FI62161B - FOERFARANDE FOER ATT FOERHINDRA TJAELUPPHOEJNINGAR I FINKORNIGMARK SAERSKILT FOER ATT FOERHINDRA TJAELBROTT I GATOR - Google Patents

Description

ΓβΙ ANNOUNCEMENT

JSTa LJ (11) UTLÄGGININOSSKRIFT 62161 (45) ^ (51) Kv.lk.3 / lnt.CI.3 Ε 01 C 3/06

FINLAND — FINLAND W Ptt * nttlh «k« mu (- Pituntanaeknlng 1310 / 7U

(22) Htkamiipilvl - Aiwttknlnpdai 29.0U.7U

(23) AlkMptlvt — GlMghuttdag 29-0U.7U

(41) Tulkit lulktoukal - Bllvlt offumlig 09.12.7U

Patent and Registration Office .... ..... , . ., .., _ ', (44) Nihttvikslpmon | -

Patent- och registerstyrelsan Amttlun utltgd och utl.tkrtftun publicund 30.07.82 (32) (33) (31) Pyydutty utuolkuu * - Begird priority 08.06.73

Austria-Austria (AT) A 505U / 73 (71) Chemie Linz Aktiengesellschaft, Postfach 296, A-U021 Linz,

Austria-Österrike (AT) (72) Wolfgang Roth, Van Nuys, California, USA (7U) Leitzinger Oy (5U) Method for the prevention of frost bumps in fine-grained countries, in particular frost fractures on the streets , särskilt för att förhindra tjälbrott i gator

It is known that soils with a grain structure containing more than 3% by weight of granules up to 0.02 mm in diameter at temperatures below 0 ° C have a tendency to frost bumps. The water between the granules freezes and the ice lenses thus formed create a vacuum in the adjacent, still unfrozen soil layer in the adjacent, water-filled capillaries, which affects the ice lenses as a strong water transfer. Thus, the ice lentils grow rapidly \ further, which eventually leads to frost bumps and softening of the subsoil during the dew cycle due to the addition of water.

The most effective measure against frost damage so far has been considered to be the replacement of soil with frost hazard - up to the expected frost depth - with frost-resistant gravel, which requires a high material cost due to high-grade gravel.

Furthermore, construction methods are known which dimension the support layers and / or carriageway pavements so strongly that they are not damaged by frost protrusions or by softening of the subfloor under traffic loads. Elevated material costs (reinforced concrete road surface, soil stabilizer and the like) also make this method very expensive.

62161 2

Attempts have also been made to successfully preserve frost-hazardous soil with thermal protection before cooling below 0 ° C. However, due to the blocked heat transfer between the road surface and the ground, slippery ice is formed substantially faster on such roads than on non-insulated roads.

Finally, there is a known method which prevents the above-mentioned water transfer with ice sealing webs below the frost boundary. In order to prevent the enrichment of seepage water in the bottom layers compacted in this way, a complex sealing must also be performed from the side and top. In particular, the overhead seal, which is just below the road surface, is then subjected to high stresses (mechanical stress on traffic and risk of breakage at frost temperatures).

The invention is based on the fact that in order to interrupt the water transfer in the soil capillaries in the area of the frost boundary a coarse-porous layer is provided and a water-permeable non-corrosive tissue, felt or fluff leakage web is arranged above and below it to prevent fouling of the filter layer from fine soil layers. Thus, it is possible to provide capillary-breaking filter layers with a thickness of only 10 cm, without the risk of limiting the soil contamination. The structure of such a thin filter layer saves high-quality gravel, as the soil must be very load-bearing below and above the thin filter, but not frost-resistant.

The present invention thus relates to a method for preventing frost bumps in fine-grained soils, in particular frost fractures in streets, by interrupting water transfer in chassis capillaries in the frost boundary area, providing a coarse-grained filter layer of gravel and stones with a grain size of 4-70 mm that the filter layer from above and below is protected against the substrate soil and the soil layer above by a water-permeable, non-rotting synthetic fibrous web of fabric, felt or fluff leaking from fine particles detached from the limiting substrate layers.

The filter layer may consist of loosely arranged granules, such as 3,626,161 gravel, slag or artificial particles, in which case the spaces between the granules must be so large that the resulting seepage water does not remain in the filter due to the capillary action. An example of this capillary effect is in T.W. Lampe & R.v. Whitman, M.I.T. "Soil Mechanics" 1969, page 245, 246 Aufschluss. Thus, a capillary saturation height of 6 cm is shown for the material with a grain size of ^10 = mm.

