Note: Descriptions are shown in the official language in which they were submitted.
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WO 2007/041975 PCT/DE2006/000611
Protective wall, dyke and method of producing a dyke
The invention relates to a protective wall
according to the preamble of patent claim 1. It also relates
to a dyke according to the preambles of patent claims 12 and
15 and to a method of producing a dyke according to the
preamble of patent claim 24.
Two centuries of floods in only five years have
again made it directly clear to people in Germany the power
and the hazard potential of rising floods and other bodies
of water. Attempts are made to improve the level of
protection by the construction of technical flood prevention
measures such as dykes, barrages, retention basins and other
protective installations (protective walls) . In this case,
special importance is attached to the construction of dykes
at rivers and coasts.
The trapezoidal cross section of a dyke is typical
of its type of construction. The dyke body usually consists
of compacted earth or construction materials with a firm,
effectively rooted grass cover or of a mixture of various
earth and construction materials. For reasons of stability,
the slopes should be 1:3 or flatter, which also brings about
advantages during maintenance and with regard to requisite
measures against wild animals. The slopes at river courses
are as a rule between 1:2 and 1:3, whereas the slopes at
coasts may also be designed to be flatter, at least on the
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sea side.
The crown height of the dykes is based essentially
on the selection of the design flood as an event with a
certain probability of occurrence (recurrence within a
certain period of time) relative to a certain water level.
It is calculated from the high-water level and the
"freeboard" (additional height for raising of the water
level by the wind, wave run-up on the slope, possibly the
effect of an ice jam, and an increased factor of safety). In
the case of new construction, there is also an additional
factor for the settling of the subsoil and the dyke body.
Seepage through the dyke, underflow of the dyke
and the safe dissipation of the seepage water are also
factors determining the cross section. High water levels
continuing for a long time and rapidly falling water levels
impair the stability of the dyke. The risk of the dyke
fracturing increases with the intensity and duration of the
inundation.
If underflow of a dyke occurs, movements of
material and further erosion occur, which make the dyke
increasingly unstable. The hydraulic loading of the dyke
body is also enormous in particular during a flood; if it
becomes too great, the dyke body becomes soaked throughout
and the water flows out of the dyke on the side facing away
from the river or sea.
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As an ideal dyke construction with regard to
stability in the case of a flood continuing for a long time,
the three-zone dyke cross section has proved successful: a
permeable earth supporting body having a water-side wedge of
less permeable earth material, said body, if required for
lengthening the flow path, being integrated with a sealing
wall (curtain wall, thin diaphragm wall, sheet pile wall) in
the subsoil under the dyke or in a deeper-lying dense
stratum. Such a dyke has been disclosed, for example, by
WO 00/34587. Provided here is a waterproof barrier which
extends in the dyke longitudinal direction and vertically up
to below the dyke crown. The barrier is positioned
approximately centrally between the two slopes. The barrier
is of multi-piece construction and has a waterproof membrane
in the center made of a synthetic material. The membrane is
fixed laterally in a foundation in a membrane section folded
like a bellows.
In another embodiment, a dyke revetment for
protecting the slope from penetrating water is provided.
Serving for this purpose is a multi-layered, waterproof
membrane which is anchored in the slope.
Proceeding therefrom, the object of the invention
is to specify a protective wall of the generic type which
effectively prevents or markedly reduces the erosion of a
coast or a bank. The protective wall is to be capable of
being produced at a low cost of construction. The object of
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the invention is also to specify dykes of the generic type
which have improved protection against erosion and can be
produced at a low cost of construction. In addition, a
rnethod of producing a dyke is to be specified.
According to the invention, the object with
respect to the protective wall is achieved by the features
of claim 1.
The protective wall has a planar, plate-shaped or
cubic design which has a section made of a waterproof
construction material. The construction material of the
protective wall is a compound of compacted, mineral
aggregates and an organic adhesive. Mineral aggregates such
as, for example, sand and gravel are construction materials
available in abundance in nature and can be procured on site
in large quantities in a simple and inexpensive manner.
Mixed with an organic adhesive, the construction material
can easily be produced and processed in a viscous
consistency. The protective wall can be extended in a
variety of ways, often in a curved manner, by appropriate
shaping.
In this connection, the good flowability is of
great importance for the processing. In the uncured state,
the construction material, in most combinations, has higher
flowability (consistency class) than freshly mixed concrete.
For the processing of the construction material in
the tidal zone or in the case of wet gravel, it is
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appropriate to use an adhesive that can be cured under the
effect of water. Other suitable adhesives are a two-
component epoxy resin adhesive, a single-component
polyurethane adhesive or a two-component polyurethane
adhesive.
