Silt Mixtures Research Articles

Influence of soil-contaminated water on clogging phenomenon of pervious concretes with different void contents

In many circumstances, water passing through pervious concrete (PC) is contaminated with soil sediments. In such cases, clogging of the PC with soil sediments affects its functional characteristics and service life. The clogging behaviour of PCs with different void contents under the influence of soil-contaminated water is not yet clearly understood. Therefore, the effects of three different kinds of soil-contaminated water (water contaminated with sand, clayey silt and a mixture of sand and clayey silt) on the pore clogging of PCs with different design void contents (DVCs) were examined. For the three types of PC with different DVCs, three different concentrations of soil-contaminated water were used to examine the clogging process. The clogging process was executed until the minimum permeability level of the PC was reached. The effectiveness of washing on the de-clogging behaviour of each clogged PC was also examined. Various characteristics of the different DVC-based PCs (strength, permeability, macroscopic pore distribution and leaching parameters) were assessed. The outcomes of this work disseminate consensus behaviour of PC, which should be helpful to provide a conceivable solution to develop desirable performance of PC for wide applications.

Nature‐based shoreline protection in newly formed tidal marshes is controlled by tidal inundation and sedimentation rate

AbstractMany tidal marshes have been lost by past land use changes, but are nowadays increasingly restored and created to provide valuable ecosystem services such as nature‐based flood and erosion protection along estuarine shorelines. To be functional for flood and shoreline erosion protection, restored and created tidal marshes should develop erosion resistant sediment beds. Here, we investigated which factors drive the spatial variations in sediment strength and erosion resistance in a developing tidal marsh restoration site. Our results show that decreasing tidal inundation frequency, decreasing sedimentation rate, and better drainage led to stronger consolidation in deeper sediment layers. This consolidation resulted in greater sediment strength, quantified here by shear strength and penetration resistance. Generally, sediment strength was greater when sediment had higher bulk density, while a higher water and fine fraction (= clay and silt) content decreased sediment strength. Overall, all measurement locations were relatively erosion resistant, likely caused by the dense root network and cohesive sediment. To restore or create resilient tidal marshes for nature‐based flood and shoreline erosion protection, we should thus aim for sites with relatively low tidal inundation frequency, moderate sedimentation rates, and cohesive sediment mixtures of clay, silt, and sand, which are well drained and have potential for vegetation establishment. These conditions have a high likelihood of resulting in restored or created tidal marshes that contribute to nature‐based flood and shoreline erosion protection.

Fine Sediment in Mixed Sand‐Silt Environments Impacts Bedform Geometry by Altering Sediment Mobility

AbstractGeometric characteristics of subaqueous bedforms, such as height, length and leeside angle, are crucial for determining hydraulic form roughness and interpreting sedimentary records. Traditionally, bedform existence and geometry predictors are primarily based on uniform, cohesionless sediments. However, mixtures of sand, silt and clay are common in deltaic, estuarine, and lowland river environments, where bedforms are ubiquitous. Therefore, we investigate the impact of fine sand and silt in sand‐silt mixtures on bedform geometry, based on laboratory experiments conducted in a recirculating flume. We systematically varied the fraction of sand and silt for different discharges, and utilized an acoustic Doppler velocimeter to measure flow velocity profiles. The final bed geometry was captured using a line laser scanner. Our findings reveal that the response of bedforms to an altered fine sediment percentage is ambiguous, and likely depends on, among others, bimodality‐driven bed mobility and sediment cohesiveness. When fine, non‐cohesive material (fine sand or coarse silt) is mixed with the base material (medium sand), an increased dune height and length is observed, possibly caused by the hiding‐exposure effect, resulting in enhanced mobility of the coarser material. However, weakly cohesive fine silt suppresses dune height and length, possibly caused by reduced sediment mobility. Finally, in the transition from dunes to upper stage plane bed, there are indications that the bed becomes unstable and dune heights vary over time. The composition of the bed material does not significantly impact the hydraulic roughness, but mainly affects roughness via the bed morphology, especially the leeside angle.

