High Void Ratio Research Articles

Application of Image Technique and Optical Fiber Sensor for Air-water Mixture Flow

Measurements of multiphase flows containing bubbles have been limited because most existing methods target one phase flows. Especially, multiphase flows with a high void ratio have been rarely successful in measurements due to the sudden change of density and thick interfaces between air and water. This study introduces two methods that are capable of measuring flow fields regardless of bubble void ratio, named bubble image velocimetry and bundle fiber optic flow meter. The calculation of the depth of field is suggested to reduce and estimate errors by perspective image velocimetry. The bundle fiber optic flow meter is designed to increase a measurement rate using many optical fibers with a thin diameter. The two methods measured bubble plumes to test reliability and the velocity measurements show good agreement. In addition a hydraulic jump, one of the multiple flows in rivers was measured to test applicability of the methods.

Investigation of shallow landslides triggered by heavy rainfall during typhoon Wipha (2013), Izu Oshima Island, Japan

Typhoon Wipha struck Izu Oshima Island on 16 October 2013, bringing heavy rainfall. It triggered widespread landslides on the western slopes of Izu Oshima Island, and caused significant loss of life and serious property damage. Authors have conducted both field investigations and laboratory experiments in an effort to understand the initiation mechanism of the shallow landslides triggered by heavy rainfall. Pyroclastic-fall deposits on the slopes are well-graded fine sand with silt, and with high specific gravity and void ratio. These soil properties will affect the mechanical and hydraulic characteristics of soil. The results of consolidated-undrained triaxial tests show that the effective internal friction angle of soil is 38.7 degrees. The results of triaxial tests using pore-water pressure control show that static liquefaction can occur in porous pyroclastic-fall deposit layers due to rainfall infiltration. The effective strength of pyroclastic-fall deposits on the upper slope is quite high. Even though the slope is very steep (over 30 degrees), it can remain stable while in an unsaturated condition. Due to heavy rainfall and the porosity of the pyroclastic-fall deposits, rainfall can quickly infiltrate into soil layer. Moreover, the interface above the underlying basalt will stop groundwater infiltration, acting as an impervious boundary. With increase of groundwater level, the effective strength of the porous soil will decrease. Finally, static liquefaction can be triggered, leading to the generation of shallow landslides on the upper slopes.

Microstructural changes of an undisturbed, reconstituted and compacted high plasticity clay subjected to wetting and drying

The behaviour of soil, and in particular compacted clay fill, can have significant implications on the safe and reliable operation of man-made infrastructure. The mechanical behaviour of soil (e.g. volume change and shear strength) is widely recognised as being associated with the microstructural arrangement (fabric/structure). In the case of high plasticity clays, despite the large amount of research carried out, soil microstructure and its evolution along mechanical and hydraulic paths are still not well understood. This makes incorporation of microstructural analysis difficult in engineering practice and highlights the need for further research. A comprehensive microstructural analysis of Maryland clay, a high plasticity residual soil, based on mercury intrusion porosimetry tests, is presented in this paper. Experimental results obtained from undisturbed, reconstituted and compacted specimens subjected to different hydraulic and mechanical paths are described. As with mechanical investigations, the reconstituted state is proposed to be used routinely as a reference state for comparison of undisturbed and compacted soil. The microstructural evolution of the compacted clay, prepared on the wet side of standard Proctor optimum water content, with an initially high void ratio, is examined along the main drying path. Importantly, a monotonic suction increase from the as-compacted state is shown to have negligible effect on the distribution of macro-pores. However, a new insight is provided based on the evolution of the dominant micro-pore entrance diameter which is shown to reduce with increased suction. This micro-pore entrance diameter is shown to correspond with the theoretical suction back-calculated from a simple capillary tube model, up to a limit. It is observed that, under oedometric conditions, the as-compacted microstructure is erased during saturation (soaking) and resembles the reconstituted microstructure. For this particular material and preparation conditions, it is demonstrated that a bimodal microstructure is not recovered on drying from a saturated state.

