Classifications

• • E—FIXED CONSTRUCTIONS
  • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
  • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
  • E01C3/00—Foundations for pavings
  • E01C3/06—Methods or arrangements for protecting foundations from destructive influences of moisture, frost or vibration

Definitions

• the present invention is related to a road or equivalent construction, and particularly to a construction which is suitable for use in arctic regions.
• the purpose of the present invention is to produce a road or equivalent construction which is light but capable of bearing a load.
• the purpose is also to produce a construction which is suitable for use in frost- susceptible conditions and in regions of permafrost.
• the purpose is to create a construction for which building materials are available also in arctic regions, for example, which do not have materials conventionally used in road building.
• a road or equivalent construction according to the present invention which consists of several layers one on top of the other, is characterized in that it includes at least one layer which essentially consists of hydrophobic peat particles.
• the hydrophobic peat particles are treated with a coating which improves hydrophobicity.
• the road construction or equivalent includes at least one layer which is an essentially continuous steel sheet construction advantageously consisting of troughs which are oriented in the longitudinal direction of the road and cightly joined to each other. It is advantageous to situate such a steel sheet construction immediately underneath the layer essentially consisting of hydrophobic peat construction.
• One advantageous embodiment of the road or equivalent construction according to the present invention includes at least one layer which forms a vapor barrier.
• the steel construction described above simultaneously functions advantageously as a vapor barrier.
• the vapor barrier may also be a layer of plastic.
• its uppermost layer is road pavement material, such as asphalt or oil gravel, which includes peat particles as a base material.
• a road or equivalent construction according to the present invention firstly has the considerable benefit of producing an extremely light and heat-insulating structure whose base material, hydrophobic peat particles, also has sufficient durability.
• the load-bearing capacity of the road is typically 10 - 20 times greater than the load-bearing capacity of the foundation soil, and in some cases it is estimated to be up to 40 times greater.
• a road essentially based on hydrophobic peat particles can be built very economically, while being in all ways extremely suitable for arctic conditions, which typically are problematic due to frost and the poor load-bearing capacity of the foundation soil.
• the steel sheet construction which is advantageous to use, can be produced quickly and easily, and its raw materials are available sufficiently and economically. Furthermore, the steel sheet construction is extremely durable. The possibility of using peat particles as a base material in road pavement further enhances the advantages of the construction according to the present invention.
• Figure 1 shows a flow chart depicting a possible method of producing hydrophobic peat particles used in a road construction according to the present invention
• figure 2(a) shows a layer-like construction of an embodiment of a road or equivalent according to the present invention
• figure 2 (b) shows an embodiment of a road construction corresponding to figure 2(a) according to the present invention
• figure 3 shows another embodiment of a road construction according to the present invention
• figure 4 shows still another embodiment of a road construction according to the present invention
• figure 5 shows an embodiment of a steel sheet construction which is included in certain embodiments of a road construction according to the present invention
• FIGS. 6(a), 6(b) and 6(c) illustrate a possible method of producing a steel sheet construction shown in figure 5 and details of said construction.
• a road or equivalent construction according to the present invention which consists of several layers, is characterized in that at least one layer essentially consists of hydrophobic peat particles.
• the production of hydrophobic peat particles is explained in the following, with references to the flow chart of figure 1, including certain alternative methods of realization, as well as characteristics of the resulting hydrophobic peat particles. It is most recommendable to produce the peat particles in a production facility, to which peat taken from a peat bog is transported and placed in a receiving funnel, for example.
• the peat material is mixed and transported by means of a mixing screw conveyor, for example, in the first phase 42.
• the peat material is transported through a press, which may be a hydraulic or mechanical press, for example. Pressing is advantageously done by means of a tapered extrusion press which shapes the peat material extruded from the press into a rod-like or ribbon-like strip which can be suitably cut, if necessary. Pressing removes water from the peat material and conditions the internal structure of the peat, which still contains a considerable amount of water, in an advantageous manner from the standpoint of further treatment.
• the surface of the rod-like or ribbon-like peat strip obtained from the press is dried in the following phase 44, after which it is capable of keeping its shape fairly well during normal handling. The surface can be dried in a suitable oven that utilizes blown warm air or heat radiation, for example.
