thus, vetiver was more effective in erosion and runoff reduction for soil with a greater percentage of sand, and soil type dominated the erosion process.

Seabed Classification Using Multibeam Echosounder Measurement Data

Multibeam Echosounder (MBES) utilizes acoustic waves emitted to the seafloor through a transmitter or transducer and records its reflective. The information obtained by MBES are depth data and the scattering value of the acoustic signal reflected by the object or the seabed, called backscatter. Acoustic backscatter can be used to classify objects or the seabed such as shipwrecks or seabed sediments. This study focuses on seabed classification using an acoustic backscatter obtained from the measurement at Alur Pelayaran Barat Surabaya (APBS). The data used in this research are acoustic backscatter from bathymetry data extraction and ground truth data of sediments. This study found the fine sand sediments with backscatter value −15.56 dB, and clayey silt sediments with backscatter value −24.36 dB. The correlations between backscatter and seabed sediments in study area were classified into four classes, clay class sediments with backscatter intensity range [(−33.81) – (−28)] dB, clayey silt class sediments with backscatter intensity range [(−27.99) – (−23)] dB, sandy silt backscatter intensity range [(−22.9) – (−18)] dB, and sand class sediments with backscatter intensity range [(−17.99) – (−10)] dB. Based on the results data are known in the study area of seabed conditions dominated by sediments type sandy silt.

Petrography and Lithogeochemistry of the Uppermost Middle Jurassic–Lowermost Lower Cretaceous Strata in the Lower Reaches of the Anabar River (East Siberia, Arctic)

Abstract —Based on the analysis of the petrographic and lithogeochemical features of the Middle Jurassic–Lower Cretaceous strata in the lower reaches of the Anabar River, we have studied the regularities of changes in the composition of the upper parts of the Yuryung-Tumus and Sodiemykha formations and the lower part of the Buolkalakh Formation. It has been established that the silt–sandy rocks of the first and basal beds of the second formation are graywacke arkoses and essentially feldspathic varieties, and most of the Sodiemykha Formation is composed of quartz–feldspathic and scarcer feldspar–quartz graywackes. A chemical classification of the rocks was made; most of them were assigned to normosiallites. The rocks of the marker beds, namely, the Fe-containing deposits of the Sodiemykha Formation, the basal glauconite bed of the Buolkalakh Formation, and the overlying clay bed, were classified as hypohydrolysates. All the studied deposits are of low sedimentary maturity, with essentially petrogenic clastic material. These are predominantly igneous rocks of intermediate and, less, felsic composition. The provenances were characterized by moderate chemical weathering. In the periods of the formation of the marker beds, chemical weathering intensified, and the amount of mafic and, partly, ultramafic rocks increased. The established changes in the composition of the parental strata are observed in the Middle Jurassic–Lower Cretaceous deposits of the entire considered petromineralogical province, which permits them to be used for correlation.

Geotechnical Mapping for Soil Physical and Mechanical Parameters and Hard Soil Depth in Badung Regency

The infrastructure is important for the great life of a region and most of the country. Therefore, infrastructure must be always in proper condition in its functionality. Furthermore, it must follow the main principle which is infrastructure asset management. In this case, geotechnical mapping is also related to the principles of Infrastructure Asset Management in planning, designing, and feasibility studies of an infrastructure project in Badung Regency, hence the infrastructure projects are better prepared. The research methods include collecting soil investigation data, processing soil investigation data, describing the results of soil investigation data with mapping tools, and geotechnical zoning with statistical analysis. The results obtain geotechnical map of Badung Regency in 2 and 3-dimensional form. The 2D results in the form of a hard soil depth map can be concluded that South Kuta District has a variation depth of 0.4 – 15 meters, North Kuta District has a variation depth of 1.5 – 5 meters, Kuta District has a variation depth of 1.5 – 10 meters, Mengwi District has a variation depth of 1.5 – 10 meters, Abiansemal District has a variation depth of 5-15 meters, Petang District has a variation depth of 5-22 meters. The 3D Zone 1 lithology map can be concluded that Zone 1 area covered with hard soil depth around 5 – 10 meter is dominated by sandy silt, silty sand, sand and a little clayey silt. That area covered with hard soil depth about 1.5 – 5 meter is dominated by clay, clayey silt, sandy silt, silty sand and sand with heterogeneous distribution. The Zone 1 area is dominated by the specific volume saturated value (γsat) range of 1.5 – 2.0 t/m3. The values > 2.0 t / m3 is found in Sading area with hard soil depth of 5-10 meters. The Zone 1 area is dominated by the range of N-SPT values = 0 - 30. The N-SPT values > 30 are found in Sading area with hard soil depth 5-10 meters.

