Some Engineering Problems Of The Panama Canal In Their Relation To Geology And Topography

EOCK MATERIAL USED IN CANAL CONSTRUCTION. 35 In the latter rock the cooling joints seem to bo far enough apart to give massive fragments large and heavy enough for “armoring” a breakwater exposed to sea waves. INTRUSIONS. As already explained, many small and large masses of lava were forced into or through the bedded rocks. Many of these intrusions locally disturbed the attitude of the invaded rock beds, tilting them up at various angles. Occasionally contact with the hot lava baked and metamorphosed the disturbed beds, but most of the intrusions caused only slight change in the beds. These intruded dikes and masses have locally acted as piers and buttresses to strengthen weak slopes against sliding. The most noteworthy of these strengthening intruded masses are Gold and Contractors Hills. ROCK MATERIAL USED IN CAN AB CONSTRUCTION. In the constructional work of the canal much nonmetallic material of local origin was used. The relative cost of excavating, loading, and transporting such material to the places where it was to be used, as well as its physical properties and general suitability for different uses, were features to bo considered in planning the location of the necessary rock quarries and gravel pits. DIFFERENT TYPES OF ROCK MATERIAL USED. In all, seven different types of rock material were used, as follows: 1. Hard, tough, crystalline igneous rock, broken so as to pass through a 3-inch or 4-incli round-hole screen. Vast quantities of this were used to mix with cement for the concrete work of the locks. 2. A considerable amount of fine screenings (inch mesh) were used for light concrete work, road work, locally for railway ballast, etc. 3. Great pieces of hard, tough, igneous rock, some weighing several tons, wore used to armor the west breakwater, Colon Harbor, against the destructive effects of ocean waves. 4. Filling material of all kinds, mostly soft rock dug out of Culebra Cut, was used to fill in swamps, build up “made land” where neces- sary, to form a large part of Gatun Dam and for the heart or.core of breakwaters. 5. Soft mud dredged out of canal channels or from borrow pits was pumped into certain swamp areas to fill them and to fill the spaces between the coarse fragments of Gatun Dam, thus creating a seal to insure water-tightness. 6. Clean sand, free from organic matter, was used for concrete and other construction. 7. Gravel was used for railway ballast and locally for concrete and for other purposes.