高山峡谷地区大跨度桥梁岸坡稳定性分析、趋势预测及应用研究

In order to realize fast development of the national economy in a healthy way and coordinate progress with whole society, the country has implemented the strategy of development of the western region. An important action of finishing this strategic task is to accelerate the highway construction in the western region, join the western region and places along the coast, the river, the border with goods and materials, technology, and personnel interchanges, and then drive development of the local economy.The western region was influenced by the Himalaya Tectonization in Cenozoic, and the crust rose and became the plateau. In the course of rising, rivers cut down sharply to form a lot of high mountains and gorges.Because of topography and geomorphology, bridges in the traffic construction in the alpine gorge area are needed. Rivers have characteristics of large flow, fast velocity and high and steep river valley, so building a pier in the river is not only very difficult, but also making the cost increase. At the same time, the impact that the pier is corroded and the bridge base that is drawn to be empty by flow are apt to cause destruction of the pier. For those reasons, suspending bridge and cable-stay bridge are usually adopted with the single and large span. For the large span bridge, the pier foundation could receive ten thousand and more vertical strength, bending moment and near kiloton horizontal thrust.Because bank slope in the alpine gorge district is cut deeply and unsettled big, natural stability is worse under endogenic and exogenic force. When bank slope bears heavy vertical strength, bending moment and horizontal thrust facing the river, it will inevitably make the balance state of rock and soil mass change, bridge bank slope deform, and even destroyed. So the key problem at the time of the large span's bridge construction in the alpine gorge area is how to make it stable.So based on the spot investigation, the Engineering Geology Analysis Method is very important to grasp the bank slope stability. It can provide the bank slope stability macroscopic ally and qualitatively, and reference to the indoor calculation. The Engineering Geology Analysis Method is that by way of analyzing and investigating terms of bank slope instability, stability development trend, the ancient rock slide and devolution in the site, stability comprehensive evaluation primarily, current and future stability of bank slope is gotten, realizing the intention to serving the concrete engineering.After the Engineering Geology Analysis Method is applied to project instances of BeiPan River Bridge and BaLin River Bridge, results are accord with bank slope actual conditions, which proves sites are suited to building bridges from site stability.we often meet bank slope stability issues in the traffic construction in the alpine gorge areao Before the evaluation of the bank slope stability, the engineering geological condition is investigated first. After that, the next exploration target and geology measures are decided. So, the Engineering Geology Analysis Method that the investigation of the engineering geological condition is the main content is quite important in practice. The other evaluations of the bank slope stability are based on it. Because foundation receives very heavy load, for the big span's bridge in the alpine gorge area, a long pile of the large diameter (D^0.8m) is usually selected. In order to reflect rock mass's deformation properties under rock-socketed pile function, the author has used the FLAG30 software for rock and soil mass and done many numerical simulations. By them, the author launches the further investigation on deformation properties of bank slope under different slope angle, pile length, diameter, elastic modulus, load, bank slope's structure, etc. Some conclusion meaningful to the design and produce are obtained.

元谋地区晚新生代河湖相沉积物磁性地层学及古环境研究

Yuanmou area lies on the southeastern edge of the Tibetan Plateau, the middlesegment of Yunnan-Sichuan North-South Extending Tectonic Belt and the upper reaches of the Yangztze River, which is renowned for its thick late Cenozoic fluvial-lacustrine sequences that yield rich mammalian fossils including hominoid and early human. The sediments provides great potentials for understanding the relationships between uplift of the Tibetan Plateau, evolution of hominoids and other mammalian and evolution and formation of basins in Southwest China since late Miocene. However, lithostratigrphic and chronologic views on them are controversial and hinder further discussion of the relationships of them. To this end, we selected the Baozidongqing section and the Dapoqing section to carry out systematic lithostratigraphic, magnetostratlgraphic and environmental magnetism researches in this area.The Baozidongqing section was dated to about 10.95-7.17 Ma. The age estimation of the topmost hominoid-bearing layer was about 7.43-7.17 Ma. Rock magnetic results show that the dominant magnetic carrier is hematite, with minor amount of magnetite. Both the composition and concentration of magnetic minerals strongly correlate with the lithostratigraphy, indicating that Yuanmou basin is characterized by alternating of long-term torrid-humid climate and short-term dry-hot climate. But the pattern of these short-term hot-dry events, including both the lasting time and the frequency of their occurrence dramatically changed since -8.1 Ma. Our results infer that the drying process of the Asian west interior and a significant uplift of the Tibetan Plateau would have probably caused jointly the extinction of hominoids, or the emigration of hominoids from Yuanmou to adjacent relatively torrid-humid areas.The strata between the upper of the Dapoqing section, the Niujianbao Hill and Shangnabang area can be linked by three mark layers of conglomerate, which is rather continuous and coherent than physical disturbance by new tectonic activities. Rock magnetic studies indicate that hematite is the main magnetic carriers. The section is dated back to about 2.8-1.37 Ma. Its paleocurrent flowed northeastward, which was a close and stagnant river and swamp environment about 2.2 Ma ago. Then it ran northwestward and turned into an open overflown and braid river sedimentary face during 2.2 to 1.57 Ma. Since 1.57 Ma, the paleocurrent flowed intensely northwestern and about 1.37 Ma ago, it ended the basically continuous fluvial-lacustrine deposition.

