Bedding plane

Physical Properties. Most of the physical properties discussed herein depend on the direction of measurement as compared to the bedding plane of the coal. Additionally, these properties vary according to the history of the piece of coal. Properties also vary between pieces because of coal s britde nature and the crack and pore stmcture. One example concerns electrical conductivity. Absolute values of coal sample specific conductivity are not easy to determine. A more characteristic value is the energy gap for transfer of electrons between molecules, which is deterrnined by a series of measurements over a range of temperatures and is unaffected by the presence of cracks. The velocity of sound is also dependent on continuity in the coal. 

Schicht, /. layer ply stratum, bed. course (when thin) film, coat lamina Ph< og.) emulsion charge (of a furnace) batch shift, turn (of work), -boden, m. (Metal.) mixing place, -dicke, /. thickness of a layer or stratum, -ebene, /. bedding plane. 

Anisotropic formation theory Stratified or anisotropic formations are assumed to possess different drillabilities parallel and normal to the bedding planes with the result that the bit does not drill in the direction of the resultant force. 

In weakly consolidated, stratified sediments, the injection pressure must be controlled so that the surrounding formation is not fractured. If fracturing occurs, there is usually a severe loss in hydraulic conductivity because the bedding planes are disturbed. Pressures that will cause fracturing range from a low of 0.5 psi/ft of depth for poorly consolidated coastal plain sediments, to 1.2 psi/ft depth for crystalline rock. For most recharge wells in unconsolidated sediments, the injection pressure should be carefully controlled so that the positive head (in psi at the surface) does not exceed 0.2 x h, where h is the depth (in ft) from the ground surface to the top of the screen or filter pack. 

There are a few main structural tends that the underground dykes follow (a) emplacement of phases 3, 4, and 5 predominantly sub-parallel to folded bedding planes near the apical Mine Stock (phase 2), or upper portions of the mine (b) 115°-295° emplacement of phases 4 and 5 sub-parallel to bedding in the lower recumbent fold limb (Fig. 2), or lower portions of the mine and (c) 040°-220° emplacement of phase 6 sub-parallel to the 5 mine-scale normal faults (Fig. 2), throughout the mine near the Mine Stock margins. Phase 6 dykes also offset other dykes and bedding in a normal sense. 

Figure 2.2. (a) Coiled whisker of rutile in cabochon-cut quartz (courtesy of E. A. Jobbins). (b) Crysotile crystals resembling stacked ice cream cones. (Transmission electron microphotograph taken by K. Yada.) (c) Pyrolusite polycrystalline dendritic pattern formed along a bedding plane of sedimentary rock. 

Marie-Therese Mackowsky Have you ever looked at polished rocks cut parallel to the bedding plane In this case you could see the effect of transport better than in rocks cut perpendicular to the bedding plane. 

A similar picture is shown by the subbituminous coals in the northern foreland of the Alps where the lines of equal moisture content also cut the bedding planes (Figure 15). It is true that in the Hausham Syncline the moisture content of the vitrites decreases with increasing age of the seams, but on the other hand there also is a distinct relation between the moisture content and the present depth of the seams. It is striking that the lines of equal moisture content stand oblique. This may result from the uplifting of the Alps which is still proceeding. 

Marlies Teichmuller. In what direction have the samples of meta-anthra-cite been cut—vertical or parallel to the bedding plane As the aromatic clusters are oriented parallel to the bedding plane you should get quite a different picture depending on the direction of cutting, supposing that you really can see the clusters under the electron microscope. 

SHALE. A fine-grained sedimentary rock whose original constituents were clays or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery, and parallel to the often indistinguishable bedding planes. 

Experimental data strongly indicates that anthracite and bituminous coal are electrically anisotropic. Higher resistivity/lower conductivity is observed for specimens oriented perpendicular to the bedding plane relative to those with parallel orientation. 

The thermal conductivity of coal generally increases with an increase in the apparent density of the coal as well as with volatile matter content, ash content, and temperature. In addition, the thermal conductivity of the coal parallel to the bedding plane appears to be higher than the thermal conductivity perpendicular to the bedding plane. 

The linear thermal expansion coefficient shows the greatest increase in temperature for bituminous coals. The values for the linear thermal expansion coefficient are less than 33 x 10-6 C 1 in the 30 to 330°C (86 to 626°F) range (van Krevelen, 1961). For anthracite, the linear thermal expansion coefficient changes very little with temperature and is accompanied by a pronounced anisotropy effect. The values for the linear thermal expansion coefficient are about twice as high for coal perpendicular to the bedding plane than for coal parallel to the bedding plane (van Krevelen, 1961). 

The variation of compressive strength with rank of coals has been noted and a plot of strength against volatile matter shows the customary minimum to be 20 to 25% dry, ash-free volatile matter (Table 8.2 and Figure 8.1) for compression both perpendicular and parallel to the bedding plane. 

A system of joint planes is often observed in coal formations, and these joint planes (cleats) are usually perpendicular to the bedding planes. Thus, cleat joints are usually vertical. The main system of joints is more commonly called the face cleat, whereas a cross-system of jointing is called the butt cleat. Furthermore, the cleat system in coal has a pronounced effect on the properties of a coal deposit. For example, holes drilled into coal perpendicular to the face cleat are said to yield from 2.5 to 10 times the amount of methane gas from the formation as holes drilled perpendicular to the butt cleat. Also, the cleat system of fracture and the frequency of cleats may determine the size of run-of-mine coal. In general, a pair of cleats will be oriented at about 90° to each other, and the orientation of the cutting elements influences the output of coal-mining machines (Figure 8.4). 

The find is associated with other specimens of the same kind and together with non-structured carbonaceous debris of similar chemical composition. The assemblages are arranged along bedding planes or other primary patterns of the sediment which is a chert, stromatolite, banded iron formation, shale or related rock. 

Fig. 2.10 Rock beds in a subsidence basin. The part above the terminal base of drainage, for example, the sea, functions as a through-flow system (arrows). The deeper rock beds are fossil through-flow systems that host stagnant groundwater as they are (1) covered by impermeable rocks, (2) bisected by plastic impermeable rocks that have been squeezed into stretch joints in the competent rock beds and in between bedding plane thrusts, and (3) placed in a zone of zero hydraulic potential.

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