• the peat strip or parts cut from the strip are dried further in an essentially airtight and watertight space. Drying can take place in said tight space, in which the peat is placed on a grate and air is forcefully blown through the pieces of peat from below. Moisture from the peat which enters the air is removed with an ordinary dehumidifying device, for example, and the dried air is recircled and blown through the pieces of peat again. Peat treated in this way shrinks very much as it dries and hardens to become a mineral aggregate-like material with a compression strength in the magnitude of 1000 N/cm 2 .
• Hard mineral aggregate-like peat particles created with said method are already hydrophobic as such. Experience has shown, however, that as such they do not withstand very prolonged contact with abundant moisture. This is thought to be so because anaerobic bacterial action first attacks and weakens the surface of the peat particles in moist conditions, allowing moisture to slowly penetrate the peat particles, whereupon bacterial action then continues within the peat particles. 'For this reason, in the next phase 47 the peat particles are treated with a coating that improves hydrophobicity. Suitable coatings include certain mineral aggregate-based coatings, such as chalk, cement and gypsum-based coatings.
• Anaerobic bacterial action is not able to penetrate the mineral aggregate layer on the surface, and the higher pH level of the surface also has a preventive effect.
• Said coatings work well against moisture in the air.
• Peat particles which will be in continuous contact with water should be coated with a film that is impermeable to water, sucn as a bitumen solution or bitumen emulsion film, a pine oil or pine resin film or a silicon film.
• the coating can be applied to the peat particles by means of spraying or immersion.
• hydrophobic peat particles can be produced at the peat bog site from peat strips dried by means of a "wave lump" method by crushing the peat strips and screening them and coating the peat particles.
• the methods suitable for pressing, drying and hardening peat material are not limited to those described above, and many other materials and methods other than those presented above are available for coating particles to improve their hydrophobicity. It is essential that peat particles are produced which are mineral aggregate-like, hardened and as hydrophobic as possible.
• Hydrophobic peat particles can function as a base material in a road construction in the same manner as mineral aggregate-like materials, and they can also function as heat insulation due to their good insulating capacity.
• Peat particles also can be used as a base material of actual paving materials, such as asphalt or oil gravel, either alone or mixed with a mineral aggregate-based base material, for example.
• the peat particles can be fractionated and also used otherwise in the same manner as mineral aggregate-based base materials in accordance with requirements set for pavement.
• the temperature should be kept below 70°C due to the inflammability of peat material.
• road paving material that utilizes peat particles as a base material is a better solution in many cases than mineral aggregate- based pavement due to its elasticity and heat insulating characteristics.
• the use of peat particles as a base material of paving material also • >s an advantageous solution in many arctic regions because it is readily available locally.
• Embodiments of a road or equivalent construction according to the present invention which are particularly intended for arctic regions are decribed in the following.
• recommendable road construction solutions are essentially dependent on whether a road is built when permafrost is prevalent, that is, in autumn, winter or spring, or whether it is built when a thawing layer is prevalent, in other words, in summer.
• the term thawing layer refers to a phenomenon in which the surface frost thaws to a depth of 1 to 2,5 meters, depending on the year, causing the surface layer of the ground to become unstable.
• the foundation soil in permafrost regions typically is very fine-grained silt covered with a rather thin, approximately 150 mm layer of horticultural peat.
• a road or equivalent construction illustrated by figures 2(a) and 2(b) is intended for arctic regions which have permafrost. Layers are built when frost is prevalent on a base 6 which is intended to remain frozen. When the foundation soil is leveled to form a base, it is recommendable that the horticultural surface l yer is not removed in order to keep the fine-grained mineral aggregate layer underneath the surface layer more stable. The purpose of the construction is to insulate the base 6 so well that the frost will not thaw in summer, in other words, an unstable layer will not appear. For this reason, a relatively thick layer of embankment material 4, which essentially consists of hydrophobic peat particles, is laid on top of the base 6.
• Peat particles are good heat insulators, and a 500 - 700 mm layer of material is sufficiently thick.
• a stiffened steel sheet construction 3 On top of the layer of embankment material 4 is a stiffened steel sheet construction 3 forming a system of compartments, which consists of trough-like parts oriented in the longitudinal direction of the road, which are made up of a bottom 31 and walls 32 rising from the bottom.
• the steel sheet construction is explained in more detail below with references to figures 5 and 6(a) - 6(c).
• a layer 2 which may be approximately 150 mm thick and which essentially consists of hydrophobic peat particles.
