Description

SUBBASE LAYER AND METHOD OF ITS REALIZATION

Technical Field

[0001] The invention relates to subbase layer of an engineering structure and method of its realization.

Background Art

[0002] The term engineering structure generally includes structures that are

supposed to transmit load being oriented vertically into the subsoil. They are usually located outdoors, i.e. where they are freely exposed to the weather, or indoors, i.e. inside a construction. The load may be of a static or dynamic character.

[0003] Engineering structures within the meaning of this solution include mainly road constructions intended primarily for road motor vehicles, railroads for rail vehicles, service roads, access roads and parking lots, industrial flooring as well as local structures resulting from modifications of already existing engineering structures, such as trenches, excavations and results of digging across and digging up. Trenches arise by digging the subsoil to a specified depth and they are used to lay pipes with various diameters or another medium carrier such as electric cables. Trenches may be dug in a natural ground - usually newly built structures, or in already existing main bodies of roads - usually reconstructions. A pipe or another medium carrier is located at the bottom of the trench, which is stabilized in space in accordance with applicable legislation. The upper level of the stabilizing layer forms the base for the other layers. Due to land ownership issues, the main bodies of roads are also often used to lay media carriers.

[0004] As a rule, subbase layers are currently created by pouring rock, e.g.

gravel, by layers, each layer being compacted to the bearing capacity prescribed by the project, which is most frequently represented by the modulus of elasticity or the modulus of deformation.

[0005] In the area of roads, the subbase layer already used is mainly cement stabilization or cement-bound aggregate, laid by means of a finisher. In the case of trenches created in the area of roads, one uses mainly soil or gravel dug out from the trench, on which sometimes cement-bound aggregate is put, although this is not always the case, and in this way a base for the application of a trafficable system of asphalt layers or for a trafficable concrete slab of the pavement is formed.

[0006] An upper bearing course is always put on the subbase layer in the case of the above-mentioned types of engineering structures. The selection of the type of the bearing course is influenced by the intended use of the engineering structure at hand. It may consist of asphalt layers, most frequently used in the case of roads for road motor vehicles and parking lots, or of a cement-concrete slab in the case of road and parking lots for motor vehicles and industrial flooring, or an upper back fill in the case of a road for rail vehicle.

[0007] The main disadvantages of the base structures, usually poured and

compacted, that have been used so far include in particular:

[0008] - high labor intensity of making them,

[0009] - the need for compacting each poured layer to the prescribed value,

which carries the risk of uneven compaction and thus also uneven bearing capacity,

[0010] - in the case of poured structures placed outdoors, atmospheric

precipitation can have a significant impact on the quality of the already made and compacted layer,

[001 ] - before applying the upper trafficable layers of a road, it is necessary to wait - usually for months - for the consolidation/natural settlement of the poured subbase layer.

[0012] - the high bulk weight of the used material, which applies load to the

subsoil and which represents a hindrance, particularly in spots where the subsoil has a low bearing capacity.

[0013] In addition, in the case of trenches, surface flatness imperfections may cause a locally increased stress of the road construction, which may result in local damage or even disruption of the road construction or of the pavement. Local damage to the road construction or pavement generally necessitates local surface patching. Possible disputes between the contractor and the client can also result from this during the warranty period for the work. The contractor must return to work after some time, which entails increased costs. The drawbacks also manifest themselves in the road traffic itself because the users of the road or pavement have to move on it at reduced speed, furthermore the chassis of motor vehicles suffer, particularly in the case of trucks on A-roads, and fuel consumption and thus also the load on the surroundings of the roads by air pollutants increases.

Disclosure of Invention

[0014] The object of the invention is to create a subbase layer of an engineering structure with a high bearing capacity, minimized thickness and uniform quality over its entire area and volume, which will, to a significant extent, eliminate the deficiencies of prior art as well as later failures in the use of the engineering structure resulting from non-uniformity/inhomogeneity of the subbase layers used so far.

[0015] Said object is achieved by a subbase layer created according to the

present invention, the essence of which is that it is made up of at least one layer of homogeneous lightweight concrete with a constant relation of components in the flowing concrete mix where at least the bottom layer has geosynthetics on its bottom side.

[0016] For a subbase layer according to the present invention having been

created in a trench or in an excavation, it is advantageous when the edges of the geosynthetics layer are led out towards the surface and are attached to the sides of the trench or excavation.

