| environ. |
soil subsidence A sinking down of a part of the earth's crust, generally due to underground excavations; soil compaction An increase in bulk density (mass per unit volume) and a decrease in soil porosity resulting from applied loads, vibration, or pressure. More compacted soils (or other materials) can support greater loads (load-bearing capacity). Bulk density can be increased by controlling the moisture content, compaction forces and treatment procedures, as well as by manipulating the type of material being compacted; subsidence 1. A sinking down of a part of the earth's crust, generally due to underground excavations. 2. The sudden sinking or gradual downward settling of the Earth's surface with little or no horizontal motion. The movement is not restricted in rate, magnitude, or area involved. Subsidence may be caused by natural geologic processes, such as solution, thawing, compaction, slow crustal warping, or withdrawal of fluid lava from beneath a solid crust; or by man's activity, such as subsurface mining or the pumping of oil or ground water; soil settling |