Visual assessment of soil structural quality across soil textures and compaction levels – Part II: Examination of profile walls vs Intact soil cores

Visual Evaluation of Soil Structure (VESS) methods receive increasing attention and are gaining popularity. Since in modern agriculture, soil structure degradation becomes very common, it is essential to protect and improve soil structure quality. Methods that enable its straightforward monitoring are therefore needed. Numerous visual soil evaluation techniques that serve this purpose exist, and are varying in objective, evaluation depth (topsoil/subsoil), evaluation method, number of criteria assessed and their final scoring. In this study, we mainly focus on three VESS methods, two of which were employed in the field along a profile wall (Visual Evaluation of Subsoil Structure, SubVESS, and Double Spade VESS method, DSVESS), and one in the laboratory on soil cores (CoreVESS). The main aim of this research was to test and compare these VESS-based methods in terms of their feasibility and repeatability in detecting soil structure degradation in the topsoil and subsoil. Sixteen cropped fields were chosen in Belgium covering six of seven major soil texture classes according to the Belgian soil textural triangle (i.e., sand, loamy sand, light sandy loam, silt loam, clay, and heavy clay). SubVESS and DSVESS were performed in the same pits until 80 cm and 40 cm, respectively. Soil cores for CoreVESS and for the determination of soil quality indicators (SQi) with conventional laboratory methods were taken from three layers, that is, the ploughed topsoil (∼10–∼20 cm, “TOP”), the compacted subsoil (∼30–∼40 cm, “CSUB”), and the deeper subsoil (∼60–∼70 cm, “SUB”), totalling 96 horizons. While SubVESS and CoreVESS were originally developed to evaluate subsoil and topsoil, respectively, they were thus used here beyond those zones. Moreover, all sampling and field evaluation was done at two positions per field - the more compacted headland and the less compacted in-field zone. It was shown that the soil quality (Sq) scores assigned to the cores with CoreVESS were not significantly influenced by operators with different backgrounds but all having received basic VESS training. When comparing field and laboratory results, positive relationships were found between Sq scores of SubVESS, DSVESS and CoreVESS. All VESS methods were able to assign significantly better soil quality (lower scores) at in-field positions (IN-FIELD) as compared to headland positions (HEAD), and significantly lower quality (higher scores) to CSUB layers than to the other two layers. Laboratory-derived SQi values presented a similar trend, with CSUB layers always indicating worse situations. There were good significant relationships between the SQi values and the different VESS-based Sq scores as well, with DSVESS showing the best correlations among the three VESS methods. The study thus confirmed that the different VESS methods all have a potential for monitoring soil structure quality in a fast, cheap, intuitive and practical way, although they all have their own advantages and disadvantages. Additionally, those methods that were employed at depths other than those for which they were developed did perform well.

