A Historical Case in the Bolivia-Brazil Natural Gas Pipeline: Slope on the Curriola River

The Bolivia-Brazil Natural Gas Pipeline has 2.600 kilometers since Rio Grande City in Bolivia until Canoas City, in south Brazil. The pipeline crosses a lot of types of geological field and difficult topography. The south spread of the pipeline is the most interesting because of its hard topography combined with the variety of geological materials, such as, colluvium deposits and debris flow areas. Curriola River is located at kilometer 408, north part of Parana State. In this area, the pipeline crosses slopes of 40 degrees of inclination. The mounting was only possible making high cuts to assure the appropriated bendings to the pipe. The high cuts generated high volumes of soil that had no place to be deposited. The construction staff decided to put all the material above the right-of-way, in down part of the slope, near Curriola River. The construction created an artificial colluvium. As well as the most colluvium mass around the world, the Curriola material is a non-resistance material, composed with clay and little rock blocks, with a high porosity. Every year, during the raining seasons, the mass movements generate tension cracks. A superficial drainage system was built in order to prevent these movements but it’s not sufficient because the embankment is more than 5 meters high. Studies have been carried out since the start of the pipeline operation. The most difficult part of the work is the access to the area that makes the whole activity a battle. The first field investigation was conclude in January 2003, composed by SPT tests, piezometer installation and investigation wells. The second part of the story will be composed by inclinometer and strain gauges installation and monitoring, together with laboratory tests with samples of the field. The aim of this paper is to present the site characterization of the Curriola River Slope, together with all the investigation made, including state of stress field, and residual stresses assessment, in order to supply the studies with condensed information for the slope stabilization and gas pipeline integrity.