ABSTRACT
The San Francisco de Asis church is a masonry building whose construction began in 1554 was finalised in 1611. A new 51 km line to expand the massive transport system in Guadalajara was built between, 2015 and 2019, includes a 5.1 km underground stretch that required a tunnel 10.6 m in diameter that was excavated with a Tunnel Boring Machine (TBM), at an average depth of 25 m.
The tunnel passes directly under the north east corner of the church. Soil strata beneath the church comprise a complex array of sandy silts and pumitic materials underlain by basalts. To reduce the risk of damage to the church related to induced settlements during the excavation process, the designers (SENERMEX) decided to use jet grouting to improve the mechanical properties of the soils directly under the church to avoid of mitigate damage induced by the excavation of the tunnel. The San Francisco church was profusely instrumented with an automatic monitoring system. Measurements showed that jet grouting induced the larger detrimental settlements, mainly along the east wall whereas settlements induced by the excavation of the tunnel and the passage of the TBM under the church were not as large. These settlements re-activated existing cracks and produced some additional cracking without compromising in anyway the security of the church. Nevertheless, a comprehensive retrofitting program was implemented to restore the structural integrity of the church.
A numerical model was used to study the dynamic response of the church with a three dimensional finite difference computer code. Despite its simplifying assumptions, the model was able to provide fairly close approximations to the overall dynamic properties of the church. The numerical analyses confirmed that jet grouting did not increase the vulnerability of the church to earthquake shaking but, on the contrary, it decreased slightly.
