The stone columns created using a vibro – replacement technique are often used technology of ground improvement. Suitable geological conditions for stone columns include loose coarse – grained soils and soft to firm fine – grained soils.... more
The stone columns created using a vibro – replacement technique are often used technology of ground improvement. Suitable geological conditions for stone columns include loose coarse – grained soils and soft to firm fine – grained soils. The stone columns cause increasing of strength and deformation properties of the original subsoil. The design of stone columns must be based on properly determined properties of original subsoil as well as properties of the material of stone columns. The article presents and analysis results of direct shear tests of three different types of coarse – grained materials which are used for stone columns. The shear strength of coarse – grained material was determined using large – dimensional direct shear apparatus, which is required for this type of soil. Shear tests were executed for different values of the unit weight. High values of peak and residual angle of shear strength were determined for all three tested materials also in the loosest state. The...
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The paper presents the results of the shear strength measurements of a soil-geosynthetic interface. The tests were executed using a large-size direct shear test apparatus. A total of 5 different samples of materials were tested, i.e.,... more
The paper presents the results of the shear strength measurements of a soil-geosynthetic interface. The tests were executed using a large-size direct shear test apparatus. A total of 5 different samples of materials were tested, i.e., ash, sand, well-graded gravel, fine poorly-graded gravel, and medium poorly-graded gravel. These materials were reinforced using different types of geosynthetics, i.e., Thrace WG80 black woven geotextile, Tencate Miragrid GX55/30 woven geogrid, and Thrace TG3030S rigid polypropylene geogrid. An interface coefficient α, which represents the ratio of the soil-geosynthetic interface shear strength to the shear strength of unreinforced material sample, was determined for given combination of the material and geosynthetics. The coefficient α reached a greater value in the critical stress state than in the peak stress state for sands and gravels reinforced using GX55/30 and TG3030S geogrids. The value of the coefficient α was in a range of 0.87 - 1.04 for gr...
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The article deals with a deformation analysis of a road embankment under different types of static and cyclic loading. A typical cross-section of a road embankment supported by geogrid retaining structures is considered. In the case of a... more
The article deals with a deformation analysis of a road embankment under different types of static and cyclic loading. A typical cross-section of a road embankment supported by geogrid retaining structures is considered. In the case of a design, the load is usually applied as a distributed static load. The analysis presented in the paper includes all the most loading methods used. Because there are only a few measurements for these types of construction in a given region, the analysis also includes a cyclic loading that aims to simulate real traffic loading. The cyclic loading considered the weights of cars and trucks and the distances between them, based on traffic intensity measurements. The study results showed how significant the differences in vertical and horizontal deformations of an embankment are when the different types and methods of static loading are used in a design. The results of the cyclic loading showed the deformations that can be expected from current real traffic.
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The paper deals with an analysis of the shear strength behaviour of coarse-grained materials using large-sized direct shear apparatus. The shear strength curve of compacted coarse-grained material allows for determining the three typical... more
The paper deals with an analysis of the shear strength behaviour of coarse-grained materials using large-sized direct shear apparatus. The shear strength curve of compacted coarse-grained material allows for determining the three typical shear strengths, i.e. the shear strength for a maximum density of the sample tested (shear strength at point A), the peak shear strength (shear strength at point P), and the critical shear strength achieved for a large horizontal movement (shear strength at point C). Professional laboratories usually apply for determining the critical shear strength two different methods. The first method considers the critical shear strength at point A and the second method considers the critical shear strength at point C. The aim of the article is not to critically evaluate both methods, but to analyze the results of shear tests of gravels. The results of a large series of tests showed that these stresses may differ from each other in some cases, especially for po...
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The foundation of the bridge pillars required the construction of cofferdams in the Danube River. The cofferdams protected the area of the excavation pit mainly against the effects of flowing water. The paper includes analysis of the... more
The foundation of the bridge pillars required the construction of cofferdams in the Danube River. The cofferdams protected the area of the excavation pit mainly against the effects of flowing water. The paper includes analysis of the cofferdam for the foundation of the main central pillar of the asymmetrical bridge. The cofferdam has the ground plan dimensions of 44 x 20 m. It’s constructed of the double-row sheet pile walls. The stability of the cofferdam was analysed using numerical modelling based on the finite element method using Plaxis geotechnical software. The level of backfilling inside the cofferdam, required for construction of the foundations, was 6 m above the bottom of the river. The depth of the excavation pit of the cofferdam was about 4 m below the river bottom. The numerical model included 15 construction phases, which corresponded to the procedure of the construction. The analysis were focused mainly on construction phases, such as, e.g., the total backfill of the...
