The construction of the Panama Canal has motivated the development of multiple ports at both ends of the 80-km long Canal. This tendency is expected to increase with the expansion of the Canal and its new NeoPanamax-size locks.
The aim of this paper is to present a general description of the Atlantic coastal areas’ geological and seismic conditions in the vicinity of the Canal. Geologic conditions involve very soft marine sediments, as well as a predominant rock formation that presents quite distinctive characteristics. Seismic conditions have been recently revised, with studies made in support of the Panama Canal Expansion Program, that concluded in 2016. Both sets of conditions pose a number of challenges for port design and construction, that can be substantially mitigated with local experience gained from previous work in the area.
The geology of the area is characterized by sedimentary formations that are usually described as soft rock. In this paper, we focus on the Gatun Formation, the predominant geologic formation in the area. Many projects involving this formation affords abundant experience with its behavior and performance. The regional extension of this geologic formation is shown in the reference: “Geologic Map of the Panama Canal and Vicinity, Republic of Panama”, compiled by R.H. Stewart et al, U.S. Geological Survey, Map I-1232 (1980). The upper surface of this formation presents a very irregular geometry. The paper presents typical ranges of the depth, strength and stiffness parameters for the rock strata that corresponds to the Gatun Formation. It also addresses specific recommendations for the compaction characteristics of these materials that have been used in many fills, including the Transisthmian Railway, the City of Colon, the Colon Free Zone, various existing ports, many road projects, and others. The paper also addresses successful practices for efficient pile construction in this type of rock.
Overlying the rock formations, much of the area exhibits soft marine sediments. These are Undivided Holocene sediments, which also include man-made fills and Holocene fringing coral reefs. These materials, which are generally called “Atlantic Muck”, are described in the cited reference. Given the erratic nature of the top surface of the rock, the thickness of sediments varies accordingly. Recommendations are given to maintain the stability of underwater slopes and above-water slopes in these materials, under static and seismic conditions. When subjected to surface loads, the soft sediments generally require preloading for consolidation and shear-strength gain, replacement with better geo-materials, or reliance on purely structural solutions, to assure adequate performance.
The paper then describes the range of geologic conditions found throughout the area of interest and lessons learned from working with these materials in the past.
The recently uncovered seismic conditions in the area, require a greater attention to ductility considerations, to maintain adequate levels of safety and reduce life-cycle costs. They also present the risk of liquefaction in the coarser components of the marine sediments. Recent studies, as well as historic descriptions of liquefaction, give some indication on the areas in which this might be a concern.
The integration of these conditions results in specific demand scenarios placed on marine structures, navigation channels, container yards and access roads. The paper describes past experiences that have been effective in defining the types of structures that have worked best. The paper also describes the analytical studies usually required for addressing conditions for which there is no precedent in recent times.
The information provided can help develop a general scope of work for new port facilities, that can form the basis of its feasibility study.