RI 6537 Development of a Rock Stress Monitoring Station Based on the Flat Slot Method of ~Measuring Existing Rock Stress
- Organization:
- The National Institute for Occupational Safety and Health (NIOSH)
- Pages:
- 70
- File Size:
- 48285 KB
- Publication Date:
- Jan 1, 1964
Abstract
A flat slot is created in rock to cause stress relief effects in a pair
of hydraulic borehole pressure cells (previously installed in drill holes
above and below the slot ) , which act as sensing devices . This relief is
annulled by repressuring the slot by means of a flat hydraulic cell . The
slot pressure at annulment is taken to be the existing ground stress at right
angles to the plane of the slot . A number of trial installations in the rib
of a mine drift showed that for a valid determination of ground stress the
sensing devices that respond to relief and repressuring must be within a
specified zone close to the pressure transmitter ; otherwise the indicated
ground stress may be excessive . By using an additional pair of borehole pressure
cells , installed a few feet away , the existing rock stress can be redetermined
at intervals , irrespective of a change of stress intensity subsequent
to the initial installation .
Based on these findings , equipment and procedures have been developed
that make possible the installation and operation of a permanent rock stress
monitoring station for observing mining - induced stress changes . The station
consists of a 12 - in - wide hydraulic pressure cell cemented in a flat slot and
four 2- by 8 - in flat hydraulic pressure cells in nearby drill holes . All
drilling for the installation can be done with an air leg drill and conventional
bits . Once the installation is completed , all required information is
obtained by Bourdon pressure gage readings . The apparatus is simple , relatively
inexpensive , and reliable under operating conditions in a wet mine .
Unlike most methods of rock stress determination , this scheme permits periodic
remeasurement of absolute rock pressure over several years , without additional
drilling or instrumentation . Similar to other flat slot procedures , stress
measurements are obtained without making auxiliary tests to determine elastic
Citation
APA: (1964) RI 6537 Development of a Rock Stress Monitoring Station Based on the Flat Slot Method of ~Measuring Existing Rock Stress
MLA: RI 6537 Development of a Rock Stress Monitoring Station Based on the Flat Slot Method of ~Measuring Existing Rock Stress. The National Institute for Occupational Safety and Health (NIOSH), 1964.