The grain size of the aggregates is preferably
between 0.1 and 0.3 mm. Good water tightness is still
provided for within this range without the screening of the
construction materials having to become too restricted.
Ideally, the permeability coefficient kf of the construction
material is at most 5 x 10-10 m/s.
If larger grain sizes are used, the water
permeability increases. The protective wall is then
suitable, when arranged in the slope region of a dyke, as
water bottom and bank protection and helps to act against
erosion in the coastal and bank region, in which waves or
the wave run-up is/are decelerated and absorbed. In this
case, favorable grain sizes of the aggregates are preferably
between 2 and 150 mm.
The density of the protective wall is also
favorable, which density is higher than that of water and if
need be can be increased and varied by the addition of
steel. The protective wall is therefore effectively
prevented from being washed away especially in the region of
the breakers.
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A further advantage lies in the environmental
compatibility of the construction material. When two-
component epoxy resin adhesive is used as organic adhesive,
for example, the construction material has no toxic effect
at all on mold fungi and is difficult to break down
inicrobially. Nonetheless, substances that can be eluted from
the protective wall can be readily broken down, as material
tests have shown. As washing tests prove, there is no
chemical interaction between water and the constituents of
the construction material. The protective wall can therefore
even be used in dams and enclosures for drinking water
reservoirs.
Finally, after its useful phase, the ground
covering according to the invention can be disposed of in a
washing plant for earth or gravel without adverse
environmental effects. Alternatively, after comminution,
reuse as granulated material is also possible.
In another embodiment, the wall thickness dW of the
protective wall is smaller than the extent in height hW and
length lw. Thus, for example, mat-shaped protective walls can
be produced on site with adhesively bonded gravel and can
then be sunk in the water on a floating pontoon in order to
be used as water bottom protection against erosion (harbors,
sheet pile walls, etc.). Protective walls in a length of 40
m max, a width of up to 25 m and a thickness of up to 50 cm
can be processed in a prefabricated manner on the
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construction site.
With regard to the dyke, the object is achieved
according to the invention by the features of claim 12.
The dyke has a dyke body having an essentially
trapezoidal cross section. A dimensionally stable protective
wall is provided between the inner slope and outer slope and
extends in the dyke longitudinal and vertical directions,
the protective wall being designed according to one of the
exemplary embodiments described above.
In this case, the protective wall acts as a seal.
The seal reduces the seepage water quantities and
contributes to the stability of the dyke. Surface seals on
the water side, as are explained later with respect to the
alternative achievement of the object of the invention
according to the features of claim 15, and core seals (inner
seals) are possible. The protective wall preferably runs in
the dyke body vertically from the dyke crown through the
dyke cross section and is integrated in the ideal case in a
dense soil stratum underpinning the dyke. The protective
wall avoids underflow of the dyke, which underflow would
result in material movements and further erosion, which make
the dyke increasingly unstable.
A barrage sealed in such a way can be designed
with steeper slope angles, as a result of which the dyke
cross section can be reduced, which is of additional
advantage in restricted spatial conditions. Asymmetrical
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positioning of the protective wall with an offset relative
to one of the two slopes is possible as a further variant,
the positioning on the water side further reducing erosion
in the slope on the water side.
Protective walls can also be installed
subsequently in already existing dyke structures and
constitute a simple and efficient method of strengthening
and repairing dykes.
A further solution according to the invention that
achieves the object with respect to the dyke is provided for
by the features of claim 15.
According to the invention, the dyke has a made-up dyke body
comprising a slope on the water side and land side, a
dimensionally stable protective wall being situated in front
of the water-side slope. The protective wall is designed
according to one of the exemplary embodiments explained
above. Favorable angles of inclination a of the protective
wall relative to the water surface lie between 15 and 90
degrees, it being possible for the angle of inclination a to
differ from the slope angle R if, for example, the protective
wall is separately embodied such as to be removed from the
slope. For reliable anchoring of the protective wall, said
protective wall can be fastened by an additional base in the
region of the dyke toe, the slope and/or in the foundation.
The dyke according to the invention has the
advantage that effective slope protection is provided for
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when positioning close to the bank or to the coast and in
the case of dykes with a lower-lying narrow foreshore. A
closed, dense and strongly rooted grass cover offers as a
rule, for dykes, sufficient and efficient slope protection
against flow and wave attack. There is also effective
protection against flotsam (e.g. including tree trunks,
possibly drifting ice floes and ice jam in winter) . This
also applies in the case of frequently recurring high water
levels continuing for a long time.
