Gravel Material Research Articles

Stress-dilatancy of Zipingpu gravel in triaxial compression tests

Experimental investigations of the dilatancy and particle breakage of gravelly material from the Zipingpu concrete-faced rockfill dam, which was subjected to high-intensity seismic load during the 2008 Wenchuan earthquake, were conducted through a series of large-scale drained triaxial compression tests. A hyperbolic relation between the input plastic work and the degree of particle breakage was found for Zipingpu gravel, independent of the initial void ratio and confining pressures. The stress-dilatancy for Zipingpu gravel was analyzed and compared with data from two rounded alluvial and three angular quarried gravelly and rockfill materials in the literature. A nearly linear relationship between the dilatancy D p and the stress ratio η was found at medium-to-large stress ratios before the peak stress ratio. The slope of the stress-dilatancy line before peak had slight dependence on the void ratio and confining pressure of the gravel. After peak, the stress-dilatancy relation shifts down compared with that before peak for the gravel specimen. The phase-transformation stress ratio decreased with increased confining pressure, with the exception of sub-rounded gravel with little particle breakage. A nearly linear relationship was found between the phase-transformation stress ratio M f and the state parameter ψ for the Zipingpu gravel, regardless of the void ratio and confining pressure of the specimens.

The geochemistry of manganese conglomerates on the Vityaz’ Rise, Japan Sea

Large conglomerate fragments up to 25 cm across were dredged off the submarine volcanic Vityaz Rise, Japan Sea in the 1600–1350 m depth range. These are the first ever that were recovered in this location. The fragments consist of pebble and gravel material that is cemented by manganese hydroxides. The cement is basal in type; the chemical composition is M2+MnO2, where M2+ = Na2, Mg, K2, Ca, Ba. The Mn/Fe ratio is 802. The upper part of the conglomerates is covered with a layered crust of the same hydroxides. A similar crust can be discerned within the conglomerate closer to the bottom of a sample. Some layers of the crusts are rich in NaCl, CaSO4, F, Co, Cu. The crusts contain inclusions of grains that consist of Ag and intermetallic compounds based on Cu and Ni. The superimposed manganese mineralization is Quaternary. The metals originated, most likely, from gas-rich hydrothermal fluids.

Deformation analysis of tunnel excavation in gravelly formation using the anisotropic degradation model

This study adopts a shear-induced anisotropic degradation model to analyze the deformation of excavation in gravelly formations. The adopted model is a variable moduli model with the following characteristics: the stress–strain relationship originates from degradation of the bulk modulus and shear modulus subjected to different loadings. Under hydrostatic loading, gravelly soil may behave as an isotropic material. However, when gravelly soil is subjected to shear loading, the material becomes anisotropic and degrades before ultimate strength is attained. Therefore, this study introduces an anisotropic factor to reflect the tendency to shear-induced volumetric deformation. To analyze the deformation of the Pakuashan tunnel, which passes through a gravelly formation in Taiwan, the model was first validated by comparing the drained triaxial test results of gravelly materials sampled from the tunnel. The proposed model is implemented with a finite element code to predict the tunnel deformation under construction. A comparison between the monitoring data and numerical analysis shows that the proposed model can reasonably simulate the behavior of a gravelly formation under excavation. Numerical analysis shows that the main deformation of the tunnel is the result of significant degradation of the moduli around the whole section, especially at the crown and invert of the tunnel.

Determination of 226Ra in building materials using ion exchange chromatography

A rapid method for 226Ra determination in building materials was developed and tested. The method is based on ion exchange mechanism with an anion exchanger and MnO2–PAN composite ion exchanger. The proposed method was applied for analysis of gravel, fly ash, sand, scree and concrete material from the Slovak Republic. 226Ra activity concentrations in the analysed building materials were in the range of 4.3–143.4 Bq kg−1.

