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Abstract: This article synthesizes the geotechnical studies conducted to design the foundations of various bridges built in the Amazonian plain of the Madre de Dios department from Peru, as part of the Southern Interoceanic Highway (Puerto Maldonado - Iberia - Iñ apari section). These studies were developed in the 1990s by the Centro de Investigaciones Sí smicas y Mitigació n de Desastres (CISMID) of the Universidad Nacional de Ingenierí a, Peru. The evaluated bridges, of medium size with spans between 25 and 60 meters, included the Yaverija, Primavera, Noaya, Marí a Cristina, and Alerta bridges.

The design of the deep foundations was based on the results of Standard Penetration Tests (SPT), which allowed the characterization of the soil stratigraphy and the determination of the mechanical properties of the soil. Using this information, the ultimate axial load capacity of the proposed piles was evaluated, employing both empirical and analytical formulas. To calculate the allowable capacity of the pile group, a group efficiency factor was estimated and appropriate safety factors were applied.

The studies also included the prediction of settlements, both for individual piles and pile groups, ensuring that the expected displacements remained within permissible limits. Steel piles were recommended as the most suitable solution due to the logistical challenges and equipment transportation difficulties to the area, as well as the scarcity of aggregates. Additionally, the construction of protective works was proposed to isolate the foundations from the effects of river erosion.

To verify the load capacity and settlements of the piles determined in the designs, load tests were suggested in areas with previously known and more unfavorable profiles. The importance of conducting pile driving tests was also emphasized to ensure the success of the design and construction.

Dr.-Ing. JORGE ALVA; Dr.-Ing. MIRIAM R. ESCALAYA

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