Angle of repose

The angle of repose or the critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°. Smooth, rounded sand grains cannot be piled as steeply as can rough, interlocking sands. If a small amount of water is able to bridge the gaps between particles, electrostatic attraction of the water to mineral surfaces will increase soil strength.

When bulk granular materials are poured onto a horizontal surface, a conical pile will form. The internal angle between the surface of the pile and the horizontal surface is known as the angle of repose and is related to the density, surface area and shapes of the particles, and the coefficient of friction of the material. However, a 2011 study shows that the angle of repose is also gravity-dependent. Material with a low angle of repose forms flatter piles than material with a high angle of repose.

Angle of Repose

Angle of Repose is a 1971 novel by Wallace Stegner about a wheelchair-using historian, Lyman Ward, who has lost connection with his son and living family and decides to write about his frontier-era grandparents. It won the Pulitzer Prize for Fiction in 1972. The novel is directly based on the letters of Mary Hallock Foote, later published as A Victorian Gentlewoman in the Far West.

Stegner's use of substantial passages from Foote's actual letters as the correspondence of his fictional character Susan Burling Ward was and remains controversial among some scholars. The controversy is somewhat tempered since Stegner had received permission to use Foote's writings, implying as much in the book's acknowledgments page.

In 1998, the Modern Library ranked Angle of Repose #82 on its list of the 100 best English-language novels of the 20th century.

Explanation of the novel's title

The title is an engineering term for the angle at which soil finally settles after, for example, being dumped from a mine as tailings. It seems to describe the loose wandering of the Ward family as they try to carve out a civilized existence in the West and, Susan hopes, to return to the East as successes. The story details Oliver's struggles on various mining, hydrology and construction engineering jobs, and Susan's adaptation to a hard life.