Effect of large dams and irrigation in the upper reaches of the Yellow River of China, and the geohazards burden

The geomorphology of the upper reaches of the Yellow River of China is composed by a sequence of fluvial terraces that were formed following phases of neotectonic uplift and subsequent river downward incision. Most of the terraces are covered by thick loess deposits. These quaternary deposits are characterized with high void ratio, vertical joint development, easy to collapse. This is particularly problematic along the terrace edge risers in the high relative relief terrain described here.Substantial water resource development projects, such as large dams and associated irrigation schemes have been developed in this region over the past 60 years. The level terrace surfaces were initially seen as ideal locations supporting migrating populations and irrigated agriculture. However, following the application of irrigation in these previously dry environments, the meta-stable loess collapsed upon wetting, causing widespread subsidence of the plateau levels (more than 2m) and the build-up of groundwater, resulting in a loss of shearing resistance along the terrace edges and the instigation of large mass movements. Several measures and some academic research have been undertaken in this area, but neither the disastrous effect upon local people nor the evolutionary trend of the hazards have been studied clearly until now. This paper provides a summary of the hazards, their study and management history based on consideration of the extensive literature covering both academic articles and project reports. The paper concludes with a discussion of opportunities for mitigation of these hazards and appropriate management strategies for the irrigated surfaces.

Importance of sedimentation process for formation of microfabric in clay deposit

When a clay sample is reconstituted from a slurry state to a normally consolidated state, a higher initial water content generally derives a higher void ratio in e–logp relationship. However, in undisturbed Holocene clay samples collected from a soil layer under the seabed, void ratio is much higher than that for the reconstituted, even though the reconstituted sample was consolidated from a sample slurry state with a very high initial water content. Therefore, the higher void ratio for undisturbed Holocene clay cannot be explained by the initial water content. There must be another key factor to explain the higher void ratio for undisturbed Holocene clay. In this study, the difference between the microfabric of deposited clay from suspension state and reconstituted clay from a slurry state is investigated to clarify the key factors contributing to the higher void ratio. The clay in this study is Osaka Bay Holocene clay sampled from GL −15 to −19m below the seabed. Sedimentation tests from the suspension state were carried out in various conditions of initial water content, salt concentration, and pH. A series of sedimentation tests was carried out with two types of hollow cylinders: an observation glass cylinder with an inner diameter of 60mm and a height of 400mm (specimen height of 350mm), and a cylindrical acrylic container with an inner diameter of 100mm and a height of 1800mm (specimen height of 1500mm). In the 100-mm diameter cylinder, the deposited sample was consolidated by a pressure of 19.6kPa, then mounted in an oedometer ring with an inner diameter of 60mm and a height of 20mm. An incremental loading oedometer test was then carried out up to 39.2kPa. The microfabric of the consolidated specimen was observed by scanning electron microscope (SEM) and quantitatively investigated by mercury intrusion porosimeter (MIP). It was shown that the high void ratio of natural clay deposit is not only due to the high initial water content but also to the sedimentation process with flocculation. This plays an important role in the formation of the microfabric of natural clay deposits characterized by a significantly higher void ratio than reconstituted samples.

Physical and microstructural impacts on the hydro-mechanical behaviour of Ypresian clays

An experimental characterisation on Ypresian clays that are considered as one of the potential geological host formations for the radioactive waste disposal in Belgium has been carried out. Physical, microstructural, hydraulic and mechanical properties were investigated on the samples taken from a cored borehole at Kallo in the Northern Belgium at 290–400m depth. Identification tests, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and oedometer tests were performed. The results obtained showed that Ypresian clays are highly plastic (large values of consistence limits, specific surface, blue ethylene value) and of relatively low density, in relation to their high swelling clay content. In addition, their physical and mineralogical properties present significant variations over depth. Two microstructural arrangements, matrix-type and aggregate-type respectively for the depths with higher and lower swelling content, were identified. The former exhibits bi-modal porosity while the latter shows a common deep sediment mono-modal porosity but with a larger dominant pore size. The permeability of the clays with matrix-type microstructure is significantly lower than that with aggregate-type despite their higher void ratio. Moreover, these microstructural features result in the initial unsaturated state of Ypresian clays sample. Typical hysteretic unloading–reloading loops are identified on both low- and high-pressure oedometer tests that can be explained by a microstructure-based swelling stress concept. The variation of this swelling stress with the corresponding initial void ratio over depth perfectly reflects the physical variations and is consistent with that of swelling stress determined from common swelling tests. The yield stress ratios are slightly higher than the over-consolidation ratio, suggesting negligible effects of diagenesis, cambering and valley bulging etc. The variations of compression index, compression and swelling slopes are consistent with the physical and microstructural variations.

