ANALYSIS OF SUPPORT PRESSURE REQUIREMENT TO MINIMIZE SQUEEZING POTENTIAL IN DEEP TUNNELS

• Main Author: Claresta, Anatasya
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/68827
• Institution: Institut Teknologi Bandung

The squeezing phenomenon generally occurs in tunnel excavation with poor rock mass class and deep overburden. Squeezing is a large time-dependent deformation that occurs around the tunnel perimeter. In many cases, squeezing exerts high pressure causing damage to the installed supports. One way to minimize the potential for squeezing is to balance the ratio between the support pressure (pi) and the in situ stress (po) to a specific limit. A study was conducted by collecting 83 strain data from convergence measurements and support pressure from supported tunnels under squeezing and non-squeezing conditions. The analysis results show that squeezing occurs when the support pressure from ground support is only 10% of the in-situ stress, with the severity of squeezing depending on the rock mass strength. Numerical modeling was carried out on 16 tunnels that experienced squeezing from literature data using the actual support pressure value and squeezing pressure simulation to obtain a modeling convergence value that is appropriate to the actual. The modeling is then continued by changing the support pressure value until the strain value is obtained at the critical strain limit. The results showed that to reduce the level of strain due to squeezing to its critical strain limit, the required pi/po ratio is 0.4 for extreme squeezing conditions, 0.3 for very severe squeezing conditions, 0.1-0.3 for severe squeezing conditions, and 0.1 for minor squeezing conditions. Where the pi/po ratio is influenced by the rock mass strength, the smaller the rock mass strength value, the greater the ratio needed to minimize squeezing potential.