Bedding Layer Research Articles

The first case study of 230Th/U and 14C dating of mid-valdai organic deposits

From the viewpoint of precision and reliability of radioisotopic dating, deposits whose quantitative age can be determined through several methods of geochronometry are of special interest. The mutually conforming finite 14C and 230Th/U dates of buried Neopleistocene organic deposits, taken from the Tolokonka section by the North Dvina River (100 km downstream from the city of Kotlas), have been obtained for the first time in Russia. The stratigraphical reference of these results to those obtained via the optically induced luminescence for upper and lower bedding layers has been established. The presented geochronometric data have allowed us to consider the age of oxbow lake organic deposits completely reliable and refer the time of their formation to the Tyrbei warming within the MIS-3. The applicability of the new version of the 230Th/U method for dating of interglacial and interstadial deposits, for the purpose of solving the Middle and Late Neopleistocene chronostratigraphy issues, is confirmed.

Origin of the structure and planform of small impact craters in fractured targets: Endurance Crater at Meridiani Planum, Mars

We present observations and models that together explain many hallmarks of the structure and growth of small impact craters forming in targets with aligned fractures. Endurance Crater at Meridiani Planum on Mars (diameter ≈ 150 m) formed in horizontally-layered aeolian sandstones with a prominent set of wide, orthogonal joints. A structural model of Endurance Crater is assembled and used to estimate the transient crater planform. The model is based on observations from the Mars Exploration Rover Opportunity: (a) bedding plane orientations and layer thicknesses measured from stereo image pairs; (b) a digital elevation model of the whole crater at 0.3 m resolution; and (c) color image panoramas of the upper crater walls. This model implies that the crater’s current shape was mostly determined by highly asymmetric excavation rather than long-term wind-mediated erosion. We show that modal azimuths of conjugate fractures in the surrounding rocks are aligned with the square component of the present-day crater planform, suggesting excavation was carried farther in the direction of fracture alignments. This was previously observed at Barringer Crater in Arizona and we show the same relationship also holds for Tswaing Crater in South Africa. We present models of crater growth in which excavation creates a “stellate” transient cavity that is concave–cuspate in planform. These models reproduce the “lenticular-crescentic” layering pattern in the walls of some polygonal impact craters such as Endurance and Barringer Craters, and suggest a common origin for tear faults and some crater rays. We also demonstrate a method for detailed error analysis of stereogrammetric measurements of bedding plane orientations.

Development and Application of Precast Decks for Composite Bridges

This paper deals with prefabricated composite bridges with full-depth precast decks. For steel–concrete composite bridges, a new shear connection and its design provisions were suggested by extensive experiments and finite element (FE) analyses. The shear connection for precast decks was investigated to consider the effects of bedding layer, filling material in shear pockets and group arrangement. For the integrity of the precast decks, longitudinal prestressing was introduced and design guidelines for the magnitude of prestress were proposed. It is necessary to keep the joints compressive during the service life of the bridge to prevent cracking and leakage at the joints. Bonding strength was neglected in the design. In order to take full advantage of precast slabs, the concept of incremental prestressing was adopted for continuous prestressed concrete (PSC) girders. Based on the experimental research on joints and connections, several model tests were performed to verify the suggested design guidelines. There are several applications using precast decks not only for steel bridges and but also for concrete ones. Among them, design characteristics and enhanced details for construction were introduced for two bridges.

Early stone emplacement in three Scottish ecclesiastical national monuments

The stonework at three well-known Scottish ecclesiastical buildings has been examined in detail. In each, the orientation of the bedding layers in individual stones in certain quoins and arch jambs, and in two instances the wall faces, indicate when these buildings were first erected. In England, the period of construction would have been described as Anglo-Saxon; in this paper the work is referred to as being of 'Patterned' style. On this evidence each building is ascribed to a particularly early origin.