Bryozoans from Rio Grande do Sul Continental Shelf, Southern Brazil

The continental shelf of Rio Grande do Sul (RS) is predominantly composed of unconsolidated sediments with a few hard substrates represented principally by beachrock. In this area there are elongate deposits of shell gravel material which are interpreted as indicators of the palaeo-shorelines. These Pleistocene deposits are overlapped by Holocene sediments (Recent), but are exposed during erosive events caused by extra-tropical cyclones, which provide the mixture of both sediments mainly during autumn and winter. The few studies on bryozoans made in this area previously recorded seven species, one fossil and the other six from Recent fluvial and marine environments. The aim of the present study was to describe the eight most abundant bryozoan species that occur in the inner RS shelf. Of these, four are new records for RS State (Arachnopusia aff. pusae, Hippomonavella brasiliensis, Turbicellepora pourtalesi, and Lifuella gorgonensis), and the other four are new to science (Chaperia taylori, Micropora nodimagna, Cellaria riograndensis, and Exochella moyani).

The Kambarata 2 blast-fill dam, Kyrgyz Republic:blast event, geophysical monitoring and dam structure modelling

The blast- and earth-fill dam of the Kambarata 2 hydropower station is situated in the seismically active Central Tien Shan region of the Kyrgyz Republic. More than 70% of the dam volume was produced during a blast event on December 22, 2009. In 2010–2011, dam construction was completed after earth filling on top of the blasted material and installing concrete and clay screens together with bentonite grouts. A geophysical survey had been completed in 2012–2013, mainly to monitor the resistivities inside the dam. The geophysical survey completed on the Kambarata 2 dam site showed lower resistivity zones in the earth fill and relatively higher resistivities in the blast-fill material. Topographic, geophysical and piezometric inputs had been compiled within a 3D geomodel constructed with GOCAD software. This model was compared with the design structure of the dam in order to define the upper limits of the underlying alluvium, the deposited blast fill, earth fill and top gravel materials (represented by the dam surface). The central cross-section of this model was extrapolated over the full length of the main dam profile. On the basis of a calibrated hydrogeological model and known geomechanical properties of the materials, dam stability calculations were completed for different scenarios considering different reservoir levels and varying seismic conditions. Some of these scenarios indicated a critical vulnerability of the dam, e.g., if impacted by a horizontal seismic acceleration of Ah = 0.3 g and a vertical seismic acceleration Av = 0.15 g, with an estimated return period of 475 years. As a general conclusion, it was noted that this case study can be used as an example for surveys on much larger natural – landslide or moraine – dams. A series of geophysical methods (e.g., electrical and electro-magnetic techniques, seismic and microseismic measurements) can be applied to investigate even very deep dam structures. These methods have the advantage over classical direct prospecting techniques, such as drilling, of using equipment that is much lighter and thus more easily transportable and applicable in difficult terrain. Furthermore, they can provide continuous information over wider areas. This specific application to a blast-fill dam allows us to better outline the strengths and weaknesses of the exploration types and geomodels as a series of investigated parameters can be verified more easily than for natural dams.

Characterization and evolution of primary and secondary laterites in northwestern Bengal Basin, West Bengal, India

It is quite impossible to travel far in India without observing the remarkable ferruginous crust to which Buchanan in 1807 gave the name of laterite. In Indian peninsula, it is a post-Cretaceous stratigraphic succession with a polycyclic nature of evolution which marks the unconformity with recent Quaternary alluvium. There are perennial problems and research gaps in the investigation of laterites in India as well as in West Bengal: (1) defining, identifying and classifying lateritic materials, (2) mode of formation of laterite and its other horizons, (3) determining the ages of laterites, (4) reliability of laterites as palaeoclimatic indicators, (5) identifying topographic requirements and pedogeomorphic processes for laterite formation, and (6) reconstructions of former lateritized landscapes. The formation of north‒south lateritic hard crust (i.e. Rarh Bengal) on the Rajmahal Basalt Traps, Archean granite‒gneiss, Gondwana sediments, Paleogene gravels and older deltaic alluvium is analyzed here to resolve the aforesaid problems and to depict the variable characteristics of laterites with special reference to its tectono-climatic evolution in the northwestern marginal part of Bengal Basin. This paper reveals that the low-level secondary laterites (probably the Pliocene‒Early Pleistocene age) of Rarh Bengal are composed of heterogeneous Fe‒Al rich gravelly materials which were derived from the high-level primary laterites (probably the Eocene‒Miocene age) of plateau since the Paleogene Period by the peninsular river system, following the underlying structure of Bengal Basin. Alongside the roles of drifting of Indian Plate, establishment of monsoon climate, neo-tectonic uplifts and re-lateritization of ferruginous shelf deposits are determined here to unearth the palaeogenesis of primary and secondary laterites in West Bengal.