Prediction of Excess Pore Water Pressure Generation in Sand–Silt Mixtures During Cyclic Loading: A Dissipated Energy-Based Model

Prediction of Excess Pore Water Pressure Generation in Sand–Silt Mixtures During Cyclic Loading: A Dissipated Energy-Based Model

Determining The Depth of Hard Soil Layers Using Geoelectric Resistivity and Cone Penetration Test Methods (Case Study: Kelurahan Bontoramba Kecamatan Somba Opu Kabupaten Gowa)

Hard soil layers can impact the loading, stability, and behavior of structures in the geotechnical field. Comprehensive understanding of the depth and properties of hard soil layers can aid in designing suitable structures. Therefore, this study employed the resistivity geoelectric and Cone Penetration Test (CPT) methods to map the features of hard soil layers. Resistivity data were acquired through measurements utilizing the geoelectric method, while data on cone resistance, shear resistance, and friction ratio were gathered through field measurements using the CPT tool. The collected data was analyzed comprehensively to obtain a complete understanding of soil conditions. Based on resistivity values, the results indicated the research site comprises alluvium, very dry clay, and dry sandy soil. Based on the CPT test, it is determined that the layers contain mixtures of fine-grained soils, clay, silt, and sand. Therefore, it can be inferred that the dense sand lithology constitutes the hard soil layer geologically. The employment of both approaches delivers supplementary details on soil features and depth.

Variability of the undrained strength of the plastic tailings from the Germano dam in Mariana, Brazil

Mining tailings may be divided in non-plastic (sand, silty sand, or sandy silt tailings) and plastic (fine tailings, usually mixtures of silt and clay-sized particles). The understanding of the behavior of these materials is a great geotechnical challenge because of their wide variations in mineralogy, physical–chemical, and geotechnical characteristics. Sand tailings have been widely studied in the last decades because they are often susceptible to liquefaction, and they usually constitute the beach of the tailings dam which is the most important zone for stability analysis in upstream dams. However, the study of the characteristics and the strength of the plastic tailings is also important since layers of plastic tailings are sometimes found in the midst of the sand tailings. The aim of this article is to study the normalized undrained strength ratio (su/σ′v) of plastic tailings of the Germano dam in Mariana, Brazil, and to present a criterion developed for their identification. The method consisted of analyzing and scrutinizing Piezocone (CPTu), Field Vane (FV) tests, and the water levels. An extensive review of the iron ore plastic tailings properties was also performed. A total of approximately 900 occurrences of plastic layers were analyzed. The results included the discovery of perched water tables and significant vertical downward flow in some locations. The conclusion is that su/σ′v histograms are well fitted by lognormal distributions and the layer thickness influences the undrained strength. Moreover, the strengths are relatively low (for example, su/σ′v = 0.11 on average for plastic layers with thickness of 1.0 m or more).

Geotechnical, microscopic and mineralogical characterization of surficial sediments nearshore the southern coast of Brazil

ABSTRACT Many important maritime projects depend on the correct characterization of surficial sediments (e.g. gas and water pipelines; dredging works; transport of sediments, and water-soil-structure interaction). However, the sampling and characterization of such sediments are very challenging due to the environmental conditions. Furthermore, the investigation often consists only of a basic granulometric analysis. In this context, this paper presents a geotechnical, mineralogical, and microscopy characterization of an offshore area on the southern coast of Brazil. Surficial samples were collected from the seabed, in water depths between 13.0 and 91.0 metres. Then, they were submitted to basic geotechnical characterization tests (size distribution by sieving and sedimentation, Atterberg limits, and basic physical properties), mineralogical analysis by X-ray diffraction tests (XRD), microscopy investigation by scanning electronic microscopy (SEM) and shear vane tests. Based on the state and index parameters of the sediments, as well as the undrained shear resistance, three main sets of sediments have been identified: group I (sands), group II (clayey sands), and group III (mixtures of sand, silt, and clay). The spatial distribution of sediments was also inferred, reflecting different deposition environments and bottom dynamics. The clay mineral quantification through XRD revealed that the predominance of 2:1 clay minerals is related to the higher plasticity found in some samples. Moreover, the presence of diatoms could explain the difference in porosity in the samples, resulting in a higher plasticity and lower shear strength.