Consolidation Properties and In-Situ Stress of the Marine Clay in Southern Korea

A very soft ground constructed by dredging and hydraulic fill has characteristics such as high water content, high initial void ratio, and very little effective stress. Estimating, with thorough considerations about consolidation properties and the initial stress associated with each layer's distinctive stress history, is essential in order to predict a reasonable consolidation settlement of soft ground. By investigating a construction project for national industrial complexes at a coastal area in southern Korea that experienced reclamation and ground improvement adapting PVD, various laboratory tests to find consolidation properties were performed with undisturbed samples collected from the entire depth of the marine clay fill layer and original clay layer. Through the investigation, this report suggests relationships of heterogeneity of permeability in both vertical and horizontal directions, void ratio-effective stress, and void ratio-permeability. Considering the fact that the original clay layer was under the process of consolidation by load due to hydraulic fill from the top, estimating the appropriate initial stress of each layer is critical to predict the future process of consolidation settlement determined by time. In order to obtain the initial stresses of two layers with different stress histories related to consolidation, cone penetration and dissipation tests were conducted.

One-Dimensional Consolidation of Sedimented Stowed Pond Ash and Pond Ash-Lime Mixture Deposits—A Comparative Study

The present study investigates the influence of slaked lime addition on the one-dimensional consolidation properties of sedimented stowed pond ash (Class F category). The effects of step incremental consolidation pressure, lime addition, and curing time on the one-dimensional consolidation characteristics such as rate of settlement, consolidation coefficients, and void ratio, of the sedimented stowed pond ash and pond ash-lime mixture deposits are investigated using a fixed ring consolidometer. The study revealed that the void ratios of both the stowed pond ash and pond ash-lime mixture deposits decrease with the applied pressure. Comparatively, the stowed pond ash-lime mixture deposit demonstrated a higher void ratio than the stowed pond ash deposit. A decrease in coefficient of consolidation (Cv) values with the increase in consolidation pressure and curing time is also observed in the case of both deposits, thereby indicating a decrease in their compressibility. Owing to the addition of lime, an improvement in the consolidation characteristics in terms of increase in Cv values and decrease in final settlement of the sedimented stowed pond ash-lime mixture deposit is generally observed at higher consolidation pressures and longer curing time.

Investigation of the permeability of porous concrete reconstructed using probabilistic description methods

Porous concrete has a high void ratio with continuously interconnected void clusters. The void distribution in concrete strongly affects its physical properties, such as strength and percolation. To investigate and quantify the spatial distribution of voids inside porous concrete specimens, computed tomography (CT) images and low-order probability functions can be used. In this study, we reconstruct porous concrete specimens with different void distributions using low-order probability functions. The void distributions of the original and reconstructed porous concrete specimens should exhibit almost the same statistical characteristics. We confirm that reconstructed porous concrete specimens generated using the proposed probabilistic optimization process have statistically identical characteristics, and exhibit similar material behaviors as with the original model. These reconstructed specimens can be utilized for numerical experiments so as to reduce the number of time-consuming real experiments.

