| Abstract: | Measurement of stress changes in rock and rock mass and structures with pressure cells. Excavations change the stresses in the surrounding rock mass. To safeguard engineered structures the rock stresses are measured with pressure cells. This recommendation describes the emplacement of pressure cells into engineered structures and the surrounding rock mass and the measurement of stress changes. Pressure cells combine with stress sensors to stress measuring devices and are filled with hydraulic fluid. The stress sensors measure either the volume change (deformation principle) or the hydraulic pressure (compensation principle) in the pressure cells. Pressure cells disturb the rock stresses least if there stiffness is equal to that of the surrounding rock. Stress concentrations can also be limited by a suitable design and a low height/width ratio of the pressure cells. The attainable measuring accuracy is determined by the selected type and calibration of the pressure cell, the quality of the emplacement, and the value of the measured stress change. The recommendation concludes with the planning and implementation of tunnel cross‐sections for stress change measurements, the data acquisition and evaluation, the reporting, and the documentation. |
