Basic references: Czubla P. Mizerski, E. PWN, Warszawa, s. Mizerski W.
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We'd like to understand how you use our websites in order to improve them. Register your interest. This paper attempts to show the relationship between joints observed in flysch formations in the field and microfracture fabrics invisible to the naked eye in hand specimens.
The spatial orientations of these microfractures have been measured, and their dynamic-elastic properties have been found to correlate with the orientation of macroscopic joint sets measured in the field.
The elastic properties measured vary because of sedimentary diagenetic processes that occured during the tectonic deformations of these flysch rocks in the Podhale Synclinorium of Poland.
The structural discontinuities detected by ultrasonic measurements can be perceived as an incipient phase of the macroscopic joints already visible in the field and are attributed to the in situ residual tectonic stresses. Such historical stresses impart a hidden mechanical anisotropy to the entire flysch sequence. The microfractures will develop into macroscopic joints during future relaxation of the exposed rock mass.
Understanding the nature and orientation of the invisible microfracture anisotropy that will become macroscopic in the future is vital for the safe and efficient engineering of any rock mass. The mechanical properties of any rock mass must be known in appropriate detail to design safe and efficient future engineering projects in, on, or under it. For example, one can deduce the effective density of a rock mass when density varies inside it along specific directions Mukherjee a , b , c , Detailed investigations of the mechanical properties e.
Mukherjee et al. Such studies should characterise the rock mass in terms of its mineralogical and petrographic characteristics as well as its structural heterogeneity, discontinuities and anisotropy of physical and mechanical properties Thiel Typical rock properties required are the types, proportions and size of the constituent minerals and their orientations together with the proportions, size and orientations of any pores and any cement filling them.
Geologic fractures are generally thought to initiate at flaws randomly dispersed throughout the host rock e. Olson , based on the experimental works of Griffith as well as field evidence that joints propagated from microfractures located at fossils or sedimentary structures e. Helgeson and Aydin ; Savalli and Engelder The issue of explaining fracture patterns, in particular how to start from an unorganised flaw distribution and produce a non-random pattern, is currently being investigated Hooker et al.
Kieslinger expressed the view that the presence of joints in the rock mass is primarily attributed to in situ residual tectonic stresses. Decrease of the overburden results in relaxation of the rock mass, which is manifested in the form of less or more advanced disintegration of the rocks into blocks. Furthermore, Boretti-Onyszkiewicz a interpreted such disintegration of rocks into blocks as a result of hidden, potential surface discontinuities.
It should be noticed that most rocks experience several different stress regimes during their history with the result that several joint sets are frequently found superimposed on each other to produce a joint network. The complex stress history, which the Podhale Synclinorium has been subjected to, implies that the local rocks are predisposed to further degradation by more of the joints than those already observed; this in turn will increase its anisotropy of elasticity.
From a practical point of view, a penetrative fracture anisotropy is of crucial importance to the capacity of the rock mass to expand laterally. The rock blocks are mainly formed as a result of joint disclosure and the related expansion of rock masses, which is connected with the increase of rock mass capacity sideways with further advancement of the relaxation process as well as during weathering.
Therefore the fracture anisotropy would be especially dangerous in slope and edge zones of valleys Boretti-Onyszkiewicz a. This paper also develops the subject of the relationship between joints and the elastic properties of rock masses, which has received plenty of attention by engineering geologists in recent years, especially to predict the mechanical competency of formations targeted for future hydrocarbon exploration Gueguen and Schubnel ; Eyinla and Oladunjoye That subject concerns the assessment of the elastic properties of rock masses in the field Vilhelm et al.
The static strength moduli can be measured by loading cylindrical core samples of standard sizes to destruction while the dynamic strength moduli can be measured by the non-destructive ultrasonic testing presented in this work.
Dynamic rock parameters can also be obtained directly in outcrops using geophysical methods. The work does not aim to establish a conversion factor between static and dynamic measurement. However, the results of the elastic properties derived from both static and dynamic methods are actually presented. The study was conducted in the Podhale Synclinorium where well-developed joints are common in rocks that have been only slightly deformed by tectonic forces.