Experimental Study on Shear Strength of Different Types of Soil

Red clay belongs to region special soil.It has engineering geological properties that are different from general soils.The natural red clay has high ratio void ratio,high moisturecontent,low density and so on.But red clay has non-corresponding high strength,bearing capacity of foundation and low compressibility. With the high speed development of China economy,the main soil named red clay in South is used as bearing stratum of many building foundations.However,when red clay is used as foundation,it is regarded as gerenal clay to consider its bearing capacity of foundation.So this will cause two disadvantages.First,potential is not given full play,resulting in considerable waste.Second,red clay has some special properties,such as high woid ratio,softening in water.These properties will bring hidden troubles,causing some bad accidents.These are caused by lacking of knowledge to engineering properties.Xiamen locates in southeast of China,and red clay is widely distributed.It is formed by accumulation through laterization of granites and basalts.So it is essential to study red clay.In this article,literatures of red clay in Xiamen are collected.Indoor conventional geotechnical tests are done,some engineering property parameters are obtained.

Evaluation of Polyphenylene Sulfide and Steel Fibers on Mechanical Properties of Pervious Concrete Pavement

Strength is the primary concern for Portland cement pervious concrete (PCPC) designs. Since PCPC has a high void ratio (often without fine aggregate due to the permeability requirement), compressive and tensile strengths tend to be lower than those of conventional concrete pavements. In this experimental study, PCPC mixes made with steel fibers and polyphenylene sulfide (PPS) fibers and various amounts of sand were evaluated. Mechanical properties, porosity, and permeability of the PCPC were tested. The results pointed out adding fibers to the mixes increased the concrete strength as well as void content. It is noteworthy to mention that PPS fibers performed better than steel fibers. Addition of a small amount of fine sand (approximate 7 % by weight of total aggregate) to the mixes with PPS fibers significantly improved the concrete strength.

A distinct element method numerical investigation of compaction processes in highly porous cemented granular materials

SUMMARYIn this paper, the results of an oedometric numerical test campaign, performed by means of a 3D Discrete Element Code on idealised cemented granular cylindrical specimens, are illustrated. The idealised microstructure taken into account is characterised by the following: (i) rigid grains bonded to one another; (ii) a high void ratio; and (iii) two different families of voids: the micro and the macro‐voids.The compaction process developing within the specimens, as well as the localization along tabular zones of pure compressive deformation (compaction banding) that in some cases takes place, are discussed. The influence on the evolution of this peculiar strain localization process of many microstructural/numerical parameters like material porosity, macro‐void size, the constitutive relationship adopted for the bonds and the bond damage rate is analysed.Tests for different values of porosity were run. Below a certain porosity threshold value, the onset of mixed modes of localisation was detected whereas the increase in the macro‐void size is observed to favour the onset of instability. Copyright © 2014 John Wiley & Sons, Ltd.

Multiple Compaction Tests on Laterite

Laterite has high void ratio, low density, high moisture content, high plasticity, but it does not match with their physical nature, which has the relatively high strength and low compressibility. In order to improve the strength of laterite and increase its compactness, we usually use the method of dynamic compaction in some large engineering projects. Its easy to find that soil compaction degree increased with the moisture content When the content of moisture is low, but soil compaction decreased after reaching the highest. Multiple compaction can effectively improve the maximum dry density and reduce optimum moisture content, but after compaction number is too much that optimum moisture content dont increase obviously.

Experimental Research of Soft Soil Ground Treatment in Yangpu Port by Static-Dynamic Drainage Consolidation

Yangpu Port has inhomogeneous soft soil with the properties of high water content, high void ratio, high compressibility and low shear strength. Based on soft soil ground treatment engineering practice, the geological characteristics are summarized, the ground treatment methods are comparatively analyzed, static-dynamic drainage consolidation method is chosen to treat the soft soil ground, the reinforcing mechanism of vertical and horizontal drainage system are discussed, the design of drainage system, preloading and dynamic consolidation are researched and the surface settlement monitoring, pore water pressure monitoring, side piling displacement monitoring, laboratory soil test and plate loading tests are carried out. The results show that average surface settlement is 1170.8 mm, the physical and mechanical properties of soft soil are improved and the characteristic value of foundation bearing capacity is greater than 120kPa.