Evaluation of resilient moduli for recycled crushed-rock-soil-mixtures using in-situ seismic techniques and large-scale resonant column tests

The objective of the paper is to develop a resilient modulus prediction model for load-bearing compaction fills of crushed-rock-soil-mixtures which start being recycled from adjacent cutting and tunneling in the recent construction of highways and high-speed railways in mountainous sites in Korea. Often, the mixture is scarcely engineered except for controlling the maximum grain size in the range of 100–300 millimeters and the grain distribution was simply represented median grain diameter (D50) in the order of 10–60 millimeters. The evaluation of resilient moduli, using the “orthodox” repeated loading tri-axial test, is not even conceivable for such a large-size gravelly material. A realistic alternative is to utilize the well-developed techniques which are currently used for measurements of subtle different modulus, such as shear modulus. The prediction model was developed by: (1) defining the model as the combination of maximum Young's modulus and its normalized reduction curve for high strain, (2) adopting the modified hyperbolic model of modulus reduction curve, and (3) converting the model parameters from in-situ maximum shear moduli and the reduction curves of modeled materials using the large-scale free-free resonant column tests. The values of model parameters were listed for the limited sites. It should be noted that, if the gradation curve widely stretched including quite an amount of fines, scalped specimens may be used to evaluate the model parameters of such a “dirty” material.

Changes of the hydrodynamic conditions in the braided river

The paper focuses on the understanding of the basic hydrodynamic conditions along the braided gravel-bed river. The measuring cross-section was located in the Ochotnica River, where its braided channel development was observed. Investigations take place from 2003 up to 2014. Measurements were performed for selected characteristic points. The study focused mostly on the measurements of water velocities under different flow conditions, and next on finding basic hydraulic parameters of flow: shear velocity, shear stresses, Reynolds number, Froude number. In addition, the gravel material from the river bed was examined, in order to find sedimentological characteristics of it.

Morphogenesis and Morphometry of Alluvial Fans in the High Atlas Morocco: A Geomorphological Model of the Fans of the Wadi Beni Mhammed, Souss Valley

Morphosedimentary study of alluvial fans formed by the Wadi Beni Mhammed, on the southern piedmont of the western High-Atlas, has indicated three main generations of deposits. Their ages range from ancient (Plio-Pleistocene) to Holocene and recent formations. The first generation, comprising small boundary fans, was deposited prior to lateral migration and subsequent entrenchment of the drainage pattern (the combination of the Wadis Aït Mekhlouf and Ida Ou Merouane). The confluence of these powerful streams gave birth to the principal fan that extends to the Souss valley. The third generation of fans was constructed after the incision of the principal fan, by the re-activation of a high secondary fan that was formed from downstream progradation. The morphological characteristics of the fans, such as their area, shape and gradient, are determined from catchment data and, in particular, from the lithology of their provenance areas, which defines the nature of gravel material, sedimentation processes and, finally, the distribtion of constituent materials. Fan shape also depends on the available accommodation space on the piedmont. The Wadi Beni Mhammed fans are elongated, because they are constrained by the mega fans of Wadis Irguitene and Aoukourta. DOI: http://dx.doi.org/10.3126/ije.v3i3.11090 International Journal of Environment Vol.3(3) 2014: 293-311