Geoarchaeology of open-air sites of the Foz do Chapecó area in the upper Uruguay river, southern Brazil

This paper presents the results of the investigations that defined the formation of the sedimentary deposits and the chronological sequence of the Foz do Chapecó archaeological area in the Volta Grande of the Upper Uruguay River, Southern Brazil. This research was undertaken to contribute to the definition of the diachronic, sedimentary and stratigraphic context of the archaeological occupations. To achieve these goals a geoarchaeological prospection by land and water was conducted, focusing on the valley bottoms, in the whole Volta Grande area. It comprehended the characterization of surface sedimentary deposits, the exposure and analysis of stratigraphic profiles, and sedimentological analysis. Four superficially exposed deposits were identified: i.e., fluvial conglomerates, fine sediments with sandy texture, clay colluviums and current and recent alluvial deposits. Six interesting points for the opening of stratigraphic profiles were identified, and subsequently resulted in the identification of sedimentary facies associated with river-bed, colluvial and colluvial-alluvial deposits. Three of these points presented a clear sequence of archaeological levels in the stratigraphic context. The results indicated that the local sediments are predominantly composed of a variable mixture of silt and clay, with sands occurring predominantly in an interdigitated form. The stratigraphic structure of the identified layers led to the establishment of 7 sedimentary facies, associated with colluvium (Cm), colluvium-alluvium (Sm) and alluvium and fluvial channels (Sm, Fl, Gms, Gt, Gp, Gh). The radiocarbon dating gives an age between 12.0 and 0.3 cal kBP, indicating that the filling of the local valley occurred during the end of the Pleistocene and throughout the Holocene by means of both fluvial and colluvial systems. Nine distinct archaeological levels, with a clear stratigraphic, chronological, and technological characterization were identified. The pre-ceramic archaeological sequence shows the following chronology: the oldest occupation occurred between 12.0 and 11.0 cal kBP (Cm facies); this was followed by an occupation between 10.5 and 9.5 cal kBP (Cm, Gt, Gp and Gh facies in three archaeological sites with eleven 14C data), then an occupation between 8.7 and 8.5 cal kBP (Cm facies), another between 5.7 and 5.5 cal kBP, one more between 4.8 and 4.6 cal kBP (Cm facies), and the last between 3.4 and 3.3 cal kBP (Cm and Sm facies). The ceramic phase seems to form a single dense component with the anthropogenic soil formation, and was dated between 0.5 and 0.3 cal kBP (Sm facies). These data present a previously unpublished chronostratigraphic sequence that is unique for the context of open-air sites in inner southern Brazil.

Projected traditions? Tracing an East German-Cuban Collaboration in Loam and Soil Cement Construction in Havana-Cocosolo

This article unveils the history of constructing the "Cocosolo Experimental House" in Havana, a collaborative endeavor involving East German and Cuban participants. This singular project was designed around 1989-90, in parallel with the end of the GDR, to serve as a prototype for “self-construction technology” making use of local soil. A crucial step in the development process of this project was the search for the most suitable construction material, ultimately leading to a choice between loam (a mixture of clay, silt, sand, and aggregates such as gravel, which does not require an additional binder) and soil cement (a mixture of local soil and cement, while cement works as binder). Although several obstacles prevented the project from being completed as planned, it was finished after the East German group from Weimar left within the framework of Cuba’s specific local self-construction system. The history of the Cocosolo project unfolds as a tapestry of experimentation, adaptation, and unintended consequences. It addresses both the socialist discourse regarding material scarcity—and the actual lack of construction materials in the Cuban context. In our article, based on archival research in Cuba and Germany as well as site surveys, we unpack the expectations of the German partners experimenting with loam abroad, as well as those of the Cuban actors, focusing on the local uses of soil cement technology. Finally, to nuance the understanding of how a Cuban loam-building tradition was imposed, we analyze the clash of expectations at the construction site.