Stress-dependent and strength properties of gas hydrate-bearing marine sediments from the Ulleung Basin, East Sea, Korea

This paper presents a comprehensive laboratory experimental characterization of the host sediment from natural hydrate-bearing sediments recovered during the Ulleung Basin Gas Hydrate Expedition 2 (UBGH2) in 2010. The basic geotechnical properties are characterized and compared with previously reported data. The mineralogy and microstructure analyses confirm that the sediments mainly consist of illite, kaolinite, chlorite, calcite, and montmorillonite, with a high concentration of microfossils (diatoms). The presence of microfossils may affect many of the geotechnical properties, including plasticity, activity, specific surface, and grain size. The tested specimens have a relatively high initial void ratio, with a high compression index (e.g., Cc ranging from 0.6 to 1.0) and swelling index (e.g., Cs ranging from 0.1 to 0.25). The shear wave velocities measured during loading indicate a high sensitivity to the stress state, which demonstrates the critical role of effective stress in controlling the stiffness of the sediments. The peak friction angles are determined to be 17.6°–24.6° for clay and silt sediments, and 27.1° for high sand fraction specimens. The stress dependent and strength parameters obtained in this study may be very useful for performing stability analyses during hydrate dissociation and production.

Temperature Effects on Geotechnical Properties of Kaolin Clay: Simultaneous Measurements of Consolidation Characteristics, Shear Stiffness and Permeability Using a Modified Oedometer

The increased worldwide use of shallow geothermal energy systems including ground source heat pumps (GSHPs) have given concerns of possible temperature effects on soil geotechnical properties. In this study, the effects of temperature on mechanical characteristics such as consolidation settlement, shear stiffness, and permeability of kaolin clay were investigated. A modified oedometer apparatus which allows the simultaneous measurements of consolidation settlement, shear wave velocity, and hydraulic conductivity was developed and used. Consolidation tests on preconsolidated kaolin samples (two sample sizes: ϕ 6 cm x H 10 cm and ϕ 6 cm x H 2 cm) were performed under sequentially increasing consolidation pressures at three different temperatures (5 °C, 15 °C, and 40 °C). Larger apparent preconsolidation pressure, Pac, was seen at higher temperature (40 °C) for both sample sizes, but only for samples having relatively high initial void ratios between 1.53 and 1.62. Relatively higher shear modulus as a function of void ratio was observed for samples at higher temperature, suggesting that changes in fabric structure (likely caused by enhanced inter-particle forces between clay particles at higher temperature) resulted in the increased shear stiffness and, thus, higher Pac at 40 °C. Oppositely, temperature effects on the Manuscript received February 5, 2013. This work was partly funded by a grant from the Research Management Bureau, Saitama University, the grant-in-Aid for Scientific Research of Japan Society for the Promotion of Science (JSPS) (No.22860012), and a JSPS bilateral research project. This work was also partially supported by a CREST project, a research grant from the Japan Science and Technology Agency (JST). E. E. Mon is with Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura ku, Saitama, 338-8570, Japan. (phone/fax: (+81) 48-858-3116; e-mail: nyima.eimon@gmail.com). S. Hamamoto, is with Graduate School of Science and Engineering, and Institute for Environmental Science and Technology, Saitama University, 255 Shimo-okubo, Sakura ku, Saitama, 338-8570, Japan. (e-mail: hamasyo@mail.saitama-u.ac.jp) K. Kawamoto is with Graduate School of Science and Engineering, and Institute for Environmental Science and Technology, Saitama University, 255 Shimo-okubo, Sakura ku, Saitama, 338-8570, Japan. (e-mail: kawamoto@mail.saitama-u.ac.jp). T. Komatsu is with Graduate School of Science and Engineering, and Institute for Environmental Science and Technology, Saitama University, 255 Shimo-okubo, Sakura ku, Saitama, 338-8570, Japan. (e-mail: komatsu@mail.saitama-u.ac.jp). P. Modrup is with Department of Biotechnology, Chemistry, and Environmental Engineering, Aalborg University, 9000 Aalborg, Denmark. (e-mail: pm@bio.aau.dk). permeability of kaolin clay were not significant within the studied temperature range between 5 °C and 40 °C.