Joint-related arrays of en echelon fractures have also been studied in the field. Such microfracture fabrics are usually attributed to the effects of natural differential stresses. Microfractures commonly form as Mode I opening fractures where the minimum principal stress exceeds the elastic tensile strength creating a narrow opening displacement; in isotropic rocks, such fractures mark the plane perpendicular to the least compressive principal stress during fracture growth Anders et al. The synclinorium developed because of the inversion of a basin filled with Paleogene flysch during Miocene.
The synclinorium is cut by regular joints network Halicki ; Boretti-Onyszkiewicza; Morawski ; Mastella and Mizerski ; Mastella and Ozimkowski ; Ludwiniak , The particular joint sets, however, occurred in different stress fields. It follows from theoretical considerations e. Moreover, the geometry of joint-related arrays of en echelon fractures points to a tendency to strike-slip movement along these joints.
In the discussed area, the process of formating of the oldest sets, i. It should be mentioned that there is only limited field evidence to suggest that these joints started to develop within poorly lithified rocks e.
Mastella ; Mastella et al. The other sets of joint were formed as a result of the WNW—ESE extension connected with the uplift of the synclinorium and subsequent in consequence of stress relaxation in the rock masses during postorogenic uplift Ludwiniak In lithostratigraphic terms, these formations classify as the lower Zakopane beds.
Detailed laboratory tests were performed on fine- and very fine-grained grey sandstones with abundant carbonate cement. Weakly sorted, poorly and averagely rounded grains of monocrystalline quartz are the dominant component of these detrital sandstones. There are also minor quantities of polycrystalline quartz, and fragments of quartz and carbonate rocks with occasional grains of partially altered plagioclases and muscovite laminae.
The rock texture is random, solid and non-porous. Ultrasonic tests in the Laboratory of the Department of Geomechanics at the Faculty of Geology of Warsaw University were preceded by field measurements of joint orientations, style and their crosscutting relationships in the same beds of sandstone Fig.
As suggested by some authors, e. Dunne and Hancocok , Twiss and Moores and Ludwiniak , the division of joints into the sets was made directly in the field by observing the surface traces of each set. Five sets of joints were recognised in the sandstone outcrops analysed. Specific sets were identified by their current orientation with respect to the regional extent of the Podhale Synclinorium see Chap.
Of the five sets of joints, two sets are oblique to the axis of fold in which they are located and considered conjugate S R and S L. Taking into account their arranged with respect to sedimentary layering and fold hinge lines, some researchers e.
Price ; Hancock named that system as conjugate hk0 fractures enclosing an acute angle about the line parallel to sedimentary layering. In addition to joint orientation, the strike and dip of the beds in monoliths containing the joints were also measured with respect to north Fig. In consequence, following Murray and Al Kadhi and Hancock , the strata together with joints were back-tilted to the horizontal Rubinkiewicz ; Mastella and Zuchiewicz ; Mastella and Konon ; Ludwiniak The mode orientations of individual joint sets were determined using contoured stereonets.
This direction of drilling was also chosen in order to exclude other factors like directional placement of grains, high porosity or lamination that could cause anisotropy of elastic properties of the sandstones. To determine whether the grains were placed directionally or if there were any structural defects, microscopic images were also taken both perpendicularly as well as parallel to the sample axis , but they are not presented in this paper. The planes were then oriented according to markings Fig.
The material prepared and described this way was used to reconstruct paleo-stresses at the initial stage when the joints formed. Methodology of ultrasonic tests Domonik , modified : a rock monoliths from which the samples were cut to the laboratory tests; b orientation of cylindrical sample within rock monolith; c spatial orientation of measuring planes along with the directions of measurement of ultrasonic waves. The heterogeneity of the internal structure and the variability of elastic properties of each of the 69 samples were assessed using ultrasound measurements.
This method is based on the direct measurement of the sound pulse transition time between the transmitting and receiving heads along a length equal with, e. This approach achieves a resultant of the wave front velocity Dziedzic The measurement consisted of applying the transmitting and receiving heads and recording the time of wave transition through sample.