Study on Static Strength of Aeolian Sand before and after Cyclic Loading

Aeolian sand is one commonly used subgrade filling in Xinjiang Oasis-desert region, engineering practices also proved its applicability as subgrade filling. In order to find the law of Aeolian sand subgrade static strength after cyclic loading, the paper studied the static strength of Aeolian sand before and after cyclic loading through the dynamic and static triaxial tests. It is concluded that the greater cyclic loading is, the more Aeolian sand static strength peak decreases. When cyclic loading is small, the bigger confining pressure and consolidation ratio are, the static strength peak increases more after cyclic loading. The bigger initial static deviator stress is, the more Aeolian sand static strength peak reduces. The frequency of cyclic loading has little effect on static strength. In order to keep the stability of low embankment, we should restrict overload , ensure subgrade and foundation consolidation adequately, at the same time using gravel or geosynthetic materials to package edge of roadbed, so as to increase confining pressure. The research results can provide reference for the design and construction of Aeolian sand low subgrade in Xinjiang Oasis-desert region.

Strength and deformation characteristics of compacted silt from the lower reaches of the Yellow River of China under monotonic and repeated loading

Silt is a widespread deposit in the lower reaches of the Yellow River, China with low plasticity and cohesion and poorly-graded characteristics. It is the primary filling material for subgrades in this region because of the lack of sand and gravel materials. Using the California Bearing Ratio (CBR) method alone to characterize the silt subgrade cannot provide an adequate assessment of its shear behaviors under monotonic and repeated loading. To improve the understanding of the strength and deformation characteristics of silt fill, a series of triaxial tests under monotonic and repeated loading were conducted. Specifically, the variations in the engineering characteristics (such as shear strength, permanent deformation, resilient modulus, and threshold stress) of silt fill caused by changes in the physical and stress states were investigated. Experimental results were used to establish empirical correlations for the strength and deformation parameters. These results provide a basis for the mechanical analysis and design of silt subgrades for stability.

Large-scale triaxial tests of dense gravel material at low confining pressures

The results of a series of large-scale triaxial tests performed on dense, prismatic gravel specimens, with a height of 50cm and a cross-section of 23cm×23cm, are described. The specimens were prepared at a density equal to approximately 95% of the maximum density at the optimum moisture content. Deformations were measured locally using vertical and horizontal local deformation transducers. Stress conditions with selected levels of very low confining pressure were used to simulate specific conditions in the case of road and railway embankments. Particular attention was paid to the bedding error at the top and the bottom ends of the specimens, and to fixing transducers onto the membrane to be used under low confining pressure. The confining pressure was applied by vacuum and varied from 10kPa to 75kPa. Unsaturated specimens were tested under drained triaxial compression using monotonic and cyclic loading with frequencies in the range of 0.5–5Hz. The effects of a large number of load cycles and of specimen preloading were investigated.

Amelioration of soil chemical constraints for revegetation on gold oxide processing residues

Gold oxide processing residues are highly alkaline, sodic and saline and initially require amelioration for plant establishment. The aim of this study was to determine the efficacy of soil covers and residue ameliorants in alleviating chemical constraints for revegetation. The effects of residue covers (10cm topsoil plus 0, 15 or 30cm gravelly sub-soil referred to as gravel), combined with gypsum (30 and 60tha−1), and compost (0 and 50m3ha−1) on chemical properties (pH, electrical conductivity (EC), exchangeable Na percentage (ESP), cation exchange capacity (CEC), total N, extractable N, P, K, S, cations and micronutrients) of gold oxide processing residue were studied in a large-scale field trial at Boddington, Western Australia in a Mediterranean climate. After the first season's rainfall, the EC1:5 decreased substantially (from 4.5–5.0 to about 1.0dSm−1) across all treatments in the 0–10cm residue layer (RES1), while topsoil and gravel materials which had low initial salinity (0.04–0.07dSm−1) increased their EC1:5 to 0.40–0.45dSm−1 in the 10cm above the residue interface in the 2nd hot-dry summer season. pH of both RES1 and the 10–20cm layer of residue (RES2) dropped from 9.0 to 8.0 over the trial period but topsoil pH remained at 5.2–5.5, regardless of treatments. Exchangeable Na percentage in RES1 and RES2 decreased, but increased from 17 to 70% in topsoil placed directly on the residue surface, compared with no increase in topsoil where there was a gravel layer separating topsoil from residue. Fertiliser added to topsoil raised extractable nutrients to levels adequate for plant growth. Nutrient elements did not differ with gypsum rate and compost amendment except for S, on account of the gypsum applied, and extractable P and Mn, which were elevated by compost. These findings indicate the efficacy of gravel plus fertilised topsoil cover on residue treated with surface broadcast gypsum to alleviate the adverse properties of alkaline, saline, sodic gold oxide processing residue as a medium for plant establishment and early growth.