ANÁLISE ECONÔMICA E AMBIENTAL DE SISTEMAS DE TERMINAÇÃO DE SUÍNOS COM A APLICAÇÃO DOS CONJUNTOS FUZZY

O artigo analisa dois sistemas de terminação de suínos (o de cama sobreposta e o de esterqueira) quanto aos seus condicionantes econômicos e ambientais. Estuda-se o caso da produção de suínos no Vale do Caí (RS). A partir da teoria dos conjuntos fuzzy é construído um modelo analítico que incorpora e hierarquiza as variáveis econômicas — através do cálculo dos custos de produção da terminação de suínos —, e as variáveis de impacto ambiental — no ar, no solo e na água - permitindo a análise do impacto econômico e ambiental total de cada sistema de terminação. O mesmo modelo pode ser utilizado para hierarquizar outros sistemas de criação e controle de dejetos.

Side-by-Side Comparison of Nitrogen Species Removal for Four Types of Permeable Pavement and Standard Asphalt in Eastern North Carolina

A 1 year-old parking lot in eastern North Carolina consisting of four types of side-by-side permeable pavement and standard asphalt was monitored from January 2007 to July 2007 for water quality differences among pavement types. The four permeable sections were pervious concrete (PC), two different types of permeable interlocking concrete pavement (PICP) with small-sized aggregate in the joints and having 12.9% (PICP1) and 8.5% (PICP2) open surface area, and concrete grid pavers (CGP) filled with sand. The site was located in poorly drained soils, and all permeable sections were underlain by a crushed stone base with a perforated pipe underdrain. Composite, flow-weighted samples of atmospheric deposition and asphalt runoff were compared to those of permeable pavement subsurface drainage for pH, TN, NO2,3–N, TKN, NH4–N, and ON concentrations and loads. All pavements buffered acidic rainfall pH (p<0.01). The pH of permeable pavement subsurface drainage was higher than that of asphalt runoff (p<0.01) with the PC cell having the highest pH values (p<0.01). Permeable pavement subsurface drainage had lower NH4–N(p<0.01) and TKN concentrations than asphalt runoff and atmospheric deposition. With the exception of the CGP cell, permeable pavements had higher NO2,3–N concentrations than asphalt (p<0.01), a probable result of nitrification occurring within the permeable pavement profile. The CGP cell had the lowest mean TN concentrations; however, results were not significantly different from those of asphalt runoff. The possible nitrogen removal exhibited by the CGP cell is similar to that observed in sand filter research, not surprising considering CGP contained a 10 cm (4 in.) sand bedding layer. Overall, different permeable pavement sections performed similarly to one another with respect to water quality, with the CGP cell appearing to best improve storm-water runoff nitrogen concentrations.

Coupling effect between reliability of bedding layer and stability of downstream concrete slab of overflow earth-rock cofferdam

The protection of downstream concrete slab is a key issue for the stability of overflow earth-rock cofferdam. The coupling effect between bedding layer and concrete slab was taken into account when the stability of downstream concrete slab was researched. The characteristics of overflow and seepage over the downstream concrete slab were investigated when floodwater passes over the cofferdam. Firstly a limit equation of seepage failure for the bedding layer was derived with the consideration of geometric and mechanical factors, and a reliability model was established and numerically simulated. Then based on the reliability calculation for the bedding layer, the coupling effect between bedding layer and downstream concrete slab was analyzed. Under the most unfavorable pressure condition for the concrete slab, its instability criterion was put forward, which offers a structural design tool of downstream concrete slab for overflow earth-rock cofferdam. Compared with model tests, it shows that the model of reliability calculation of bedding layer and the stability analysis of downstream concrete slab are effective.

Sedimentology of the Semantan Formation (Middle - Upper Triassic) along the Karak-Kuantan Highway, central Pahang

Outcrops of the Semantan Formation (Middle to Upper Triassic) along the Karak-Kuantan Highway at km 114.7, km 115, km 140 and km 149.3 were studied. Some beds were found to contain bivalves (Entolium subdemisum Muenster, Neoschizodus sp., Costatoria pahangensis(Kobayashi and Tamura) and Costatoria chegarpahangensis (Kobayashi and Tamura)) and gastropod (?Nerita sp.), which support the Middle to Upper Triassic age for the Semantan Formation. Sedimentary facies and facies associations were examined to gain a better understanding of deep-marine sedimentation processes in relation to submarine fan models. The main facies recognized in the field include conglomerate, pebbly sandstone, thick-bedded sandstone, interbedded sandstone-shale, contorted sandstone-shale, and shale-dominated heterolithics. The facies associations include fining- and coarsening-upward fan-lobe parasequences, slump deposits, and outer fan/basin plain shales. The sediments therefore represent a range of subenvironments from slope to outer fan. Both debris flow and turbidity current deposits are recognized as the main depositional processes in Semantan Formation. Features, such as disorganized clasts in conglomerate, floating mudclasts, and scour-and-fill structures indicates debris flow processes whereas normal graded bedding (fining upward) and thin waning-flow sandy layers in shale indicates turbidity current processes.