A Study on Behaviour of Clayey and Silty Soils with Granite Dust

A massive amount of granite dust is produced as a byproduct of processing granite rock. Disposing of granite dust is a fatal to human health and is a environmental toxic for land disposal. An attempt was made to use such a material in construction, decrease the disposing problems. Soil, an important material bearing the load of the resisting structure can be available in various layers beneath the earth. Clayey soil and mixture of silt in soil layers exhibits inadequate load bearing ability and shows significant changes in volume with respect to changes in moisture levels. Stabilization of soil is the process that improves the behavior of soil properties. The study investigates the percentage of granite dust that can be a best stabilizer to silty and clayey soil. A series of laboratory tests were conducted to investigate the effects of granite dust. Artificial soil sample were prepared with 0%, 12%, 16%, 20%and 24% with additive as granite dust on silty and clayey soils. Chemical composition of the granite dust was studied for the application of granite dust as a stabilizer. Comprehensive soil tests like liquid limit, plastic limit, Maximum dry density, swell index, shear strength, CBR were performed. A significant decrease was observed in liquid and plastic limit varying with granite dust for both the soils. The dry density increases with an increase in % of granite dust. Swell index shows a decrease rate with increase in granite dust. The shear strength and CBR values gave appropriate increase conclude that granite dust can acts good soil stabilizer for clayey and silty soils.

A comprehensive analysis of time-dependent performance of a solar chimney power plant equipped with a thermal energy storage system

Solar Chimney Power Plants (SCPP) are among the promising solar thermal electricity generation technologies. Equipped with a Thermal Energy Storage (TES) system, such technologies can overcome variations in the main driving factors such as solar radiation and ambient air temperature. This article presents a comprehensive semi-analytical model of a TES to predict the time-dependent performance of an SCPP. By introducing a Quality Factor of power generation (QF) that includes energy conversion efficiency and capacity factor, the effects of 15 TES materials have been studied on the plant performance. Results indicate no significant difference between water TES and clay or soil type, and water-filled bags or tubes are relatively ineffective in improving performance compared to them. Among the various TES materials analyzed, a type of wet soil, i.e., the specific wet mixture of clay, sand, and silt in closed and dark-colored bags, show excellent performance in both QF enhancement and having low Heat Penetration Depth (HPD) simultaneously. The QF and HPD are directly affected by thermal effusivity and thermal diffusivity, respectively. Implementing wet soil TES for the studied power plant (Manzanares) enhances the QF from 7.46 % (for limestone soil) to 10.95 %. Water-filled bags demonstrate a heat penetration depth of 0.4 m, while wet soil exhibits a slightly greater depth of 0.5 m. Furthermore, water-filled bags experience a broader temperature range of 40 °C, whereas wet soil undergoes a comparatively smaller temperature variation of 26 °C. Furthermore, the capacity factor raises from 41.18 % to 61.07 % when utilizing wet soil TES compared to water-filled bags.

Local or imported? The origin of the raw material used in manufacturing bricks from castles of the Teutonic knights in north‐central Poland and their significance to our understanding of medieval construction techniques

AbstractThis article presents the results of research on bricks from medieval castles in north‐central Poland. They were characterised based on petrographic analyses of thin section and mutually complementary instrumental methods. The bricks came from the oldest parts of the castles preserved to this day, or from castles not preserved but examined and excavated during archaeological research. The data obtained allowed for the identification of building materials that shared similar material and technical properties and that can be associated with different phases of the castles. Based on the results, it was found that the Pleistocene tills commonly found around the castles were not used in the manufacturing of the bricks. Small local deposits of fatty clays were used—Pleistocene varved clays or Miocene variegated clays. The buildings differed in the composition and texture of their bricks, indicating that the local clay raw material was extracted for each building separately. The share of raw material brought in from larger exposures further afield was small. Analyses of brick samples indicate the use of a fatty clay raw material that was improved by the addition of clastic material (quartz sand or a mixture of sand and quartz silt of various fractions).

Role of Temperature-Dependent Interfacial Tension on Shear Wave Velocity for Energy Geosystems.

