Embankment Dams

Spatial variability of material properties is inherent in both natural soil deposits and earth structures, yet it is often ignored during geotechnical design. With the objective of developing novel methods for assessing the effects of soil variability on groundwater flow, this study presents a stochastic finite element model of seepage through a flood defense embankment with randomly heterogeneous material properties. Stochastic modeling is undertaken by means of a Monte Carlo simulation which involves a large number of finite element analyses, each with randomly varied porosity at element level, which leads to a corresponding random variation of both permeability and water retention properties across the embankment domain. This provides a statistical distribution of responses, such as total flow rate and time to reach steady state, instead of a single deterministic result as in conventional studies of seepage through unsaturated heterogeneous soils. As the degree of heterogeneity increases, water tends to flow along the most permeable paths inside the soil mass, resulting in an irregular shape of the predicted wetting fronts and pore pressure contours. The mean and standard deviation of the computed quantities strongly depend on the statistics of the input porosity field. Simulations are also conducted to compare the statistical variation of flow rate with and without dependency of the water retention curve on porosity. With recent growth in computer speed, stochastic finite element models based on the Monte Carlo approach can become a powerful design tool, especially if a quantitative assessment of geotechnical risks is required. Copyright © 2011 John Wiley & Sons, Ltd.

Il Grand Inga Dam Project rappresenta un mastodontico progetto idroelettrico sul fiume Congo dal costo stimato di circa 80 miliardi di dollari. Il grosso della spesa dovrebbe essere sostenuto dalla Cina, mentre in minima parte alcune organizzazioni internazionali sono state coinvolte nel finanziamento. I benefici che tale progetto apporterebbe al Congo e a tutta l’Africa sub-sahariana sono molti, soprattutto in termini di produzione di energia idroelettrica e di impiego. Allo stesso tempo, si riscontrano varie criticità, su tutte in merito all’impatto ambientale che un’infrastruttura così massiccia potrebbe causare ad intere regioni. L’obiettivo di questo paper è di fare chiarezza su questo grande progetto e sulle effettive conseguenze, positive e negative, che esso potrebbe comportare per molti milioni di Africani.

Dams are very important infrastructure to any country where they serve for different purposes. Unfortunately, they represent risks to life and property due to their potential to fail and cause catastrophic flooding. Recent studies indicate the possibility of Mosul Dam failure. For this reason different failure models were used to estimate the consequences of such failure. Almost all models applied gave similar results. It is assumed that in case the water level in Mosul Dam reservoir is at its maximum operational level the effected population will reach 6,248,000 (about one million will lose their life) and the inundated area will be 7202 square kilometer. This catastrophe requires prudent emergency evacuation planning to minimize loses.

Piled embankments provide an economic solution to the problem of constructing embankments over soft soils. The piles and geosynthetic combination can alleviate the uneven surface settlements that sometimes occur in embankments supported by piles without reinforcement. The main focus of this paper is to present a new method for analysis of an embankment of granular fill on soft ground supported by a rectangular grid of piles and geosynthetic. This method is based on consideration of the arching effect in granular soil and similar to the method proposed by Low, B.. The main refinements are: inclusion of a uniform surcharge load on the embankment fill, individual square caps were used, and taking into account the skin friction mechanism, which contributes to soil–geosynthetic interface resistance. Using this method, the influence of embankment height, soft ground depth, soft ground elastic modulus, and geosynthetic tensile stiffness on efficiency, stress concentration ratio, settlement ratio, tension of geosynthetic, and axial strain of geosynthetic are investigated. The results show that inclusion of a geosynthetic membrane can increase the fill load carried by piles. As a result, both the total and differential settlements of the embankment can be reduced. The new design method was verified against several current design methods. Theoretical solution showed that BS8006 [1995. Code of Practice for Strengthened/Reinforced Soils and other Fills. British Standards Institution, London, p. 162] and Guido, V.A., Kneuppel, J.D., Sweeny, M.A. [1987. Plate loading tests on geogrid-reinforced earth slabs. In: Proceedings of the Geosynthetics '87, New Orleans, USA, IFAI, pp. 216–225] methods overpredict the vertical stress acting on the geosynthetic due to that the reaction of the soft ground on the geosynthetic is not considered in their methods. It also showed that the present method is in good agreement with Low, B.

