Sand Containers Research Articles

Evaluation of Pore Water Pressure Generation in Sands Containing Kaolin Clay

The main aim of this study is to investigate the excess pore water pressure development of clayey sand under dynamic loads using three different models from the literature. For this purpose, stress-controlled dynamic triaxial test were performed on specimens prepared with three different kaolin clay contents (FC=5-15) to measure excess pore water pressure generation at various cyclic stress amplitude ratios. The tests were conducted under an effective confining pressure of 100 kPa. The results were used to obtain excess pore water pressure development of clayey sands under undrained dynamic conditions. Then, the results were compared with three different pore water pressure generation models to update the model coefficients for sands containing kaolin.

THE JOURNEY FROM THEORY TO APPLICATION IN COASTAL MANAGEMENT – A REGIONAL PERSPECTIVE FROM SOUTH WESTERN AUSTRALIA

This paper traces the journey from theory to application in several projects undertaken in a regional area of Western Australia. This includes design and construction of coastal rock revetments, low profile geotextile sand container groynes, and beach nourishment projects. The importance of understanding the subtleties of coastal dynamics in a particular area, the application, and limitations of widely applied coastal engineering practices, and the importance of positive relationships with experienced local contractors in delivering coastal projects is outlined.

FRAGILITY ANALYSIS OF DUNES REINFORCED WITH GEOSYNTHETIC SAND CONTAINERS

Encroachment of infrastructure on the natural beach system constrains dune volumes and necessitates construction of structural and nonstructural mitigation measures to improve coastal resilience. Nature-based solutions, such as dunes reinforced with geosynthetic sand containers (GSCs), are increasingly being used to stabilize coastlines and protect communities from smaller storm events (e.g. 50-year storms) while at the same time providing flexibility in design considering the uncertainty regarding rates of sea level rise and the increasing destructive power of storm events. Using risk-based hazard assessments, such as fragility curves, it is possible to quantify the resiliency of reinforced coastal systems to address these dynamic conditions. A fragility curve represents the conditional probability of failure of a coastal structure (e.g. natural dune, reinforced dune, seawall, etc.) as a function of a certain stress acting on the structure (typically water level, wave height/period; Gruhn et al. 2012). The main advantage of a fragility curve, compared to a damage function that quantifies a deterministic degree of damage directly to a stress, is that it can account for uncertainties in both the structural resistance (i.e. capacity) and the environmental stress (i.e. demand) of the system. The objective of this research is to present a fragility analysis of a U.S. Federally funded GSC-reinforced dune in Montauk, NY. This dune was constructed in 2016 and experienced significant erosion of the protective berm and sand covering the GSCs during a 1-year storm event that same year.

Assessment of a new pluviation system designed to prepare uniform samples of sand

In soil and soil-structure interaction laboratory experiments, the technique applied to prepare the sand deposit remarkably influence the performance of the system, including the stress–strain behavior. Air pluviation techniques represent the most suitable choice when a wide range of densities is required. This study presents the details of a simple and effective air pluviation system designed to be suitable for reconstituting small specimens of sand. Many of the previous studies have focused on traveling the pluviator in the horizontal direction only, without paying much attention to the vertical movement during pluviation. The apparatus described in this paper has the ability to overcome this issue by providing automatic lifting tools to the sand container while the thickness of the sand deposit builds up inside the collecting mold. To understand the influence of grain size distribution of sand on the achieved relative density (RD), three different samples of poorly graded sands were used in the experiments. Parametric studies, including the influence of the height of drop (HD) and deposition intensity (DI) on the relative density, were carried out on the three sand samples. It was observed that the range of obtained RDs depends mainly on the grain size distribution of the sand used. Three distinguished zones were observed in the RD-HD relationship, starting with a linear variation, followed by a nonlinear relationship until achieving a constant RD regardless of the increase of HD value. The uniformity of pluviated sand was assessed using a cone penetration test (CPT). Results of the CPT test showed that denser and more uniform samples could be obtained by raising the container up during the pluviation process.

Hydraulic Performance of Geotextile Sand Containers for Coastal Defenses

Laboratory experiments were performed in the wave flume of the Laboratorio di Idraulica e Costruzioni Marittime of the Università Politecnica delle Marche (Ancona, Italy) to study the hydrodynamic performance of coastal protection structures made of a new type of geotextile sand containers (GSCs). Such structures are used as softer and flexible alternatives to traditional hard coastal defenses made of concrete or rubble mound material. The GSC structures can also be used as temporary coastal protections during the winter period. The physical model reproduced two main configurations: in the former one, the GSCs were used as coastal revetments with three different slopes. In the latter one, the GSCs were applied to make detached submerged breakwaters with different submergences and berm widths. The geometric scale of the models was 1:10, and the weight of each GSC in the prototype was 5 t. The geotextile material of the containers and the wave characteristics were reproduced by using the Reynolds and the Froude similarity criteria, respectively. Reflection coefficients and hydraulic stability behaviors for the revetments, as well as transmission coefficients and piling-up amount for breakwaters, were obtained.

