The Elements of economic geology

Bibliographic data

Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

Usage license:: Get license information via the feedback formular.

Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part IV. Engineering geology

Collection:: Economics Books

228 ECONOMIC GEOLOGY interspace is equal in a clay and in a conglomerate of uniform spherical pebbles; the interspace is larger in a clay than in a conglomerate with sand grains between the pebbles. Inaclay the amount of pore-space available for water-storage is high; in a sandy conglomerate it may be low. The amount of space for water-storage depends also on the denseness of the rock. In newly-deposited mud the particles are loosely packed and the interstices are occupied by water; when the mud is compressed into clay or shale the particles are closer together; the bed may be reduced to a sixth of its original volume, and its water-storage is greatly reduced. The connate water is expelled as the material shrinks. The permeability of a rock is its capacity for the entrance and passage of water. Clay is impermeable because its pore-spaces are so small that the water can only enter them by surface-tension. Sand is permeable because water readily flows through its wide spaces. Permeable rocks allow water both to enter and drain away quickly, and thus wells in them may yield large supplies. . The imbibition of a rock is its hold on the water in its pores. Chalk has a large water-storage, and readily absorbs water; but its particles are so minute that they have a large internal surface and hold water firmly. Hence though a bed of chalk may contain much water, unless a well in it reach a water-charged fissure the yield may be small; for owing to the high imbibition of chalk little of its water would flow into the well. The three properties may be illustrated by the following comparison :— Sandstone . Clay . . Chalk Water-storage. Often low Large | | Permeability. High’ Low High Imbibition. Low High | Per Cent. of Water avail- able from Wells. High Nane I.0w The yield of water from rocks often depends on the joints and fissures. The water capacity of many compact igneous

Access restriction

Copyright

fullscreen: The Elements of economic geology

Monograph

Chapter

Table of contents

Download

Monograph

Chapter

This page

Image fragment

Citation links

Citation recommendation