This paper presents the case history of the construction of a 3 m high embankment on the geocell
foundation  over  the  soft  settled  red  mud.  Red  mud  is  a waste  product  from  the  Bayer  process  of
Aluminum industry. Geotechnical problems of the site, the design of the geocell foundation based on
experimental investigation and the construction sequences of the geocell foundations in the field are
discussed in the paper. Based on the experimental studies, an analytical model was also developed to
estimate the load carrying capacity of the soft clay bed reinforced with geocell and combination of
geocell and geogrid. The results of the experimental and analytical studies revealed that the use of
combination of geocell and the geogrid is always beneficial than using the geocell alone. Hence, the
combination of geocell and geogrid was recommended to stabilize the embankment base. The reported
embankment is located in Lanjigharh (Orissa) in India. Construction of the embankment on the geocell
foundation  has  already  been  completed.  The  constructed  embankmenthas  already  sustained  two
monsoon rains without any cracks and seepage.

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Negli ultimi anni l’acqua ha assunto un ruolo di primissimo piano nella politica internazionale. Il cambiamento climatico, la crescita esplosiva della popolazione mondiale, la progressiva urbanizzazione di massa in molte aree del globo e la massiccia desertificazione che ha interessato diverse zone geografiche sono solo alcune delle ragioni che hanno contribuito ad accrescere l’importanza dell’acqua nelle relazioni tra gli Stati. In virtù di ciò, appare quanto mai evidente un’analisi approfondita dell’idro-diplomazia, una nuova strategia di politica estera adottata ormai da molte nazioni. Cosa si intende esattamente per idrodiplomazia? Quali sono le sue principali caratteristiche? Chi ne fa uso più assiduamente nel contesto globale? In questo seminario il Think Tank AB AQUA risponderà ai precedenti quesiti ed analizzerà i principali dossier diplomatico-internazionali che coinvolgono l’”oro blu”.

Mosul and Haditha Dams are the two largest dams of Iraq. They were constructed in localities having completely different materials for use in the core and rip-rap. While clay for the core was abundant in Mosul Dam site it was completely missing in the other dam site. Where solid and sound limestone for the rip-rap was available in large quantities in Mosul dam only dolomitic limestone of inferior quality was there in Haditha Dam site. In Haditha Dam, the use of the only available material for the core was mealy dolomite and it was used successfully, but the addition of an asphaltic concrete diaphragm was necessary to improve impermeability of this core. The use of this material for the first time in the world was a challenging task to the engineers, who could not have done this without carrying out first comprehensive field and laboratory research. Even sand and gravel materials were available in the two sites in ways that borrowing and using them required completely different techniques in the two sites. In the shells of Mosul Dam, they were placed and compacted after minimum treatment, filter material; however, had to be sorted out and mixed in screening plants. In Haditha Dam site dredging of the materials from the river channel resulted in adopting a hydraulic filling procedure in building the shells and eliminating the filter zones. Good quality limestone was used in Mosul Dam rip-rap but the missing of such rock quality in Haditha Dam dictated the use of concrete facing protection placed by mechanical means. The different construction materials used in the two dams resulted in producing two contrasting designs which had also required different

Climate change has the potential to have significant effects on the stability and serviceability of earthworks slopes, impacting on the performance of transport infrastructures. This paper describes how a unique facility for engineering and biological research was established in NE England through the BIONICS Project (Biological and Engineering Impacts of Climate Change on Slopes). It describes the building and monitoring of a full-scale embankment representative of road/rail embankments in the UK. The paper presents the results of monitoring of pore water pressure carried out between 2007 and 2009. The pore water pressures within the upper 3 m of the embankment have been largely positive, in some case approaching hydrostatic conditions after wetter periods. This is largely due to the wet nature of the summers in both 2007 and 2008 since monitoring began, as well as the application of artificial inundation using a climate control system. Negative pore water pressures (suctions) of the order of 230 kPa were recorded at greater depths below 3 m. The experimental facility provides essential field measurements that can be used to calibrate numerical models of soil responses to climatic changes and gain a better understanding of the response of engineered UK fills to climate events.