陆相砂泥岩层序的高精度检测方法研究及应用

Ordos Basin is a typical cratonic petroliferous basin with 40 oil-gas bearing bed sets. It is featured as stable multicycle sedimentation, gentle formation, and less structures. The reservoir beds in Upper Paleozoic and Mesozoicare are mainly low density, low permeability, strong lateral change, and strong vertical heterogeneous. The well-known Loess Plateau in the southern area and Maowusu Desert, Kubuqi Desert and Ordos Grasslands in the northern area cover the basin, so seismic data acquisition in this area is very difficult and the data often takes on inadequate precision, strong interference, low signal-noise ratio, and low resolution. Because of the complicated condition of the surface and the underground, it is very difficult to distinguish the thin beds and study the land facies high-resolution lithologic sequence stratigraphy according to routine seismic profile. Therefore, a method, which have clearly physical significance, based on advanced mathematical physics theory and algorithmic and can improve the precision of the detection on the thin sand-peat interbed configurations of land facies, is in demand to put forward.Generalized S Transform (GST) processing method provides a new method of phase space analysis for seismic data. Compared with wavelet transform, both of them have very good localization characteristics; however, directly related to the Fourier spectra, GST has clearer physical significance, moreover, GST adopts a technology to best approach seismic wavelets and transforms the seismic data into time-scale domain, and breaks through the limit of the fixed wavelet in S transform, so GST has extensive adaptability. Based on tracing the development of the ideas and theories from wavelet transform, S transform to GST, we studied how to improve the precision of the detection on the thin stratum by GST.Noise has strong influence on sequence detecting in GST, especially in the low signal-noise ratio data. We studied the distribution rule of colored noise in GST domain, and proposed a technology to distinguish the signal and noise in GST domain. We discussed two types of noises: white noise and red noise, in which noise satisfy statistical autoregression model. For these two model, the noise-signal detection technology based on GST all get good result. It proved that the GST domain noise-signal detection technology could be used to real seismic data, and could effectively avoid noise influence on seismic sequence detecting.On the seismic profile after GST processing, high amplitude energy intensive zone, schollen, strip and lentoid dead zone and disarray zone maybe represent specifically geologic meanings according to given geologic background. Using seismic sequence detection profile and combining other seismic interpretation technologies, we can elaborate depict the shape of palaeo-geomorphology, effectively estimate sand stretch, distinguish sedimentary facies, determine target area, and directly guide oil-gas exploration.In the lateral reservoir prediction in XF oilfield of Ordos Basin, it played very important role in the estimation of sand stretch that the study of palaeo-geomorphology of Triassic System and the partition of inner sequence of the stratum group. According to the high-resolution seismic profile after GST processing, we pointed out that the C8 Member of Yanchang Formation in DZ area and C8 Member in BM area are the same deposit. It provided the foundation for getting 430 million tons predicting reserves and unite building 3 million tons off-take potential.In tackling key problem study for SLG gas-field, according to the high-resolution seismic sequence profile, we determined that the deposit direction of H8 member is approximately N-S or NNE-SS W. Using the seismic sequence profile, combining with layer-level profile, we can interpret the shape of entrenched stream. The sunken lenticle indicates the high-energy stream channel, which has stronger hydropower. By this way we drew out three high-energy stream channels' outline, and determined the target areas for exploitation. Finding high-energy braided river by high-resolution sequence processing is the key technology in SLG area.In ZZ area, we studied the distribution of the main reservoir bed-S23, which is shallow delta thin sand bed, by GST processing. From the seismic sequence profile, we discovered that the schollen thick sand beds are only local distributed, and most of them are distributary channel sand and distributary bar deposit. Then we determined that the S23 sand deposit direction is NW-SE in west, N-S in central and NE-SW in east. The high detecting seismic sequence interpretation profiles have been tested by 14 wells, 2 wells mismatch and the coincidence rate is 85.7%. Based on the profiles we suggested 3 predicted wells, one well (Yu54) completed and the other two is still drilling. The completed on Is coincident with the forecastThe paper testified that GST is a effective technology to get high- resolution seismic sequence profile, compartmentalize deposit microfacies, confirm strike direction of sandstone and make sure of the distribution range of oil-gas bearing sandstone, and is the gordian technique for the exploration of lithologic gas-oil pool in complicated areas.