[0017] Said object is also achieved by a method of creating the subbase layer of an engineering structure according to the present invention, the essence of which is that a geosynthetics layer is laid on the prepared subgrade and the first, lowermost layer of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix is poured on it, and after the first layer has become hard enough to walk, at least one additional layer of homogenous lightweight concrete with a constant relation of the components in the flowing concrete mix is poured, with each further layer being poured when the previous layer has become hard enough to walk on. If the subbase layer is created in a trench or

excavation, it is advantageous when the edges of geosynthetics are led out towards the surface and are attached to the sides of the trench or excavation.

[0018] The lightweight concrete, poured into the space between the prepared subgrade and the upper bearing course, is superimposed gradually, each layer of the lightweight concrete being poured after the previous layer has set, and reinforcement in the form of selected geosynthetics can be placed below each layer of the poured lightweight concrete.

[0019] It is thus advantageous when at least one homogeneous layer of

lightweight concrete with a constant relation of components in the flowing concrete mix above the lowermost layer has a layer of geosynthetics on the bottom side. For a subbase layer created, in this case, in a trench or excavation, it is advantageous when the edges of the said next

geosynthetics layer are led out toward the surface and are attached to the sides of the trench or excavation.

[0020] Consequently, if the method of creating the subbase layer according to the present invention is applied, it is advantageous to lay a geosynthetics layer on the previous layer before pouring the next layer. If a subbase layer is created in a trench or excavation, it is advantageous when the edges of the said next geosynthetics layer are led out towards the surface and are attached to the sides of the trench or excavation.

[0021] In the case of an engineering structure, e. g. a road or its fragment, forces acting from above affect the individual layers and the composition of the layers has to be adapted to the transmission of those forces. The biggest forces/stresses in materials are on the surface and the individual layers gradually spread them to an increasingly large area, so that the contact stress at the interface of adjacent layers gradually decreases as one moves downward. Because lightweight concrete can be manufactured in a wide range of bulk densities, it is thereby possible to change the modulus of elasticity in a suitable way. This means that lightweight concretes with the highest bulk density can be in the highest position, and downwards the density can decrease to a level where the modulus of elasticity

corresponds to e. g. to the modulus of elasticity of the surrounding soil or subsoil.

[0022] It is thus advantageous when a layer of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix below the next layer of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix has a lower bulk density or a lower modulus of elasticity.

[0023] The following relationship between bulk density and the modulus of

elasticity holds for lightweight concretes: the lower the bulk density, the lower the modulus of elasticity, and vice versa. However, this relationship is not a relationship of direct proportionality.

[0024] Lightweight concrete may be effectively poured and in one layer also

effectively processed at a minimum thickness of 5 cm, which in

combination with possibly used geosynthetics on the bottom side of each layer can create a light sandwich construction with a minimum thickness and maximum bearing capacity.

[0025] It is thus also advantageous when each layer of the homogenous

lightweight concrete with a constant relation of components in the flowing concrete mix above the lowermost layer has a layer of geosynthetics on its bottom side. If such a subbase layer is created in a trench or excavation, it is advantageous when the edges of the geosynthetics are led out towards the surface and attached to the sides of the trench or excavation.

[0026] The term lightweight concrete means a mixture of cement, water, additions (they do not have to be included), filling material (it does not have to be included) and admixtures, characterized by a bulk density of less than

[0027] The term prepared subgrade means the original rock or the original subsoil compacted or otherwise processed to the bearing capacity level

prescribed by the detailed design sheet of the construction.

[0028] The term cement means a binder with hydraulic properties in general, i. e. of various kinds and types. [0029] The term water means for example water available at the site of lightweight concrete production, usually potable, but waste water - if its chemical composition is known - or water contaminated by sludge or waste water with an increased pH level is not ruled out.

[0030] The term addition means for example various types of aggregates,

including lightweight aggregate, sand, fine inorganic waste material, sludges, fiber for polydisperse micro-reinforcement etc.

[0031] The term filling material means for example crushed polystyrene waste, crushed polyurethane waste, other crushed waste materials, and possibly also bulk material made from waste materials which mostly end up in a landfill or waste incinerator.

[0032] The term admixture, as a rule, means a chemical admixture modifying the properties of a fresh cement mix, for example a plasticizer improving fluidity, a foaming agent, an air-entraining agent, a retarding or

accelerating admixture, or an admixture curing the cement composite during the start of of the setting process as well as the subsequent hardening process.