Preliminary investigation on stability and hydraulic performance of geotextile sand container breakwaters filled with sand and cement

Breakwaters are essential constructions providing tranquility to ports and harbour structures, when there is a lack of natural protection measures. Traditionally these massive structures are constructed using natural rocks weighing tonnes. In the present scenario, obtaining huge natural rocks are difficult as well as non-eco-friendly. Geotextiles sand containers (GSCs) emerges as a suitable alternative for the rock armour units of breakwaters and various literatures supports its efficacy. The present investigation aims at analysing the performance of GSCs when filled with a calculated amount of cement and sand. The Hydraulic performance and stability analysis of cement and sand filled geotextile breakwater models are carried out in a 1:30 scaled monochromatic wave flume. When GSC breakwaters are filled with sand and cement, up to 43% increased stability is observed with a considerable decrease in wave runup, rundown and reflection, than sand-alone filled units. As a result, cement-sand filled GSC units can be suggested as a possible alternative to sand alone filled units where vandalism has to be countered.

Lift Energy Storage Technology: A solution for decentralized urban energy storage

The world is undergoing a rapid energy transformation dominated by growing capacities of renewable energy sources, such as wind and solar power. The intrinsic variable nature of such renewable energy sources calls for affordable energy storage solutions. This paper proposes using lifts and empty apartments in tall buildings to store energy. Lift Energy Storage Technology (LEST) is a gravitational-based storage solution. Energy is stored by lifting wet sand containers or other high-density materials, transported remotely in and out of the lift with autonomous trailer devices. The system requires empty spaces on the top and bottom of the building. An existing lift can be used to transport the containers from the lower apartments to the upper apartments to store energy and from the upper apartments to the lower apartments to generate electricity. The installed storage capacity cost is estimated at 21 to 128 USD/kWh, depending on the height of the building. LEST is particularly interesting for providing decentralized ancillary and energy storage services with daily to weekly energy storage cycles. The global potential for the technology is focused on large cities with high-rise buildings and is estimated to be around 30 to 300 GWh.

Effect of armour unit layers and placement mode in the determination of stability of geotextile sand container (GSC) breakwaters

Geosynthetic Sand Containers (GSCs) are increasingly harnessed for their coastal protection capabilities. Recent studies point to its efficacy to be used even as armour units of breakwaters. The current investigation aims at understanding the effect of armour unit layers and placement modes in altering the stability of GSC breakwaters. Single-layered and double-layered GSC structures with slope parallel and perpendicular placement are tested for stability against wave conditions of the Mangaluru coast. A 1:30 scaled monochromatic wave flume model study is adopted to detail the damage levels and stability of various GSC breakwaters. It is observed that the stability of structure increased by up to 17% when supplemented with double layers. Structure tends to be stable with increasing armour units size and fill percentage. Larger bags stacked to double layers is found to be the most stable configuration. 80% filled, slope parallel placement exhibited the least stability. The paper dealt with all factors affecting structure stability and deduced stability nomograms helpful for coastal engineers to design GSC breakwaters.

Influence of Lateral Stress Ratio on N-Value and Cyclic Strength of Sands Containing Fines

Influence of Lateral Stress Ratio on N-Value and Cyclic Strength of Sands Containing Fines

Physical model studies on damage and stability analysis of breakwaters armoured with geotextile sand containers

Harnessing the advantages of geotextile sand containers (GSCs), numerous submerged breakwaters and shoreline protection structures have been constructed worldwide. But an emerged breakwater structure with geotextile armour units, capable of replacing the conventional structures, is rarely discussed. A 1:30 scaled physical experimentation is chosen as a preliminary investigation to test the feasibility of using GSCs as breakwater armour units. Structural design is evolved based on a comprehensive literature survey. The paper focuses on the stability parameters and damage characteristics of the proposed structure. Four different configurations are subjected to waves, confining to Mangaluru's wave parameters. Effect of armour unit size and sand fill ratio on the stability of the structure is analysed and it is concluded that changing sand fill ratio from 80% to 100% shot up the structural stability to a maximum of 14%. Increasing bag size also resulted in the increased stability up to 8%. Experiments revealed that the best performing configuration could withstand wave heights up to 2.7 m. Stability curves for all tested configurations are discussed and can serve as an effective guideline for designing GSC breakwaters.

