AE Monitoring of rock structure during excavation at Underground LPG Storage, Namikata, Japan - LAZOC

When designing underground structures there is a large amount of uncertainty due to a large number of factors:

  • Uncertainties in the geomechanical parameters
  • Large simplifications made to model the ground and the natural stresses
  • Limitation of geological-geotechnical explorations due to financial reasons

This is why there is the need of a system of control that enables us:

  • To check during the construction the hypothesis that were taken during the design, verifying that the computational predictions of the behavior of the ground correspond to reality. If deviations arise and these are too large, then a back analysis of the input parameters is made.
  • To detect in advance imminent damages or collapses, allowing to take measures on time

In order to establish a control system, monitoring of different parameters is made by means of different techniques and tools:

Parameter recorded Tool
Settlement at the surface Levelling
Displacements and convergences in the opening skin Tachymeter, tunnel scanner, extensive tape, etc
Displacements within the rock mass Extensometers , sliding micrometers, inclinometers, deflectometers
Stresses on support Pressure cells
Strains on support Strain gauges
Primary or natural stresses in the ground Hydraulic fracturing, unloading drills,

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