Interfacial tension varies with temperature. This paper investigates the effects of temperature-dependent interfacial tension on shear wave velocity. We designed a nylon cell equipped with bender elements in a cross-hole configuration to measure the shear wave velocity of nine sand-silt mixtures with different degrees of saturation (S = 0%, 2.5%, 5%, 10%, and 100%). All specimens were subjected to a temperature change from 10 °C to 1 °C. The results demonstrate that shear wave velocity tends to be very sensitive to changes in temperature at a low degree of saturation. Particle-scale analyses overlapped with the experimental results and captured the critical role of temperature-dependent interfacial tension in small-strain skeletal stiffness. In fact, the temperature should be considered during laboratory and field shear modulus measurements of the long-term performance of energy geosystems subjected to thermally induced repetitive loads.

Correlations for Estimating Coefficients for the Prediction of Maximum and Minimum Index Void Ratios for Mixtures of Sand and Non-Plastic Silt

One common method of estimating emax and emin for mixtures of sand and silt requires that the values of several empirical constants be determined. These empirical constants are the filling coefficients, a, and embedment coefficients, b, which can be determined either via lab testing or correlations. The study reported here developed simple correlations for estimating the filling and embedment coefficients using readily obtained laboratory data. These models were found to be excellent in producing filling and embedment coefficients that accurately predicted values of the index void ratios for sand and silt mixtures, with most R2 values being 0.94 or greater.

Cyclic Behaviors of Anisotropically Consolidated Gravelly Soils under Triaxial Condition: Effects of Sand Gradation Part of the Soil

Abstract Previous studies have extensively examined the effects of silt contents and gradations on the cyclic behavior of sand and silt mixtures. However, comparable data on the mixture of sand and gravel are limited because of the experimental challenges of getting reliable testing results from gravel-size particles. Furthermore, in several case histories in which liquefaction occurred, the liquefied soils had experienced initial static shear stress because of the sloping ground conditions or the presence of structures and buildings on the site. The effects of initial static shear stress on the cyclic behavior of clean sands have been widely studied, and some recommendations have been suggested for practical engineers. This research aimed to evaluate the effects of the sand gradation part on the cyclic behavior of two gravelly soils, both with 60 % gravel and 40 % sand but different gradations (well-graded vs. uniformly graded). A total of 26 cyclic triaxial tests were carried out on moist-tamped reconstituted specimens of the tested gravelly soils. The specimens were anisotropically consolidated to assess the effects of initial static shear stress combined with sand gradation on cyclic behaviors of the tested gravelly soils. Results of the tests indicated that the gravelly soil with uniform sands had a greater resistance against liquefaction than the one with well-graded sands. The lower cyclic resistance of the gravelly soil with well-graded sands can be attributed to its lower permeability associated with wider gradation and finer particles of the sand part, leading to higher excess pore pressure buildup during cyclic loading. Moreover, a similar increase in the level of initial static shear stress resulted in an increase in the liquefaction resistance of the gravelly soils, whereas the soil with uniform sands experienced a higher increase than the soil with well-graded sands.

Effects of Mud Content on the Setting Time and Mechanical Properties of Alkali-Activated Slag Mortar.

High mud content in the sand has a negative impact on cement mortar but there is little research on Alkali-activated slag (AAS) mortar. In order to explore the impacts of mud content in the sand on the performance of AAS mortar, this paper used sand that contains silt, clay, and a mixture of silt and clay; tested the setting time of AAS with different mud contents of 0%, 2%, 4%, 6%, 8%, and 10%; and measured the unconfined compressive strength and beam flexural strength of 3 d, 7 d, and 28 d AAS mortar specimens. The microstructure of AAS mortar with different kinds of mud was observed by scanning electron microscope (SEM), the elemental composition of the hydration product was tested by energy dispersive spectroscopy (EDS), and the AAS interaction mechanism with different kinds of mud was analyzed. The main conclusions are: the higher the mud content in the sand, the shorter the initial setting time and the longer the final setting time of AAS, mainly because the mud in the sand affects the hydration process; mud content above 4% causes a rapid decrease in the compressive and flexural strengths of AAS mortar, mainly because the mud affects the hydration process and hinders the bonding of the hydration product with the sand. When there is no mud in the sand, the main hydration product of AAS is dense calcium-alumina-silicate-hydrate (C-A-S-H) gel. When the sand contains silt, the hydration product of AAS is loose C-A-S-H gel. When the sand contains clay, the hydration products of AAS contain C-A-S-H gel and a small amount of sodium-aluminum-silicate-hydrate (N-A-S-H), and needle-like crystals. Loose gel and crystals have a negative effect on the AAS mortar strength.

