Estimating the yield zone boundaries of weak zone of in underground openings by pressuremeter tests: a case study in Canakkale, Turkey

The use of rod extensometers is one of the most commonly used monitoring methods for the prediction of yielding zones of underground openings. However, this method requires expensive and long-term measurements. In this study, comprehensive investigations were carried out to determine the performance of the pressuremeter test as for rapid in situ measurement methods to expeditiously estimate the boundary of the yielding zone. An unstable tunnel of the Cokal Dam in Gelibolu County of Canakkale was chosen for investigations. Laboratory tests, drilling, topographic measurements, pressuremeter tests, and rod extensometer measurements were performed in order to assess the instability and to determine the boundaries of the yielding zone. The in situ tests revealed that the boundaries of the weak zone, determined using the pressuremeter tests, was in good agreement with the failure depths determined by the rod extensometer measurements.