• an actual pavement layer 1 On top of said layer 2 is an actual pavement layer 1, which may be approximately 120 mm thick and which may be, for example, asphalt or oil gravel which includes peat particles as a base material.
• a pavement layer 1 naturally is to prevent meltwater or rainwater from entering the construction and to function as a surface for traffic.
• the construction is a typical embankment construction with slopes 7 which usually have a surface layer 9 to protect the embankment and help keep the embankment coherent.
• the slopes extend to conventional ditches 8 which lie alongside the embankment.
• the purpose of the layer 4 mainly forming the embankment, which is essentially made up of peat particles, is to bear the load formed by the pavement construction and traffic and distribute the load against the base 6 as evenly as possible.
• the purpose of said layer is to function as a principal heat insulator of the construction and particularly to keep the base 6 frozen in permafrost conditions.
• the purpose of the steel sheet construction 3 on top of said layer 4 is to even the load on said layer 4 and thereby on the base 6 and to improve the load-bearing capacity of the construction in general.
• the layer 2 consisting of essentially hydrophobic peat particles together with the stiffened, compartmented steel sheet 3 form a slab which distributes the load and funct"ions as a base for the pavement layer 1. h ⁇ compartmented construction, in which each adjacent compartment or trough is filled, evens the load in the same manner as do railroad ties when the spaces between the ties are filled.
• the described steel sheet construction is estimated to improve the overall load- bearing capacity by 10 - 20 times compared to conventional embankment solutions.
• the compartmented construction also efficiently prevents the layer 2 on top of the steel construction from spreading and giving way under a load.
• the tight sheet construction 3 together with the layer 2 on top of the sheet construction prevent moisture and heat from entering the layer 4 below.
• the embodiment in figure 3 is intended to be implemented in arctic regions in summer when an unstable layer is prevalent, in other words, when frost in the surface of the ground has partly thawed.
• the purpose of this construction is to improve the load-bearing capacity of the foundation soil which functions as a base 6 and to prevent water and moisture from entering the upper load- bearing layers.
• a plastic film which advantageously is 2 mm thick continuous heavy-duty plastic, is placed on top of the base 6, that is, the unstable foundation soil layer.
• the principal layer 4 of the embankment, which is on top of the plastic may be made up of mineral aggregate material available near the building site, such as silt or fine sand. The thickness of this layer may be 1 meter, for example.
• a steel sheet construction 3 corresponding to the embodiment shown in figure 2 (b) is on top of the principal layer and a layer 2 essentially consisting of hydrophobic peat particles is on top of the steel sheet construction and an actual pavement layer 1 is topmost.
• the thickness of the layer 2 made up of hyrophobic peat particles could be 400 - 500 mm and the thickness of the pavement layer 1 could be approximately 120 mm.
• the embankment construction shown in figure 3 is essentially the same as the construction in figure 2 (b) and its corresponding layers with the same reference numbers have mainly the same functions as in the construction in figure 2(b). Also in this case, it is recommendable that the foundation soil which functions as a base 6 is not loaded in advance and the horticultural layer is not removed from the surface, to keep the foundation soil as stable as possible.
• the purpose of a plastic film 5 is to prevent water from entering the uppermost layers of the construction from the base 6 by means of capillary action or evaporation.
• the foundation soil which functions as a base 6 has very poor load-bearing capacity, due to it being very watery, for example, it may be advantageous to use a sheet construction indicated by reference number 3 in place of a layer of plastic in the interface between said layers.
• the purpose of a compacted layer 4 made up of mineral aggregate material is to improve the load-bearing capacity of the base and even the load caused by the slab construction and traffic.
• the purpose of the steel sheet construction 3 in this case is particularly to prevent water from entering the uppermost layers of the construction from the compacted layer 4 by means of capillary action or evaporation.
• the layer 2 consisting of essentially hydrophobic peat particles is the only actual heat isolating layer, and it is therefore recommendable that it is sufficiently thick to protect the embankment construction below it.
• An embodiment of a road construction according to the present invention shown in figure 4 is especially intended for use in regions with poor load-bearing capacity, such as bogs, clayey areas or soft ground.
• the layers 1. 2 and 3 which form the upper construction of the road are directly on top of the foundation soil which forms the base 6.
• the thickness of the pavement layer 1 may be approximately 120 mm in this case, also, and the thickness of the layer 2 consisting of essentially hydrophobic peat particles may be 500 - 600 mm.
• the basis regarding the foundation soil which forms the base 6 is that unusually large ditches 8 are capable of containing the meltwater and water released by the surroundings so that the water is not able to wet the load-bearing constructions.