A Quantitative Study on Paleo—River Environment During Late Jurassic on yaojie Region,Minhe Basin

Fluvial Sedimentation of alluvial facies prevailed during the Late Jrassic in the Minhe Basin.On the basis of the study of sedimentary facies of the Upper Jurassic series.this paper focuses on the river types suing the "Architecture Element" analysis method proposed by Miall,and calculated all the quantitative parameters to reflect the characteristics of the stream channel geometry and hydrodynamic conditions of paleo-rivers with the equations of ethrideg,schumm et al.Finally,we discussed the characteristics of environmental evolution of palsorivers on the quantitative basis.Our conclusion indicates that the evolution of paleo-rivers during the Late Jurassic,from early to late,shows such a tendency as alluvial fan river→ braid river→alluvial fan river→mid-sinuoisty river→ high-sinuosity river.

河流相砂岩油藏剩余油分布预测方法和富集规律研究

针对我国中、新生代陆相已开发油藏特点，选择非均质性严重的注水开发河流相砂岩油藏作为研究对象，结合胜利油区主力油田孤东油田七区西馆陶组的实例，着重油藏地质精细研究，采用动静态相结合的方法，研究特高含水期剩余油分布的预测方法，准确确定剩余油的相对富集部位。分布规律及控制因素，为高含水后期油田调整开发方案。制定挖潜增产措施、控水稳油。提高采收率提供科学依据。该论文取得以下主要研究成果：1。以油藏地质精细研究为基础，形成了利用开发地质学、水淹层测井评价、生产动态分析、油藏数值模拟及油藏工程等多种方法对剩余油进行综合预测的方法和技术，其中流动单元约束下的测井评价和油藏数值模拟技术是综合预测剩余油分布的新的方法和技术。2。在纵向上从层间至层内，对储层开展多层次逐级细分研究，精细至流体流动单元，为细致地揭示平面上，垂向上层间及层内剩余油的不均一分布创造了条件。3。引人流体流动单元新概念，提出了非均质综合指数法和岩性单元流动分层指标法识别流体流动单元的新方法，通过流动单元的识别和划分，揭示了油藏非均质性，开展了从流动单元角度进行剩余油的预测方法与富集规律研究。4。在理论上阐明特高含水期河流相储层剩余油形成机理、分布规律和控制因素，提出特高含水期强非均质性河流相砂岩油藏，剩余油储量主要富集在主力相带边滩微相的新观点和新认识，改变了以往剩余油主要富集在非主力相带的观点和认识。5、研究得到的剩余油富集规律新观点和新认识，在实际应用中得到验证，取得了显著的经济效益和社会效益。

Levantamento semidetalhado dos solos do Projeto Jaíba (etapa III), Estado de Minas Gerais.

