Tekhné

11

Authors: Rafael Bécemberg

It is undeniable that the Bolivarian Republic of Venezuela is exposed to significant risks presenting a high vulnerability associated with the large concentration of population that is settled in areas without urban planning, specifically in the northern coastal strip, exposed to a set of threats, both natural and anthropic, among which are those of the oceanographic and climatic type whose study is little developed in the country, which could be justified by the fact that its influence is relatively moderate compared to others countries Among the most relevant "threats" is the one associated with the phenomenon El Niño / Southern Oscillation (ENSO), which is undoubtedly the most important interannual climate variability that has been identified at the present time, due to the effects that has on the weather conditions both in the vicinity and in places very distant from their place of origin, especially on parameters such as water temperature, marine currents, wind patterns, rainfall regime, and in general on economic and human activities, being in fact, responsible for a large part of the changes that occur year after year in local weather conditions in many regions of the world. In this work we found a relationship that allows us to forecast with a high level of certainty what a year will be like, from the point of view of whether it will be a "El Niño" year, a "La Niña" year or a "Neutral" year with the associated considerations regarding the number and intensity of the phenomena that could occur during the study period, highlighting the fact that the prediction can be made without using large and complicated climate models, using only the data of the sea surface temperature anomalies that the National Oceanic and Atmospheric Agency (NOAA) periodically registers in the Pacific Ocean.

20

Authors: Heriberto Echezuría

It is demonstrated that the change from plastic to non plastic behavior is a complex process which depends on the interaction of the soil particles of the plastic component of the soil mix with the free water. That is, when the non plastic soil skeleton begins to transmit the forces among particles but the plastic component forms a “paste” with the free water, similar to that in a mortar. That gives plastic properties to grain movement but forces are transmitted by the non plastic component. When a high fine non plastic component is present the void ratio increases and so does the free water up to reach concentrations much higher than the liquid limit. Thus, the paste behaves as a viscous fluid within the porous spaces. These concepts apply to all kind of soils, i.e. CL, CH, ML and MH. With these criteria it was established for five clay samples from Mesa Formation in eastern Venezuela with high non plastic components that four of them lie within the transition zone and would exhibit high friction angles even though they also present plasticity. The other sample had two parameters very close to the threshold values for change in plastic to non plastic behavior which makes it very susceptible to have undrained behavior as a non plastic material. For the clays of the Mesa Formation it is the fine silt with sizes within the clay range which controls the change in plasticity as well as the specific gravity values.