Bubbling behavior of a fluidized bed of fine particles caused by vibration-induced air inflow

We demonstrate that a vibration-induced air inflow can cause vigorous bubbling in a bed of fine particles and report the mechanism by which this phenomenon occurs. When convective flow occurs in a powder bed as a result of vibrations, the upper powder layer with a high void ratio moves downward and is compressed. This process forces the air in the powder layer out, which leads to the formation of bubbles that rise and eventually burst at the top surface of the powder bed. A negative pressure is created below the rising bubbles. A narrow opening at the bottom allows the outside air to flow into the powder bed, which produces a vigorously bubbling fluidized bed that does not require the use of an external air supply system.

Unsteady Cavitation Analysis Using Phase Averaging and Conditional Approaches in a 2D Venturi Flow

The present study refers to a cavitating Venturi type section geometry characterized by a convergent angle of 18° and a divergent angle of about 8° where the sheet cavity presents typical self-oscillation behavior with quasi-periodic vapor clouds shedding. This work is an extension of previous works concerning void ratio measurements and velocity fields using double optical probe and constitutes a complete analysis of the two-phase structure of unsteady cavitating flow. This paper provides a new method based on conditional and phase averaging technique with wall pressure signal to treat experimental data in order to evaluate more precisely time-averaged and rms values of the void ratio and instantaneous velocity fields. Conditional analysis shows a different behavior of the two-phase flow dynamics leading to highlight high void ratio events linked to the break-off cycle. Unsteady phase averaging of the optical probe signal gives the evolution of the void ratio at each studied location in the venturi and shows that the fluctuations close to the wall (where the re-entrant jet is predominant) are in phase with the upper part of the cavity instead of the thickness of the cavity which is unchanged.

The Small-Strain Shear Modulus and Damping Ratio of Quartz and Volcanic Sands

Abstract The dynamic properties of soils in the region of very small strains are essential for any seismic design. This paper aims to investigate the dynamic small-strain shear modulus (GO) and damping ratio (DO) of reconstituted dry sands of variable mineralogy, shape, and grain-size distribution. In particular, the low-amplitude torsional resonant column test results of 31 specimens are synthesized, 19 specimens of natural and quarry sands predominately composed of quartz particles, and 12 specimens of volcanic sands composed of rhyolitic glassy rock of porous particles. It is concluded that the volcanic sands exhibit significantly lower GO values and slightly lower DO values in comparison to the quartz ones whilst the response of the quartz sands is significantly affected by the shape of the particles. The differences in the observed responses between quartz and volcanic sands are partially attributed to the variability in particles density, morphology, and mineralogy, as well as the higher void ratio and the lower dry density that the volcanic sands exhibit in comparison to the quartz ones. Overall, the effects of the mean effective confining pressure (σm′), the void ratio (e), and the grain-size distribution on the dynamic response of the volcanic soils follow a similar trend as in the quartz sands. Using the general form of available relationships presented in the literature, and after modifying the “constant” parameters, appropriate equations, stemming from the low-amplitude resonant column data test, are proposed that may be used for the estimation of the small-strain shear modulus and damping ratio separately for natural quartz sands, quarry quartz sands, and volcanic granular soils.

Permeability Coefficients of Dredged Slurries at High Void Ratio

According to sediment rates of slurries in initial stages, permeability coefficients of samples applied in this article is obtained. It shows that the permeability coefficients of dredged slurry determined from sedimentation tests are feasible. In bi-logarithm coordinates, permeability coefficients of dredged slurries increase linearly with the increasing of void ratio. Permeability coefficients, however, increase abruptly when slurries change from soil state into fluid state. At last, a model on the relationship between void ratio and permeability coefficients of dredged slurries is obtained.