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Effects of porosity and composition on seismic wave velocities and elastic moduli of lower cretaceous rocks, central Lebanon

Salah M. K., Alqudah M., El-Aal A. K. A, Barnes C.

Acta Geophysica

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2018

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Vol. 66, no. 5

867--894

EN

We collected 40 rock samples from the Cretaceous strata exposed at central Lebanon in order to study the effects of porosity and rock composition on their seismic wave velocities and elastic moduli. Several sedimentological and mineralogical studies were conducted to evaluate the rock composition, provenance, depositional conditions, and the diagenetic history of the studied rocks. Porosity, bulk and grain densities and seismic wave velocities were measured for 35 drilled core samples at ambient conditions in the laboratory. Velocity measurements were conducted on the dry core samples utilizing the pulse transmission technique. Petrographically, four lithofacies have been identified under the polarizing microscope. From oldest to youngest, these comprise arenitic sandstone, lithic limestone, oolitic limestone, and micritic limestone. Investigations of representative rock samples under the SEM revealed that a number of diagenetic processes have impacted the studied rocks, and thereby affected their petrophysical properties. The XRD analysis, on the other hand, revealed that quartz and calcite are the dominant minerals in the sandstones of the Chouf Formation and the limestones of the Abeih and Mdairej Formations, respectively. The measured porosity, bulk density, and compressional and shear wave velocities of the investigated rocks vary, respectively, between 2.14–10.05%, 2.41–2.67 g/cm3, 3885–6385 m/s and 2246–3607 m/s. The grain density was calculated from the measured porosity and bulk density data and varies narrowly between 2.64 and 2.78 g/cm3. We further calculated the Poisson’s ratio and the moduli of shear, bulk, and Young from the measured bulk density and seismic wave velocities. Calculated values of these parameters vary between 0.18–0.28, 1.23–3.43 × 1010 Pa, 2.03–6.18 × 1010 Pa and 3.06–8.69 × 1010 Pa, respectively. The generalized mixture rule is used to provide a unified description of the physical properties of the studied rocks regarding their component properties, volume fractions, and microstructures. We constructed a number of relationships between the measured petrophysical and elastic properties to evaluate the mutual interdependence of these parameters and assess the effects of porosity and rock type on these important rock characteristics.

2

Metody geofizyczne w geologii inżynierskiej

Bestyński Z.

Biuletyn Państwowego Instytutu Geologicznego

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2011

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nr 446 (1)

175--182

PL

W artykule scharakteryzowano podstawowe metody geofizyczne stosowane w geologii inżynierskiej, tzn. metody geoelektryczne i sejsmiczne. Podano ich podstawy fizyczne oraz zalety i ograniczenia w rozwiązywaniu zadań geologii inżynierskiej. Przedstawiono przykłady badań geofizycznych do oceny warunków geotechnicznych budowy tuneli, stanu technicznego budowli i stateczności zboczy osuwiskowych, jak również warunków hydrogeologicznych podłoża tras komunikacyjnych.

EN

This article presents geophysical methods used for geological engineering investigations, theirs physical basis, and advantages and limitations in geological engineering study. Some examples of geophysical investigations for solving different geological engineering problems are also presented.

3

Badania geofizyczne w budownictwie hydrotechnicznym

Bestyński Z.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2009

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T. 35, z. 2/1

393-403

EN

Geophysical investigations are used at every stage of designing, building and exploitation of hydraulic objects. There are presented three examples of such investigations in this project: 1- investigation for recognition of geotechnical conditions of excavation and support hydraulic tunnels of Świnna Poręba dam, 2- investigation for estimation of efficiency of works for Wapienica concrete dam sealing and strengthening, 3- investigation for estimation of landslides slope stability at the costal area of man-made water reservoirs of Czorsztyn, Niedzica and Świnna Poręba.

4

Badania geofizyczne w rozpoznaniu warunków geotechnicznych budowy tuneli

Bestyński Z., Thiel K.

Górnictwo i Geoinżynieria

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2007

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R. 31, z. 3

37-43

PL

Wybór optymalnej trasy i konstrukcji tunelu wymaga rozpoznania geotechnicznego stosunkowo dużego obszaru jego potencjalnej lokalizacji. Rozpoznanie takie jest możliwe do wykonania odpowiednio dobranym zestawem metod geofizycznych. W rozpoznaniu geofizycznym masywów fliszowych, budujących południową część obszaru Polski, najbardziej efektywne okazały się badania sejsmiczne i elektrooporowe. Badania te umożliwiają rozpoznanie podstawowych charakterystyk fliszu, tzn. jego litologii i tektoniki. Liczne badania geofizyczne wykonane na terenie Karpat fliszowych dla potrzeb geotechniki wykazały również, że parametry geofizyczne charakteryzujące flisz, tzn. prędkość fal sejsmicznych i oporność elektryczna, są wystarczające do opisu jego właściwości geotechnicznych wyrażonych klasą geotechniczną. Formułę na określenie geofizycznego wskaźnika klasyfikacji geotechnicznej, nazwanego KFG, określono metodami statystyki matematycznej w taki sposób, aby był on równoważny liczbie klasyfikacyjnej RMR Z.T. Bieniawskiego. Wskaźnik KFG z powodzeniem zastosowano do wyboru tras i techniki drążenia sztolni hydrotechnicznych. Zastosowano go również do rozpoznania tras tuneli komunikacyjnych projektowanych w Karpatach fliszowych. Metody sejsmiczna i elektrooporowa okazały się również skuteczne w rozpoznaniu osadów wodno-lodowcowych występujących wzdłuż trasy tunelu projektowanego w Gdańsku.

EN

The choice of optimal route and construction of the tunnel requires a geotechnical recognition of a wider area where the tunnel might be located. The recognition is possible if we use a proper suite of geophysical methods. In case of geophysical recognition of flysch formations in southern Poland, seismic and geoelectric surveys were proven as the most efficient. The surveys make it possible to characterize basic features of flysch, as lithology and tectonic. Numerous geophysical surveys carried out on area of flysch Carpathians to geotechnical purposes have proven also that geophysical parameters characterizing flysch (seismic wave velocity, electric resistivity) are sufficient to describe its geotechnical properties as geotechnical class. The formula on geophysical index of geotechnical classification, called KFG, was determined using statistical methods in a manner ensuring the index is equivalent to RMR Bieniawski value. KFG index was successfully applied to proposing routes and technology of boring of hydrotechnical galleries. It was also applied for reconnaissance of routes of communication tunnels planed in flysch Carpathians. Seismic and resistivity methods appeared to be very effective in recognition of fluvio-glacial deposits occurring along the tunnel route planned in Gdańsk.

5

Sejsmiczna struktura litosfery i górnego płaszcza Ziemi kontynentów

Grad M.

Przegląd Geofizyczny

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2000

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Z. 1

43-61

EN

Seismic models of the continental lower lithosphere and upper mantle obtained from interpretation of body P waves are discussed. The models of the lower lithosphere differ in the character of veloc-ity distribution, the number of layers, and the presence of the lower-velocity layers. This is the con-sequence of inhomogeneity of the lower lithosphere, but also follows from the differing accuracy and quality of seismic data. The differences in models resulting from the use of seismological methods based on earthquake observations and experiments on long-range profiles are pointed out. In all continental mantle models, both the "410" km and "660" km discontinuities were clearly ob-served. The "520" km boundary is observed for some models (for some models only a gradient change is observed). So, the global existence of this boundary for P waves seems to be still contro-versial.