Development and calibration of an experimental test bench simulating solar reflectors erosion

The main objective of this paper is to design, calibrate and make functional a horizontal test bench used to carry out the experimental simulation of solar reflectors erosion induced by sand particles. The developed equipment provides the possibility to control the air speed, the impact angle between the fluid flow and the target surface as well as the mass rate of the ejected particles. The originality of this work lies on the introduction of a new parameter, identified as, the unified sand mass received by the samples in each test, without considering the experiments conditions (air speed, impact angle, etc.) by acting on the ejected sand mass poured in the sand container. To make the setup operational, a set of calibration tests was conducted under multiple scenarios. The collected data from the calibration tests were analyzed to choose the appropriate configuration. A multiple linear regression function was applied to analyze the influence of the inputs parameters on the tests repeatability. A descriptive equation calculating the amount of sand needed to ensure the unified sand mass, homogeneity and repeatability of the experiments is introduced. The results of erosion simulation carried on solar glass reflectors are also presented; for an air speed of 25 m/s, the reflectance loss is two times greater in 90° (11.03%) than the registered in 45° (5.31%). The developed bench should help researchers to set up their devices for the conduction of advanced experiments ensuring that the obtained results are as repeatable as efficient.

Closure to “Predicting the Maximum Shear Modulus of Sands Containing Nonplastic Fines” by Meisam Goudarzy, Negar Rahemi, Md. Mizanur Rahman, and Tom Schanz

Closure to “Predicting the Maximum Shear Modulus of Sands Containing Nonplastic Fines” by Meisam Goudarzy, Negar Rahemi, Md. Mizanur Rahman, and Tom Schanz

SCOUR PROTECTION AROUND A SINGLE SLENDER PILE EXPOSED TO WAVES

The study of the scour around a monopile foundation and, in particular, the evaluation of the performance of alternative scour protection systems made of geotextile sand containers (GSCs) are here presented. Different configurations of the scour protection system were experimentally analyzed. The scour protection efficiency has been tested with both regular and random waves. A design dynamic formula for the scour protections is developed based on the stability of the GSC and, hence, on the evaluation of the weight of the geotextile sand container by means of the stability number. A damage level has been defined and related with the modified stability number. The paper provides useful information for the design of the scour protections made of geotextile sand containers, for the evaluation of the performance of such systems in terms of scour reduction, sinking and damage level of the scour protections.

Uplift Capacity of Single Pile Embedded in Partially Submerged Sand

This article illustrates experimentally the effect of the groundwater level rising on the soil pile interaction under uplift load. A series of model test for piles embedded in partially submerged sand along pile depth under pull out loads were carried out. A rigid steel cylindrical cell measuring 315 mm inside diameter with 850 mm high was used as a sand container. Investigations were done by varying parameters as the ratio between groundwater height to embedded pile length (hw/L), pile stiffness (L/D), installation method and sand density. Results showed that there is a considerable decrease in the uplift capacity of the piles due to increase in the groundwater level. It has been found that the variation of the submerged pile length ratio from 0 % to 100 % leads to decrease in the uplift capacity as much as 60% of its initial value in dry condition.

Effect of Particle Morphology, Compaction, and Confinement on the High Strain Rate Behavior of Sand

The effect of grain shape, size distribution, intergranular friction, confinement, and initial compaction state on the high strain rate compressive mechanical response of sand is quantified using Long Split Hopkinson Pressure Bar (LSHPB) experiments, generating up to 1.1 ms long load pulses. This allowed the dynamic characterisation of different types of sand until full compaction (lowest initial void ratio) at different strain rates. The effect of the grain morphology and size on the dynamic compressive mechanical response of sand is assessed by conducting experiments on three types of sand: Ottawa Sand with quasi-spherical grains, Euroquartz Siligran with subangular grains and Q-Rok with polyhedral grain shape are considered in this study. The adoption of rigid (Ti64) and deformable (Latex) sand containers allowed for quasi-uniaxial strain and quasi-uniaxial stress conditions to be achieved respectively. Additionally, the effect of intergranular friction was studied, for the first time in literature, by employing polymer coated Euroquartz sand. Appropriate procedures for the preparation of samples at different representative initial consolidation states are utilized to achieve realistic range of naturally occurring formations of granular assembly from loose to dense state. The results identify material and confining sample state parameters which have significant effect on the mechanical response of sand at high strain rates and their interdependency for future integration into rate dependent constitutive models.

