Transparent Sand Research Articles

Model tests on chain-soil interaction of anchor pile for taut mooring system through transparent sand

The pile response of taut mooring systems considering chain-soil interactions remains unclear. In this study, model tests on the performance of anchor piles and the surrounding soil displacement field were conducted using transparent sand. Cyclic motion was imposed at the top end of the chain. The effects of pad eye location (z), motion velocity (v), motion amplitude (A), and amplitude increment (Ai) are discussed. In the constant-amplitude tests, the soil displacement caused by chain motion was apparent near the dip-down point, and the soil displacement increased with z and A. The maximum chain tension decreased owing to chain-soil interactions. The maximum tension with z = 0.55L and 0.67L (where L is the pile length) increased 9% and 15%, respectively, compared with that with z = 0.40L, and the maximum tensions at A = 80 and 120 mm decreased 15% and 29%, respectively, of that at A = 40 mm. In the incremental-amplitude tests, soil displacement was evident around the dip-down point and pile. The maximum tension during each cycle increased almost linearly with the number of cycles before pile failure, and the maximum tension during the entire test increased with z and v.

Centrifuge model tests on an anchor pile under cyclic oblique pullout load using transparent sand

Cyclic load on anchor piles of single point mooring systems is an important issue, and the cyclic behavior of anchor piles has a connection with the surrounding soil displacement. Based on transparent sand and particle image velocimetry (PIV) technique, centrifuge model tests on the pile subjected to oblique pullout load were conducted. The cyclic pile performance and the soil displacement field under various cyclic load characteristics were studied. The mechanism for the cyclic response of anchor piles was investigated. It can be observed by transparent sand that the failure mode of the pile is a combination of vertical and lateral translation without rotation. The post-cyclic pullout bearing capacities are decreased with the increasing of the cyclic amplitude and number of cycles, but the pile vertical displacement and the soil displacement are increased at the same post-cyclic reload. During the cyclic load period, the pile produces cumulative displacement due to soil particle movement, especially vertical displacement that can reduce embedment depth and bearing capacity. However, the shakedown behaviors of the cumulative displacement and post-cyclic bearing capacity of the pile occur, because the increasing rate of the soil displacement is decreased with loading cycles.

The Meioflume: A New System for Observing the Interstitial Behavior of Meiofauna.

Meiofauna (benthic invertebrates<1 mm in size) facilitate sediment biogeochemical cycling, alter sediment microbial community structure, and serve as an important trophic link between benthic micro- and macrofauna, yet the behaviors that mechanistically link individuals to their ecological effects are largely unknown. Meiofauna are small and sediments are opaque, making observing the in situ activities of these animals challenging. We developed the Meioflume, a small, acrylic flow tunnel filled with grains of cryolite, a transparent sand analog, to simulate the in situ conditions experienced by meiofauna in an observable lab environment. The Meioflume has a working area (28.57 mm×10.16 mm×1 mm) that is small enough to quickly locate fauna and clearly observe behavior but large enough that animals are not tightly confined. When connected to a syringe press, the Meioflume can produce low velocity flows consistently and evenly across the width of its working area while retaining the contents. To demonstrate its functionality in observing the behavior of meiofauna, we placed individual meiofaunal animals (a protodrilid annelid, a harpacticoid copepod, and a platyhelminth flatworm) in Meioflumes and filmed their behavioral response to a sudden initiation of porewater flow. All animals were clearly visible within the flume and could be observed responding to the onset of flow. The design and construction of the Meioflume make it an accessible, affordable tool for researchers. This experimental system could be modified to address many questions in meiofaunal ecology, such as studying behavior in response to chemical cues, allowing us to observe meiofaunal behaviors to better understand their ecological effects.

Quantification of geogrid lateral restraint using transparent sand and deep learning-based image segmentation

An experimental technique is presented to quantify the lateral restraint provided by a geogrid embedded in granular soil at the particle level. Repeated load triaxial tests were done on transparent sand specimens stiffened with geosynthetic inclusions simulating geogrids. Images of laser illuminated planes through the specimens were segmented into particles using a deep learning-based segmentation algorithm. The particle outlines were characterized in terms of Fourier shape descriptors and tracked across sequentially captured images. The accuracy of the particle displacement measurements was validated against Digital Image Correlation (DIC) measurements. In addition, the method's resolution and repeatability is presented. Based on the measured particle displacements and rotations, a state boundary line between probable and improbable particle motions was identified for each test. The size of the zone of probable motions was used to quantify the lateral restraint provided by the inclusions. Overall, the tests results revealed that the geosynthetic inclusions restricted both particle displacements and rotations. However, the particle displacements were found to be restrained more significantly than the rotations. Finally, a unique relationship was found between the magnitude of the permanent strains of the specimens and the area of the zone of probable motions.

