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

42 ENGINEERING PROBLEMS OF PANAMA CANAL. monts and formed a thoroughly compact center mass or core which is practically water-tight. Later this puddled core was covered with coarse material as a sort of facing and the water-line area of the o.oo dam was faced with hard basalt fragments. In this general way a spoil dam with a water-tight clay- puddlod heart was built. DIFFICULTIES WITH HYDRAULIC FILLING MATERIAL, El The groat magnitude of this dam may be realized by remembering that it is over 7,900 feet long, about 2,000 feet wide at the base, and 105 feet high. Figure 5 shows a cross section of it and gives some idea of its composition and plan. One of the construction diffi- culties was the excessive quantity of clay in the hy- draulic filling material. This retarded drainage, and at times gave some difficulty in covering the puddled-in core with the dry-fill facing. The drainage of the core material was assisted by 20-incli drain pipes to remove the surface water and the very thin mud from the hydraulic-fill “pond” or sump. By varying tho depth of this “pond” a greater or lesser amount of clayey material could be drained off. As tho work progressed, the great mass of the dam slowly settled and became consolidated, and now seems to bo almost as stable as a natural ridgo or hill. SOME DETAILS OF LOCK CONSTRUCTION. Tho locks proper are founded on the bedrock of the Gatun formation, but tho guide wall that extends out into Gatun Lake had to be built on an artificial founda- tion, because the bodrock is here about 150 feet below sea level. This wall is cellular and is built of reinforced concrete. Tho natural ground underlying it was about 8 feet above sea level. On this a wide fill with flat slope was made up to an elevation of 35 foot. Through this fill piles about 60 feet long and spacod 4 feet apart from center to center wore driven and their heads were inclosed in a heavy reinforced concrete slab. On this tho wall was constructed. As tho work progressed a slow settling took place; however, the completed wall is now practically stable. For tho construction of tho north guide and flare walls, founda- tional excavations to depths of about 70 feet below sea level had to bo mado before bodrock was reached. Tho material removed was too soft to pennit loading with steam shovels and so was excavated