This paper presents an underpinning method with permanent fixation hydraulic pats. The function of this system is to preload the construction simultaneously on several points. It is necessary to drill holes in the shoes for installing bored piles as a basement.

The collapsing soil profile is described with laboratory and field tests results and the selected structures and places include: Primary school in Añelo City, Province of Neuquén, Argentina; Swimming pool and Supermarket in Rincón de los Sauces City, Province of Neuquén, Argentina; CPEM N° 40 school in Neuquén City, Argentina.

Similar characteristics were found in the three working places. The soil profile is composed of fine siliceous sand, reddish, and loose to very loose compactness in 10/11 meters long. From hydrometrics and grain-size distribution tests, Cu is determined, and from pressure-void ratio curves the “collapsing relation” value with the Denisov´s relation is determined. There are microscopic photographs showing cementation with salts and their dissolution in the saturated soil. In one place we treated an inundation area, and we measured a settlement of 12 cm when the soil completed the saturation-collapse process.

Then, after a detailed study of the building, the Provincial Board of Education decided to repair it by underpinning. It was necessary to drill holes in the shoes, on several points, to install bored piles. This system allows preloading simultaneously on several points with equals deformations and the piles length was designed as a friction pile, to calculate the resistance by skin friction. A friction bored pile compressive load test, used as a basement to the underpinning system is attached together with photographs of collapsing field tests equipment, the general conditions of the buildings and the execution sequence of the underpinning method.