This procedure was repeated 18 times. The last one measurement consisted of applying the heads across the sample at its vertical axis. Altogether 19 measurements were made per sample. Using the ultrasonic tests, the variability of the internal composition of rock material can be determined. It is due to the fact that pores, laminae, microfractures, directional placement of mineral grains and other heterogeneities of the internal composition are reflected by the variability of the ultrasonic wave propagation.
The propagation of artificially generated ultrasonic elastic waves through the rock samples allows, not only the detection of defects and their spatial distribution in the sample, but also the characterisation of the spatial variations in dynamic elastic properties they impose. Each microfracture that was perpendicular or inclined at a high angle to the beam suppresses or entirely mutes the wave pulse that would normally be present in an area without defects Domonik Therefore, E d was calculated using Eq.
The measured velocity of the ultrasonic waves depended on the direction of measurement as illustrated in Fig. The longitudinal waves that travelled parallel with the macroscopic joint surfaces were much less attenuated and hence had higher wave velocities Fig. Diagrams of distribution of ultrasonic wave velocity in oriented Zakopane sandstone depending on measuring directions against joint set dominants determined in the field drawn for arithmetic mean values of 69 samples: a longitudinal wave velocity; b shear wave velocity.
The dispersions of the v d values are significant for all adopted measurement directions; the highest values are measured parallel to the joint sets measured in the field Fig. Therefore, the elastic properties have a similar anisotropy to the individual directions of measured values of V p Fig.
The elastic properties were also assessed using static strength tests. The elastic properties were calculated along the sample length and compared with the dynamic values computed in the same direction.
In previous works, e. The issue of subdivision of the joint network into sets through observation of the morphology of joint traces as well as crosscutting relationships was not considered. It resulted in including joints having similar directions but different morphological features and different origins e. Ludwiniak , reviewed some of the opinions included in the aforementioned works, which was a great progress.
It was possible due to his own more thorough measurements in individual outcrops. Among other things, Ludwiniak noticed, for example, that none of the above-mentioned authors distinguished the set T , despite the fact that there were many outcrops in situ, where this set occurred although in less quantity than sets S R and S L.
Moreover, insightful observations of the joint networks in the field, as suggested by Dunne and Hancocok as well as Twiss and Moores , allowed the researcher to determine the origin of the joint network five sets in the Western Podhale region and reconstruct the paleo-stresses responsible for its development.
The joint sets determined this way could influence the assessment of the results of the strength as well as the ultrasonic tests. Domonik has in fact determined the acoustic and mechanical anisotropy, however, only for the above-mentioned four sets.
Perhaps the subtle variations of wave velocity were omitted, which could suggest the existence of additional planes of microfractures. This relationship is reinforced by the distribution of orientations of the macroscopic joint sets measured in the field being so like the orientations of microfractures in samples of rock that look isotropic to the eye. This means that the value of dihedral angle may turn out to be slightly higher than in the field measurements.
The velocities of the ultrasonic waves varied only with their direction of measurement.
Geologia dynamiczna mizerski pdf chomikuj filmy
Plik W. Jaroszewski Przewodnik do cwiczen z geologii dynamicznej. Procesy Geologia dynamiczna - M. Kosmiczne katastrofy w historii Ziemi.
We'd like to understand how you use our websites in order to improve them. Register your interest. This paper attempts to show the relationship between joints observed in flysch formations in the field and microfracture fabrics invisible to the naked eye in hand specimens. The spatial orientations of these microfractures have been measured, and their dynamic-elastic properties have been found to correlate with the orientation of macroscopic joint sets measured in the field. The elastic properties measured vary because of sedimentary diagenetic processes that occured during the tectonic deformations of these flysch rocks in the Podhale Synclinorium of Poland. The structural discontinuities detected by ultrasonic measurements can be perceived as an incipient phase of the macroscopic joints already visible in the field and are attributed to the in situ residual tectonic stresses.
According to the definition by Depciuch and Lis it is "a set of tectonic structures formed by a single, distinct tectonic phase". Formations which together form a structural stage are not a result of continuous sedimentation, but were tectonically deformed together. They are also characterised by a similar stage of metamorphosis. Therefore, any structural level is a product of one phase of the tectonic evolution of a continental platform which relates both to the crystalline basement and the sedimentary cover. This structural stage constitutes a single sedimentary-diastrophic cycle.
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