Com o objetivo de prover informações dos recursos de solos da área de expansão do projeto de irrigação do Jaíba (Etapa III, que abrange 12.015 ha), a fim de possibilitar o adequado planejamento e monitoramento das atividades agrossilvipastoris e de preservação ambiental, foi realizado o levantamento de solos em nível de semidetalhe, na escala 1:50.000, conforme as normas preconizadas pela Embrapa. Predomina cobertura sedimentar cenozóica sobre rochas do Grupo Bambuí, dispostas em superfície aplainada, amplamente dominante, pontuada por dolinas e uvalas, além de um trecho de planície fluvial, ao longo do rio Ilha do Retiro. A região é caracterizada por temperaturas médias elevadas, precipitações médias abaixo dos 900 mm anuais e deficiência hídrica anual de 450 mm a 500 mm, evidenciando o curto período favorável ao crescimento das plantas em sequeiro, nas estações de primavera e verão. O ambiente seco também é evidenciado pela vegetação natural, dominada por florestas decíduas e caatingas, ou transição entre essas formações vegetais. A diferenciação de solos na área está bem condicionada ao nível topográfico relativo dos terrenos. Da superfície plana do topo da paisagem em direção às depressões semicirculares dispersas na área têm-se uma topossequência característica, com Latossolos Amarelos de caráter distrófico e textura média leve dominante na ampla área em nível topográfico superior; e solos dessa mesma classe, mas em geral com saturação por bases alta (eutróficos) e teores de argila ligeiramente mais elevados, localizados em depressões suavizadas, ou nas bordas ligeiramente inclinadas das dolinas; seguidos de Cambissolos Háplicos Tb Eutróficos (petroplínticos, endorredóxicos ou gleissólicos) de textura argilosa, em nível topográfico intermediário; aos quais se sucedem Planossolos e Gleissolos, que ocorrem associados nos fundos das dolinas e uvalas, mais rebaixadas. O vale do ribeirão Ilha do Retiro, por outro lado, apresenta um padrão de distribuição de solos distinto, com domínio de Neossolos Flúvicos, desenvolvidos de material de textura média ou argilosa de deposição aluvionar, ocorrendo nas partes topográficas inferiores, em associação com Chernossolos Rêndzicos, que tendem a predominar no segmento de nível topográfico um pouco mais alto, limitando-se no topo da encosta com a área de Latossolos Amarelos. A extensa área aplainada apresenta boas condições para agricultura intensiva com irrigação, porém com restrições decorrentes da baixa capacidade de água disponível, elevada taxa de infiltração e baixa fertilidade natural. Em direção aos níveis topográficos mais baixos, há uma tendência geral de aumentar as limitações à utilização agrícola, sobretudo em decorrência da deficiência de aeração, imposta pela dificuldade de drenagem e escoamento, assim como pela possibilidade de encharcamento por afluxo de água proveniente dos terrenos circundantes.

Quaternary palaeogeomorphologic evolution of the Wadi Faynan area, Southern Jordan

McLaren, S. Gilbertson, D. Grattan, J. Hunt, C. Duller, G. Barker, G. Quaternary palaeogeomorphologic evolution of the Wadi Faynan area, Southern Jordan. Palaeogeography, Palaeoclimatology, Palaeoecology. 2004. 205. pp 131-154

Early-Holocene environments in the Wadi Faynan, Jordan

Hunt, C. Elrishi, H. Gilbertson, D. Grattan, J. McLaren, S. Pyatt, B. Rushworth, G. Barker, G. Early-Holocene environments in the Wadi Faynan, Jordan. The Holocene. 2004. 14,6 pp 921-930

In Comes I: Performance, Memory and Landscape

Pearson, Mike, In Comes I: Performance, Memory and Landscape (Exeter: University of Exeter Press, 2007) RAE2008

Transformation from natural (thermal contraction) to anthropogenic (resource exploitation) depressions in the Krotoszyn-Koźmin-Raszków area (Polish Lowland)

An exceptional concentration of almost identical depressions exist near the small towns of Krotoszyn, Koźmin and Raszków (southern Wielkopolska). Their origin is, however, different from that of the typical post glacial-relief: they are Man-made enlarged thermal-contraction structures that developed at the very end of the Middle Polish (Warthian) glaciation and during the North Polish (Weichselian) glaciation, most probably under periglacial conditions.

Global Rates of Free Hydrogen (H2) Production by Serpentinization and other Abiogenic Processes within Young Ocean Crust

The main conclusion of this dissertation is that global H2 production within young ocean crust (<10 Mya) is higher than currently recognized, in part because current estimates of H2 production accompanying the serpentinization of peridotite may be too low (Chapter 2) and in part because a number of abiogenic H2-producing processes have heretofore gone unquantified (Chapter 3). The importance of free H2 to a range of geochemical processes makes the quantitative understanding of H2 production advanced in this dissertation pertinent to an array of open research questions across the geosciences (e.g. the origin and evolution of life and the oxidation of the Earth’s atmosphere and oceans).