• the surface layer of the foundation soil which forms the base 6 is not broken up, but that, for example, fine-grained mineral aggregate-based material is used to level the base, if necessary.
• a particular function of the steel sheet construction 3 which improves the load-bearing capacity is to prevent water from entering the uppermost layers of the road construction by means of capillary action or evaporation.
• the function of the two topmost layers 1 and 2 is the same as in the embodiment shown in figure 3.
• the purpose of the embodiment shown in figure 4 is to create a construction which is as light as possible with as good a load-bearing capacity as possible for regions with ground that has very poor load- bearing capacity. It should be notec that, particularly in boggy areas, a stiffened and compartmented steel sheet construction according to the example embodiments improves the load-bearing capacity more than it normally would. The improvement in load-bearing capacity may be as much as 40 times as great.
• Figure 5 shows a cross sectional perspective view of a steel sheet construction which consists of trough-like parts oriented in the longitudinal direction of a road, which have a bottom 31 and sides 32a and 32b rising from the bottom.
• the walls of adjacent troughs which are placed against each other are joined together at their upper edges by means of seams 33.
• Figure 6(a) shows a cross sectional view of a trough before it is joined to other troughs. It has a bottom 31 and side walls on the left 32a and right 32b whose upper edges have corresponding parts 33a and 33b bent for the purpose of making a seam.
• Figures 6(b) and 6(c) show the walls of troughs which are placed against each other and the manner in which the troughs are joined together.
• the bent part 33a of the upper edge of a wall 32a of a first trough is placed on top of the bent part 33b of the upper edge of a wall 32b of a second trough and bent further with a seaming device so as to bend and squeeze it tightly on top of the bent part 33b of the upper edge of the second trough.
• This forms a tight, four-layered seam which can be bent, if necessary, as shown in figure 6(c) to make the seam even tighter and slightly stiffer.
• This method efficiently stiffens the steel construction and produces very tight seams.
• the troughs are joined together at the upper edges of their walls, their bottom ed es are able to move away from each other an flex, and the construction has the benefit of being able to adapt well to temperature changes, for example.
• Figures 5 and 6 show the trough construction only schematically, and the scale is not true.
• the width of the bottom of the trough may be approximately 30 cm and the walls may be approximately 12,5 cm high, for example.
• the troughs and the steel sheet construction can be produced at a building site from 60 cm wide rolls of thin sheet steel. Easily transportable devices exist for this purpose which, on the one hand, are capable of forming a trough similar to the described trough from material unrolled from a roll and, on the other hand, are capable of joining the troughs together. Said devices are quite automated and easy to use.
• the steel sheet may be 1 mm thick construction steel-quality Z32-strength steel sheet, for example.
• troughs can be produced from noticeably wider thin sheet. In that case, it may be necessary and advantageous to profile the bottom of the trough to add stiffness to the trough.
• this type of steel sheet construction and the method of producing it also can be used in a road or equivalent construction in other ways than together with hydrophobic peat particles to improve the load- bearing capacity of the construction, even the load on the construction and keep the layer of material coherent which is above the steel sheet construction and which fills its troughs or compartments. It is equally as clear that a steel sheet construction which fulfils the same function may be shaped in many other ways which provide sufficient stiffness and which has troughs, compartments or similar forms which, when filled with base material, have an enhancing effect on the load-bearing capacity and coherence of the load-bearing construction.
• a road construction that utilizes hydrophobic peat material also does not necessarily have to include a steel construction like the one presented above or any other similar construction which improves load-bearing capacity, evens the load and strengthens the road construction, and on the other hand, the presented steel sheet construction is a solution that is deemed most advantageous at the present because its raw material is readily available, building can be implemented advantageously at the site with available devices and the result contains many excellent characteristics. An expert in the field can easily visualize very many alternatives for this construction, in which the material and form may be greatly varied.

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• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Road Paving Structures (AREA)
• Building Environments (AREA)

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Cited By (7)

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Citations (3)

• 1994
  • 1994-10-11 FI FI944760A patent/FI103523B/fi active
• 1995
  • 1995-10-11 RU RU97107479A patent/RU2135682C1/ru active
  • 1995-10-11 AU AU36555/95A patent/AU3655595A/en not_active Abandoned
  • 1995-10-11 WO PCT/FI1995/000561 patent/WO1996011302A1/en active Application Filing
• 1997
  • 1997-04-10 SE SE9701312A patent/SE509023C2/sv not_active IP Right Cessation

Patent Citations (3)

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