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The article deals with designing and analysing a wrapped geogrid reinforced structure (GRS) with a passive facing system. The analysis has been done using analytical calculation and numerical modelling. The analytical calculations were... more
The article deals with designing and analysing a wrapped geogrid reinforced structure (GRS) with a passive facing system. The analysis has been done using analytical calculation and numerical modelling. The analytical calculations were executed using FINE Geo5 geotechnical software, and numerical modelling was executed using Plaxis 2D software. The analysis is focused mainly on comparing tension forces in geogrids and the stability of the reinforced embankment determined using both computational methods. The deformation analysis was done only using numerical modelling. The numerical modelling allowed for a more detailed analysis of the wrapped GRS. Each construction phase was modelled step by step according to an actual construction procedure. Two complex road embankments supported by GRS were modelled and analysed. The first model consisted of three GRS, which not affected each other. In the second model, the GRS at each side of the embankment influenced each other. The analysis re...
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Designing the improvement of soil using stone columns is usually based on simplified analytical or numerical models. Stone columns installed using a vibro-replacement technique can cause radial displacement of the original soil. It can... more
Designing the improvement of soil using stone columns is usually based on simplified analytical or numerical models. Stone columns installed using a vibro-replacement technique can cause radial displacement of the original soil. It can cause radial compaction of the soil and increase the values of the strength and deformation properties, which are usually ignored in a practical design. The paper presents the results of a numerical analysis of a road embankment based on subsoil improved using stone columns. The changes in the properties of the original subsoil compacted by stone columns were analysed and taken into consideration in the models. The results showed that a model with homogenization of the subsoil and a model with stone columns transferred to continuous walls show similar results of the final settlement as well as the consolidation times. The differences between the values computed and measured were about 28 - 36 %. Taking into account the compacting effect of the origina...
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The paper deals with the laboratory testing of coarse-grained soils that are reinforced using a geogrid. The shear strength properties were determined using a large-scale direct shear test apparatus. The tests were executed on original as... more
The paper deals with the laboratory testing of coarse-grained soils that are reinforced using a geogrid. The shear strength properties were determined using a large-scale direct shear test apparatus. The tests were executed on original as well as on reinforced soil, when the geogrid was placed on a sliding surface, which permitted determining the shear strength properties of the soil-geogrid interface. The aim of the tests was to determine the interface shear strength coefficient α, which represents the ratio of the shear strength of the soil-geogrid interface to the unreinforced soil. The tests were executed on 3 samples of coarse-grained materials, i.e., poorly graded sand, poorly graded fine gravel and poorly graded medium gravel. Two types of geogrids were tested, i.e., a woven polyester geogrid and a stiff polypropylene geogrid. The results of the laboratory tests on the medium gravel showed that the reduction coefficient α reached higher values in the case of the stiff polypro...
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Stone columns made of coarse-grained materials and crushed stone are one of the most-used technologies for soil improvement all over the world. Stone columns improve the strength and deformation properties of subsoil and reduce the time... more
Stone columns made of coarse-grained materials and crushed stone are one of the most-used technologies for soil improvement all over the world. Stone columns improve the strength and deformation properties of subsoil and reduce the time required for the consolidation of fine-grained soils. The impact of the improvement depends on the properties of the original subsoil as well as the properties of the coarse-grained materials used for the stone columns. The article deals with the effects of the properties of coarse-grained materials for stone columns on the settlement and consolidation times of improved subsoil for the foundation of a factory. Numerical modeling as a 2D task was performed using Plaxis geotechnical software. The numerical analysis included two methods of modeling stone columns in a plane strain model, i.e., one method often used by practical engineers in the region of Slovakia, and one modified method, which allowed for a more accurate determination of the final settl...
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Temporary cofferdams for foundations of bridge pillars are ranked among the demanding constructions, and they often require high resources for their construction. The newly planned bridge over the Danube River in the Komarno city between... more
Temporary cofferdams for foundations of bridge pillars are ranked among the demanding constructions, and they often require high resources for their construction. The newly planned bridge over the Danube River in the Komarno city between Slovakia and Hungary has been designed as an asymmetric cable-stayed bridge with single pillar. The cofferdam made of double – row sheet pile wall of ground plan dimensions of 20 × 44 m is designed for foundation of the pillar. A narrow space between sheet piles will be filled by an atypical concrete.