Abstract:

Enhancing the seismic resistance of underground utility tunnels and their support systems is essential for ensuring the safe operation of urban lifeline infrastructure and promoting resilient cities. Considering the characteristics of heavy pipe loads, limited installation space, and densely arranged components inside utility tunnels, a compact rubber isolator with adjustable design parameters is developed for installation between pipe supports and pipelines to improve seismic performance. Finite element analyses are conducted to evaluate its parameter influence and isolation effectiveness. Full-scale shaking table tests on cable supports equipped with two types of rubber isolators (with or without lead core) are further performed. The results indicate that the proposed isolation measure can significantly reduce seismic demand and structural response. Under environmental vibration simulated by white noise, the horizontal acceleration response of the cable is reduced by 40%–60%. Under minor earthquakes of seismic intensity VIII, the stress at the support base decreases by 40%–50%, and the isolation effectiveness becomes more pronounced with increasing seismic intensity. Under major earthquakes of seismic intensity VIII, due to damage accumulation in the isolators, the reduction effect declines to approximately 30%. The isolator without lead core performs better under small earthquakes, whereas the lead-core rubber isolator provides superior mitigation under major earthquakes. With small size and easy installation/replacement, the proposed rubber isolators can effectively enhance the seismic resilience of utility tunnel support systems.

Key words: underground utility tunnel, support system, rubber seismic isolator, shaking table test, seismic isolation performance