Wyniki wyszukiwania - BazTech

1

Prefabricated fractured rock under stepwise loading and unloading

Zhang Wei, Zhao Tongbin, Yin Yanchun

Journal of Theoretical and Applied Mechanics

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2022

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Vol. 60 nr 1

167--179

EN

After the engineering rock mass has been affected by comprehensive effects of mining and disturbance, it experiences an input of external energy as well as dissipation and release of internal energy. From the viewpoint of energy, characteristics of rock failure are studied, and the law of rock unstable deformation and energy evolution is analyzed. The damage mechanism of rock is revealed easily. A gradual loading and unloading test of fractured rock is carried out to analyze deformation characteristics of the fractured rock during the load- -bearing process, and to study the law of energy dissipation and release under different load- ing and unloading stress levels. The results show that: (1) the load-bearing time, loading and unloading stress level, stress at crack initiation and peak stress of fractured rock gradually decrease with an increase in the number of cracks, and the descending speed decreases grad- ually with the increase in the number of cracks; (2) the strain at crack initiation and peak strain of the fractured rock increase gradually with an increase in the number of cracks, and the gathering speed decreases with the increase of the number of cracks; (3) the released strain energy and dissipation energy of fractured rock increase with an increase of loading and unloading stress levels, and the increasing rate gradually slows down; (4) the number of acoustic emission events is positively related to the degree of rock damage, and the increase in the number of cracks will prolong duration of the number of acoustic emission events. The results have a theoretical value for energy evolution and deformation damage of fractured rock masses, and also provide experimental experience to study the instability precursor information of rock materials from the viewpoint of energy.

2

An experimental study on the complex resistivity of fractured rock under different saturation conditions

Pan Baozhi, Ruhan A., Guo Yuhang, Zhang Lihua, Wei Boyang, Zhou Weiyi

Acta Geophysica

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2022

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Vol. 70, no 3

1061--1081

EN

The fracture can be a good channel for oil and gas migration, which has a great influence on the permeability of the reservoir. Therefore, it is of major significance to identify fractures and determine the characterization parameters and physical proper ties of fractured reservoirs. In this study, homogeneous sandstone was used to simulate different artificially fractured rocks. The fractured rock samples had different fracture widths, fracture numbers, and fracture dip angles. In addition, the complex impedance and weights of the rock samples were measured during the process of natural evaporation, and the relationships between the water saturation and the complex resistivity values at different frequencies were examined. The frequency range is 100 Hz–10 kHz. It was found that the influence effects of frequency on the resistivity, dielectric constant, and loss factor had differed among the homogeneous samples and the fractured rock sample. The fracturing had led to the resistivity index and the water saturation curves separating under the different frequencies, and the degree of the dielectric constant index and water saturation curve separation became larger. Furthermore, the influencing effects of the fracture widths, fracture numbers, and fracture dip angles mainly occurred in terms of three aspects. The first was the slope of the resistivity index and water saturation curves (IR–Sw). The second was the slope of the dielectric constant index and water saturation curves (Iε–Sw), and the third was the loss tangent D and water saturation Sw curves.

3

Zasięg strefy spękań w otoczeniu wyrobiska wykonanego w samodzielnej obudowie kotwowej

Czarnecki Zbigniew, Niedbalski Zbigniew, Nita Łukasz, Śpiechowicz Marcin

Przegląd Górniczy

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2021

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T. 77, nr 1-3

48--58

PL

W artykule przedstawiono wyniki badań dołowych zasięgu strefy spękań górotworu wokół wyrobiska w samodzielnej obudowie kotwowej wykonanych endoskopem otworowym. Pomiary zrealizowane były w chodniku Bw-1n badawczym w pokładzie 401, który drążony jest przy pomocy kombajnu Bolter Miner. Następnie wykonany został model numeryczny z wykorzystaniem opartego na metodzie elementów skończonych programu Phase2, w celu określenia możliwości prognozowania zasięgu stref spękań.. Na koniec wykonano analizę porównawczą wyników badań dołowych z wynikami z modelu numerycznego.

EN

This article presents the results of underground research on the extent of the rock mass fracture zone around excavation with rock bolts only. The measurements were conducted by borehole endoscope in the gallery Bw-1n in the 401 coal seam, which is being driled by Bolter Miner entry driver. A numerical model was also built using the finite element-based program Phase2 to evaluate the fracture zone extent. Finally, the results of the underground research with the results of the numerical model were compared.

