NO147114B - APPLICATION OF ONE OR MORE COMBINED TEXTILE SURFACE ELEMENTS AS PROTECTIVE MATTER - Google Patents

Abstract

1. A protective mat for covering articles which are to be explosively blasted, characterized in that it consists of a nonwoven textile sheet-like structure of synthetic continuous filaments or staple fibres, which on determination of the tension-elongation behaviour according to DIN 53857 has a tensile strength of 30-100 n/5 cm at 10 % elongation, a tensile strength of 100-400 N/5 cm at 30 % elongation, a tensile strength of 300-800 N/5 cm at 50 % elongation, a tensile strength of 500-950 N/5 cm at 70 % elongation and a tensile strength of 600-1100 N/5 cm at 90 % elongation, and a weight per unit area of at most 800 g/m**2, or that it consists of a plurality of such nonwoven textile sheet-like structures joined side by bonding, such as welding or stitching.

Description

The present invention relates to the use of one or more non-woven textile surface elements joined by welding or sewing, made of staple fibers or preferably endless threads of thermoplastic plastics, preferably of polypropylene or polyester, which surface elements are fixed by thermal treatment or by needling, as a protective mat for uncovering objects to be blown up.

Because in the case of civil blasting work, which frequently has to be carried out in residential areas and industrial areas in the vicinity of objects that must not be damaged or put at risk due to unwanted rubble, being able to capture the detonation wave and possibly thrown fragments of the blasted object, until now the object which were to be blown up, especially at the high-risk points for splinters, covered with straw bales or other pressure-absorbing and in themselves relatively rigid materials such as old spiked rubber tires and the like, at a certain distance from the exposed surroundings so that the detonation wave could distribute over this distance and is intercepted frontally by the detection device.

However, this kind of cover or protection device is expensive to transport and store and requires a considerable amount of work to set up.

It has now surprisingly been found that blast sites can be easily and safely uncovered if they are loosely covered with a fiber pile of endless fibers or stacked fibers of thermoplastic material, and which correspond to special requirements in the force-strain ratio. This loose cover, which must protrude above the blast site to some extent, is raised somewhat by the detonation wave and catches flying rubble without breaking. They can even, very surprisingly, be successfully used several times in succession.

The present invention thus relates to application

of one or more non-woven textile surface elements joined by joining such as welding or sewing of staple fibers or preferably endless threads of thermoplastic plastics, preferably of polypropylene or polyester,

which surface elements are fixed by thermal treatment or by needling, which when determining the tensile-strain ratio according to DIN 53857 at 10% expansion have a tearing strength of 30 - 100 N per 5 cm, at 30% expansion has a tearing strength of 100 - 400 N per 5 cm, at 50% expansion has a tearing strength of 500 - 950 N per 5 cm and at 90% expansion has a tearing strength of 600 - 1100 N per 5 cm, and has a surface weight of no more than 800 g per m <2>, as a protective mat for uncovering objects to be blown up.

The fleece used as a protective mat can be tied either by sewing or thermally. Polypropylene, crystalline copolymers of propylene and ethylene and polyester should be mentioned above all as thermoplastic material that can be used for the production of the protective mat.

A method for uncovering objects to be blasted using one or more such protective mats consists in the place to be blasted being loosely uncovered with one or more such mats, so that these cover the blasting site and a zone of at least 1, 5 m around the blast site.

If the blasting mat is to fulfill its function with high safety and with repeated use, a stress in the average strain range of 10 - 80% is appropriate, so that irregular pressure shocks, or breaking impacts, which are caused by unpredictable inhomogeneities in the object's structure, safely can be intercepted. If a larger mat surface is required for the safe detection of the blasting object than the normal web width for the floor allows, two or more floor sheets can be tied together along the edges by overlapping welding or stitching, or a 1.5 - 2 m wide overlapping , loose pavement already be sufficient to capture the detonation wave. Furthermore, it may be appropriate when laying out the mats to fold in the outermost 0.5 m on the underside. When laying out, care must be taken that the flora remains mobile everywhere. Binding or weighing down the mat will lead to damage or penetration. It is advantageous on the surface of the blasting field, i.e. under the mat, to cover laid-out detonating fuses, explosive caps, electric igniters and detonation delays with sand against the mat, or possibly to lay the mat at a small distance from the detonation points.