Particle size distribution effects on cavitation erosion in sediment suspensions

Synergistic cavitation–particle erosion often occurs in high-speed sediment-laden flow in hydraulic structures and machines. However, erosion prediction is challenging due to the unclear relationship between erosion and the characteristics of sand- and silt-sized sediments, particularly the sediment particle size distribution (PSDS). In this study, vibratory erosion tests for carbon steel were conducted in suspensions of continuously graded sand–silt mixtures, and the influence of PSDS characteristics, such as the number of modes and sand-to-silt ratios, was investigated. The results indicated that both the total sediment concentration and PSDS parameters had a major impact on synergistic erosion. The changes in the PSDS patterns resulted in different erosion behaviors, even when the sand and silt concentrations were fixed. Based on the viscosity-enhancing effects of silt particles and the impinging effects of sand particles, a new theoretical model for determining the particle impact energy was developed by incorporating PSDS. A deeper understanding of the influence of PSDS and the application of the PSDS-based model can help predict and prevent synergistic erosion.

Factors Affecting Small-Strain Shear Modulus of Sand–Silt Mixture Considering Different Moisture Contents

Factors Affecting Small-Strain Shear Modulus of Sand–Silt Mixture Considering Different Moisture Contents

Effect of Simulated Drought and Rainfall Fluctuation on Seedling Growth of Two Savannah Trees Species in Sudan: An Experimental Exploration

Climate change scenarios project that several regions, especially in dryland areas of sub-Saharan Africa, will undergo increasing aridity and, subsequently, expanding land degradation. The study aims to investigate the effect of two drying treatments on establishing and growing Hashab (Acacia senegal) and Boabab (Adansonia digitata) in nursery conditions. Through a 2×2 factorial experiment, seedlings grown in a mixture of silt and sand soil (2:3) were treated by irrigation intervals of one or two liters every three days for 14 weeks to simulate rainfall fluctuation patterns. Seedling germination rate, leaf number, stem height, and diameter were measured weekly; taproot length, shoot, and root dry weights were also assessed. The results showed that neither drying treatment significantly affected A. senegal and A. digitata seedling growth parameters. However, an interaction effect was found in the height and diameter for A. senegal and shoot dry weight for A. digitata. The study concluded that A. senegal and A. digitata seem tolerant to drying treatment. Therefore, the two species are recommended for afforestation programs in areas with relatively harsher conditions. Also, exposing the seedlings of these studied species to similar, extended periods of simulated drought (e.g., 6 – 12 months) is recommended for future studies.

Soil water retention curves of a silty clayey sand compacted at different dry density

The study of the hydraulic behaviour of compacted soils in partially saturated conditions is essential for understanding the engineering performance of geotechnical structures such as river embankments. The paper presents the results of an experimental study focusing on the effects of the initial water content and dry density on soil water retention curve (SWRC) and volume change of a compacted soil mixture under hydraulic loading. For this purpose, soil specimens compacted at different water contents(dry, wet and optimum water content), chosen on the basis of standard Proctor compaction test, were used. Specimens of a mixture composed of 70% Ticino sand (TS) and 30% Pontida silt (PON) have been tested. This is a heterogeneous mixture of sand and silt, that usually constitute the embankments of tributaries of river Po (Italy). The SWRCs along drying paths were performed by means of evaporation tests starting from the saturated conditions gained in permeameter tests. For the investigation of the change in the void index during the evaporation test, the volume variation of the tested specimens was estimated by means of a calliper and photographic comparison. Changes in the SWRCs are consistent with changes in specimen initial condition while the soil volume change exhibited at the end of evaporation test is always negligible.