[0033] The bulk density of lightweight concrete for the present invention can vary typically in the range of 100 to 1500 kg/m ³ , with the use of higher and lower bulk densities not being excluded. As a rule, the decisive factor for the selection of the appropriate bulk density is the modulus of elasticity.

[0034] The term geosynthetics means a fabric made of synthetic fibers. It can be woven or non-woven. It can be of flat shape or spatial shape. It can be reinforced in one, two or all directions.

[0035] Lightweight concrete with a permanently constant relation of its

components in the flowing concrete mix after pouring it onto the

designated area or into the designated space will create, in conjunction with the selected geosynthetics layer, a "sandwich construction", reinforced against tensile stresses arising at the bottom side/level of its layer under the influence of the load coming from above. The

reinforcement/armoring is created by the fact that the liquid component of the lightweight concrete flows into the structure of the geosynthetics, which entails a joint of the two layers that cannot be dismantled without damaging at least one of the two materials.

[0036] The main advantages of the present invention include a reduced labor intensity compared to the current situation and the resulting reduction of the construction time. It is not necessary to compact the subbase layer. The lightweight concrete perfectly fills the space into which it has been poured, thereby eliminating the formation of pockets. In the case of a trench or excavation, by flowing into the uneven parts of the sides of a trench or excavation, the lightweight concrete creates a local firm fixing, which also contributes to the creation of the required bearing capacity of e. g. a road. Due to the permanently constant relation of its components in the flowing concrete mix, the lightweight concrete creates a homogenous layer with continuous properties all over the cross section, after it has hardened.

[0037] By appropriate selection of the bulk density of each layer, one may also achieve minimization of the thickness of the whole engineering structure while meeting the required bearing capacity in relation to the bearing capacity of the subsoil. Minimizing the thickness of the engineering structure will, in turn, save implementation costs as compared to a replacement of the subsoil, the implementation of which is now in many cases necessary when the subsoil has a low bearing capacity. In the case of a trench or excavation, one may also achieve minimization of the width of the trench or excavation in the road while meeting the required bearing capacity in relation to the bearing capacity of the subsoil. Minimizing the width of the trench or excavation will, in turn, save implementation costs.

[0038] By appropriate selection of the bulk density of the lightweight concrete, it is possible to achieve a different time of the start of the hardness of the layer, which enables acceleration of the application of the upper e. g. trafficable layer, which is important e. g. in road construction.

[0039] By appropriate selection of the bulk density of each layer of the lightweight concrete, it is also possible to achieve a situation where it is possible to perform the usual mounting activities - i.e. for example in halls with mounted technology - on the surface of a layer created in this way, without damaging the surface of the lightweight concrete layer. The upper bearing course can then be applied only after the completion of the mounting of the technology or of the equipment of the hall, i. e. the risk of damaging the upper bearing course during mounting work is eliminated.

Brief Description of Drawings

[0040] The invention is explained in detail in figures, which show schematically a cross section of the layers of the engineering structure with the subbase layer according to the present invention, where

[0041] fig. 1 shows the subbase layer of an engineering structure according to the present invention with one layer of lightweight concrete,

[0042] fig. 2 shows the subbase layer of an engineering structure according to the present invention with several layers of lightweight concrete, and

[0043] fig. 3 shows the subbase layer of an engineering structure according to the present invention in a trench or excavation.

Mode(s) for Carrying Out the Invention

[0044] The examples 1 to 3 below refer to fig. 1 , examples 4 to 6 to fig. 2 and example 7 to fig. 3.

[0045] Example 1

[0046] Layer 2 of selected geosynthetics with lapped joints of min. 5 cm is

loosely laid on the prepared subgrade and the subbase layer 3 consisting of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and thickness according to the project or static calculation is poured on it.

[0047] The subbase layer 3 serves to create the surface of the cover of the

already prepared subgrade 1_, e. g. treated subsoil, as well as to create the subbase layer of the engineering structure. If lightweight concrete with self-levelling properties is used, the processing is very fast and simple. After the subbase layer 3 has become hard enough (to walk on), as a rule after 24 hours, the bearing course 7 with strength parameters and with a composition of layers as prescribed by the project or static calculation is put on the surface prepared in this way. [0048] The function of the bearing course 7 is to spread the load, to which the whole system of layers of the engineering structure is exposed when it is used, and to transmit it to the subsoil. The bearing course 7 may be made up of various materials depending on the intended use of the engineering structure, e. g. asphalt, concrete, earth road construction and the like.