Use of Fungal Rhizomorphs as Nesting Material by Glaucomys volans (Southern Flying Squirrels)

We examined 53 nests of southern flying squirrels constructed within nest boxes in Mobile County, AL. Of those containing a bedding layer (n = 35), 80% contained fungal rhizomorphs of Marasmius brevipes. Rhizomorphs of this genus have been reported in bird-nest descriptions, but have not been documented in flying squirrel nests. M. brevipes was common on our study site, and its use by flying squirrels may be unique to the area. Nevertheless, this and similar species of rhizomorph-producing fungi occur in other portions of the flying squirrel's range, and the nondescript nature of rhizomorphs may lead to their misidentification. Our observations appear to constitute the first description of an ecological relationship between this fungus and a mammalian species.

The Effect of Bedding Layer on the Strength of Shear Connection in Full-Depth Precast Deck

Shear connection in a steel-concrete composite bridge with a full-depth precast deck is characterized by the material properties of the non-shrink mortar, which is the filler in the pockets for the shear connectors, and the existence of a bedding layer between the precast deck and the steel girder. As a consequence, the behavior of the shear connection is very different from that of the more widely used cast-in-place concrete deck. Experiments on push test specimens with several parameters varied, such as the cross-sectional area of the stud connectors, the compressive strength of the mortar, and the thickness of the bedding layer, were performed to evaluate the ultimate strength of the shear connection in the precast deck. The test results have shown that the effect of the compressive strength of the mortar on the ultimate strength of the shear connection is insignificant within the limit of these tests. The ultimate strength of the shear connection decreases considerably with an increase of the bedding layer thickness. An empirical equation for the ultimate strength of the shear connection considering the effect of the bedding layer thickness is presented in this paper. Based on the results, recommendations for the design of the stud shear connection in a full depth precast deck are suggested.

Grouted Connection Tests in Development of Precast Bent Cap System

Tests were conducted as part of the first two phases of a research project that developed a design methodology, construction guidelines, and design details for connecting precast concrete bent caps to cast-in-place columns or precast concrete trestle piles in nonseismic regions. Three types of precast connections were addressed: grout pockets, grouted ducts, and bolted connections. The first phase of testing included 32 pullout tests of epoxycoated straight and headed bars embedded in a grout pocket or grouted duct. The yield strength of the bars was developed in grouted connections at an embedment depth of 13 bar diameters or less. Pullout capacity of single- and multiple-headed bars in grout pockets was predicted closely by the concrete capacity design method equations modified by a cracking factor of 0.75 to account for grout-pocket cracking. A development length equation based on a uniform bond stress model was derived for anchorage of straight bars in grouted ducts. The second phase of testing included a full-scale bent cap-to-column connection test for each connection type. Specimens in these proof tests exhibited minor levels of cracking and connector strain in the connection region at factored levels. Failure tests demonstrated adequate connector anchorage, large connector ductility, and negligible influence of shims and the grout bedding layer on response. Results from Phase 1 and Phase 2 tests were used to develop anchorage design provisions that are incorporated in the complete design methodology.

Mechanics of extension and inversion in the hanging walls of listric normal faults

