1094
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
great humidity and soil covered by a dense tropical vegetation
(Carrillo-Gil & Dominguez , 1996).
3 SOIL FORMATION
In this study, many researches and recollections of punctual
data from the Amazon Plain were validated. The main
watersheds from the most important rivers (Amazonas,
Marañón Huallaga, Ucayali and Madre de Dios) were
considered in order to establish their behavior characteristics in
detail (Fig 2). According to the gathered database that consists
of 1,318 samples tested in Peruvian tropical soils, forty typical
samples were chosen to verify the original rocks that originate
residual material. It was found some differences with the mother
rock that is generally mention for another regions in South
America.
Figure 2. Main jungle watershed located in the Peruvian Map.
4 CLIMATE CONDITIONS
The regional pluviometric level, where in some cases reach
until 4,000 mm annually, depends in the temperature, density,
absolute moisture, and other air mass characteristics. The
climate acts in the decomposition of the soil and its original
material throughout many agents that act in variable conditions
and determine a wide quality range of soils. This complexity
can be seen in how much different are their properties even
though they are located very close among them. However, each
of these tropical soils can be very similar to others located at
thousands of kilometers of distance (Carrillo-Gil, Carrillo D &
Cardenas, 1995).
5 MEASUREMENT
It was necessary to establish measurements conditions as non-
saturated soils to evaluate SWCC for each hydrographic
determined watershed. Curves were obtained using alternatives
methods based on the soil property index and some direct
measures by a suction cell prepared especially for these soils.
The method for the adjusted estimate is performed using
Fredlund & Xing models (1994) and Van Genuchten (1980)
because they provide with better adjustment for the available
data (Carrillo-Gil, 2008). The suction measurements in the
Peruvian Amazon Plain are shown figures 3, 4, 5, 6, and 7.
Figure 3. SWCC ranges for the Maranon River Watershed.
Figure 4. SWCC ranges for the Huallaga River Watershed.
Figure 5. SWCC ranges for the Amazon River Watershed.
Figure 6. SWCC ranges for the Madre de Dios River Watershed.
