WO2005017266A1

WO2005017266A1 - Resilient bearing assembly for reinforcement of a non-bearing subsoil

Info

Publication number: WO2005017266A1
Application number: PCT/CZ2004/000046
Authority: WO
Inventors: Ladislav Ptacek; Jan Novotny; Ladislav Halamka; Vaclav Kuba
Original assignee: Quail Spol. S R. O.
Priority date: 2003-08-14
Filing date: 2004-08-10
Publication date: 2005-02-24
Also published as: PL1658404T3; HRP20090552T1; EP1658404B1; EP1658404A1; ES2331885T3; SI1658404T1; DE602004022057D1

Abstract

The invention concerns to a resilient bearing assembly for reinforcement of a non-bearing subsoil. The assembly comprises at least one matrix layer formed by at least one layer of entire tires placed on their sides, and at least one bond layer formed by pieces of portioned rubber products, especially tires. At least 10 percent of weight of the bond layer is formed by the pieces of portioned rubber products. The largest size of the pieces is at least 10 centimetres. In the case the assembly comprises more than two layers, the matrix layer and the bond layer are arranged alternatively within the assembly.

Description

Resilient bearing assembly for reinforcement of a non-bearing subsoil

The present invention concerns to a resilient supporting assembly which enables to perform a groundwork on non-bearing and saturated ground surfaces, especially of sludge beds originated after hydrometallurgic metal processing, and on old dumps .

Number of various reinforcement processes to reinforce non- bearing subsoils were already used with a partial success in the past. For example, material with a low density was placed on a non-bearing saturated surface to create a sort of floating plate which, after a certain period of stabilization, enabled further building activity on such reinforced non- bearing surface. Disadvantage of this method is achievement of only a low strength in tension of the surface layer created in this way and high consumption of the above mentioned material following a caving in of the layer. Another method of reinforcing a non-bearing subsoil consisted in depositing several layers of special textiles inlaid with a mat onto the non-bearing subsoil. Disadvantage of this method is that it is rather costly and special placing devices such as cranes with a long crane arm are necessary. Recently used technology of reinforcement of non-bearing subsoil is described in Czech Republic utility model no.10584. This solution consists in creating a bearing plate consisting of alternating layers formed -by worn-out tires and mixture of ground material and crushed tires. Disadvantage of this reinforcement technique consists in that it can hardly be used in a larger scale so that homogeneity of the layer formed by the mixture of ground and crushed tires is achieved and in that a special device such as loader with a long arm is necessary and in addition, the bearing plate has to be built from one place at the same time in at least three layers so that it is safe to travel thereon. However, substantial disadvantage of this solution is that from, the geomechanic point of view each of the relative thin sub-layers forms a horizontal sliding surface, which considerably decreases strength in tension of the resulting bearing plate.

The object of the invention is to provide supporting assembly, having a satisfactory strength in tension, to be placed on a non-bearing surface and possibly overlaid by soil or similar material .

The object is achieved by resilient supporting assembly according to the present invention, substance of which consists in that it comprises at least one matrix layer formed by at least one layer of entire tires placed on their sides, and at least one bond layer formed by pieces of portioned rubber products, especially tires, wherein at least 10 percent of weight of the bond layer is formed by pieces of portioned rubber products, the largest size of the pieces being at least 10 centimeters, and in the case the assembly comprises more than two layers, the matrix layer and the bond layer are arranged alternatively within the assembly.

Preferably, bond layer of resilient supporting assembly according to present invention comprises at most 25 % by weight, based on the bond layer total weight, of portioned waste non-rubber elastic products especially based on elastomers . Relating to the invention, based upon several experiments, it has been . surprisingly found that fraction of soil material in a bond layer according to CZ UN 10584 i.e. in layer formed by mixture of soil fraction and crushed tires considerably decreases strength in tension of the built bearing layer which, after being overlaid with soil and consolidated by travel or suitable device, tends to deform while creating depressions, which consequently means that the bearing layer forms relatively unstable base for subsequent reclamation or structural activity. Without relying on any particular theory explaining the inconvenient low strength in tension of the bearing plate according to CZ UV 10584 the applicant supposes that strength in tension of bearing plate, after it is compressed, is proportional to a degree of interlinking the layer of entire tires with the layer of portioned tires and that the fraction of soil material in the layer formed by mixture of soil material and crushed tires prevents the interlinking. The term "interlinking" here means an accidental penetration of pieces of portioned tires into integral tires while creating a sort of resilient mattress showing during tensile stress a considerable horizontal resistance. However, it has been found during detailed examination of structure of already compressed bearing plate according to CZ UV 10584 that in places of mutual contact of surface areas of crushed tire pieces and in places of contacts of these areas with side surfaces of integral tires soil material acts as solid lubricant promoting relative sliding movement of the surface areas and thus preventing mutual interlinking of individual components of the bearing plate during its loading.