Fault shape, material properties and bedding anisotropy determine the style of deformation in the hanging walls of listric normal faults. We use numerical models to study this deformation in both extension and inversion during displacement on a variety of master fault shapes. Elastic‐plastic material properties in the models allow the development of shear bands, which simulate secondary faults within the hanging wall. If the master fault is composed of a planar ramp and planar flat separated by a sharp fault bend, a series of antithetic normal shear bands develops in the hanging wall, propagating up from the fault bend. Each shear band is progressively abandoned as displacement on the master fault moves it away from the fault bend. Displacements on the antithetic faults produce the limb of a hanging wall monocline and bound one side of a graben, the other side of which is bounded by the master fault. The antithetic shear bands are not rotated, and layering within the graben remains subhorizontal. On the other hand, if the fault bend is curved rather than sharp, symmetrical nested graben develop in the upper part of the hanging wall above the base of the ramp. Displacement on the master fault moves these shear bands away from the fault bend, after which they are abandoned in favor of new shear bands. Early formed synthetic shear bands become shallower and concave upward because of the folding and rotation of the hanging wall. With increasing radius of curvature of the master fault, localization into shear bands decreases and, with a large radius of curvature, shear bands do not develop. If weak bedding layers are included within the hanging wall, they become sites of bedding‐parallel shear bands that accommodate flexural slip folding and replace the synthetic shear bands that develop in homogeneous models. If extension is followed by shortening and inversion, normal shear bands that developed during extension are reactivated as reverse shear bands but are also crosscut by new reverse shear bands. The models produce results that are similar to both natural structures and analogue models and provide explanations for many observations of deformation in seismic profiles through extensional terranes.

Design of shear connection in composite steel and concrete bridges with precast decks

For the design of the shear connection in steel–concrete composite bridges with precast decks, design considerations were discussed, and experimental works on the push tests and the bridge model test were performed. The characteristics of the shear connection in a precast deck system are the filling material in shear pockets and the bedding layer between the precast deck and the steel girder. Also, it is necessary to evaluate the structural behavior of the shear connection in case of uniformly distributed shear connectors through experiments. Based on the push tests, the behavior of the shear connection in a precast deck was discussed. In addition, the ultimate strength and the fatigue endurance of the shear connection were estimated. As the thickness of the bedding layer increases, the ultimate strength decreases. The shear load redistribution between shear connectors was verified through the experiment on the bridge model, and shear connectors can therefore be distributed uniformly along the span. Using the experimental results and the finite element analysis based on the partial interaction theory, the shear stiffness of the shear connection and the flexural stiffness of the bridge were evaluated.

Reliability analysis of geotechnical failure modes for vertical wall breakwaters

Vertical wall breakwaters are usually designed as concrete caissons placed on the top of a rubble mound foundation or a rubble bedding layer. The purpose of the breakwater is usually to protect the area behind the breakwater from being flooded by large waves. The area protected can for example be a harbour of small or large importance, an important industrial area or a heavily populated coast line. This implies that vertical wall breakwaters are used under quite diAerent conditions and therefore the consequences of a complete or partial failure also are very diAerent. This implies that the accepted probability of failure also varies considerably which also can be observed from the actual observed failure rates. A number of diAerent failure modes are relevant to consider for vertical wall breakwaters (e.g. [1]). Foundation failure modes include sliding of the breakwater relative to the rubble mound and diAerent foundation failure modes with failure within the rubble mound and the subsoil (sand or clay). Hydraulic failure modes include wave overtopping, wave transmission and wave reflection. Structural failure modes involve failure or partial failure of the concrete caissons. In this paper only geotechnical failure modes are considered. In order to estimate the reliability, stochastic models for the uncertain parameters in the limit state functions are formulated. The main horizontal and vertical (uplift) loading on vertical wall breakwaters are wave loads, including both pulsating and impact wave loads. Stochastic models for the wave loading are presented. These

The behaviour of shear connections in a composite beam with a full-depth precast slab

For the design of shear connections with a full-depth precast slab, it is necessary to investigate strength, stiffness, slip capacity and fatigue endurance. For these purposes, push-out tests were performed with variations of the stud shank diameter and the compressive strength of the mortar. From the experimental work, it could be observed that the deformations of the studs in a full-depth precast slab were greater than those in a cast-in-place slab. The static strengths of the shear connections obtained agree approximately with those evaluated from the tensile strength of the stud shear connectors owing to the effect of the bedding layer. An empirical equation for the initial shear stiffness of a shear connection is also proposed. On the basis of the results of push-out tests, a full-scale composite beam with 8·0 m span was designed and fatigue tests were carried out to study the behaviour of the stud shear connection and its effects on the flexural behaviour of the beam. The bonding and friction between the concrete slab and the steel beam considerably increased the fatigue endurance of the shear connection. Discussions about design are also presented.

