Little rock Anderson, Karen
2010., 20131110, 2013, 2010, 2010-01-01, Letnik:
66
eBook
The desegregation crisis in Little Rock is a landmark of American history: on September 4, 1957, after the Supreme Court struck down racial segregation in public schools, Arkansas Governor Orval ...Faubus called up the National Guard to surround Little Rock Central High School, preventing black students from going in. On September 25, 1957, nine black students, escorted by federal troops, gained entrance. With grace and depth, Little Rock provides fresh perspectives on the individuals, especially the activists and policymakers, involved in these dramatic events. Looking at a wide variety of evidence and sources, Karen Anderson examines American racial politics in relation to changes in youth culture, sexuality, gender relations, and economics, and she locates the conflicts of Little Rock within the larger political and historical context.
A Social History of Early Rock 'n' Roll in Germany explores the people and spaces of St. Pauli's rock'n'roll scene in the 1960s. Starting in 1960, young British rockers were hired to entertain ...tourists in Hamburg's red-light district around the Reeperbahn in the area of St. Pauli. German youths quickly joined in to experience the forbidden thrill of rock'n'roll, and used African American sounds to distance themselves from the old Nazi generation. In 1962 the Star Club opened and drew international attention for hosting some of the Beatles' most influential performances. In this book, Julia Sneeringer weaves together this story of youth culture with histories of sex and gender, popular culture, media, and subculture. By exploring the history of one locale in depth, Sneeringer offers a welcome contribution to the scholarly literature on space, place, sound and the city, and pays overdue attention to the impact that Hamburg had upon music and style. She is also careful to place performers such as The Beatles back into the social, spatial, and musical contexts that shaped them and their generation. This book reveals that transnational encounters between musicians, fans, entrepreneurs and businessmen in St. Pauli produced a musical style that provided emotional and physical liberation and challenged powerful forces of conservatism and conformity with effects that transformed the world for decades to come.
All stars are celebrities, but not all celebrities are stars, states David Shumway in the introduction to Rock Star, an informal history of rock stardom. This deceptively simple statement belies the ...complex definition and meaning of stardom and more specifically of rock icons. Shumway looks at the careers and cultural legacies of seven rock stars in the context of popular music and culture—Elvis Presley, James Brown, Bob Dylan, the Rolling Stones, the Grateful Dead, Joni Mitchell, and Bruce Springsteen. Granted, there are many more names that fall into the rock icon category and that might rightfully appear on this list. Partly, that is the point: rock star is a familiar and desired category but also a contested one.
Shumway investigates the rock star as a particular kind of cultural construction, different from mere celebrity. After the golden age of moviemaking, media exposure allowed rock stars more political sway than Hollywood's studio stars, and rock stars gradually replaced movie stars as key cultural heroes. Because of changes in American society and the media industries, rock stars have become much more explicitly political figures than were the stars of Hollywood’s studio era. Rock stars, moreover, are icons of change, though not always progressive, whose public personas read like texts produced collaboratively by the performers themselves, their managers, and record companies. These stars thrive in a variety of media, including recorded music, concert performance, dress, staging, cover art, films, television, video, print, and others.
Filled with memorable photographs, Rock Star will appeal to anyone interested in modern American popular culture or music history.
When rock samples are loaded until macroscopic fractures develop, the failure process can be divided into several stages based on axial and lateral strain responses or the acoustic emission sequence ...during uniaxial compression tests. Several stress thresholds may be identified: the crack closure stress
σ
cc
, crack initiation stress
σ
ci
, crack damage stress
σ
cd
, and uniaxial compressive strength
σ
ucs
; these may be used as a warning indicator for rock rupture. We investigated the crack damage stress
σ
cd
, its threshold, and a possible relationship between
σ
cd
and the uniaxial compressive strength. The
σ
cd
of different rock types were compiled from previous studies based on uniaxial compression tests. The results showed that the overall averages and standard deviations of
σ
cd
/σ
ucs
for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.11), ~0.85 (±0.11), and ~0.73 (±0.18), respectively. There were no significant differences in
σ
cd
/σ
ucs
between the different rock types, except that the sedimentary rock had a slightly larger standard deviation attributed to the variation of porosity in the samples, while the metamorphic rock had higher average
σ
cd
/σ
ucs
resulting from the small statistical sample size. By excluding the higher-porosity (>10 %) rock samples, the averages and standard deviations of
σ
cd
/σ
ucs
for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.09), ~0.85 (±0.09), and ~0.78 (±0.11), respectively. The results imply that the rock origin process (i.e., igneous, metamorphic, and sedimentary) has a minimal effect on
σ
cd
/σ
ucs
. The ratio
σ
cd
/
σ
ucs
could be an essential intrinsic property for low-porosity rocks, which could be used in rock engineering for predicting the failure process.
An energy-absorbing rock support device, called a D bolt, has been recently developed to counteract both burst-prone and squeezing rock conditions that occur during underground excavation. The bolt ...is a smooth steel bar with a number of anchors along its length. The anchors are firmly fixed within a borehole using either cement grout or resin, while the smooth sections of the bolt between the anchors may freely deform in response to rock dilation. Failure of one section does not affect the reinforcement performance of the other sections. The bolt is designed to fully use both the strength and the deformation capacity of the bolt material along the entire length. The bolt has large load-bearing and deformation capacities. Static pull tests and dynamic drop tests show that the bolt length elongates by 14–20% at a load level equal to the strength of the bolt material, thereby absorbing a large amount of energy. The impact average load of a 20
mm D bolt is 200–230
kN, with only a small portion of the load transferred to the bolt plate. The cumulative dynamic energy absorption of the bolt is measured to be 47
kJ/m. D bolts were tested in three deep mines. Filed measurements show that D bolts are loaded less than rebar bolts. This paper presents the layout and principle of the D bolt, and corresponding results from static, dynamic, and field tests.