Locomotory Palp Function in Interstitial Annelids.

AbstractThe interstitial environment of marine sediments is a complex network of voids and pores that is inhabited by a diverse and abundant fauna. Animals living within these interstitial spaces show widespread functional adaptations to this environment and have developed many strategies for moving and navigating through small spaces. Interstitial annelids demonstrate a remarkable level of morphologic diversity, and some possess dexterous, filiform palps (tentacle-like appendages common across Annelida). The function(s) of these palps in interstitial spaces has not been closely examined, and we propose that they serve a sensory role in the navigation of interstitial spaces. We investigated the locomotory function of long, dexterous palps in three families of interstitial annelids to determine their role in interstitial navigation. We observed two species of protodrilids (Protodrilidae), Pharyngocirrus eroticus (Saccocirridae), and Protodorvillea recuperata (Dorvilleidae), as they moved through two transparent sand analogs: cyolite and glass beads. All four species of annelids consistently used their palps to probe the interstitial environment while locomoting, and the distance probed with their palps was greater than the distance traveled with their heads, indicating a sensory form of palp-based navigation. The functionality of palps as sensory organs in the interstitial environment raises interesting questions about interstitial navigation and how fauna without appendages map their surroundings. The discovery of this previously undocumented function was possible only through the direct observation of interstitial behavior and emphasizes the importance of developing new techniques to study these animals in more natural habitats.

Visualization Investigation of the Plugging Effect on Open-Ended Pipe Pile Jacked in Transparent Sand

Visualization Investigation of the Plugging Effect on Open-Ended Pipe Pile Jacked in Transparent Sand

Centrifuge model tests on anchor pile of single point mooring system under oblique pullout load using transparent sand

Single point mooring system anchored by piles has been widely used to support floating offshore platforms. However, the failure mechanism and soil displacement of the anchor pile subjected to oblique pullout loads are still unclear. Based on transparent sand and PIV technique, a visual centrifuge test system for anchor piles of single point moorings was established. A series of centrifuge model tests were performed on the pile under oblique pullout loads, and the measured soil displacement field results were compared with the finite element simulation, indicating that the centrifuge modeling using transparent sand are suitable for studying the anchor pile behaviors and soil deformation. A modified semi-empirical method was also proposed, which can predict the bearing capacity of piles under difference loading angle and loading position in sand. It shows that with the increasing loading angle and pad eye depth, the pile horizontal translation and soil horizontal deformation become more obvious, and the pullout bearing capacity increases. The proportion of the soil horizontal displacement for θ = 75° is nearly 4.1 times of that for θ = 37°, and the horizontal displacement proportion for z = 0.75L increases approximately 25% of that for z = 0.67L.

Sand ecologies, livelihoods and governance in Asia: A systematic scoping review

Sand, gravel, and crushed rock – known as construction aggregates – are in high demand in the Asian region. Such demand is driven by high rates of urbanization, infrastructure development, and dam building: an unprecedented amount of sand is being extracted from the region's river, delta and estuary areas, only to be transported for infill or construction purposes elsewhere. This systematic scoping review examines the state of knowledge in the peer review literature on sand ecologies, livelihoods, and governance in Asia. We find that the literature mainly focuses on the ecological implications of sand mining, namely biotic and abiotic components: sand mining is linked with many forms of ecological degradation, although partial ecosystemic recovery may be possible when sand mining stops. In contrast, the limited analysis on livelihoods suggests that violence, work-related injuries, and precarious jobs are common for those working in the sand industry, with sand mining producing different types of work depending on the level of mechanization. We conclude by noting several gaps in the literature, including the narrow geographical focus (mainly India and China), the lack of attention to the intersection between sand mining and other anthropogenic disturbances, and the need to establish transparent sand governance processes within this region.

Discussion: “Physical and numerical modelling of strip footing on geogrid reinforced transparent sand”By Jianfeng Chen, Xiaopeng Guo, Rui Sun, Sathiyamoorthy Rajesh, Song Jiang, Jianfeng Xue, J. Geotextile Geomembr, 49 (2), (April 2021), 399–412

• The results of the performed experiments may be impacted by the boundary effect. • To ensure the validity of the simulated model, the use of parameters that are representative of the test conditions is required. • The response of the geogrid employed is highly nonlinear, which is particularly important for the strain level considered in the analyses.

Reply to discussion by Mirmoradi on “Physical and numerical modelling of strip footing on geogrid reinforced transparent sand”

• The chosen test configurations have insignificant boundary effect and would not alter the failure mechanism of foundations. • The load-strain behavior obtained from geogrid tensile test can represent the behavior of reinforcement in foundation soils. • Numerical analysis by introducing the plane strain friction angles is of significance for comparison with existing study.