The first component of this dissertation (Chapter 2) examines H2 produced within young ocean crust [e.g. near the mid-ocean ridge (MOR)] by serpentinization. In the presence of water, olivine-rich rocks (peridotites) undergo serpentinization (hydration) at temperatures of up to ~500°C but only produce H2 at temperatures up to ~350°C. A simple analytical model is presented that mechanistically ties the process to seafloor spreading and explicitly accounts for the importance of temperature in H2 formation. The model suggests that H2 production increases with the rate of seafloor spreading and the net thickness of serpentinized peridotite (S-P) in a column of lithosphere. The model is applied globally to the MOR using conservative estimates for the net thickness of lithospheric S-P, our least certain model input. Despite the large uncertainties surrounding the amount of serpentinized peridotite within oceanic crust, conservative model parameters suggest a magnitude of H2 production (~1012 moles H2/y) that is larger than the most widely cited previous estimates (~1011 although previous estimates range from 1010-1012 moles H2/y). Certain model relationships are also consistent with what has been established through field studies, for example that the highest H2 fluxes (moles H2/km2 seafloor) are produced near slower-spreading ridges (<20 mm/y). Other modeled relationships are new and represent testable predictions. Principal among these is that about half of the H2 produced globally is produced off-axis beneath faster-spreading seafloor (>20 mm/y), a region where only one measurement of H2 has been made thus far and is ripe for future investigation.

In the second part of this dissertation (Chapter 3), I construct the first budget for free H2 in young ocean crust that quantifies and compares all currently recognized H2 sources and H2 sinks. First global estimates of budget components are proposed in instances where previous estimate(s) could not be located provided that the literature on that specific budget component was not too sparse to do so. Results suggest that the nine known H2 sources, listed in order of quantitative importance, are: Crystallization (6x1012 moles H2/y or 61% of total H2 production), serpentinization (2x1012 moles H2/y or 21%), magmatic degassing (7x1011 moles H2/y or 7%), lava-seawater interaction (5x1011 moles H2/y or 5%), low-temperature alteration of basalt (5x1011 moles H2/y or 5%), high-temperature alteration of basalt (3x1010 moles H2/y or <1%), catalysis (3x108 moles H2/y or <<1%), radiolysis (2x108 moles H2/y or <<1%), and pyrite formation (3x106 moles H2/y or <<1%). Next we consider two well-known H2 sinks, H2 lost to the ocean and H2 occluded within rock minerals, and our analysis suggests that both are of similar size (both are 6x1011 moles H2/y). Budgeting results suggest a large difference between H2 sources (total production = 1x1013 moles H2/y) and H2 sinks (total losses = 1x1011 moles H2/y). Assuming this large difference represents H2 consumed by microbes (total consumption = 9x1011 moles H2/y), we explore rates of primary production by the chemosynthetic, sub-seafloor biosphere. Although the numbers presented require further examination and future modifications, the analysis suggests that the sub-seafloor H2 budget is similar to the sub-seafloor CH4 budget in the sense that globally significant quantities of both of these reduced gases are produced beneath the seafloor but never escape the seafloor due to microbial consumption.

The third and final component of this dissertation (Chapter 4) explores the self-organization of barchan sand dune fields. In nature, barchan dunes typically exist as members of larger dune fields that display striking, enigmatic structures that cannot be readily explained by examining the dynamics at the scale of single dunes, or by appealing to patterns in external forcing. To explore the possibility that observed structures emerge spontaneously as a collective result of many dunes interacting with each other, we built a numerical model that treats barchans as discrete entities that interact with one another according to simplified rules derived from theoretical and numerical work, and from field observations: Dunes exchange sand through the fluxes that leak from the downwind side of each dune and are captured on their upstream sides; when dunes become sufficiently large, small dunes are born on their downwind sides (“calving”); and when dunes collide directly enough, they merge. Results show that these relatively simple interactions provide potential explanations for a range of field-scale phenomena including isolated patches of dunes and heterogeneous arrangements of similarly sized dunes in denser fields. The results also suggest that (1) dune field characteristics depend on the sand flux fed into the upwind boundary, although (2) moving downwind, the system approaches a common attracting state in which the memory of the upwind conditions vanishes. This work supports the hypothesis that calving exerts a first order control on field-scale phenomena; it prevents individual dunes from growing without bound, as single-dune analyses suggest, and allows the formation of roughly realistic, persistent dune field patterns.

