Failures Inspire Progress: Protecting Sensitive Buildings from Tunnelling

by Eduardo Alonso Pérez de Ágreda, Ph.D., Professor of geotechnical engineering at the Polytechnic University of Catalonia in Barcelona, Spain.,,

Serial Information: Geo-Strata —Geo Institute of ASCE, 2019, Vol. 23, Issue 5, Pg. 34-39

Document Type: Feature article

Abstract: Tunnelling in urban areas is always a challenge, and it’s especially so when construction is proximate to densely populated districts. Such was the case on January 25, 2005, when a 10-m length of a Barcelona Metro tunnel under construction (6.5 m wide × 6.85 m high) collapsed. The Carmel Tunnel is 32 m deep and was excavated using the New Austrian Tunnelling Method (NATM), whereby the strength of the surrounding ground is engaged to strengthen the tunnel structure. The rock into which the tunnel was cut is a series of alternating layers of sandstone and shales. Despite the high cover ratio, (32 m/6.5 m ≈ 5), the failure progressed upward, and two days later a large sinkhole, 30 m in diameter, developed. The sinkhole engulfed an entire building, damaged dozens more, and required evacuation of 1,000 people. Economic losses amounted to 100 million euros, with 30 percent of the payout devoted to building rehabilitation and 70 percent to monetary compensation to the affected people. Fortunately, there were no casualties or injuries.

Subject Headings: Tunnels | Structural strength | Failure analysis | Tunneling | Construction management | Sinkholes | Urban areas | Subways


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