The term engineering rock mechanics is used to describe the engineering
application of rock mechanics to civil, mining, petroleum and
environmental engineering circumstances. The term mechanics, means
the study of the equilibrium and motion of bodies, which includes statics
and dynamics l. Thus, rock mechanics is the study of mechanics applied
to rock and rock masses. ’Engineering rock mechanics’ is this study
within an engineering context, rather than in the context of natural processes
that occur in the Earth‘s crust, such as folding and faulting.
The rock mass around an underground opening is subjected to a unique stress path that results in low radial
confinement and both tangential loading and unloading conditions near the wall. As a result, the rock
mass strength near underground excavations is controlled by failure mechanisms dominating at low confinement.
Hence, when constructing underground works in hard rock, two general scenarios are encountered:
(1) structurally controlled gravity-driven failures; and (2) stress-induced failure with spalling and
Tham khảo sách 'engineering rock mechanics: part 2 iilustrative worked examples.chile continuous, homogeneous,', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả
high heats by mass removal. Their most common use is as an external heat shield to protect supersonic aerospace vehicles from an excessive buildup of heat caused by air friction at the surface. The ablative material must have a low thermal conductivity in order that the heat may remain concentrated in the thin surface layer. As the surface of the ablator melts or sublimes, it is wiped away by the frictional forces that simultaneously heat newly exposed surfaces. The heat is carried off with the material removed. The less material that is lost, the more efficient is the ablative material....
The earliest stone tools were crude, being little more than a fractured rock. In the Acheulian era, beginning approximately 1.65 million years ago, methods of working these stone into specific shapes, such as hand axes emerged. The Middle Paleolithic, approximately 300,000 years ago, saw the introduction of the prepared-core technique, where multiple blades could be rapidly formed from a single core stone.
The internal combustion engine was originally selected for the automobile due to its flexibility over a wide range of speeds. Also, the power developed for a given weight engine was reasonable; it could be produced by economical mass-production methods; and it used a readily available, moderately priced fuel - petrol.
The invention of the wheel revolutionized activities as disparate as transportation, war, and the production of pottery (for which it may have been first used). It did not take long to discover that wheeled wagons could be used to carry heavy loads and fast (rotary) potters' wheels enabled early mass production of pottery. But it was the use of the wheel as a transformer of energy (through water wheels, windmills, and even treadmills) that revolutionized the application of nonhuman power sources....
The suggested guidelines in this manual have been developed from a number of sources,
and most are applicable to a wide range of mass public gatherings. These sources focused
on youth audiences attending large rock concerts and competitive sporting events because
of the difficulties and major incidents historically associated with such events. Many of the
guidelines derived from such experiences are applicable to a broad range of other events
that present their own challenges.
Certain types of events have an inherent capacity for special management problems.
I came into this world on the Shrove-Tuesday of the year 1499, just as they were coming together for mass.
From this circumstance, my friends derived the confident hope that I should become a priest, for at that time
that sort of superstition was still every where prevalent. I had one sister, named Christina; she alone was with
my mother when I was born, and she afterwards told it me. My father's name was Anthony Platter, of the old
family of Platter, who have their name from a house which stands on a broad plat (Platte). This plat is a rock
on a very high...
"IN ONE fell swoop," declared Professor C. Cydwick Ohms, releasing a thin blue ribbon of pipe-smoke and rocking back on his heels, "—I intend to solve the greatest problem facing mankind today. Colonizing the Polar Wastes was a messy and fruitless business. And the Enforced Birth Control Program couldn't be enforced. Overpopulation still remains the thorn in our side. Gentlemen—" He paused to look each of the assembled reporters in the eye. "—there is but one answer." "Mass annihilation?" quavered a cub reporter. "Posh, boy! Certainly not!" The professor bristled.
One afternoon, at low water, Mr. Isbister, a young artist lodging at Boscastle,
walked from that place to the picturesque cove of Pentargen, desiring
to examine the caves there. Halfway down the precipitous path to
the Pentargen beach he came suddenly upon a man sitting in an attitude
of profound distress beneath a projecting mass of rock. The hands of this
man hung limply over his knees, his eyes were red and staring before
him, and his face was wet with tears.
He glanced round at Isbister's footfall.