Experimental and theoretical investigation of transparent sand composing of fused quartz and calcium bromide solution

The thermal conductivity of soil is a fundamental physical property related to heat conduction and also one of the widely applied parameters in geotechnical engineering. Thermal needle tests were performed to measure the thermal conductivity of transparent sand. The thermal conductivity of three particle sizes of transparent sand was measured at different porosities and temperatures. The result shows that the thermal conductivity of transparent sand decreases with the increase of porosity and temperature. A modified model is proposed to calculate the thermal conductivity of the tested sand. Compared with the literature models, which are only suitable for room temperature, the modified model in this paper is applicable to a wider temperature range, ranging from 5∘C to 45∘C. It will also be beneficial to future studies on thermal reponses of granular materials, i.e., energy pile model test using transparent sand.

Physical and numerical modelling of strip footing on geogrid reinforced transparent sand

This paper presents the results of laboratory scale plate load tests on transparent soils reinforced with biaxial polypropylene geogrids. The influence of reinforcement length and number of reinforcement layers on the load-settlement response of the reinforced soil foundation was assessed by varying the reinforcement length and the number of geogrid layers, each spaced at 25% of footing width. The deformations of the reinforcement layers and soil under strip loading were examined with the aid of laser transmitters (to illuminate the geogrid reinforcement) and digital camera. A two-dimensional finite difference program was used to study the fracture of geogrid under strip loading considering the geometry of the model tests. The bearing capacity and stiffness of the reinforced soil foundation has increased with the increase in the reinforcement length and number of reinforcement layers, but the increase is more prominent by increasing number of reinforcement layers. The results from the physical and numerical modelling on reinforced soil foundation reveal that fracture of geogrid could initiate in the bottom layer of reinforcement and progress to subsequent upper layers. The displacement and stress contours along with the mobilized tensile force distribution obtained from the numerical simulations have complimented the observations made from the experiments.

Influence of surface footing loading on soil arching above multiple buried structures in transparent sand

Constructing a new buried structure nearby an existing one or constructing multiple buried structures in close proximity may change overburden stresses, induce ground movement, and affect soil–structure interaction. Such issues become more complex when these nearby buried structures are subjected to surface cyclic footing loading. Cyclic loading is expected to have different influences on the buried structures from static loading. This paper presents two-dimensional trapdoor tests with transparent soil to investigate the influences of static versus cyclic surface loading, number of trapdoors, overburden soil height, and load frequency on soil arching above single or multiple adjacent buried structures. The particle image velocimetry technique was adopted to monitor soil movements during testing. The test results showed that soil arching degraded more under cyclic loading than under static loading. The interaction of buried structures, the thin overburden soil, and the high load frequency accelerated soil arching degradation and induced larger ground surface displacement.

Pore scale and macroscopic visual displacement of oil-in-water emulsions for enhanced oil recovery

In-situ formation of emulsions has been observed in a large amount of chemical flooding pilots, and their effect on oil recovery is of great interest to petroleum engineers and researchers. In this study, microfluidic and transparent sand pack models were used to investigate mechanisms of emulsion propagation and plugging in both pore and macro scales. A microfluidic chip consisting of high- and low-permeability areas was fabricated to represent a heterogeneous area. Another chip was created with the same throat width but enlarged pore sizes (1.5 times larger) and reduced throat lengths. Two microscopic displacement experiments were conducted to compare the effect of pore structure on residual oil displacement after surfactant/polymer (SP) flooding by injecting the same emulsion slug. Meanwhile, the macroscopic flow path of the displacing fluid in the emulsion flooding was investigated using a relatively homogeneous transparent 2D sand pack. The emulsion plugging was proved to be a complicated process, and it could be strongly affected by pore throat structures. Fluid division and high oil recovery could only be achieved during the emulsion flooding in the condition with properly matched sizes of emulsion droplets and pore throats. For a relatively homogeneous 2D sand pack model, oil bank formation and enlarged sweep volume were observed in the emulsion flooding even though it was conducted after SP flooding. As suggested by results of this study, the in-situ formation of emulsion might significantly contribute to the oil recovery in reservoirs with tortuous pore structures, while making little difference in those with large pore throat channels that emulsion couldn’t be trapped in.

Cyclic undrained behavior and liquefaction resistance of transparent sand manufactured by fused quartz

In this paper, a series of cyclic torsional shear tests (TST) were used to study the cyclic undrained behavior and liquefaction resistance of saturated transparent sand manufactured by fused quartz. It was found that the saturated transparent sand has the similar cyclic undrained behavior with saturated natural sands. The mobilized angle of shearing resistance of saturated transparent sand is around 42.6° within the range of saturated natural sands which have angular shape. The saturated transparent sand has a similar trend of shear stress ratio versus number of cycles, but the liquefaction resistance is a little of higher than saturated natural sands.

