Protection Embankments Research Articles

Real-scale investigation of the kinematic response of a rockfall protection embankment

Abstract. This paper addresses the response of rockfall protection embankments when exposed to a rock impact. For this purpose, real-scale impact experiments were conducted with impact energies ranging from 200 to 2200 kJ. The structure was composed of a 4 m high cellular wall leaned against a levee. The wall was a double-layer sandwich made from gabion cages filled with either stones or a sand–schredded-tyre mixture. For the first time, sensors were placed in different locations within the structure to measure real-time accelerations and displacements. The test conditions, measurement methods and results are presented in detail. The structure's response is discussed in a descriptive and phenomenological approach and compared with previous real-scale experiments on other types of embankments.

Consanguinity and Other Marriage Market Effects of a Wealth Shock in Bangladesh

This paper uses a wealth shock from the construction of a flood protection embankment in rural Bangladesh coupled with data on the universe of all 52,000 marriage decisions between 1982 and 1996 to examine changes in marital prospects for households protected by the embankment relative to unprotected households living on the other side of the river. We use difference-in-difference specifications to document that brides from protected households commanded larger dowries, married wealthier households, and became less likely to marry biological relatives. Financial liquidity-constrained households appear to use within-family marriage (in which one can promise ex-post payments) as a form of credit to meet up-front dowry demands, but the resultant wealth shock for households protected by the embankment relaxed this need to marry consanguineously. Our results shed light on the socioeconomic roots of consanguinity, which carries health risks for offspring but can also carry substantial benefits for the families involved.

Improving three-dimensional rockfall trajectory simulation codes for assessing the efficiency of protective embankments

Trajectory simulation codes are widely used for assessing and zoning rockfall hazards in view of land use planning. Theses tools may also be used to estimate the benefit in terms of risk reduction derived from the construction of protection structures such as embankments. This paper investigates the relevance of currently used trajectory analysis tools for this purpose through a real case study. The trajectory analysis is first used to assess the hazard and define the embankment geometry. In a second time, it is used to assess the embankment protection efficiency after its insertion in the digital terrain model. Results reveal abnormal trajectories in the vicinity of the embankment suggesting limitations related to both the spatial resolution of the terrain model and to the rebound models. To cope with these limitations, an innovative approach is proposed and evaluated for improving the ability of the simulation code in assessing the residual hazard down the embankment.

Assessing the Flood Impacts and the Cultural Properties Vulnerabilities in Ayutthaya, Thailand

The Historic City of Ayutthaya, founded in ca.1350 as the second capital of the Kingdom of Siam after Sukhothai, is a World Heritage site locating on an island of the Chao Phraya, Lopburi and Pa Sak rivers. The severe flood in Thailand, lasted for three months, since October-December 2011 has inundated the World Heritage properties and historic monuments around the city of Ayutthaya. Because of the extreme height of the flood, the protective embankments could no longer withstand the 2011 flood as they did before. In fact Ayutthaya has long been flooded. In the past, the local people solved this problem by digging canals we still can find today many canals and water gates at most of the rivers around and inside the Ayutthaya Island. As current situations change, canal digging is no longer an appropriate way for the city flood protection. The previous flood has damaged the historic monuments in the historic city of Ayutthaya. To conserve those historic monuments, it is important to assess the damages in terms of environmental damage, external damage and internal damage. The levels of damage; high risk, medium risk and low risk respectively, are also assigned. Furthermore, the historic monument values are ranked as high, medium or low values. These two factors are employed as indicators for setting the priorities of historic monument site conservation. The research found out that highest risk damages for the historic monument sites were the level above the mean sea level and the distance from the rivers or canals. To protect those valuable historic monument sties in future, all stakeholders should be involved in the conservation plan.

Use of External Testing Methods to Assess Damage on Rockfall Protection Structures

This paper deals with the evaluation of damage due to boulder impact on rockfall protection embankment thanks to external methods. A 4 m high, 8 m long three layered structure is built using cells filled with different material according to their location in the structure. The structure is impacted by a 6500 kg spherical boulder with a maximal impact energy of 2000 kJ. The behaviour of the structure is first investigated using topographic surveys. Then, the results are compared with geophysical measurements. Results show that a low-energy impact leads to (i) the densification of both front and inner-layers associated with the swelling of the materials of the rear layer in the impact plane, and (ii) to the readjustment of internal materials which induces a local densification in a plane offset of 2 m. A high-energy impact induces large deformations on both inner and rear layers. These results are confirmed by seismic velocities which decrease with successive impacts.