In contradistinction to the above described prior art solution resilient supporting assembly according to the present invention, bind layer of which does not comprise a soil material, shows, when loaded, substantially perfect interlinking of its components, which leads to a high strength in tension of the compressed bearing assembly and achievement of long term very stable base for subsequent groundwork. Bearing assembly according to invention features, in addition to the already mentioned high tension strength, also a convenient elasticity due to use of a rubber-based material, which eliminates possibility of breaking the bearing assembly during loading or as a consequence of fluctuation of water table.

The term "integral tire" (or "entire tire") for the purpose of this invention means worn-out tire of motorcycles, cars and mobile working machines. However, also worn-out retreated tires, unused defective tires and unused new tires to be disposed of for any reason are meant to fall within the term. Term "tires placed on their sides" here means a tire reclining upon a non-bearing subsoil, upon a preceding tier of tires or upon a bond layer not with its tread but with one of its bases. The term "tire" itself here means tire casing.

Depending upon state of non-bearing subsoil the matrix layer of a resilient bearing assembly according to the present invention may be formed by one layer of tires placed on their sides or by more tiers of tires, one tier on the other, placed on their sides. Tires in each tier of tires placed on their sides are advantageously arranged so that tread of each tire is in contact with treads of adjacent tires. Though the invention mentions as advantageous embodiment of resilient bearing assembly embodiment in which it is a matrix layer of tires placed on their sides that is in contact with a non- bearing subsoil, the invention does not exclude embodiment in which a bond layer formed by pieces of portioned rubber products contacts the non-bearing subsoil. The latter embodiment may be used for example in case of less saturated subsoil when the bond layer promotes a better horizontal anchoring of resilient bearing assembly. Similarly, even if it is advantageous that an upper layer of resilient bearing assembly according to the invention be formed by a bond layer formed by pieces of portioned rubber products, the invention does not exclude solution where the upper layer of resilient bearing assembly is formed by a matrix layer formed at least by one layer of entire tires placed on their sides. This embodiment may be used for example in case of using a relative thin layer of overlaying soil, when the upper matrix layer promotes creation of a firmer surface of reclaimed area.

Term "a rubber product" here means especially a tire as defined above, though other rubber objects, e.g. hoses, fall within the term providing that, after portioning the objects, the resulting pieces are large enough to meet the obligatory requirement for size of the pieces being at least 10 cm in the case the bond layer is formed by these "non-tire" objects (products) only. In the case the bond layer is formed by mixture of portioned tire products and the above mentioned non-tire products and the obligatory requirement mentioning that at least 10 % of the weight of the bond layer should be formed by pieces whose largest size is equal to at least 10 cm is fulfilled by tire fraction itself, then it is possible to use also portioned smaller rubber products in the bond layer, where the obligatory requirement for the minimal size of portioned pieces of 10 cm could not be met. Bond layer of resilient bearing assembly according to the present invention may include portioned waste non-rubber elastic products, especially based on elastomers, forming up to 25 % of the total weight of the bond layer. This embodiment is advantageous in case of need of an ecological utilization of not only rubber waste but also other elastic waste, especially elastomers. All that has been mentioned above for "non-tire" products holds true for non-rubber waste, too.

To achieve mutual interlinking of individual components of the bearing assembly according to the invention and thus to achieve a high strength in tension of the assembly it is necessary that at least 10% of weight of bond layer be formed by pieces of portioned rubber products whose largest size is equal at least to 10 cm. It has been found that when using pieces having a smaller largest size the strength in tension of the assembly decreases rapidly under an acceptable limit. In most cases an optimal situation is when a major part of pieces of the bond layer has its largest size within the range from 15 cm to 100 cm.