Rock and rock-like materials such as concrete, soil, and underground backfilling materials are considered to be geomaterials. Geomaterials are essential for life due to human construct extraction, ...mining, storage, and transport areas in the Earth’s crust for raw material. Drilling and excavations of underground openings in the Earth’s crust are requirements for the exploitation and utilization of mineral resources, energy resources, and underground spaces. The deepest drilling depth has exceeded 12 km, and the deepest underground excavation now operates mines with depths exceeding 4 to 5 km. Drilling, excavation, and rock support processes largely rely on the physical and mechanical properties of geomaterials. Rock excavations are faced with some instability phenomena, such as caving, rock bursts, slabbing, large deformation, and zonal disintegration, posing a serious threat to the safety of mining and tunneling operations. Rock drilling also encounters many challenges deep underground. Deformation, fracture, failure, and fragmentation are the different stages of geomaterials, the monitoring and control of which are essential for ensuring drilling and excavation safety. Therefore, understanding the response processes of geomaterials during drilling and excavation activities depends on the precise characterizations of geomaterials.
In deep underground coal mining, engineering activities are performed within anisotropic in-situ stress fields due to engineering disturbances and tectonic stress. Many such activities involve the ...development of excavations in soft rock and anisotropic coal. Accordingly, studying the mechanical properties of soft rocks is important for the stability of deep underground excavations. In this study, the deformation, strength, and failure characteristics of soft sandstone and raw coal under two different true triaxial loading paths were investigated using a self-developed true triaxial test apparatus. The results indicated that the inelastic strain in the pre-peak stage of sandstone and coal gradually increased with increasing intermediate principal stress. Also, the strength-drop in the post-peak stage increased. The crack initiation stress, crack damage stress, and peak strength of sandstone and coal first increased and then decreased with increasing intermediate principal stress for a given σ3. Moreover, with increasing intermediate principal stress, the failure mode of sandstone and coal changed from shear to tensile shear, and from brittle to semi-brittle. The linear Mogi criteria as found to characterize the true triaxial strength of coal well, while the modified Lade criteria was more applicable to soft sandstone. Owning to the symmetry assumption, the linear Mogi criteria predicted low strength when the intermediate principal stress coefficient exceeded to 0.5. In addition, the peak strength curve of rock on the π plane and the influence of weak structures on the failure mode of anisotropic coal was discussed. Weak structures have an important influence on the failure mode of coal, which depends on the strength difference between the structural plane and the coal rock mass. The strength envelope on the π plane had a significant stress Lode angle effect, which gradually decreased as the mean stress increased.
•Influence of the intermediate principal stress on deformation, strength, and failure mode of sandstone and coal.•Different Mogi-type strength criteria were discussed and compared.•The interval effect of intermediate principal stress on coal rock strength was discussed.•The envelope of true triaxial strength of rocks on the π plane was discussed.•The influence of weak structures on the failure mode of coal was discussed.
The synthetic rock mass approach for jointed rock mass modelling Mas Ivars, Diego; Pierce, Matthew E.; Darcel, Caroline ...
International journal of rock mechanics and mining sciences (Oxford, England : 1997),
02/2011, Letnik:
48, Številka:
2
Journal Article
Recenzirano
This paper describes synthetic rock mass (SRM) modeling, a new approach for simulating the mechanical behavior of jointed rock mass. This technique uses the bonded particle model for rock to ...represent intact material and the smooth-joint contact model (SJM) to represent the in situ joint network. The macroscopic behavior of an SRM sample depends on both the creation of new fractures through intact material and slip/opening of pre-existing joints. SRM samples containing thousands of non-persistent joints can be submitted to standard laboratory tests (UCS, triaxial loading, and direct tension tests) or tested under a non-trivial stress path representative of the stresses induced during the engineering activity under study.
Output from the SRM methodology includes pre-peak properties (modulus, damage threshold, peak strength, etc.) and post-peak properties (brittleness, dilation angle, residual strength, fragmentation, etc.). Of particular interest is the ability to obtain predictions of rock mass scale effects, anisotropy, and brittleness, properties that cannot be obtained using empirical methods of property estimation. This paper presents the theoretical background of the SRM approach along with some example applications.
Cubic specimens of granite, marble, and sandstone, with side lengths of 50 mm, were prepared in the laboratory. True triaxial compression tests were conducted on each rock type with minor principal ...stress (σ3) magnitudes of 10, 20, 30, 50, and 100 MPa and the intermediate principal stress (σ2) varying from σ2 = σ3 to σ2 = σ1 (where σ1 represents the major principal stress). The experimental results demonstrated that the failure strength, fracture dip angle, non-linear behavior and failure mode of these rocks under true triaxial conditions were affected by both σ2 and σ3, as well as by the rock lithology. When σ3 was kept constant and σ2 increased, failure strength showed an initial increase followed by a decrease, whereas the fracture dip angle increased monotonically. The non-linear behavior before the peak strength point of granite became more apparent by the increase of σ3, whereas σ2 had an opposite effect on the non-linear behavior of granite under high σ3 (e.g. 100 MPa). The non-linear behavior before the peak strength point was always found in marble and sandstone for all of the stress state conditions. Analyses of fracture dip angle and failure mode showed that when σ3 = 10, 20, and 30 MPa and σ2/σ3 ≥ 5, 7.5, and 10, respectively, the failure mode of granite changed from shear to slabbing, whereas marble and sandstone always fractured in the shear direction. This study confirms that rocks may experience slabbing failure under true triaxial stress, and slabbing failure mode is likely to be induced in high-strength and brittle rocks under low σ3 with the stress ratio of σ2/σ3 exceeding a particular threshold value.
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