Feasibility of soil erosion measurement using time domain reflectometry

Scientific research and control technology of soil erosion both rely on accurate and efficient soil erosion measurements. Based on the principles of locating interfaces in layered media and measuring dielectric properties by time domain reflectometry (TDR), we developed TDR-based measurement of changes in the air–soil interface along the TDR probe for soil erosion measurement, and simultaneously measuring volumetric soil moisture content (θv). Part of a three-rod TDR probe was inserted in the soil and the rest exposed to air, so changes in the air–soil interface could be denoted by changes in the length of exposed probe (Lair). TDR waveforms were analyzed using a combination of tangent line method and second-order bounded mean oscillation methods to identify time points at positions of impedance discontinuity in electromagnetic propagation, then converting these data to Lair and θv by calibrated equations. According to the laboratory experiment using sandy loam and silt loam, Lair could be effectively measured within a wide soil moisture range by the calibrated equation and the thickness of the eroded soil layer could thus be determined. The RMSE of θv measurement ranged between 0.003 and 0.025 cm3 cm−3, which enabled the identification of the appropriate soil moisture range for measuring Lair, and achieve reliable simultaneous measurement of soil erosion and soil moisture content. The simulated rainfall experiment using sandy loam and silt loam and field scouring experiment conducted in loam also indicated that the proposed method could achieve high measurement accuracy in erosion environments, for which Lair with the RMSE from 1.8 to 2.1 mm and θv with the RMSE from 0.007 to 0.024 cm3 cm−3. The proposed method has various advantages, including versatility, minimal disturbance, easy automation of measurement at multiple positions, etc., could serve as a new technical option for soil erosion measurement, and extend the utilization of TDR.

Source-to-sink process and risk assessment of heavy metals for the surface sediment in the northern South China Sea.

Heavy metal input from the coastal urbanization and industrialization and their potential ecological risks have been a great concern in the northern South China Sea (NSCS). Our results showed that the surface sediments in the NSCS mainly include sand, silt, and sandy silt. CaO and Sr are fixed in the fine-grained biogenic calcareous debris. Sc, V, Cr, Co, Ni, Ba, and REE are the least contaminated and mainly of felsic crustal origin, with the supply largely from the Han and Pearl River estuaries in the Eastern and Western NSCS, respectively. Enrichment in Cu-Pb-Zn might be from both natural and anthropogenic inputs, and their contamination is generally at a low-risk level. As-Cd accumulation is mainly from anthropogenic provenance related to the aerosol precipitation. The anthropogenic As-Cd contamination resulted both from the industrial/urbanized discharge along the Guangdong Eastern Coastal and the agricultural/aquafarming activities along the Moyang River Estuary-Hainan Eastern Coastal.

Monotonic and cyclic properties of silty sand and sandy silt for foundation design of offshore windfarms

This paper presents results of a series of monotonic and cyclic direct simple shear laboratory tests performed on reconstituted samples of two silty sands and one sandy silt. The laboratory program aimed to determine the cyclic shear strength and deformation characteristics of soils to be used in the offshore wind turbine foundation design. Various cyclic contour diagrams including cyclic shear strength and average and cyclic shear strains for different number of cycles were provided. The effect of strain rate for drained monotonic tests and overconsolidation ratio effect on both monotonic and cyclic properties were discussed. This study indicated that the fines content plays an important role in static and cyclic shear strength of silty soils, in addition to mineralogy and coefficient of uniformity.

Effects of soil structure on cyclic freeze-thaw induced volumetric behaviour using a modified double-cell triaxial system

Weather induced freeze-thaw cycles can cause significant alternation on soil volume and hence induce serviceability issues to earthen and structures facilities. However, the contribution of soil structure has rarely been considered in this process. In this research, a modified double-cell triaxial system is employed to accurately measure soil volume change under stress-controlled condition during freeze-thaw cycles. The device is adopted to investigate the volumetric behaviour of reconstituted and compacted sandy silt specimens under different confining pressures. The test results reveal that the change of freezing expansion slightly decreases with increasing number of freeze-thaw cycle because the dissipation of water is negligible. However, the thawing contraction decrease with freeze-thaw cycles. Thus, the total volume of soil tends to be stable when thawing contraction yields to be equal to freezing expansion. This trend is independent with preparation methods and confining pressure. Under 100 kPa of confining pressure, compacted specimen results in less plastic strain during freezing and thawing process compared with reconstituted specimen. A possible reason is that clay-formed aggregates enhance the soil skeleton, which is evidenced by MIP test result. Under 200 kPa confining pressure, two specimens using different preparation methods have almost identical volumetric behaviour which is attributed to the degradation of soil structure resulting from the increase of confining pressure.