Assessment of water retention behaviour in compacted fills

This paper presents the water retention behaviour of a fill used to build a flood protection embankment in Scotland. The water retention curve was obtained in the laboratory using three different techniques: high-range psychrometer, contact filter paper, and by interpreting mercury intrusion porosimetry data, to cover a relatively wide suction range. The behaviour of the fill has been studied further in a physical model embankment constructed in the laboratory inside an environmental chamber that allowed full control of the environmental conditions. The well-instrumented scaled embankment was subjected to controlled cycles of wetting and drying, and the evolution of the main variables of the problem (i.e. water content and soil suction) was monitored. The assessment of the water retention behaviour of the fill in ‘as-constructed' state under variable environmental conditions has been made possible by means of tensiometers and ThetaProbe water content probes strategically located in the compacted soil. A good agreement was found between the ‘as-compacted' water retention behaviour obtained in the laboratory and that of the ‘as-constructed' in the environmental chamber.

Experiments on Rockfall Protection Embankments with Geogrids and Cushions

There are various protection measures against rockfalls. An embankment is effective in rockfall hazard mitigation at a dangerous slope end. The slope rockfall tests on full-scale embankments have been carried out. These embankments are made of sandy soil reinforced with geogrids. The cushioning layers which are made of geocells filled with crushed stones of 5-13 mm in diameter are also placed on the mountain side of the embankment. A boulder, i.e., RC block rolls down the test-site slope, and hits against the embankment. A new system of measuring instruments is employed in order to evaluate the impact force and the impact energy. One of important observations is a possibility that a rolling boulder carries it toward the top of an embankment because of its rolling momentum. The experimental results, especially the relationship between impact force and impact energy is discussed in this paper.

Rockfall Impact Parameters on Embankments: A Discrete Element Method Analysis

The design of protection structures remains a difficult task for high-energy impact, and official regulations do not exist yet. In order to contribute to developing the efficiency of embankments subjected to rockfall impacts, a numerical approach based on the discrete element method (DEM) is proposed to study the impact process. Particular attention is given to the modeling of soil, in quasi-static configurations as well as in impact loading cases. From a reference configuration of an impacted embankment, a parametric study was carried out to investigate the role of the impacting block parameters on the response of the structure. Depending on the major impact parameters’ values, suggestions have been made to help in designing protective embankments.

Integrating rockfall risk assessment and countermeasure design by 3D modelling techniques

Abstract. Rockfall risk analysis for mitigation action design requires evaluating the probability of rockfall events, the spatial probability and intensity of impacts on structures, their vulnerability, and the related expected costs for different scenarios. These tasks were integrated in a quantitative risk assessment procedure supported by 3D rockfall numerical modelling performed by the original code HY-STONE. The case study of Fiumelatte (Varenna, Italy), where a large rockfall in November 2004 resulted in 2 casualties, destruction of several buildings and damage to transportation corridors, is discussed. The numerical model was calibrated by a back analysis of the 2004 event, and then run for the whole area at risk by considering scenarios without protection (S0), with a provisional embankment (S1), and with a series of long-term protection embankments (S2). Computed impact energy and observed damage for each building impacted in 2004 were combined to establish an empirical vulnerability function, according to which the expected degree of loss for each element at risk was computed. Finally, costs and benefits associated to different protection scenarios were estimated, in order to assess both the technical performance and the cost efficiency of different mitigation options.

Experimental study of the impact response of geocells as components of rockfall protection embankments

Abstract. Rockfall protection embankments are ground levees designed to stop falling boulders. This paper investigates the behaviour of geocells to be used as components of these structures. Geocells, or cellular confinement systems, are composite structures associating a manufactured envelope with a granular geomaterial. Single cubic geocells were subjected to the impact resulting from dropping a spherical boulder. The geocells were filled with fine or coarse materials and different boundary conditions were applied on the lateral faces. The response is analysed in terms of the impact force and the force transmitted by the geocell to its rigid base. The influence on the geocell response of both the fill material and the cell boundary conditions is analysed. The aim was to identify the conditions resulting in greatest reduction of the transmitted force and also to provide data for the validation of a specific numerical model.