[0049] Example 2

[0050] Layer 2 of selected geosynthetics with lapped joints of min. 15 cm is

loosely laid on the prepared subgrade and the subbase layer 3 consisting of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and thickness according to the project or static calculation is poured on it.

[0051] The subbase layer 3 serves to create the surface of the cover of the

already prepared subgrade 1_, e. g. treated subsoil, as well as to create the subbase layer of the engineering structure. If lightweight concrete with self-levelling properties is used, the processing is very fast and simple. After the subbase layer 3 has become hard enough (to walk on), as a rule after 24 hours, the following is put on the surface prepared in this way: a layer of damp insulation against earth moisture, on which a protection layer -e. g. a selected type of geosynthetics or a separating foil - is put, on which the bearing course 7 with strength parameters and with a composition of layers as prescribed by the project or static calculation is laid.

[0052] The function of the damp insulation layer is to constitute a barrier against the penetration of moisture or e. g. of radon from the subsoil, to which the upper bearing course as well as e. g. the interior of the built structure would be exposed in the case of industrial flooring if there was no damp insulation in the engineering structure. The damp insulation layer may be made up of various materials depending on the intended use of the engineering structure, e. g. weld-on asphalt sheets, plastic foils and the like.

[0053] Example 3

[0054] A layer of selected geosynthetics with lapped joints of min. 15 cm is

loosely laid on the prepared subgrade 1_. A layer of damp insulation against earth moisture is put on the surface prepared in this way. Layer 2 of selected geosynthetics with lapped joints of min. 15 cm is loosely laid on the damp insulation layer. A subbase layer 3 consisting of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and thickness according to the project or static calculation is poured on layer 2.

[0055] The subbase layer 3 serves to create the surface of the cover of the

already prepared subgrade 1_, e. g. treated subsoil, as well as to create the subbase layer of the engineering structure. If lightweight concrete with self-leveling properties is used, the processing is very fast and simple. After the subbase layer 3 has become hard enough (to walk on), as a rule after 24 hours, first a layer of selected geosynthetics or a separating foil and then a bearing course 7 with strength parameters and with a composition of layers as prescribed by the project or static calculation is put on the surface prepared in this way.

[0056] The function of the damp insulation layer is to constitute a barrier against the penetration of moisture or e. g. of radon from the subsoil, to which the upper bearing course 7 as well as e. g. the interior of the built structure would be exposed in the case of industrial flooring if there was no damp insulation in the engineering structure. The damp insulation layer may be made up of various materials depending on the intended use of the engineering structure, e. g. weld-on asphalt sheets, plastic foils and the like.

[0057] Example 4

[0058] Layer 2 of selected geosynthetics with lapped joints of min. 15 cm is

loosely laid on the prepared subgrade 1_. The first, lowermost layer 3 consisting of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and thickness according to the project or static calculation is poured on layer 2.

[0059] The first, lowermost layer 3 serves to create the cover of the surface of the already prepared subgrade 1_, e. g. of treated subsoil, e. g. against atmospheric precipitation or mechanical load, as well as to create the first, lowermost layer of the subbase layer of the engineering structure. If lightweight concrete with self-leveling properties is used, the processing is very fast and simple. After the layer 3 of lightweight concrete has become hard enough (to walk on), as a rule after 24 hours, the next geosynthetics layer, if it is prescribed by calculation, may be laid on the surface prepared in this way and another layer of lightweight concrete 4 may be put on it. After the setting layer 4 of lightweight concrete has become hard enough (to walk on), as a rule after 24 hours, the next layer of geosynthetics, if it is prescribed by calculation, may be laid on the surface prepared in this way and another layer of lightweight concrete 5 may be put on it.

[0060] The bulk density of the lightweight concrete in each layer 3, 4, 5, the

thickness of each layer 3, 4, 5 and the possible place of application of the geosynthetics layer below the individual layers 4, 5 is prescribed by the project or static calculation.

[0061] An additional layer, e.g. the bearing course 7 with strength parameters and with a composition of layers as prescribed by the project or static calculation, may be laid on the surface of the uppermost layer 5 of lightweight concrete.