Effect of the covariance matrix type on the CPT based soil stratification utilizing the Gaussian mixture model

Abstract The identification and stratification of soils represent an essential step in designing various geotechnical structures. The cone penetration test (CPT) measurements are used widely to classify the soil; however, the soil classification charts such as the Robertson chart undergo uncertainty from different sources that make overlapping of soil types. This article aims to develop a probabilistic approach employing clustering with Gaussian mixture model, which can deal with the uncertainty and classify the soil based on CPT. The spatial parameters were obtained assuming the different types of covariance matrices. The data utilized in this study represent the results of CPT in four locations in Nasiriyah, Iraq. Both spatial and feature patterns were produced and used to classify the soil. This research revealed that the soils deduced from the Robertson chart were clay, silt, and sand. No gravelly sand appeared on the chart. The soil at shallow depth was clay soils, and it changed to be sandy silt at fairly great depth. They were close to the boundary curve between the stiff clay and sand zones and relatively existed at great depth. The probabilistic approach can detect the soil layers fast without experience-based decisions. Moreover, the type of assumed covariance matrix may affect the soil profile.

Soil–Foundation–Structure Interaction of Inelastic Structural Systems on Unsaturated Soil Layers

Recently, progress has been made toward understanding the seismic response of structures placed on unsaturated soil layers. A missing link, however, involves the influence and assessment of the underlying soil saturation conditions on the expected superstructure seismic demands. Simplified soil–structure interaction procedures that can be used to predict superstructure seismic demands have not been explicitly extended to incorporate the influence of unsaturated soil on the system response. In this paper, results from a series of six centrifuge tests are compared. In each test, an inelastic single-degree-of-freedom physical model was shallowly embedded in a sandy silt with a distinct water table elevation or a completely dry soil condition. The soil-structure system was subjected to a series of earthquake motions. The response of the system was evaluated to assess the influence of the soil saturation condition on the seismic response. Specifically, a conventional analytical procedure for predicting the influence of inertial interaction on the seismic response of the structure was extended to consider the water table elevation and underlying soil saturation condition and evaluated for its reliability. Analytical flexible-base modal parameters were compared with those determined from experimental results to judge the potential of the analytical procedure to be used in practice. Experimental results suggest that as the water table elevation was lowered from the fully saturated condition, both the flexible-base system period and damping ratio reduced. Therefore, the system behaved stiffer in the unsaturated soil compared with the dry and fully saturated conditions. The stiffer response reduced the seismically induced foundation settlements and rotations but amplified superstructure seismic demands in the form of accelerations, flexural drifts, and bending strains.

Measurements of Geologic Characteristics and Geophysical Properties of Sediments From the New England Mud Patch

The characterization of physical, geological, and geophysical properties of sediments within the New England Mud Patch (NEMP) was undertaken to provide a physical basis for acoustic inversions associated with the SeaBed Characterization EXperiment 2017 (SBCEX17). Using a suite of 89 sediment cores (piston/trigger, gravity [acoustic], and vibracore), a comprehensive database of laboratory-based sediment analyses, geophysical core logs, and the results of seismic reflection profiling, we formulate a three-layer lithostratigraphic model of the area within and immediately adjacent to the SBCEX17 focus area, referred to as the seabed experiment area (SEA). The uppermost lithostratigraphic unit, Unit 1, is relatively homogenous clayey- to sandy silt, with consistent downcore textural, mineralogical, and physical property attributes. Unit 2 is a variable-thickness transitional layer between Unit 1 and Unit 3, whose properties reflect a decrease in proximal erosion and transition to a lower energy depositional environment. Unit 3 is clean quartz sand containing abundant shells and shell fragments that was regionally deposited during Holocene sea-level rise. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">210</sup> Pb and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> C radiocarbon geochronologies spanning the past 13 000 years are used to facilitate intercore comparison across the SEA. Analytical results and laboratory methods used in the derivation of those results are described in detail, serving as a reference for ongoing and future investigation of the SEA and entire NEMP. Although the derived lithostratigraphic model of the SEA is in good agreement with past evaluations of the regional sedimentology, comparisons of the lithostratigraphic and seismostratigraphic models highlight several significant incompatibilities that remain to be satisfactorily explained.