The Wheels of Watermills and the Wheel of Fortune

Along with two well rehearsed quaestiones disputatae, Bartolus de Saxoferrato’s repetitio ad l. Quominus constitutes the cornerstone of the medieval elaboration of legal issues relating to rivers. Ranging from the construction of watermills to protective embankments, and from the maintenance of water canals to the reconstruction of run-down structures, the eighteen questions of the repetitio prepared students for situations they would likely encounter when practising law. A legal opinion (consilium) penned by one of Bartolus’ disciples, Donato Aldighieri, in response to the doubts the Abbot of Vallombrosa had concerning damage inflicted on his monastic estate by the Arno river, illustrates the legal fertility of Bartolus’ seminal discussion. In addition, the consilium also attests to the complexity of the efforts of a medieval commune, Florence in this specific case, to gain control of a resource like the Arno, essential for the economic development of the city. Unable to shoulder alone the financial burden of preventing floods, the commune had no other option than to enlist the help and know-how of a monastic institution. Though the whole city benefited from the preventive work of the monks, the new embankment engendered an unexpected conflict with other adjacent land owners. The politically prominent Donato was called in to negotiate the abbot’s rights against the claims of the adjacent owners and the policy of the city. Recommended citation: Cavallar, Osvaldo, The Wheels of Watermills and the Wheel of Fortune. A consilium of Donatus Ricchi de Aldighieris, in: Rechtsgeschichte - Legal History Rg 13 (2008) 80-116, online: http://dx.doi.org/10.12946/rg13/080-116

Construction of a pile-based offshore airport

The feasibility of construction of a pile-based offshore airport in open sea is considered. The concept of a pile-based airport relies on technology used to construct long concrete bridges, over sea arms and straits, during the last four decades. The features of four major bridges, in conjunction with prefabrication of prestressed structural elements, are described. The airport platform, which is set 16 m above sea level, obviates the need for protective embankments. The platform consists of modular units, supported by piers, which are based on foundations of steel piles. The modular units comprise tube girders, 35–60 m long, set on piers 15 m apart. Longer girder spans are expected to diminish the impact of the airport on the coast. Cost estimates are provided for a pile-based offshore airport serving medium haul aircraft, using 45×15 m 2 and 60×15 m 2 grids, and long haul aircraft, using 60×15 m 2 grids. Cost comparison with a fill island airport is provided using two different geometries. It is shown that the pile-based airport is a viable option, both technologically and economically. This new concept provides advantages over the fill island option regarding the requirement of materials, technology of construction, the modular approach and the diminished environmental impact.

New Method for Meander-Loop Cutoffs

When a reach of a meandering river becomes very sinuous, and thereby causes significant problems for navigation and flood discharge, cutoff works in the narrow-neck portion of the river bend may be carried out. It is common practice to excavate a small slightly bending cutoff channel, referred to as pilot channel, which is gradually scoured and enlarged toward the concave bank by the river flow. In the design of the Wujiadu cutoff in the Caoe River (already constructed in 1998), the authors proposed a new method for constructing meander-loop cutoffs. Using this technique, the new cutoff channel on the concave bank side and the flood protection embankments are formed during construction, allowing the nonprotected convex bank and the bed of the new cutoff channel to be scoured and be enlarged by flood. Thus, the amount of excavation of the cutoff works can be significantly reduced and the construction period can be largely shortened. In this way, the lines of the new cutoff channel may be unified with the overall river alignment. This paper presents the design philosophy and major points of the method for meander-loop cutoffs.

Lake Evolution of Jianghan Plain: A Case Study of the Hebosuo Reduction & Emergence in the Ming Dynasty

