Panama Canal-Culebra Cut

Landslides 

The excavation of the cut was one of the greatest areas of uncertainty in the creation of the canal, due to the unpredicted large landslides. The International Board of Consulting Engineers had mistakenly decided that the rock would be stable at a height of 73.5 metres with a slope of 1 in 1.5; in practice, the rock began to collapse from that slope at a height of only 19.5 metres. The misjudgment was in part due to unforeseen oxidation of the underlying iron strata due to water infiltration, which caused weakening and eventually a collapse of the strata.

The first and largest major slide occurred in 1907 at Cucaracha. The initial crack was first noted on October 4, 1907, followed by the mass wasting of about 382,000 m³ (500,000 cu yd) of clay. This slide caused many people to suggest the construction of the Panama Canal would be impossible; Gaillard described the slides as tropical glaciers, made of mud instead of ice. The clay was too soft to be excavated by the steam shovels, and it was therefore largely removed by sluicing it with water from a high level.

After this, the sediment in the upper levels of the cut was removed, resulting in less weight over the weak strata. Landslides continued to be a problem after the canal's opening, causing intermittent closures.