Predicting the Maximum Shear Modulus of Sands Containing Nonplastic Fines

There are some attempts to evaluate Hardin’s equation for transition soils, i.e., sand mixed with a systematic increase of fines (particle size≤0.075 mm) content, fc. The most common finding is that maxmium shear modulus, Gmax, decreases with increasing fc, and there are attempts to capture the effect of fc on Gmax by considering Gmax of clean sand as a reference. These are done by (1) developing empirical relations of A, n, c, or d with fc; (2) using equivalent granular void ratio, e*, instead of void ratio, e in Hardin’s equation; and (3) using a critical state (CS) approach. This paper presents 288 resonant column Gmax data for clean Hostun sand and Hostun sand mixed with 5, 10, 20, and 30% nonplastic quartz powder. It is found that when e in a pre-established Hardin equation for clean Hostun sand is replaced by e*, Hardin’s equation can predict Gmax for Hostun sand with fc with good accuracy. Only soil grading properties, e.g., D10 and d50, are required as inputs to convert e to e*. This is a significant advantage over a recently proposed CS approach which requires critical state lines (CSLs) data for each fc.

Load distribution in pile group embedded in sandy soil containing cavity

The present study investigates the influence of presence of cavities on the bearing capacity and settlement of piled foundation. The work included experiments carried out to study the behavior of pile models constructed in sand with a dry unit weight 16.8 kN/m3. Pile models were tested in a sand container under a load applied through a hydraulic mounted jack and measured using a load cell. Three strain gages were proved to piles to evaluate the strains and then estimate the load transformed to each pile in the group by a strain indicator. Three groups of piles (single pile, group of piles (1 × 2), and group of piles (2 × 2)) were tested in the laboratory as a free standing pile group. A prototype of a cavity was used and placed adjacent to the piles at various distances from the centerline of piles and various depths below the surface. The effect of variation of cavity location (X), cavity depth (Y), and cavity diameter (d) on the load and settlement of the pile and groups of piles has been studied for all tests. It was found that the load in pile increases with increase of (X/D, D is the pile diameter) due to decrease of the zone affected by the presence of cavity. When the cavity is located at a close distance to the pile, it will reduce the soil density and hence decrease the shaft friction along the pile and lead to decrease in the pile failure load. The failure load is not affected by the presence of a cavity at a distance of 5.5 pile diameters at all depths. The presence of the cavity in the soil reduces the ultimate failure load of the pile. For pile group (1 × 2), the reduction rate is about (40% to 80%) at (d/D = 1), while the rate at (d/D = 2) is about 65% to 85%.

Wave Transmission over the Low-Crested Sand Container Breakwaters

Breakwaters made of sand container is one of the most economical options for wave protection at coastal areas. These breakwaters have been adopted with mixed success at several locations in Malaysia. Nevertheless, the performance of these structure has not been properly studied and documented to date. This study is undertaken to study the wave transmission ability of the submerged sand container breakwater with respect to its width and height as well as the water depth. A number of experiments have been conducted in a wave flume to quantify the wave transmission coefficient of the test models of different layouts when exposed to regular waves. The experimental result has shown that the breakwater is effective in arresting the shorter period waves, particularly in shallow water. The height of the breakwater has to be increased in order to arrest the longer period waves.

No drone zone

Here, Baraniuk discusses how technology to ground drones is taking off. Last week, someone landed a drone on the roof of the Japanese prime minister's office in central Tokyo. It carried a container of sand with traces of non-harmful radioactive isotopes Caesium 134 and 137. A 40-year-old man admitted to the stunt, saying it was a protest over Japan's nuclear power program. Modern drones are cheap and easy to fly. They're small enough to evade traditional surveillance and many worry that this will make them attractive to terrorists and other criminals. However, it may now be possible to clip their wings.

Optimization of Production Parameters of Geotextiles Used for Shoreline Protection

The use of geotextile sand containers (GSCs) in shoreline protection systems has moderately grown since the first applications in the 1970s and increasingly used as an alternative to natural stone, slag, and concrete. Due to their economical, technical and ecological advantages, the use of geotextiles and geocomposites for filter and drainage functions is increasing worldwide and has a 40 year history already. For coastal protection measures, nonwovens are proven to have long-term resistance against ultraviolet radiation and saltwater. High elongation behavior provides superior properties during loading in coastal protection means, which is determined as being the biggest risk for damaging geotextiles. Such applications require certain functional characteristics in the geotextiles, besides their basic properties, which are required to be engineered by the judicious optimization of the needlepunching process. In this study, the effect of the process parameters including punch density and depth of needle penetration has been investigated on the mechanical (tensile strengths in the machine and cross-machine directions) properties of needlepunched nonwoven geotextiles. These process parameters are then empirically related to the fabric properties by using a multiple regression technique.