Geoscience Reference
In-Depth Information
Point of
blasting
Principal stress in
circumferential direction
Principal stress in
radial direction
Radial direction
100%
Point of
interest
75%
(Plan view)
Circumferential dir.
Time
Fig. 15.9. Schematic diagram of stress variation induced by singleshot of blasting
10
8
6
4
100%
2
0
-
2
-
4
79%
Measured at 20 m distance
-
6
Sato Kogyo construction company
Japan, 1999
-
8
-
10
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Time (s)
Fig. 15.10. Example of soil particle velocity inradial direction asinduced by single
blasting
The impact produced by a single cycle of P wave can be understood by Figure15.10
whichillustratesthesoilparticlevelocityintheradialdirectioninducedbyablasting.Itis
seentherethatthefirstcompressionalimpactissignificantandthefollowingextensionis
oflessmagnitude,whilethefollowingstressvariationisnegligibleforpracticalpurposes.
When the P wave velocity in soil is designated by
Vp
, the radial displacement,
u
, due to
blasting isexpressed as
u
(
r
,
t
)
=
U
(
t
−
r
/
Vp
)
(1)
