What Does Rock Burst Mean?
Rock burst in the context of in-situ stress refers to the spontaneous failure of rock mass due to high levels of in-situ stress. During borehole excavation, in-situ stresses can be released causing rockburst, buckling and other ground control problems.
Measuring in-situ stress is therefore very important for determining the strength condition of rock below the earth's surface for safety, stability and to determine the right excavation method for trenchless pipeline installation projects.
Trenchlesspedia Explains Rock Burst
In situ stress test is carried out to determine the stresses in rocks through which drilling operations may have to be carried out because stress conditions in faults, dikes, and joints often change significantly. Mechanical properties of rock formation and In-situ stresses are vital factors in assessing wellbore construction and production.
During trenchless excavation processes, there is a redistribution of stress that induces changes in elastic energy and dissipated energy of the rock. Rock burst occurs when the stored elastic energy that is accumulated by the elastic strain of the rock, exceeds the storage limit.
Seismic refraction and other tests are carried out to determine the sub-surface geology and in-situ stress in rocks. Reflection seismology is also used to image the earth's sub-surface geological structure. The hydraulic fracturing test is another geotechnical investigative method used to determine in-situ stresses in boreholes.
The test is conducted at near-surface formations or underground formations in a test hole which is inherently free from fractures.