Paleoenvironmental reconstruction of the coastal Monte Léon and Santa Cruz formations (Early Miocene) at Rincón del Buque, Southern Patagonia: A revisited locality

© 2015 Elsevier Ltd.Sedimentological, ichnological and paleontological analyses of the Early Miocene uppermost Monte León Formation and the lower part of the Santa Cruz Formation were carried out in Rincón del Buque (RDB), a fossiliferous locality north of Río Coyle in Santa Cruz Province, Patagonia, Argentina. This locality is of special importance because it contains the basal contact between the Monte Léon (MLF) and the Santa Cruz (SCF) formations and because it preserves a rich fossil assemblage of marine invertebrates and marine trace fossils, and terrestrial vertebrates and plants, which has not been extensively studied. A ~90m-thick section of the MLF and the SCF that crops out at RDB was selected for this study. Eleven facies associations (FA) are described, which are, from base to top: subtidal-intertidal deposits with Crassotrea orbignyi and bioturbation of the Skolithos-Cruziana ichnofacies (FA1); tidal creek deposits with terrestrial fossil mammals and Ophiomorpha isp. burrows (FA2); tidal flat deposits with Glossifungites ichnofacies (FA3); deposits of tidal channels (FA4) and tidal sand flats (FA5) both with and impoverish Skolithos ichnofacies associated; marsh deposits (FA6); tidal point bar deposits recording a depauperate mixture of both the Skolithos and Cruziana ichnofacies (FA7); fluvial channel deposits (FA8); fluvial point bar deposits (FA9); floodplain deposits (FA10); and pyroclastic and volcaniclastic deposits of the floodplain where terrestrial fossil mammal remains occur (FA11).The transition of the MLF-SCF at RDB reflects a changing depositional environment from the outer part of an estuary (FA1) through the central (FA2-6) to inner part of a tide-dominated estuary (FA7). Finally a fluvial system occurs with single channels of relatively low energy and low sinuosity enclosed by a broad, low-energy floodplain dominated by partially edaphized ash-fall, sheet-flood, and overbank deposits (FA8-11). Pyroclastic and volcaniclastic materials throughout the succession must have been deposited as ash-fall distal facies in a fluvial setting and also were carried by fluvial streams and redeposited in both estuarine and fluvial settings. These materials preserve most of the analyzed terrestrial fossil mammals that characterize the Santacrucian age of the RDB's succession. Episodic sedimentation under volcanic influence, high sedimentation rates and a relatively warm and seasonal climate are inferred for the MLF and SCF section.Lateral continuity of the marker horizons at RDB serve for correlation with other coastal localities such as the lower part of the coastal SCF south of Río Coyle (~17.6-17.4Ma) belonging to the Estancia La Costa Member of the SCF.

Costos de localización : análisis comparativo de los complejos agroindustriales arroceros de la Argentina y de Uruguay

La producción primaria de arroz en Argentina ha sufrido en su evolución cambios en su localización geográfica, ubicándose actualmente en la región Litoral. En los últimos años, por diversas causas, hubo un desplazamiento de la producción hacia el norte de dicha región. En este contexto, los molinos arroceros tuvieron un proceso de concentración geográfica y de reducción de capacidad de elaboración -por cierre de plantas-, pero no cambiaron su localización. Como consecuencia, se afectaron los márgenes de comercialización y los ingresos de los productores. En Uruguay, el cultivo comenzó en el Este, y luego tuvo una expansión al Centro y Norte del país. Esto obedeció a razones de índole estructural inherentes a la expansión de la actividad y al tipo de articulación entre la producción y la industria, por lo que la localización de estas últimas acompañó dicha expansión. El objetivo de éste trabajo es realizar una caracterización de la organización técnica, económica y social del sector arrocero, cuantificar los costos de transporte inherentes a la localización de la producción primaria con respecto a los molinos para Argentina, evaluar cambios de la última década, realizar un análisis comparativo respecto de Uruguay, y elaborar para el caso de Argentina un modelo de transporte que incluya operatorias de tipo multimodal, con la utilización del ferrocarril y del transporte fluvial por los ríos Paraná y Uruguay. Para ello se han elaborado modelos de programación lineal en los cuales los resultados obtenidos son la minimización del costo de transporte, las rutas, los medios utilizados y la información que brindan los costos de oportunidad y de sustitución en caso que los mismos resultaron relevantes. Los resultados del modelo señalan que debido a la estructuración del CAI arrocero argentino los costos de transporte se han duplicado entre 1998 y el año 2006, cuando eran aquel año similares a los costos en Uruguay. La incorporación de transporte ferroviario y fluvial al modelo disminuye parcialmente dicho encarecimiento.

