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Numerical modelling of gabion retaining wall under loading and unloading

Grodecki Michał

Archives of Civil Engineering

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2021

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Vol. 67, nr 2

155--164

EN

Main goal of this paper is to present results of the numerical simulations of a real-scale gabion retaining wall tests. 4.5 m high wall was loaded and unloaded with water pressure, displacements of the crest of the wall were measured. Finite Element Method was used to simulate experiment and obtained results are compared with experimental ones. Usage of homogenized Coulomb-Mohr type continuum for gabions is proposed. Strength parameters of the model (cohesion and friction angle) are estimated on the base of large scale triaxial tests of the gabions and static tensile tests of the mesh. Influence of the “cut-off” condition on obtained results is analyzed. Elastic model for gabions is used for comparison of the results. Interface elements and truss joints between the gabions are used to simulate joints between gabions with limited strength. Good correlation between displacements obtained in experiment and numerical simulations was observed, especially in loading phase, so presented methodology of numerical modelling allows to model gabion retaining walls behavior close to the reality and could be used in engineering practice.

PL

Artykuł przedstawia wyniki symulacji numerycznych testów rzeczywistego muru oporowego z gabionów. Mur o wysokości 4.5 m był obciążany ciśnieniem wody i odciążany, mierzono przemieszczenia jego korony. Metoda Elementów Skończonych została wykorzystana do zasymulowania badań laboratoryjnych, porównano uzyskane wyniki z otrzymanymi doświadczalnie. Zaproponowano wykorzystanie zhomogenizowanego ośrodka typu Coulomba - Mohra do modelowania gabionów. Parametry wytrzymałościowe (kohezję i kąt tarcia wewnętrznego) oszacowano na bazie testów trójosiowych gabionów i testów statycznego rozciągania siatki. Analizowano wpływ warunku „cut-off” (braku nośności na rozciągania) na uzyskiwane wyniki. Dla porównania wykorzystano model sprężysty gabionów. Elementy kontaktowe i łączniki kratownicowe wykorzystano do zamodelowania połączeń pomiędzy gabionami o ograniczonej wytrzymałości. Zaobserwowano dobrą zgodność obliczonych numerycznie i pomierzonych laboratoryjnie przemieszczeń (szczególnie w fazie obciążenia), tak więc zaprezentowana metodologia pozwala na bliskie rzeczywistości zamodelowanie zachowania się konstrukcji z gabionów i może być wykorzystywana w praktyce inżynierskiej.

2

Ścieżki równowagi statycznej belek żelbetowych wzmacnianych taśmami z włókien węglowych

Korentz J.

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

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2017

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z. 64, nr 3/I

213--222

PL

Wyniki badań doświadczalnych i analiz numerycznych pokazują, że istotny wpływ na pracę wzmacnianych belek żelbetowych mają techniki naprawcze i właściwości mechaniczne zastosowanych materiałów naprawczych. Właściwości mechaniczne materiałów naprawczych oraz techniki wzmacniania decydują nie tylko o nośności belek po wzmocnieniu, ale także o ich odkształceniach. Ponadto wzmocnienia belek mogą być wykonywane przy zastosowaniu różnych metod. Wzmocnienie można wykonać przed obciążeniem belki lub po jej obciążeniu. Można też belkę odciążyć przed wzmocnieniem, albo sprężyć ją materiałami naprawczymi. Wymienione metody naprawcze mają również wpływ na pracę wzmacnianych belek żelbetowych. Projektując wzmocnienia belek żelbetowych trzeba być świadomym konsekwencji stosowania dostępnych technik naprawczych, materiałów naprawczych, a także wyboru metody wykonywania wzmocnień. W artykule przedstawiono ścieżki równowagi statycznej belek żelbetowych wzmacnianych różnymi materiałami naprawczymi przy zastosowaniu różnych technik wzmacniania i metod wzmacniania, ze szczególnym uwzględnieniem wzmocnień taśmami z włókien węglowych. Przeprowadzone analizy mogą być pomocne w projektowaniu wzmocnień belek żelbetowych.

EN

The results of experimental tests and numerical analyses indicate that repair techniques and the mechanical characteristics of repair materials have a very strong influence on the behaviour of strengthened reinforced concrete beams. The mechanical characteristics of materials used for strengthening elements and the strengthening techniques determine not only the load bearing capacity of beams after strengthening, but also their deformations. Other important factors also affect the behaviour of such beams, which include the time when the strengthening is done, i.e. before or after loading the beam. It is also important whether the beams are compressed with repair materials while they are being strengthened, or whether the load is taken off the beams before strengthening, or whether intermediate supports are used while strengthening the beams. All the factors mentioned have an influence on the behaviour of strengthened reinforced concrete beams. While designing strengthening elements for reinforced concrete beams, it is necessary to be aware of the consequences of using available repair techniques, repair materials, as well as the technology and stages of the construction of strengthening elements. The paper presents the static equilibrium paths of strengthened reinforced concrete beams with special attention to the repair techniques possible to implement while strengthening the beams. These analyses can be useful for designing strengthening elements for reinforced concrete beams.