Resistance of Steep Concrete Block Pavements to High-Velocity Water Flow

In some locations, the use of concrete block pavement (CBP) involves the combination of a very steep and storm-sensitive region with the consequent risk of high-velocity water flow on pavements. Under these conditions, and because of the special characteristics of CBP and its unknown response to high-velocity water flow, two problems must be addressed: ( a) the danger of sand erosion from the bedding layer and the joints between the blocks, because of surface drainage and water flow, and ( b) the danger of development of uplift forces from the downward water seepage. The cumulative effect of these two dangers may cause a gradual loss of support of the CBP, leading to total failure. CBP was tested under high-velocity water flow on a one-to-one scale, with definition of flow and failure mechanisms in the CBP and with the adoption of proper solutions. Five tests were performed in an experimental water flume, differing in type of bedding. Use of conventional sand bedding under continuous water-flow conditions was found to be inappropriate. Such bedding cannot provide the necessary stability for the CBP. However, the use of fine aggregate as bedding material ensured the stability of the CBP under continuous supercritical flow velocities and steep channel slopes. Excellent performance of the CBP was observed with the underlying fine aggregate bedding. The use of sufficiently coarse aggregate as bedding material is the proper engineering solution for preventing erosion and ensuring the absolute stability of a CBP under high water-flow velocities under supercritical conditions.

Response of Finite Depth Seabed to Waves and Caisson Motion

The response of a poroelastic seabed to waves and caisson motion is modeled using Biot consolidation theory. The caisson is founded on a rubble bedding layer overlying a seabed of finite depth. Two approximations are employed to solve the boundary‐value problem analytically: (1) A boundary layer approximation to decouple pore pressure and soil motion in the Biot equations; and (2) a contact solution approximation for a thin elastic layer to address the mixed‐type mud line condition. The analytical solution is verified by comparison with finite element model results and large‐scale experiments. The analytical and finite element model estimates of the soil stresses and surface displacements are in good agreement. Experimental and analytical comparisons for pore pressure are in agreement but the displacement comparisons are quite scattered.

Optical anisotropy in cokes from high-rank coals

Samples of cokes, obtained by carbonizing crushed coal to 1000 °C at 5 °C min −1, have been re-examined in an attempt to resolve why anisotropic textural components, all originally classified as flow-type, could be formed during the carbonization of high-rank coals of widely differing character by different formation routes. It was found that sub-division of this category of material into striated-flow, broad-flow and patterned anthracitic sub-groups permitted the clearer differentiation between cokes from high-rank coals according to their rank. Negligible fluidity and relatively little structural change appear to be involved in the formation of patterned-anthracitic components, the patterning reflecting variations of bedding layers in the coal. In contrast, both flow categories of component are formed from reactive coal constituents that exhibit some fluidity during carbonization. However, both components can be formed from the parent vitrinite either directly or via the intermediate formation of mosaic anisotropic components.

Stratigraphic filter theory: Combined effects of parallel bedding and random inhomogeneities

Mean field renormalization techniques determine the phase distortion (time delay) and effective attenuation as functions of frequency for a plane acoustic wave, normally incident on a layered medium, when the medium also contains a distribution of scattering centers at random sites. The power spectra of impedance fluctuations of both the bedding layers and the random centers contribute to the time delay and mean field effective attenuation. At low frequencies (long wavelengths), the power spectrum of the bedding planes dominates the mean wave response, producing most of the time delay and the effective attenuation. At high frequencies (short wavelengths), the random scattering centers dominate the mean wave behavior. The wave no longer propagates exactly perpendicularly to bedding planes since the random scattering centers cast energy into directions transverse to the normal to the bedding planes. The precise frequency dependence of both the time delay and the effective attenuation of the mean wave are sensitive to the power spectrum of impedance fluctuations of the bedding planes relative to the power spectrum of the random scattering centers.

AN ANALYTICAL MODEL FOR OCEAN WAVE-SOIL-CAISSON INTERACTION

An analytical model is developed to predict the soil responses induced by waves and caisson motion. The caisson is founded on a rubble bedding layer overlying a soil of finite depth. The responses are modeled by the Blot consolidation equations. Two approximations are employed to reduce mathematical difficulties: 1) a boundary layer approximation^ to decouple pore pressure and soil motion in the Blot equations and 2) a contact solution approximation for a thin elastic layer to address mixed-type boundary-value problems.