Thermal effects on the drilling performance of a limestone: relationships with physical and mechanical properties

This work evaluates the effect of high temperatures and cooling methods on the drillability of Prada limestone. Samples from boreholes drilled during the design stage of the Tres Ponts Tunnel in the Catalan south Pyrenean zone (Spain) were subjected to temperatures of 105, 200, 300, 400, and 600 °C, and then cooled at a slow rate or by quenching. Sievers’ J-value (SJ) and brittleness (S20) were determined on thermally treated samples, and the drilling rate index (DRI) was calculated for each temperature. The results show that thermal treatment implied a sustained increase in the drillability of the rock of up to 40% at 600 °C and a change in the drillability category (from medium to high). At 600 °C, SJ and S20 tripled and doubled, respectively, the initial values obtained for the intact rock. The results were inconclusive about the influence of the cooling method on the drilling performance of Prada limestone for the tested range of temperatures. The substantial improvement observed in the drillability of Prada limestone when heated, measured in terms of DRI, could help in the development of novel thermally-assisted mechanical excavation methods. Additionally, strong correlations between drillability variables (i.e., SJ and S20) and physical and mechanical variables of Prada limestone (i.e., P- and S-wave velocities, uniaxial compression strength, elastic modulus, and Poisson’s ratio) are proposed. Correlations will help make preliminary predictions of drillability based on properties such as uniaxial compression strength and ultrasound wave velocities.The authors wish to acknowledge David Benavente and Juan Carlos Canaveras from the University of Alicante, for their valuable help on mineralogical and petrographic description of the rock. Additionally, Kreum SA, Ayesa SA, Infraestructures de la Generalitat de Catalunya, S.A.U., and the Lleida regional roads authority (Servei Territorial de Carreteres de Lleida, Generalitat de Catalunya) for providing rock samples. This work was supported by the Department of Geological and Geotechnical Engineering, Universitat Politecnica de Valencia

ENTRAVES AO DESENVOLVIMENTO DA CAJUCULTURA NO NORDESTE: MARGENS DE COMERCIALIZAÇÃO OU AUMENTOS DE PRODUTIVIDADE E DE ESCALA?

O artigo revela que a produção de caju no Nordeste está relativamente estagnada desde a década de 80 e que as políticas visando a modernização do setor não tiveram o efeito desejado, principalmente por não ter escolhido como alvo dessas políticas um segmento capaz gerar economias de escala e de internalizar tecnologias avançadas de produção que gerassem aumentos de produtividade e renda

Managing agricultural insurance in Brazil

Serie COMUNIICA 4Se exponen diversos temas y propuestas para enfrentar los problemas del actual sistema de seguros rurales en Brasil, que surgieron del Seminario Riesgo y Gestión del Seguro Rural de Brasil, realizado del 24 al 26 de junio de 2008 en el Instituto de Economía de la Universidad de Campinas (UNICAMP). Los principales temas abordados corresponden a la ventaja de un sistema de seguro en relación con las prórrogas de deudas, las subvenciones a las primas cuando los riesgos son muy altos, la necesidad de un sistema de informaciones que trabaje con datos detallados de los agricultores en vez de promedios que no reflejan la verdadera situación del agro. También se hace referencia a la posibilidad de instaurar un fondo de catástrofe en Brasil que garantice de forma efectiva el pago de las indemnizaciones extraordinarias, en vista de que a la fecha no se ha logrado implementar un sistema eficiente de protección contra los riesgos de plagas y eventos climáticos en Brasil.This article presents different topics and proposals for solving the problems facing the rural insurance system in Brazil, addressed at the seminar “Risk and the Management of Rural Insurance in Brazil,” held on June 24-26, 2008, at the Economics Institute of the University of Campinas (UNICAMP). Much of the discussion focused on the advantages of operating an insurance system vs. extending debt repayment dates; the subsidizing of premiums when risks are high; and the need for an information system that can operate with detailed data on farmers rather than averages, which do not reflect the true situation in agriculture. Reference was also made to the possibility of creating a Catastrophe Fund in Brazil to provide victims with additional indemnification, since to date it has been impossible to implement an efficient system of protection against the risks posed by pests and climatic events in Brazi