[0062] The function of the bearing course 7 is to spread the load, to which the whole system of layers of the engineering structure is exposed when it is used, and to transmit it to the subsoil. The upper, bearing course 7 may be made up of various materials depending on the intended use of the engineering structure, e. g. asphalt, concrete, earth road construction and the like.

[0063] Example 5

[0064] Layer 2 of selected geosynthetics with lapped joints of min. 15 cm is

loosely laid on the prepared subgrade 1_. The first, lowermost layer 3 consisting of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and thickness according to the project or static calculation is poured on layer 2.

[0065] The first layer 3 serves to create the cover of the surface of the already prepared subgrade 1_, e. g. of treated subsoil, e. g. against atmospheric precipitation or mechanical load, as well as to create the first subbase layer 3 of the engineering structure. If lightweight concrete with self- leveling properties is used, the processing is very fast and simple. After the setting first subbase layer 3 has become hard enough (to walk on), as a rule after 24 hours, the next geosynthetics layer, if it is prescribed by calculation, may be laid on the surface prepared in this way and another layer of lightweight concrete 4 may be put on it.

[0066] The bulk density of the lightweight concrete in each layer 3, 4, the

thickness of each layer 3, 4 and the possible place of application of the geosynthetics layer below the layer 4 is prescribed by the project or static calculation.

[0067] Damp insulation against earth moisture and, on it, an additional layer, e.g. the bearing course 7 with strength parameters and with a composition of layers as prescribed by the project/static calculation, may be laid on the surface of the layer 4 of lightweight concrete being the uppermost layer in this case.

[0068] The function of the bearing course 7 is to spread the load, to which the whole system of layers of the engineering structure is exposed when it is used, and to transmit it to the subsoil. The upper, bearing course 7 may be made up of various materials depending on the intended use of the engineering structure, e. g. asphalt, concrete, earth road construction and the like.

[0069] The function of the damp insulation layer is to constitute a barrier against the penetration of moisture or e. g. of radon from the subsoil, to which the upper bearing course 7 as well as e. g. the interior of the built structure would be exposed in the case of industrial flooring if there was no damp insulation in the engineering structure. The damp insulation layer may be made up of various materials depending on the intended use of the engineering structure, e. g. weld-on asphalt sheets, plastic foils and the like.

[0070] Example 6

[0071] A layer of selected geosynthetics with lapped joints of min. 15 cm is

loosely laid on the prepared subgrade 1_. A layer of damp insulation against earth moisture is put on the surface prepared in this way. A layer of selected geosynthetics 2 with lapped joints of min. 15 cm is loosely laid on the damp insulation layer. The first, lowermost layer 3 consisting of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and thickness according to the project or static calculation is poured on layer 2.

[0072] The first layer 3 serves to create the surface of the cover of the already prepared subgrade 1_, e. g. of treated subsoil, e. g. against atmospheric precipitation or mechanical load, as well as to create the first, lowermost subbase layer of the engineering structure. If lightweight concrete with self-leveling properties is used, the processing is very fast and simple. After the setting first subbase layer 3 has become hard enough (to walk on), as a rule after 24 hours, the next geosynthetics layer, if it is prescribed by calculation, may be laid on the surface prepared in this way and another layer of lightweight concrete 4 may be put on it.

[0073] The bulk density of the lightweight concrete in each layer 3, 4, the

thickness of each layer 3, 4 and the possible place of application of the geosynthetics layer below the layer 4 is prescribed by the project or static calculation.

[0074] An additional layer, e.g. the bearing course 6 with strength parameters and with a composition of layers as prescribed by the project/static calculation, may be laid on the surface of the layer 4 being the uppermost layer in this case.

[0075] The function of the bearing course 7 is to spread the load, to which the whole system of layers of the engineering structure is exposed when it is used, and to transmit it to the subsoil. The upper layer 5 may be made up of various materials depending on the intended use of the engineering structure, e. g. asphalt, concrete, earth road construction and the like.

[0076] The function of the damp insulation layer is to constitute a barrier against the penetration of moisture or e. g. of radon from the subsoil, to which the upper bearing course 7 as well as e. g. the interior of the built structure would be exposed in the case of industrial flooring if there was no damp insulation in the engineering structure. The damp insulation layer may be made up of various materials depending on the intended use of the engineering structure, e. g. weld-on asphalt sheets, plastic foils and the like.