本文以一种执行经济功能为主的税收机构──河泊所为切入点,探讨了明初江汉平原中小湖泊的分布及明中后期该类湖泊的淤塞演变过程,揭示出江汉湖群演变的时间特点和空间规律.时间特点:成化(1465年)以前,淤积缓慢;成化至弘治间(1465-1505年),淤积加快,但淤塞仍轻;正德末(1517-1521年)以后,众湖群迅速淤浅、淤废,直至明末空间规律;汉水泥沙自上游向下游依次淤积;江水泥沙先自上游向下游淤积,而后又向上游回溯淤积.;There were many medium and small-sized lakes in the early Ming dynasty, which were linked each other by many deep or shallow canals in Jianghan plain.Along with the economic development, population growth, protective embankments in lakeside areas mushrooming and booming, there broke out more and more inundation after Chenghua(1465-1487).From the last phase of Zhengde (1506-1521) to early stage of Wanli (1573-1620),many medium-sized and small-sized lakes had been silting-up from the Yangtze River and Hanshui River, The spatial-temporal distribution of the lake evolution were different duo to the following reasons: Mire and sand from Hanshui River were deposited from the upper reaches to the lower reaches, while those from the Yangtze River were firstly silted up from the upper reaches to the lower reaches, then deposited back to the upper reaches.We can see this evolving trend clearly from the reducing and merging process of Hebosuo, an organization for levying piscatorial taxes.

ジオシンセティックスで補強した防護盛土擁壁への現場載荷実験

ジオシンセティックスで補強した防護盛土擁壁への現場載荷実験

Channel change and flood events since 1783 on the regulated river tay, Scotland: Implications for flood hazard management

AbstractAn analysis of old maps and documentary sources reveals that major changes in river channel planform have occurred over the last 200 years on the River Tay system, Scotland, UK. Reaches showing natural river channel planform change, however, are relatively small and a stable planform is characteristic of many sections of the river. River planform instability appears to be controlled by channel bed slope, sediment load and the enhanced vulnerability of former river channel courses to erosion. Flood protection embankments built in the 19th and 20th centuries modified unstable multichannel wandering gravel bed river sections to narrower single‐channel reaches, with limited lateral migration. On the River Tummel, 20th century impoundment has caused further geomorphological change in response to clearwater erosion close to the dam and aggradation processes within the regulated river downstream, but isolation of the effects of impoundment from those of channelization are problematic. An examination of the geomorphic effects of a high magnitude flood event in 1990 and historical accounts of earlier large floods reveal that the 1990 flood was the third largest since 1800 in the study area. Despite river regulation and bank protection the zones naturally characterized by instability are still susceptible to planform changes causing flood embankments to be breached, channel shifts and development of gravel bars.

Étude sur les fortifications de l'Inde. I. Les fortifications de l'Inde ancienne

English summary Based on the study of 20 sites (8 from the Harappan period, 22 from Early Historical India), the present paper seeks to analyse the main features of ancient Indian fortifications. Our documentation on the fortified cities of the Harappan period, entirely founded on the results of archaeological excavations, shows that their thick ramparts or bunds, built up of mud and mud-brick, sometimes reinforced by rectangular towers or salients with elaborately designed gateways, were not only meant to be defence walls or protective embankments against floods , but probably also had a social function to perform. For the study of defence architecture in Early Historical India, the most reliable source of information is also archaeological evidence (though, in many cases, detailed excavation- reports are not available), to which may be added literary and iconographie data. In North- West India is found a type of fortification having curtain walls pierced with loopholes, semi-circular hollow towers, corresponding to the representations of the Gandha- ran carvings which depict ramparts provided with merlons topped by a hip-roof and gateways capped with a rectangular cabin projected out on corbels, a kind of oriel. In the rest of the Indian peninsula, excavations broadly corroborate the information furnished by the literary sources and show that the most persistent features of the early fortifications are massive and compact earthen walls, provided with a burnt-brick or stone facing, surrounded with wide and deep ditches. These ramparts are, in some cases, reinforced, at regular intervals, with solid quadrangular towers. Gateways are very elaborate and are probably the strongest part of the defence : in certain places, the wall turns inwards so as to form two quadrangular structures ; in others, it turns outwards and at both ends joins the heel of a massive L-shaped gateway flank, or the opening is strengthened by two powerful towers with an open courtyard. Regarding the crenelation of the curtain walls, the narrative reliefs of the great buddhist stupa show that the merlons were triangular or rectangular. In this system the defence is not through the loopholes of the ramparts, like in the strongholds built-up on the Central Asian pattern, but it is from the top, from the battlements, a high position which enables the defenders to dominate the besiegers. As proved by excavations, this concept of fortification was already defined from the middle of the first millenium and it is manifest that defence architecture in the Indian subcontinent has retained its distinctive features for more than one thousand years, except in the North-West, more sensitive to foreign influences during the Greek and Kusâna periods.