George Nunes Soares (Universidade Federal do Ceará) [email protected]
Luís Felipe Cândido (Universidade Federal do Ceará) [email protected]
Resumo:
A produtividade é uma ferramenta importante no processo de tomada de decisão. Muitos gestores não mensuram a produtividade de sua obra e com isso não tem o controle da execução dos seus serviços, logo do planejamento do empreendimento. Esse trabalho consiste em um estudo de caso descritivo no qual se avaliou a atividade de aterro dentro do serviço de terraplenagem. A obra reside na cidade de Teresina-PI, onde se avaliou a produtividade de três combinações diferentes de maquinário. O qual se chamou de grupo 1, 2 e 3. Avaliou-se os impactos dessas mudanças nos números de produtividade e auxiliou-se os gestores nas suas tomadas de decisões.
Palavras chave: Produtividade, tomada de decisão, Aterro.

Productivity analysis of activity in embankment grading service

Abstract


Productivity is an important tool in the decision making process. Many managers do not measure the productivity of your work and it does not control the performance of its services, then the planning of the project. This work is a descriptive case study which evaluated the activity within the embankment grading service. The work resides in the city of Teresina-PI, which evaluated the productivity of three different combinations of machinery. Which is called group 1, 2 and 3 evaluated the impacts of these changes on productivity figures and helped himself managers in their decision making.

Key-words: Productivity, decision making, embankment.

It is estimated that in Europe there exist over 7000 large dams, classified as having heights greater than 15m, with thousands more planned to be built in the next years. According to the ICOLD register, worldwide the are more than 58000 large dams, with millions more in existence that are currently un-registered. More than 85% of the existing dams worldwide is expected to exceed their average 50-year lifespan within the next two decades. Future projections also highlight that the frequency of shifting weather events is anticipated to increase, with severe consequences on the structural integrity of hydro-infrastructure due to high potential of extreme drought and flood events. As a result, hydro-assets that they were initially constructed for flood control and hydroelectric purposes may actually be the cause of more destructive hazards due to their potential failure, with significant environmental, social and economic risks and consequences. The ageing dam structures alongside with shifting environmental conditions are considered major factors contributing to the growing infrastructure crisis. Relationships and models describing the short and long-term behaviour of dams are still based on empirical relationships, usually not considering the changing environmental conditions. Such models are also not always representative as dams of similar size and type can behave differently. Of particular importance is therefore the assessment of the ongoing performance of a dam, the validation of laboratory and empirical models and the assessment of different engineering designs. Investigations about the post-construction behaviour of dams will also enable to deliver key information about the climate change effects on hydro-assets, provide early warning signs of an impending failure and ensure operation within safety limits. This study initially presents recent cases of incidents and failures of high-hazard dams triggered by severe environmental events. An overview of the methods that are currently employed to monitor and assess the condition of dam infrastructure is also presented. This investigation then focuses on providing an insight of the complexity of the deformation mechanisms for earth-fill dams during critical periods in their lifespan, such as the first impoundment of the reservoir and their long-term mature behaviour. The post-construction behaviour of two of the largest earth-fill dams in Europe is investigated and compared with models derived from other dam studies that are described in the international literature. Finally, existing and future challenges for climate-resilient dam infrastructure are discussed.

