Walter Roldán

In the world, the hazards of intense rainfall are recurrent and increasing. In addition, they are one of the natural hazards that cause the most severe damage to infrastructure and even cause deaths every year. Flow-type landslides are capable of develop in areas with different geomorphological, geological and climatic characteristics. In hyper-arid zones such as the Atacama Desert, these hazards are capable of develop in a timely manner, causing catastrophes. This study analyzes the flow-type landslide in a hyper-arid mountainous area in La Chimba basin of Antofagasta city (Chile). For this, a hydrometeorological analysis is carried out through a pluviometric analysis, statistical analysis of frequencies through the Gumbel probabilistic method of extreme values and determination of maximum flows by obtaining IDF (intensity-duration-frequency) curves and design rainfall intensity as a function of concentration time. To obtain the maximum flows of liquid runoff and debris, for different return periods, the rational method was used with the method proposed by O’Brien. For the determination in the impact zone, the modeling software HEC-RAS (Hydrologic Engineering Center’s River Analysis System) and RAMMS (Rapid Mass Movements). Hydrographs are used for a return period of about 200 years, considered the most unfavorable scenario with the Voellmy–Salm model. To validate the modeling, a morphometric, sedimentological and comparative analysis is carried out between real impact zones of 1991 event and those generated in this study. It is concluded that the sedimentological and morphometric characteristics indicate that the type of flow that it can originate would have a rapid response to rainfall events of great intensity or duration. The modeling provided by HEC-RAS represents a fluvial-type flow, while the RAMMS modeling is closer to the consistency of a flow-type landslide, which is estimated to be closer to reality. The results show that despite being in a hyper-arid zone, the rainfall factor is capable of landslides triggering in mountainous areas.

Tests are carried out on various specimens of concrete block masonry, replacing Portland cement with pozzolans available in the region of Antofagasta, Chile (fly ash, volcanic ash and desert dust). To characterize the strength of the masonry, individual blocks, prisms and small walls are tested, made of concrete with different binder combinations «cement-pozzolan»; the obtained resistances are compared with standard mixture (100% cement). The results indicate that it is feasible to replace a percentage of Portland cement with pozzolans, obtaining very similar resistance, contributing to reduce construction costs and also, contributing to the environment by reducing cement demand and thereby reducing emissions of greenhouse gases that are generated in the calcination of the raw material. It is also pretension to enhance the importance of the masonry of concrete blocks in the construction of low-cost housing (economic and ecological).

DOI: 10.7764/RDLC.17.2.296 Through a very simple washing process with water, the unburned carbon is separated and removed from the fly ash. In this work, mixtures of mortar with 30% Portland cement replacement are made by different additions: integral fly ash (obtained from thermoelectric), washed fly ash (removing unburned carbon by washing), unburned carbon and limestone filler (limestone rock dust). To determine better the pozzolanic contribution of the additions, 5% gypsum (with respect to the weight of the binder) is added to the mixtures not hardened. With these mixtures, specimens are made for tests to rupture at 7, 28 and 90 days of age, kept submerged in water and also special specimens kept in similar condition measuring length variations. It is detected that the substitution of portland cement by unburned carbon, significantly reduces the mechanical resistance at any age and does not contribute to protection against sulphate attacks. It is concluded that the unburned carbon does not possess pozzolanic properties and its withdrawal generates benefits to the fly ash in the search to improve the pozzolanic performance in concrete mixtures.