4

Fractured-bedrock aquifer studies based on a descriptive statistics of well-logging data: A case study from the Dajia River basin, Taiwan

Chou P.-Y, Hsu S.-M, Chen P.-J, Lin J.-J., Lo H.-C

Acta Geophysica

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2014

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Vol. 62, no. 3

564--584

EN

A simple descriptive-statistical approach is proposed for evaluating the transmissivity of fractured-bedrock under field conditions. Based on standard well logging and identification of structural discontinuities from borehole televiewer, the approach consists of four steps: (1) determination of discontinuity properties, namely the frequency of discontinuities and the ratio of open fractures along the borehole; (2) ranking the three well logs and the discontinuity properties into tertiles (high-to-low); (3) performing statistical analysis (F-test) for the three well logs to assess the significance of open fractures on the water-transmitting potential and then assigned a weighting factor; and (4) a semi-quantitative indicator, RGVFO, is obtained by multiplying all predictive indexes and weighting factors. It is a multi-criteria evaluation procedure that elucidates the quantitative and qualitative importance of all selected geophysical indexes. A high cross-correlation between transmissivity to RGVFO value is found, which indicates that by a combined consideration of well logging and structural discontinuities, an appropriate estimate of bedrock water-transmitting potential can be derived.

5

Analiza zjawisk wchłaniania kapilarnego w szczelinowatych utworach dolomitu głównego

Lubaś J., Masłowski M.

Prace Naukowe Instytutu Nafty i Gazu

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2010

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nr 170 wyd. konferencyjne

247--254

PL

Wykorzystując analityczny model Aronofsky'ego przedstawiono analizę zjawisk odzysku ropy podczas wchłaniania kapilarnego w procesach nawadniania złóż szczelinowatych. Badania laboratoryjne nasycania wodą próbek rdzeni z dolomitu głównego zawierających ropę złożową prowadzono w funkcji czasu, w okresie 30 dni. W referacie przedstawiono krzywe odzysku ropy otrzymane podczas eksperymentalnego wypierania wodą, które określiły bardzo niską sprawność procesu. Wykazano, że wchłanianie kapilarne nie może stanowić dominującego mechanizmu wydobywania ropy w procesach nawadniania tego typu kolektorów.

EN

The analysis of imbibition waterflooding in naturally fractured reservoirs has been presented with the use of Aronofsky analytical model describing oil recovery. Water imbibition for core samples of the Main Dolomite containing reservoir oil was conducted during 30 days. The oil recovery curves obtained from water imbibition laboratory experiments presented in the article indicated a very low rate of the process. Spontaneous imbibition will not be a dominating mechanism of oil production during the waterflooding in this type of rocks.

6

Reassessment of the effect of water saturation on intact rock and fractured Rrck

Reddish D. J., Li Z., Sheng Y.

Archives of Mining Sciences

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2006

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Vol. 51, no 1

13-34

EN

Water is one of the many factors influencing the strength of geomaterials. In this paper, multistage triaxial compressions were performed to investigate the weakening effect of water on intact and fractured sandstone specimens. Laboratory testing results are presented and discussed with particular reference to the change of the mechanical properties of the rock. A trend of strength reduction for both intact and fractured rocks can be generalized from the testing results. It is also observed that the fractured rock is more reactive to the water even though no apparent soluble gouge is sandwiched in the related rock fractures. Additionally, theoretical formulations are derived to characterize the strength reduction on the basis of the understanding of the physical process. Properties of a single rock joint are correlated with the tangential plastic energy of the shearing plane with the non-associated plastic flow rule during shearing. The degree of saturation Sw is introduced into Patton's model as an additional parameter to predict the shear strength evolvement with the degree of water saturation.

PL

Woda jest jednym z wielu czynników decydujących o wytrzymałości geo-materiałow. W niniejszej pracy przeprowadzono próby wielostopniowego trójosiowego ściskania skał, w celu zbadania w jaki sposób woda będzie zmniejszać wytrzymałość nienaruszonych i popękanych próbek piaskowca. Przedstawiono i przedyskutowano wyniki badań laboratoryjnych, zwłaszcza w kontekście zmian właściwości mechanicznych skał. Na podstawie wyników badań zauważono wyraźny trend do obniżenia wytrzymałości zarówno próbek skał nienaruszonych jak i popękanych. Zauważono także, że skały popękane bardziej reagują na wodę, pomimo, że w pęknięciach nie stwierdzono żadnych substancji rozpuszczalnych. Ponadto, opracowano teoretyczne wzory określające obniżenie wytrzymałości, w oparciu o zachodzące procesy fizyczne. Właściwości pojedynczego ciosu skały skorelowano z energią pochodzącą od odkształcenia stycznego płaszczyzny ścinania bez powiązania z zasadą płynięcia plastycznego w czasie ścinania. Do modelu Pattona wprowadzono stopień nasycenia Sw, jako dodatkowy parametr pozwalający na przewidywanie zmian odporności na ścinanie przy zmianie stopnia nasycenia wodą.