Soft soil strengthening by stone columns: case of the embankment under the bridge “Moulay Youssef” (Rabat/Salé)

The soil is generally a heterogeneous material presenting very variable characteristics. In a general way, the main problems related to soils are: low bearing capacity, deformations under static or dynamic loads, large displacements and large settlements of soft soil where the soil moves according to a fixed ground water table. The development of soil mechanics and geotechnical engineering has led to the amelioration of a wide range of soil improvement techniques. These techniques consist in modifying the characteristics of the ground by physical action or by incorporating columnar inclusions made of highly compacted gravel or granular material into the original soil. Stone column is one of the soft ground improvement methods, applicable to a wide range of soil strata and an economical method of support in compressible and cohesive soils. However, there are many difficulties in quantitative analysis of soil column interaction due to the fact that bearing capacity and consolidation behavior of stone column-mat foundation system is affected by various parameters. In the present study, mechanism and various parameters of stone column behavior are investigated by loading tests. Also, tests results are compared to the finite element numerical modeling “Plaxis 2D” (case study: the embankment under the bridge “Moulay Youssef, Rabat/Sale”).

Evaluation and Analysis of Botswana Gravel Road Condition for District Transportation Networks Monitoring

Gravel roads are majorly affected by deterioration which manifests as loss of gravel materials due to traffic and environmental conditions. District Road Maintenance Managers are faced with competing investment demands to maintain gravel road networks in the best condition due to inadequate intelligent techniques of evaluating the roadway performance. The aim of evaluating the road network performance is to reduce the rate of deterioration so that maintenance interventions could be extended. Road condition data is a precursor for road monitoring and is collected on a periodic basis by road authorities to assist in transportation planning. The primary objective of this paper was to evaluate and analysis the trend of Botswana gravel road condition which best captures the effects of gravel road condition influencing factors. This was achieved by carrying out exploratory statistical analysis. Gravel road condition data were collected through the Botswana Roads Department covering 2002, 2005 and 2008 for Botswana district gravel road networks. The variables required for the analysis were clustered and pre-processed to determine their suitability. The analysis results gave a broad overview of the extent to which gravel road condition trends lend credence to their usefulness in district transportation networks monitoring in Botswana.

Bacterial Diversity at Abandoned Uranium Mining and Milling Sites in Bulgaria as Revealed by 16S rRNA Genetic Diversity Study

Radionuclide and heavy metal contamination influences the composition and diversity of bacterial communities, thus adversely affecting their ecological role in impacted environments. Bacterial communities from uranium and heavy metal-contaminated soil environments and mine waste piles were analyzed using 16S rRNA gene retrieval. A total of 498 clones were selected, and their 16S rDNA amplicons were analyzed by restriction fragment length polymorphism, which suggested a total of 220 different phylotypes. The phylogenetic analysis revealed Proteobacteria, Acidobacteria, and Bacteroidetes as the most common bacterial taxa for the three sites of interest. Around 20–30 % of the 16S rDNA sequences derived from soil environments were identified as Proteobacteria, which increased up to 76 % (mostly Gammaproteobacteria) in bacterial communities inhabiting the mine waste pile. Acidobacteria, known to be common soil inhabitants, dominated in less contaminated environments, while Bacteroidetes were more abundant in highly contaminated environments regardless of the type of substratum (soil or excavated gravel material). Some of the sequences affiliated with Verrucomicrobia, Actinobacteria, Chloroflexi, Planctomycetes, and Candidate division OP10 were site specific. The relationship between the level of contamination and the rate of bacterial diversity was not linear; however, the bacterial diversity was generally higher in soil environments than in the mine waste pile. It was concluded that the diversity of the bacterial communities sampled was influenced by both the degree of uranium and heavy metal contamination and the site-specific conditions.