El rol del facilitador más allá del de ingeniero agrónomo : una experiencia de intervención comunitaria con pueblos originarios

La intervención de un extensionista - ingeniero agrónomo de la Agencia de Extensión Rural Orán, del Instituto Nacional de Tecnología Agropecuaria/INTA- en el territorio de una Comunidad Tupí Guaraní del norte salteño, exige una profunda revisión de antecedentes dando lugar a reflexiones, interrogantes y propuestas relacionadas con distintos aspectos del trabajo de campo que trascienden a esta situación en particular. Esto está aquí directamente relacionado a la evolución y al desarrollo de esta zona de históricos conflictos de intereses, desigualdad social creciente y fuertes procesos de aculturación. Incluso existen contradicciones dentro de las instancias del Estado relacionadas con el desarrollo rural, en donde el INTA no constituye una excepción, generándose arduas discusiones internas. En este escenario, la praxis destaca la importancia de las técnicas participativas como la mejor metodología para sustentar procesos de desarrollo local, ya que es en terreno se debe trabajar dentro de un proceso de pérdida de la percepción social -pero más importante aún, de la propia percepción- en la que los pueblos originarios se consideren como un actor más. Entonces es desde la revalorización de las propias capacidades y posibilidades de la comunidad que se analiza una experiencia que refleja cómo, a partir del único agente del estado presente en terreno, se intenta avanzar en la trasformación de la realidad en donde se ve naturalizada y no problematizada la diferencia en la distribución de los ingresos y la pobreza estructural. El comienzo de la intervención, por lo tanto, se inició con la identificación clara de una amenaza -el avance de la erosión del río sobre la seguridad y posesiones de los campesinos/aborígenes- lo cual creó la necesidad ineludible de trabajar comunitariamente. Esta coyuntura generó la necesidad de organizarse para llevar a cabo el proyecto necesario para superar la emergencia, que gracias a la forma participativa de encarar el trabajo, así como el trabajo inter-institucional de los técnicos del INAI (Instituto Nacional de Asuntos Indígenas) y del INTA, confluyeron en crear un capital social entre productores y técnicos/instituciones. La articulación interinstitucional lograda hizo posible la formulación y ejecución en forma participativa de un proyecto evaluado satisfactoriamente -social e institucionalmente-, ya que posibilitó controlar la erosión fluvial evitando nuevas pérdidas de tierras, fortaleciendo a la vez a la organización comunitaria y los vínculos con distintos actores públicos, revalorizando sus propias capacidades.

Costos de localización : análisis comparativo de los complejos agroindustriales arroceros de la Argentina y de Uruguay

La producción primaria de arroz en Argentina ha sufrido en su evolución cambios en su localización geográfica, ubicándose actualmente en la región Litoral. En los últimos años, por diversas causas, hubo un desplazamiento de la producción hacia el norte de dicha región. En este contexto, los molinos arroceros tuvieron un proceso de concentración geográfica y de reducción de capacidad de elaboración -por cierre de plantas-, pero no cambiaron su localización. Como consecuencia, se afectaron los márgenes de comercialización y los ingresos de los productores. En Uruguay, el cultivo comenzó en el Este, y luego tuvo una expansión al Centro y Norte del país. Esto obedeció a razones de índole estructural inherentes a la expansión de la actividad y al tipo de articulación entre la producción y la industria, por lo que la localización de estas últimas acompañó dicha expansión. El objetivo de éste trabajo es realizar una caracterización de la organización técnica, económica y social del sector arrocero, cuantificar los costos de transporte inherentes a la localización de la producción primaria con respecto a los molinos para Argentina, evaluar cambios de la última década, realizar un análisis comparativo respecto de Uruguay, y elaborar para el caso de Argentina un modelo de transporte que incluya operatorias de tipo multimodal, con la utilización del ferrocarril y del transporte fluvial por los ríos Paraná y Uruguay. Para ello se han elaborado modelos de programación lineal en los cuales los resultados obtenidos son la minimización del costo de transporte, las rutas, los medios utilizados y la información que brindan los costos de oportunidad y de sustitución en caso que los mismos resultaron relevantes. Los resultados del modelo señalan que debido a la estructuración del CAI arrocero argentino los costos de transporte se han duplicado entre 1998 y el año 2006, cuando eran aquel año similares a los costos en Uruguay. La incorporación de transporte ferroviario y fluvial al modelo disminuye parcialmente dicho encarecimiento.