To avoid the danger of static charging of the mat, which can lead to premature and uncontrolled ignition of detonating fuses and the like, the mat should undergo an antistatic treatment before use.

The object of the invention shall be explained in more detail with the help of the accompanying examples.

The fleece used had the following technical data: Polypropylene fiber fleece of continuous fibers, sewn. Pile strength: 3.5 mm.

Weight: 350 g/m<2>.

Fracture expansion, wet-frozen at -20°C: 40%. Tensile expansion ratio according to DIN 53857: 100 N/5 cm at 10%, 400 N/5 cm at 30%, 600 N/5 cm at 50%, 700 N/5 cm at 70% and 900 N/5 cm at 90 % strain.

Impact strength: No impact at 30 kg dropped from a height of 2 m.

This fleece was obtained by a common production method for fiber fleece with endless fibers by spinning, pulling through air and depositing on a suitable substrate.

Example 1

Blasting of 4 concrete pillars (for former mineral oil tanks) in an urban area in the immediate vicinity of an electrified railway line.

Explosive object's target:

Length: 2.40 m, width 0.48 m,

height: between 0.90 and 1.40 m.

Mass: approx. ch /socket.

Reinforcement: 10 pieces of "Tor" steel, diameter 14 mm as longitudinal reinforcement and "Tor" steel hoops as

transverse reinforcement.

Drill holes: 5 pieces, diameter 36 mm, depth 70 - 89 cm. Charge: 90 g gelatin donarite 1, caliber 30 mm/borehole. Filling: complete filling.

Ignition: Electric with time steps 1-5 from south to north. Objects to be protected: in the west: railway lines.

in the north: road and building.

in the east: operational building, fire wall.

in the south: car park and building.

Uncovering blast fields: 2 pcs. sewn together polypropylene fiber pile mats of endless fibers measuring 5-10 m. The mats were laid by two men so that they protruded approx. 1.5 m out over the blast field and overlapped each other by 1.5 m. At the edges, they were bent under the mat approx. ch.

Spreading effect: negligible due to the explosion. Some smaller pieces of concrete were found in approx. 5 m distance from the blast field.

The mats were completely intact after the explosion.

Example 2

Blasting of a further 4 concrete plinths east of the blasting site. Prerequisites as in example 1.

Spreading effect: small, no damage.

The condition of the mats as before test 1 and 2. The mats were not damaged to any significant degree either in two further tests.

Example 3

Flat blasting in a quarry for stone production for gravel works.

Dimensions: 4 drill holes, diameter 36 mm, depth 0.75 m, 1 drill hole

36 mm diameter, depth 1 m.

Filling length: 60 - 80 cm (complete filling). Drill hole distance: approx. 80 cm.

Charge: 4 x 130 g and 1 x 178 g gelatin-donarit 1, caliber 30/200.

Ignition: electric torque ignition.

Uncovering the blast field: 1 pc. sewn together polypropylene endless fiber mat with dimensions 5 x 5 m, which gave a cover of approx. 2 m beyond the blast field.

Condition of the mat after blasting: completely fine, none

damage.

Example 4

Blasting of two concrete plinths below those in the example

2 stated assumptions. In contrast to example 2, a needle-fastened polypropylene staple fiber pile with the following characteristics was used as a cover mat:

Flat weight: 400 g/m<2>.

Stretch-expansion ratio according to DIN 53857: 70 N/5 cm at 10%, 300 N/5 cm at 30%, 550 N/5 cm at 50%, 700 N/5 cm at 70% and 800 N/5 cm at 90% strain.

With the same filling and ignition conditions, no significant spreading effect could be determined and only fairly minor damage to the mat.

Claims (1)

Application of one or more joined non-woven textile surface elements of staple fibers or preferably continuous threads of thermoplastic plastics, preferably of polypropylene or polyester, which surface elements are attached by thermal treatment or by needling, which are joined by welding or sewing, which when determining the tension-strain ratio according to DIN 53857 at 10% expansion has a tear strength of 30 - 100 N per 5 cm, at 30% expansion has a tearing strength of 100 - 400 N per 5 cm, at 50% expansion has a tearing strength of 300 - 800 N per 5 cm, at 70% elongation has a tearing strength of 500 - 950 N per 5 cm and at 90% expansion has a tearing strength of 600 - 1100 N per 5 cm, and has a surface weight of no more than 800 g per m 2, as a protective mat for uncovering objects to be blown up.