Geotechnical properties of a transparent glass sand saturated with a blend of mineral oils

A new type of transparent sand composed of a fused quartz sand (i.e., glass sand) and the mixture of two white mineral oils is introduced as a material for geotechnical visualized model tests in this paper. The glass sand has the refractive index identical to that of the mixture of two white mineral oils as pore fluid. The transparent sand possesses significant advantages in transparency. In interior natural lighting environment, the transparent sand has a clear visible depth of 14 cm and a maximum visible depth of 20 cm. It also has advantages in non-toxicity and stable nature. Laboratory tests including direct shear, one-dimensional compression, compaction, consolidation-drained triaxial and permeability tests were conducted to demonstrate physical, mechanical, and permeability properties of the transparent sand agree with those of natural sands. As a comparison and reference for the further study, the main properties of available water-saturated fused quartz and transparent sands by other researchers were also summarized in this paper. The transparent sand described here can be broadly applied in visualized model tests in geotechnical and geological engineering fields.

Transparent Sand Experimental Method for Geotechnical Physical Modeling Using Digital Imaging of Particle Image Velocimetry

By means of the technology of particle image velocimetry (PIV), the physical modelings, using transparent sand and natural sand, were set up to simulate the shallow foundation, respectively. The transparent soil is composed of fused quartz and correspondingly refractive index-matched flammable liquid. The flammable liquid is blended by two white mineral oils, Krystol40 and Puretol7. Transparent sand model was projected by a laser light sheet; meanwhile, the digital images of soil deformations caused by shallow foundation were captured. The PIV was employed to obtain the generated displacement fields from the digital images. The experimental results indicate that the deformation trends in transparent sand model are consistent with that in natural Ottawa sand model; however, the influential region is expanded by about 1.5 times, and the zone and magnitude of down-drag subsidence are extremely enlarged in transparent soil model, compared with those in Ottawa sand model. The verification of test results shows that the shallow strain path method is not suitable for the small-scale transparent sand and natural sand models.

Geotechnical Properties of a Transparent Sand

A new type of transparent sand made of a fused quartz sand (i.e. glass sand) and the mixture of two white mineral oils was introduced as a material for geotechnical visualization model tests in this paper. The transparent sand possessed significant advantages in transparency. In indoor natural light environment, the clear visible depth of the transparent sand was 14cm, and the maximum visible depth can be 20cm. Laboratory tests including direct shear, one dimensional compression, compaction, consolidation-drained triaxial and permeability tests were conducted to investigate the geotechnical properties of the material. The results showed that the material was similar in many properties to natural sands. The transparent sand had great potential to be used in laboratory tests on geotechnical structures in observing soil deformation.

Physical modelling of pipe piles under oblique pullout loads using transparent soil and particle image velocimetry

A small-scale physical modelling method was developed to investigate the pile bearing capacity and the soil displacement around the pile using transparent soil and particle image velocimetry (PIV) technique. Transparent sand was made of baked quartz and a pore fluid with a matching refractive index. The physical modelling system consists of a loading system, a laser light, a CCD camera, an optical platform and a computer for image analyzing. A distinctive laser speckle was generated by the interaction between the laser light and transparent soil. Two laser speckle images before and after deformation were used to calculate the soil displacement field using PIV. Two pipe piles with different diameters under oblique pullout loads at angles of 0°, 30°, 45°, 60° and 90° were used in tests. The load-displacement response, oblique pullout ultimate resistances and soil displacement fields were then studied. The test results show that the developed physical modelling method and transparent soil are suitable for pile-soil interaction problems. The soil displacements around the pipe piles will improve the understanding on the capacity of pipe piles under oblique pullout loads.

Observations of projectile penetration into a transparent soil

In this study, a transparent sand surrogate was employed along with high-speed imagery to un-intrusively visualize the penetration of a spherical projectile into the center of a saturated granular target, representing angular sand, at speeds ranging between 60 and 150m/s. The transparent sand was made by saturating an angular granular fused quartz waste product with a matched refractive index pore fluid made of sucrose. A distinct zone of opacity was observed traveling ahead of the projectile. The opacity zone appears circular during initial penetration and transitions into the shape of an elongated cone in shots with higher initial velocities. Some healing was also observed with time and some increase in transparency was observed. Some of the opacity is attributed to dilatancy of the granular fused quartz during penetration, and healing is attributed to flow of pore fluid into the dilated zone.