EP0009272B1

EP0009272B1 - A method for the stabilization of hydraulics works using an open bituminous mixture and a chute for use in this method

Info

Publication number: EP0009272B1
Application number: EP19790200480
Authority: EP
Inventors: Gerardus Rinkel
Original assignee: Bitumarin BV
Current assignee: Bitumarin BV
Priority date: 1978-09-14
Filing date: 1979-08-31
Publication date: 1982-12-22
Also published as: DE2964359D1; EP0009272A1; JPS5539600A; ES484121A1; DK380779A; NL7809351A

Description

Hydraulic works, such as dikes, dams, jetties and breakwaters, are usually subject to severe attack by waves and currents. Fluctuating water levels may also cause loads on the lining of the dam or dike body. In order to protect such works as far as possible against wave action and currents, the slopes are lined with basalt or concrete blocks or with heavy stones. However, it has been observed that such a lining ultimately deteriorates by wave and current action unless artificial elements of very large dimensions are chosen. In particular at high tide and in stormy weather, linings of normally available stones are not always stable enough to withstand the heavy attack by waves and currents. Stabilization against such attack can be obtained by grouting with bitumen or bituminous mixtures so that a water-impermeable structure is obtained.
It has been observed that such a structure has certain drawbacks in that, due to its impermeability to water, a water pressure builds up which may impair the stability of the revetment.
The build-up of a water pressure under the revetment may be caused by the tide, wave suction and as a result of ground water flow.
The invention relates to the use of bituminous mixtures for the stabilization against wave and current action of bottom and bank linings of dikes, canals, dams, harbours, beds formed by dropping aggregate, etc. and to the method for applying said mixtures, in such a way that the build-up of a water pressure under the revetment (designated below as lining or covering course) is prevented.
From the Netherlands patent application No. 6918752 a method is already known for the stabilization against wave attack of hydraulic works, such as banks, dikes and dams, the linings of which are made of stones, which method comprises the laying of a bituminous mixture in patches which penetrate into the lining and thereafter from a discontinuous layer underneath the surface of the lining. This bituminous mixture is an impermeable mixture of bitumen, mineral aggregate and filler.
According to the invention the envisaged object may be achieved in a more effective way by using an open mixture of mastic and mineral aggregate. By mastic is meant here a mixture of bitumen and filler. Open bituminous mixtures, such as for example sand asphalt, generally have insufficient flow properties for good penetration between the stones. However, it has surprisingly been found that certain mixtures of round mineral aggregate and mastic indeed exhibit sufficient flow properties. As a result the use of patches may be dispensed with and complete penetration achieved, while appropriate choice of the mineral moreover gives filter properties to the protecting layer.
The invention relates to a method for the stabilization of hydraulic works, such as linings on slopes, dikes, dams, beds formed by dropping aggregate, which contain a covering course of stone, said course being penetrated with a bituminous mixture, the bituminous mixture being an open mixture of a mineral aggregate and a mastic asphalt, characterized in that the mineral aggregate contains round gravel, and that the mixture is applied so as to penetrate the covering course completely or substantially completely to provide a continuous or substantially continuous layer of the mixture beneath the covering course.
CH-A-496 857 already discloses linings for hydraulic works, which linings consist of an open mixture of bitumen and fine aggregate. To improve the water-permeability the addition of 2-7% of a low molecular weight polymer to the bitumen is said to be essential.
In col. 3, I. 51-55, of this citation it is stated that round aggregates can result into a more favourable water permeability of the open mixture than sharp aggregates. However, nothing is said about penetrating a covering course of stone nor about the present idea of improving the penetrating capacity when penetrating a covering course of stone with the present open mixture.
Furthermore DE-B-1091044 discloses applying a mixture of bitumen, filler, sand and/or gravel under water to stabilize hydraulic works, such as a sub-layer made of gravel, broken stones or other coarse material. The present idea of using an open bituminous mixture containing round gravel and the advantages thereof are not mentioned.
The lining of the present invention is preferably at least 30 cm thick and preferably comprises stones having dimensions of at least 20 cm. It is also possible to apply to the bottom a continuous coating of the bituminous mixture, thereby consolidating the subsurface without allowing groundwater pressures to arise. The round gravel, which is preferably a round and natural gravel or gravel sand, preferably has dimensions of 0.4-15 mm, in particular 1-8 mm, and is preferably mixed with 4-18% by weight, in particular 6-12% by weight, of mastic asphalt which preferably comprises filler, for example approximately 40-60% by weight, in particular approximately 50% by weight, and approximately 60-40% by weight of bitumen, in particular approximately 50% by weight. A particularly suitable bitumen is road-building bitumen having a penetration of 300-1000, in particular of 500-800 (1/10 mm, 25°C, 5 sec., 100 g); plasticizers, such as a mineral oil, and other additives may also be added, such as, for example, natural rubber or synthetic rubber, for example thermoplastic rubber of the poly- styrene/polyisoprene or polybutadiene/poly- styrene type.
The mastic asphalt is prepared separately, and the round, heated and dried gravel is subsequently mixed with the mastic asphalt. After mixing at, for example, 90-140°C the mixture is ready and then preferably contains at least approximately 20% of void volume.
The stone course is preferably completely penetrated with this hot mixture.
By using the present bituminous mixture containing round gravel it is possible for the stone course to be penetrated to be arranged practically directly on any existing sub-layer, it having been found that in addition to a sufficient penetrating capacity and a sufficient filter effect - also in the case of a silt-containing subsurface - sufficient stability is obtained. For these properties it has been found that the use of round gravel is essential.
The wide limits which are given should therefore be viewed in the light of the requirements which the subsurface sets in respect of the filter stability, a coarse, permeable gravel-containing subsurface requires a high degree of permeability; a subsurface of fine sand requires a lower permeability in order to be able to form a sufficiently stable filter.
It has further been found that the present bituminous mixture is capable of filling the voids between the stones within a reasonable period of time, if necessary under water by cold flow.
The method of applying the bituminous mixture may be carried out with a crane, also under water. However, preference is given to a method wherein the covering course is under water, and wherein use is made of a pipe in which the water column present is displaced with the aid of air pressure, the upper end of the pipe being connected to a hopper via an airlock, which prevents air from flowing from the pipe to the hopper but allows the bituminous mixture to pass from the hopper to the pipe and the lower end preferably with a distributing device..
The invention also relates to this method as well as to a chute adapted to apply a bituminous mixture under water, comprising a hopper and a pipe adapted to contain the bituminous mixture, characterized in that the upper end of the pipe is connected to the hopper via an airlock, which prevents air from flowing from the pipe to the hopper but allows the bituminous mixture to pass from the hopper to the pipe; and in that means is provided to supply pressurized air to the pipe.
The pipe as well as the outlet of the pipe are preferably insulated.
The pipe is preferably provided with a pressure relief device of sufficient capacity, preferably comprising a small diameter pipe running parallel with the pipe, the outlet being below the lower extremity of the pipe.
From FR-A-501636 a chute for applying concrete to hydraulic works under water is known.
This chute comprises a closed hopper containing the concrete, a pipe connected to the lower end of the hopper and an inlet for pressurized air at the upper end of the hopper.
Furthermore the above-mentioned DE-B-1091044 discloses a chute for applying a bituminous mixture to a hydraulic works, which chute contains a pipe with an outer skirt which latter one is connected with an inlet for pressurized air. There is no inlet for pressurized air for the (inner) pipe adapted to contain the bituminous mixture, nor is there an airlock at the upper end of the pipe.
Although the water in the pipe is displaced with pressurized air, the difference with the present chute is, that the upper end of the pipe and not the upper end of the (closed) hopper has an inlet for pressurized air. This means that batch-operation, only, is possible with this closed hopper, it having to be filled each time again. The present chute, also owing to the airlock, can operate continuously.
An example of the chute according to the invention is shown in the Figure, in which:

1. represents a hopper
2. an airlock comprising a finned casing
3. an inlet for pressurized air to the insulated pipe 5
4. the water level
5. an insulated pipe
6. a pressure relief device for the insulated pipe 5
7. a distributing device
8. a distance of approximately 5 cm
9. insulation.

With the aid of a chute of this type the bituminous mixture is passed in hot condition to just above the point of application as a result of the fact that the water column present in the pipe is displaced by air. Preferably the bituminous mixture is continuously supplied to the pipe.

Claims

1. A method for the stabilization of hydraulic works, such as linings on slopes, dikes, dams, beds formed by dropping aggregate, which contains a covering course of stone, said course being penetrated with a bituminous mixture, the bituminous mixture being an open mixture of a mineral aggregate and a mastic asphalt, characterized in that the mineral aggregate contains round gravel, and that the mixture is applied so as to penetrate the covering course completely or substantially completely to provide a continuous or substantially continuous layer of the mixture beneath the covering course.

2. A method as claimed in claim 1, characterized in that the covering course which is penetrated is at least 30 cm thick and contains stones having dimensions of at least 20 cm.

3. A method as claimed in claim 1 or 2, characterized in that the round gravel is a round and natural gravel or gravel sand having dimensions of 0.4-15 mm.

4. A method as claimed in any one of the preceding claims, characterized in that 4-18% by weight of mastic asphalt is present in the bituminous mixture and that the mastic asphalt contains approximately 40-60% by weight of filler and approximately 60-40% by weight of bitumen.

5. A method as claimed in any one of the preceding claims, characterized in that the bitumen has a penetration of 300-1000.

6. A method as claimed in any one of the preceding claims, characterized in that the bituminous mixture has a void volume of at least 20%.

7. A method as claimed in any one of the preceding claims, characterized in that the covering course is under water and that use is made of a pipe (5) in which the water column present is displaced with the aid of air pressure, the upper end of the pipe being connected to a hopper (1) via an airlock (2) which prevents air from flowing from the pipe to the hopper but allows the bituminous mixture to pass from the hopper to the pipe.

8. A chute in particular for use in the method of any one of the preceding claims adapted to apply a bituminous mixture under water, comprising a hopper (1) and a pipe (5) adapted to contain the bituminous mixture, characterized in that the upper end of the pipe (5) is connected to the hopper via an airlock (2), which prevents air from flowing from the pipe to the hopper but allows the bituminous mixture to pass from the hopper to the pipe, and in that means (3) is provided to supply pressurized air to the pipe (5).