When applying the resilient bearing assembly according to the invention to reinforce a non-bearing subsoil it is possible to proceed for example as follows. Approximately half-meter thick matrix layer of worn-out tires is deposited manually or for example by means of a dredge with jaw grab onto a non-bearing subsoil, wherein the tires are deposited side by side so that they lie on side. If the tires are to be deposited onto a place submerged in water e.g. on a sludge lagoon, it is suitable to lower the water level beforehand so that entire tires extend above water lever at least by 15 cm. If it is not technically possible, the matrix layer may be made high up to about 1 meter by laying two layers of tires resting one on the other. Further, the above defined bond layer of portioned tires being high at least 1,5 m is laid onto the matrix layer of entire tires by means of tracked dozer or already mentioned dredge. The thickness of the bond layer is inversely proportional to penetration resistance of redeveloped non- bearing subsoil. When using a tracked dozer, the bond layer of portioned tires must be deposited in parallel to surface that has already been reinforced so that one track of dozer presses freshly delivered layer and the second track moves onto reinforced ground. After depositing resilient bearing assembly according to the invention onto the non-bearing subsoil, the assembly is preferably overlaid with at least 80 cm of soil or similar material and subsequently compacted by travel or by means of a suitable compacting device. In this regard it is to be mentioned that already the uncovered resilient bearing layer is suitable for tracked working machines to travel thereon. During the compacting the bond layer or bond layers are compressed by up to 50% and their components are interlinked with matrix layer of entire tires while creating a resilient bearing mattress which thickness is preferably from 1,5 m to 2,5 m. Surface that has been prepared by the above described procedure enables travel of a heavy mechanization and follow-up works.

Example of embodiment

In the following example a sludge lagoon of uranous slime having width of 50 m and length of 250 m was bridged over to enable a travel of road train with weight of up to 40 t and a heavy structural mechanization over the bridged sludge lagoon. With a view to achieve this entire worn-out tires were distributed at the ends of the sludge lagoon to minimize a gap between the tires. Smaller tires were put into the bigger ones-. When depositing tires towards center of the sludge lagoon, thickness of layer of entire tires was increased according to height of water level up to three times. A bond layer of portioned tires and other products based on rubber mixtures was placed onto the matrix layer of entire tires created in the above described way by means of mechanization. Proportion of coarse fraction having size from 100 mm to 300 mm and length of torn pieces up to 1000 mm prevailed in the bond layer. Thickness of the bond layer at the ends of the sludge lagoon, depending on a degree of delving, was 0,5 m and in its center up to 2,5 m. Layer of soil about 80 cm thick was pushed onto the bond layer by means of a truck dozer and subsequently compacted by travel. Thus, created resilient bearing assembly and especially the bond layer of portioned tires was compressed by up to 40%. As a result, bearing capacity of the resilient bearing assembly covered with soil was considerably increased and especially strength in tension of the assembly was strongly improved. When performing the above mentioned works, care has been taken to minimize pouring of soil into the upper bond layer of portioned tires and to substantially prevent penetration of soil into the interface between the bond layer of portioned tires and matrix layer of entire tires in view of the fact that soil that poured between portioned tires and especially penetrated into said interface prevents mutual interlinking of pieces of portioned tires and their fixation into the matrix layer of entire tires during the compacting of resilient bearing assembly. Before commencement of overbridging works surface of thixotropic slime was provided with monitoring signs, by means of which delving of resilient bearing assembly into sludge bed was measured. After finishing the works, the delving of construction of resilient bearing assembly into the sludge was 0,4 m, which was measured by five signs positioned with mutual distance of 50 meters. During another phase of testing the technology of overbridging a part of a finished assembly was locally loaded by pouring 6 m high block of soil weighing 10 000 t. In this case the delving of the assembly into the sludge was 2,2 m. Thus, it has been certified that it is possible to perform the overbridging of non-bearing surfaces through the technology, resulting in a considerable acceleration of works and savings of used material, since in the case of redeveloping of a similar sludge bed at the same site by a different method the delving made up to 5 meters.

Claims

1. Resilient bearing assembly for reinforcement of a non- bearing subsoil, characterized in that it comprises at least one matrix layer formed by at least one layer of entire tires placed on their sides, and at least one bond layer formed by pieces of portioned rubber products, especially tires, wherein at least 10 percent of weight of the bond layer is formed by the pieces of portioned rubber products, the largest size of the pieces being at least 10 centimeters, and in the case the assembly comprises more than two layers, the matrix layer and the bond layer are arranged alternatively within the assembly.

2. Resilient bearing assembly according to claim 1, characterized in that the bond layer comprises at most 25 % by weight, based on the bond layer total weight, of portioned waste non-rubber, especially elastomers based, elastic products.