Multidisciplinary Assessment of Nature-Based Strategies to Address Groundwater Overexploitation and Drought Risk in Medina Del Campo Groundwater Body

[EN] Five decades of intensive groundwater exploitation have brought important economic, social and environmental changes in Medina del Campo Groundwater Body (MCGWB). Declining piezometric levels have worsened water quality, increased the costs of water supply and abstraction, and drained connected wetlands and rivers. This chapter presents the different methods and tools developed to assess the impacts and effectiveness for adaptation to droughts of the selected NAS strategies in biophysical, economic and social terms. It follows the methodologies presented in Chaps. 4, 5 and 6. It also summarizes the approaches for integrating all these assessments, as well as the main conclusions and lessons learnt. Important progress has been achieved on understanding and modelling the aquifer-system dynamics and functioning. First, geological and geophysical data analysis, debugging and integration have provided a basis for constructing a set of geological models of the MCGWB. Second, water balance components need to be updated through a deeper analysis of the recharge and groundwater abstractions (pumping). Third, a trend analysis of critical groundwater-related ecosystem services (GRES) and piezometric levels points at groundwater abstraction reductions as the most effective measure for a widespread recovery of the groundwater levels and storage. Fifth, the proposed managed artificial recharge would have limited effects on the recovery of the surface water bodies and no effect on the groundwater bodies. Sixth, the environmental reconstruction from a sedimentary record of the main wetland bed (Lagunas Reales) provides a reference knowledge base to understand the system response to human and climate changes. Finally, different barriers for design and implementation of NAS strategies have been identified and evaluated. Particularly, the lack of effective interaction mechanisms among the different actors involved/interested in the process could play a key role in the future.Peer reviewe

Variation of Drilling Rate Index (DRI) with temperature and its relationship with thermal damage on 'Prada' limestone

This research evaluates the variation in the Drilling Rate Index (DRI) and its relationship with thermal damage on thermally treated rocks. Samples from 'Prada' limestone, a lower cretaceous formation in the southern Pyrenees (Lleida, Spain), were subjected to temperatures of 105, 300, 400 and 500 °C and then cooled at a slow rate. Ultrasound P-wave velocity tests were performed before and after heating the samples to evaluate the thermal damage experienced by the rock. Sievers' J miniature drill and brittleness tests were conducted on intact and thermally treated samples, and then resulting SJ and S20 values were combined to determine DRI. The obtained results show that thermal treatment allowed an increase of 34% in the DRI of 'Prada' limestone at 500 °C. DRI exhibited the same variation trend than S20, so we can conclude that thermal variation in DRI is more influenced by S20 than by SJ in 'Prada' limestone. We also report a strong relationship between DRI and P-wave velocity, confirming a tight dependence between the drilling performance and the thermally induced damage on the limestone. The observed substantial improvement in the drillability of the rock when heated, measured in terms of DRI value increase, could help in the advance on the development of thermally assisted mechanical excavation methods.This work was supported by the Department of Geological and Geotechnical Engineering, Universitat Politècnica de València

Implications of the shift in United States farm policy

Includes bibliographyThis article sets out to describe the main features of the new farm legislation in the United States, assess the extent to which it conforms to World Trade Organization (WTO); rules, and provide a preliminary assessment of its impact on Latin America. The article first looks at the new United States Farm Security and Rural Investment Act of 2002, identifying the different mechanisms used to support the country's farm producers. It then analyses that Act, referred to hereinafter as the 2002 Farm Act, in the light of the rules established and the commitments made in the Uruguay Round of the General Agreement on Tariffs and Trade (GATT);. This is followed by an analysis of the possible impact of the new law on Latin American agriculture. Lastly, reference is made to recent developments in multilateral trade negotiations and the way they relate to the 2002 Farm Act