In any case, the effect according to the invention is achieved only when no capillaries are filled with water over the entire height of the filtrate layer. This is achieved, for example, if a layer height of at least 10 cm is provided with a grain size of 4 mm. If the grain size is smaller, the layer must be raised accordingly, as well as the layer thickness could be reduced with a larger grain size.

The depth position of the pore layer depends on the expected frost penetration depth of the substrate formed or arranged above the filter medium. In principle, the filter should be considered to be below the 0 ° C limit; however, with the good strength and technical properties of the on-top carrier layer, the frost limit below the filter layer can also be calculated without any damage, in which case the resulting ice lenses below the filter are kept within the limits of the high load from the carrier layer and the road surface. In addition, the entire structure above the filter acts as a smoothing layer for both local bumps in the frost period and also in the dew cycle, whereby the ice lenses melt below the filter. In this case, the protection of the filter is particularly important with a fine, water-permeable web of fabric, felt or fluff leakage, as softened soil would otherwise clog the filter pores.

If there is lateral longitudinal drainage, the filter layer should be bent to a roof and connected to it for better drainage. If drainage is missing, then the filter layer can be raised laterally to avoid edge disturbances, in which case it should be noted that the intrusion of daywater is prevented by compaction. Edge disturbances can also be prevented by lateral sealing with soil layers on top of the filter with sealing webs. The protection of the streets against frost damage according to the invention can already be achieved when the filter layer is at least 10 cm high and in the case of a loose mass 4 62161 the minimum grain size is only 4 mm. It is expedient to use filter heights between 15 and 25 cm, in which case the granular material should expediently have a grain size of 8-50 mm. Suitable water-permeable, non-corrosive webs are preferably webs made of thermoplastic active ingredients, such as polyvinyl chloride, polyester, etc. Polyolefins, in particular polypropylene, polyethylene and a copolymer of propylene and ethylene, are particularly preferred due to their ineffective nature.

As such, each of the aforementioned fabric or fluff webs is useful for the purpose of the invention, but protective webs of spunbonded endless yarns are particularly suitable, as they have the advantage of high strength and do not require any chemical bonding. It is sufficient, for example, to be freely reinforced with a needle.

The drawing schematically illustrates the invention with application examples.

Figure 1 shows the arrangement of the filter layer below the expected 0 ° C limit.

Figure 2 shows the case of the 0 ° C limit falling below the filter layer.

Figure 1 shows a road surface pavement made as usual. 2 shows a substrate above a filter layer which is very load-bearing but not frost-proof and thus has no binding property. If the 0 ° C limit 3 is above the filter, then water transfer from the lower base layer 7 is not possible when the pores of the filter layer 5 are so large that they are not filled with water by capillarity and thus cannot act as water transfer bridges between the upper base layer 2 and the lower base layer. 7 between. The upper fabric, felt or fluff bleed web 4 prevents large filter granules from being compressed into the upper substrate layer 2 and fine substrate particles from penetrating from this layer by seepage water. The lower fabric, felt or fluffy leak web 6 serves to protect the filter layer 5 from being pressed into the lower substrate layer 7. In addition, this layer 6 prevents the softened substrate 7 from pumping up 0 ° C below the limit 3 below the filter (see Figure 2).

62161 5

Figure 2 shows the case of lowering the 0 ° C limit 3 to the lower substrate layer 7. When the frost boundary moves due to the interruption of water transfer in the filter layer 5, no water is absorbed from the lower substrate layer 7, additional water is now absorbed from elsewhere. However, the formation of ice lenses in the base layer 7 due to the load thereon from the road surface 1, the upper base layer 2 and the filter layer 5 is strongly prevented. In addition, the upper layers 1, 2 and 5 act as smoothing layers for possible strong local elevations. In dew cycles, the area above the lower base layer 7 has an increased water content and thus a lower bearing capacity due to the melting of the ice lenses formed therein. However, the load-distributing effect of the layers 1, 2 and 5 prevents the road surface 1 from being damaged by traffic loads during the dew cycle. The lower fabric, felt or fluff bleed web 6 then protects the filter layer from penetration or "height pumping" of the softened substrate 7.

Example

To build the street with a bituminous pavement on a clay substrate with a high water content, a lifting transfer was made to a depth of about 66 cm. A needled polypropylene - endless - fiber flow with a surface pressure of 400 g / m 2 was placed and with a tear strength of 16 kp / cm this flux was coated with a 20 cm thick layer of fine gravel with a grain size of 15 to 70 mm in diameter. The gravel layer was covered with polypropylene leak with the same characteristic as the leak under the rolling gravel. A 40 cm thick sealant was then filled and a 6 cm bitumen coating was applied.

The street, which was often a dangerous street area, did not show any frost damage after one winter.