3

Can Potentilla fruticosa Linn. shrubs facilitate the herb layer of heavily grazed pasture on the eastern Tibetan Plateau

Li P., Krusi B., Li S., Cai X., Yu F.

Polish Journal of Ecology

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2011

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Vol. 59, nr 1

129-140

EN

The facilitative and competitive effects of shrubs on herbaceous species have been extensively studied, but little is known about the roles of the shrub distribution patterns in such effects. On a heavily grazed pasture on the Tibetan Plateau, we investigated the effects of Potentilla fruticosa Linn. shrubs of different distribution patterns on the small-scale vegetation pattern of the herb layer. We made same-sized releves at five micro-site types, i.e., beneath and outside the canopies of solitary Potentilla individuals, beneath and outside the canopies of edge-of-patch individuals and at the central openings of torusshaped large Potentilla patches. Shrubs protected certain species by increasing their frequencies of occurrence or flowering. However, only few species benefited from shrubs and more occurred or flowered more frequently outside. The data at community level indicated that species richness and diversity index were higher outside. The patch openings did not benefit species richness, pooled cover, diversity index or evenness of central vegetations. No special species was found growing beneath shrubs exclusively and few species were found with higher occurrences beneath shrubs. Furthermore, no significant difference was found between the two different distribution patterns at either community or species level. Vegetation ordinations confirmed this and vegetations beneath and outside the shrubs were distinguished merely. In conclusion, Potentilla facilitated some species in the herb layer and the patch openings did not show large protective effects. Also, distribution patterns of Potentilla did not affect the difference between vegetations beneath and outside shrub canopies.

4

Benefits of low-intensive grazing : co-occurrence of umbelliferous plant (Hladnikia pastinacifolia Rchb.) and opilionid species (Phalangium opilio. L) in dry, calcareous grassland

Sajna N., Kusar P., Slana Novak L. L., Novak T.

Polish Journal of Ecology

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2011

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Vol. 59, nr 4

777-786

EN

The impact of grazing has been discussed in many organisms, and it has been shown that it has considerable influence on the structural variation of vegetation, resulting in its tussocky appearance. Such spatial heterogeneity results in plants formations that facilitate other species by providing safe sites against predation and physical stress. On the Trnovski gozd plateau in western Slovenia, a secondary habitat of the rare, monotypic endemic umbelliferous species, Hladnikia pastinacifolia, was colonized by a relatively isolated population of the wide spread opilionid species, Phalangium opilio. We hypothesized that in this stony pasture, the impact of the structurally heterogenous vegetation that results from low-intensity grazing benefits both species on hot summer days. For this purpose, we classified vegetation formation types (VFT) and measured temperature and relative humidity in places settled by Ph. opilio individuals during their daily rest. According to the predominant species, we recognized six VFTs: Carlina acaulis, Ruta divaricata, Koeleria pyramidata, Juniperus communis, understory vegetation and grazed turf. Only the spiny C. acaulis and unpalatable R. divaricata facilitated H. pastinacifolia, while also acting as nurse plants. On the other hand, Ph. opilio preferred the understory, but also settled on the other VFts, except Ruta. During the highest daily temperature of about 38[degrees]C, Ph. opilio avoided the grazed turf. Temperature preferences refer to frequencies of individuals rather than to absolute temperature values. The frequencies were independent of sex and the VFTs. Females were more frequently found in tussocks showing higher temperature profiles (Juniperus, Koeleria). During the hot daytime, Ph. opilio was most sensitive to relative humidity, and less so to temperature, whilst the height of settlement varied in adjusting these two environmental factors. The distribution of males significantly differed between the subsequent morning, midday and evening series, but not between the morning and evening ones, while in females it differed between all the three time series. In habitats, such as stony dry pastures, low grazing intensity can maintain persistent populations of H. pastinacifolia and Ph. opilio even in extremely hot weather. Such grazing is the most convenient measure for protecting both species, especially the highly endangered Hladnikia. The major threat to such habitats is afforestation by Pinus nigra, which deserves additional management. We found that in stony pastures, low grazing intensity assures the structural heterogeneity of vegetation required to maintain persistent populations, of both H. pastinacifolia and Ph. opilio.

5

Styropian jako lekkie wypełnienie nasypu przy przeciążonej konstrukcji oporowej

Grzegorzewicz K., Rychlewski P.

Materiały Budowlane

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2003

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nr 3

42-42