[0077] Example 7

[0078] Layer 2 of selected geosynthetics with lapped longitudinal and vertical joints of min. 15 cm is laid loosely on the prepared subgrade 1_ into a trench or excavation. The edges of layer 2 of geosynthetics are attached to the sides of the trench or excavation by means of pegs 8. Layer 3 of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and with a thickness according to the project or static calculation is poured on layer 2. This means in practice that the space delimited by the sides of the trench or excavation, the surface of the prepared subgrade 1_ and the upper level of the excavation reduced by the thickness of the upper layers, such as a road, is filled with homogeneous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and the corresponding modulus of elasticity according to the project or static calculation.

[0079] If lightweight concrete with self-leveling properties is used, the processing is very fast and simple. After the setting subbase layer 3 has become hard enough (to walk on), as a rule after 72 hours, the trafficable system of layers of the road, i. e. the bearing course 7 with strength parameters and with a composition of layers as prescribed by the project or static calculation, may be put on the surface prepared in this way.

[0080] The function of the bearing course 7 is to spread the load, to which the whole system of layers is exposed when the road is used and to transmit it to the subsoil. The bearing course 7 may be made up of various materials depending on the intended use of the road, e. g. asphalt, concrete, earth road construction and the like.

[0081] The subbase layer according to the present invention, as illustrated in the figure, can also contain additional layers 4, 5 made of a homogeneous lightweight concrete with a constant relation of components in the flowing concrete mix. [0082] In such an example, layer 2 of selected geosynthetics with lapped joints of min. 15 cm is laid loosely on the prepared subgrade 1_ into the trench or excavation. The edges of layer 2 of geosynthetics are attached to the sides of the trench or excavation by means of pegs 8. The first, lowermost layer 3 of homogenous lightweight concrete with a constant relation of components in the flowing concrete mix with a bulk density and with a thickness according to the project or static calculation is poured on layer 2.

[0083] The first, lowermost layer 3 serves to create the cover of the surface of the already prepared subgrade 1_, e. g. of treated subsoil, e. g. against atmospheric precipitation or mechanical load, as well as to create the first, lowermost layer of the subbase layer of the engineering structure. If lightweight concrete with self-leveling properties is used, the processing is very fast and simple. After the layer 3 of lightweight concrete has become hard enough (to walk on), as a rule after 24 hours, the next geosynthetics layer, if it is prescribed by calculation, may be laid on the surface prepared in this way and another layer of lightweight concrete 4 may be put on it. After the setting layer 4 of lightweight concrete has become hard enough (to walk on), as a rule after 24 hours, the next layer of geosynthetics, if it is prescribed by calculation, may be laid on the surface prepared in this way and another layer of lightweight concrete 5 may be put on it.

[0084] When the additional geosynthetics layers below the additional layers 4, 5 are used, it is also advantageous to attach the edges of the layer of geosynthetics to the sides of the trench or excavation.

[0085] The bulk density of the lightweight concrete in each layer 3, 4, 5, the

thickness of each layer 3, 4, 5 and the possible place of application of the geosynthetics layer below the individual layers 4, 5 is prescribed by the project or static calculation.

[0086] An additional layer, e.g. the bearing course 7 with strength parameters and with a composition of layers as prescribed by the project or the static calculation, may be laid on the surface of the layer 5 being the uppermost layer.

[0087] The above examples are not limiting in terms of, in particular, the number of additional layers 4, 5, 6 of the entire subbase layer body according to the present invention and combinations of the placement of additional layers of geosynthetics below those additional layers 4, 5, 6. The final number and combination of layers of the whole subbase layer body according to the present invention depends on the particular conditions of use and construction requirements at hand.

Industrial Applicability

[0088] The subbase layer according to the present invention can be used for all engineering structures such as built transportation facilities intended primarily for road motor vehicles, transport tracks for rail vehicles, service roads, access roads and parking lots, industrial flooring as well as local structures resulting from modifications of already existing engineering structures, such as trenches, excavations and results of digging across and digging up. The main reason is the low own weight of the subbase layer, which therefore does not apply load on the subsoil, but it is able to transmit the load from above. The wide variability of the strength parameters of lightweight concrete allows to design a composition of layers of lightweight concrete that, in conjunction with the bearing course, meets the required bearing capacity under various conditions of subsoil bearing capacity and, at the same, due to its minimized thickness enables to minimize the volume of earthwork associated with the implementation of the engineering structure at hand.