Літологічна і седиментологічна характеристики алювію шостої тераси Дністра (поверхні Лоєвої) у розрізі Торгановичі 2

The main lithological characteristics of the alluvium of the sandy-gravelly bed of the sixth terrace of the Dniester river (Loyeva level) at environs of Sambir was analysed, in particular textural elements, granulometric and petrographic composition of the gravelly material (enclosing coarse sands, granules, pebbles, cobbles and boulders), its roundness, and the orientation of grains. The conditions of sedimentation of the studied alluvial sandy-gravelly bed of the sixth terrace of the Dniester river (Loyeva level) were reconstructed. Key words: granulometric composition, petrographic composition, roundness, sorting, imbrication, braided channel, depositional conditions.

Seepage behavior of drainage zoning in a concrete faced gravel-fill dam via centrifuge and numerical modeling

Sandy gravel materials have recently been utilized in place of crushed rock materials as the main rockfill materials in Concrete Faced Rockfill Dams (CRFD) to address geological and environmental problems. In this paper, an experimental scheme for centrifuge modeling was developed to simulate a Concrete Faced Gravel-fill Dam (CFGD). The dam considered in this study was designed to implement a drainage zone of high permeability in the main gravel-fill zone to enhance safety against accidental water infiltration into the dam. Two centrifuge tests were performed and compared to investigate the performance of the drainage zone. The first test was done with the drainage zone and the second without the drainage zone. In the centrifuge tests, water infiltration was simulated by raising the water table over pre-implemented cracks on the model face slab. The infiltration behaviors were monitored by pore water pressure transducers. The centrifuge tests showed that the drainage zone of the CFGD effectively drains infiltrating water out of the dam body in a short time. Numerical modeling was also performed to help understand the process of seepage through cracks.

Continuous resistivity profiling survey in Mersin Harbour, Northeastern Mediterranean Sea

No detailed information has previously been available on the geological and geophysical characteristics of the sea floor and the underlying strata of Mersin Harbour, Northeastern Mediterranean Sea (Turkey). Continuous resistivity profiling (CRP) and borehole data from Mersin Harbour were used to interpret geoelectric stratigraphy of Neogene-Quaternary sediments in the area. This represents one of few such detailed case studies that have applied these valuable CRP techniques for the purpose of marine stratigraphic imaging. It was found that the Neogene-Quaternary sedimentary succession in the area consists of three geoelectric units (GU1, GU2, and GU3 from base to top). The lowest unit, GU1, has a resistivity value of greater than 20.0 ohm-m and consists of Miocene aged limestone and marl. The middle unit, GU2, is characterized by resistivity values ranging from 3.0 to 20.0 ohm-m. Its thickness is greater than 90 m, with the upper section being composed of stiff clay sequences which are Plio-Pleistocene in age. The uppermost unit, GU3, has resistivity values varying from 1.0 to 3.0 ohm-m. This unit displays a maximum thickness of 15 m, and is composed of Holocene muds together with gravel, sand, silt and clay (sometimes incorporating shells) materials of the Plio-Pleistocene age and their various mixtures, silty/clay limestone, and conglomerate sandstone. Comparisons of the geoelectric units with the depositional sequences interpreted from the available seismic data outwith, but close to, Mersin Harbour reveal that the geoelectric unit GU3 corresponds to the depositional sequences C (mainly Holocene) and B (mainly Plio-Pleistocene). The geoelectric unit GU2 partly correlates with the depositional sequence B which appears to be Plio-Pleistocene in age. The geoelectric unit GU1, which has not been encountered in previous seismic surveys, is a new discovery within Mersin Harbour. Limited correlation between the seismic and resistivity structures in the study area is attributed to differences in the acoustic impedance and resistivity contrasts of sub-bottom layers, as well as the penetration versus resolution performance of the systems.