Halda, one of the major tributaries of the mountainous river Karnaphuli, is well known as the country's only natural carp spawning ground. Naturally fertilized eggs of carps collected from Halda River are hatched in mud-made scoops on the river bank for aquaculture purposes. However, the river habitat is under constant threat due to human interventions like loop cutting, pollution from the paper mill and power plant, blocking natural water flow of larger tributaries by introducing sluice gates, embankments and rubber dam over the river at upstream, as well natural causes like siltation, erosion and climate change impacts. A study is conducted to address the issues of the ecosystem, sustainable management and the flow regulation impacts of dams in the Halda River, although the flow regulation assessments are conducted based on the macroinvertebrate, index-based framework, land-use effects on the hydrology, new indicators development, hydrologic impact assessment, hydrodynamics in dam regulated rivers, surface-water hydrodynamics and regimes of a small mountain stream and wide range of initiatives. In our case, we considered runoff flow, mountainous flow and dams in the rivers are primary parameters for assessment, so based on previous studies we decided to simulate a hydrologic and hydrodynamic model for the dam and without dam scenarios. Major difficulties and challenges for the environmental flow analysis of a river are continuous data availability. In this research, a hydrologic model ArcSWAT has been built to assess the contribution of rainfall on the river discharge to be used as output from the tributaries in the hydrodynamic model Delft3D. The research findings help us to perceive the effect of the dams on fish breeding condition in the river. In order to perform the environment flow analysis of the river, Tennant method has been followed in the study, which is a secure and reliable approach. The flow regulation impacts are assessed for fish habitat and spawning in the river area based on the simulations. Finally, the findings are further analyzed for velocity profiles for dams by building block method for the sustainable aquatic habitat in the Halda River.

Nonostante le sue esigue dimensioni territoriali e demografiche Gibuti è probabilmente la nazione più importante a livello strategico di tutta l’Africa. A riprova di ciò si tenga presente che l’unica base americana sul continente, Camp Lemonnier, si trova proprio in questo piccolo Stato affacciato sul Golfo di Aden. Gli Americani non sono gli unici ad essere presenti in forze a Gibuti. Molte nazioni, tra cui anche l’Italia, hanno basi militari ivi operanti. Recentemente anche la Turchia ha dimostrato un interesse geopolitico rilevante nei confronti di questo piccolo ma strategico Paese africano. Tuttavia, a differenza di molte nazioni, Ankara non ha una base militare operante sul territorio. Nonostante ciò, la presenza turca a Gibuti è molto forte. Ciò è dovuto alle strategie di idro-diplomazia che la Turchia ha messo in atto nel corso del tempo. Nello specifico, i Turchi si sono resi responsabili della costruzione di una diga che aiuterà Gibuti a prevenire le alluvioni nei pressi del proprio aeroporto internazionale, situato nella città di Ambouli. Questo paper farà luce sul crescente ruolo dell’idro-diplomazia, in questo caso turca, nelle relazioni internazionali e, nello specifico, nel tessuto socio-politico gibutiano.

L’altopiano tibetano è una delle regioni più strategiche non solo per il continente asiatico, ma nel contesto globale. La ragione di ciò è in massima parte legata al fatto che i maggiori fiumi dell’Asia sud-orientale, che è la più popolosa macroregione al mondo, nascono proprio in Tibet. Fiumi del calibro del Mekong, Gange, Indo, Brahmaputra e Sutley sgorgano proprio dalle montagne di questa scoscesa ed impervia area montana. La Cina, in virtù della propria favorevole posizione geografica “a monte” di questi grandi corsi d’acqua, è la nazione che beneficia maggiormente delle grandi ricchezze idriche tibetane. Lo sfruttamento dell’energia idroelettrica tibetana effettuato da Pechino nel corso degli ultimi tempi ha creato non poche tensioni nella regione. L’obiettivo di questo report è di valutare da un punto di vista idro-strategico la rilevanza del Tibet nel contesto asiatico e di mettere a fuoco le politiche idriche cinesi degli ultimi anni.