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Effect of load rate on wood crib behavior.

Authors
Barczak-TM; Schwemmer-DE
Source
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9161, 1988 Jan; :1-11
Link
NIOSHTIC No.
10005980
Abstract
The effect of load rate on the load-carrying capabilities of wood cribs is investigated in this Bureau of Mines study. The modulus of deformation (stiffness) of wood crib blocks has been shown to increase with increases in rates of load application, causing larger load reactions for increases in convergence rates. Since wood cribs are tested in the laboratory at convergence rates that are orders of magnitude faster than typically would occur underground, wood cribs tested in the laboratory will react larger loads than the same cribs would react underground for the same displacement. Tests conducted in the Bureau's mine roof simulator on green wood crib blocks indicate that the increase in stiffness for increasing load rates diminishes at displacement rates beyond 0.1 In/min, making crib load nearly independent of load rate for rates faster than 0.1 In/min. Seasoned wood specimens were not as consistent in load-rate dependency. Some possible explanations of observed load-rate behavior on wood crib specimens are also postulated in this paper.
Keywords
Underground-supporting; Crib-walls; Wood; Coal-mining; Shoring; Loading-rate; Timbering-supporting; Mining-engineering; Stress-analysis; Cribs; Underground-mining; Loads-Forces
Publication Date
19880101
Document Type
IH; Report of Investigations
Fiscal Year
1988
NTIS Accession No.
PB88-230966
NTIS Price
A03
Identifying No.
RI-9161
NIOSH Division
PRC
Source Name
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9161
State
PA
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