Enhanced sealing against underflow and seepage can
be effected by virtue of the fact that the protective wall
extends from the dyke body right into the foundation.
The invention permits the construction of steep
slopes (steeper than 1:3), since it protects the dyke body
against damage when embodied as planar protection. In the
case of a rapidly falling water level, a heavy and water-
permeable protective wall as (open) revetment is required
for reasons of stability. An advantageous property of the
invention, according to which the water permeability of the
protective wall can be determined according to the selection
of the grain size, becomes noticeable here. If the
protective wall is to be designed to be water-permeable as
for the above application, grain sizes of roughly above 2 mm
should be used for the mineral aggregates. The grain size
for a waterproof protective wall is accordingly below this.
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A dyke having a protective wall which extends into
the dyke body is constructed by the following method steps:
= incorporating a trench which extends from the dyke crown
or the slope into the depth of the dyke body and in the
longitudinal direction of the dyke,
= filling the trench with a protective wall made of a
construction material consisting of mineral aggregates and
an organic adhesive,
= compacting the construction material, and
= curing the construction material.
In a type of construction in which the protective
wall is put onto the slope, the gravel is in each case
applied in layers up to a height of 300 mm and is then
adhesively bonded with an organic adhesive.
Advantageous embodiments of the invention are
explained below with reference to the attached drawing, in
which:
fig. 1 shows a dyke, designed according to the prior art,
without a protective wall,
fig. 2 shows a schematic cross section of a dyke having a
protective wall extending into the dyke body,
fig. 3 shows a schematic cross section of a dyke having a
protective wall put onto the slope, and
fig. 4 shows a cross section of a dyke having a protective
wall put on a base.
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Fig. 1 shows the typically trapezoidal cross
section of a dyke. The dyke body 1 is constructed above the
foundation 2. In the region of the foundation 2, over the
entire width of the dyke, the "dyke bed", the dyke body 1
runs out into tongue-shaped banquettes 3 on the water and
land side.
The dyke body 1 terminates at the top with the
dyke crown 4. It is usually inclined or arched for draining
toward the water. If not negotiable, it is protected against
erosion (earth removal) by sods. If the dyke crown 4 is used
for inspection with lightweight vehicles or for bicycle
traffic, a paving is required. Banquettes 3 placed on the
land side increase the stability and carry as a rule the
dyke defense path which serves for the maintenance of the
dyke and, in the event of extreme flooding, for the defense
of the dyke. With regard to route directing, dimensions and
paving, the dyke defense paths must therefore permit speedy,
risk-free flow of traffic in an extreme situation and must
be able to absorb the loading by heavy vehicles and
equipment.
Shown in fig. 2 on the basis of the fundamental
type of construction of a dyke is a first embodiment of the
invention, in which the trapezoidal dyke body 1 has a
vertical protective wall 5 for sealing it against erosion.
The essentially flat, plate-shaped protective wall 5 extends
in the longitudinal direction of the dyke and in its height
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froin the foundation 2 right up to the dyke crown 4. Roughly
one fifth of the height of the protective wall 5 extends
into the foundation 2. With its crown-side end, the
protective wall 5 terminates flush with the dyke crowrl 4 and
could serve as part of a dyke path (not shown in any more
detail) . In further sections (not shown) of the dyke, the
protective wall 5 also extends beyond the dyke crown 4. In
its longitudinal direction, the protective wall 5 is
composed of a plurality of wall elements adjoining one
another. As can be seen, the wall thickness dW of the
protective wall 5 is markedly smaller than the extent in
height hw and length lw.
The construction material of the protective wall 5
is a compound of sand and an organic adhesive. Mineral
aggregates such as, for example, sand. The grain size is
between 0.1 and 0.3 mm; therefore the protective wall is
virtually watertight and thus prevents soaking or flushing
of the dyke body.
A second embodiment of a dyke can be seen in fig.
3. There, the protective wall 5 is inclined at an angle of
inclination a to the plane of the foundation 2 and is put
onto the water-side slope 6. In this embodiment, the angle
of inciination a is equal to the slope angle P. The height hw
of the protective wall 5 projects just above the design
high-water level. On the base side, the protective wall
extends right under the low-water level in order to avoid
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erosion even at low water and make possible reliable
anchoring.
An embodiment having improved stability of the
slope-side protective wall 5 in comparison with the second
embodiment is shown with the third exemplary embodiment in
fig. 4. Here, a base 7 anchored in the water-side slope 6
serves for fixing the protective wall 5 against drifting or
sagging in the event of underscouring.
In the second and third embodiments of the
protective wall 5, watertight or water-permeable
compositions of the mineral aggregates are possible.
Of great advantage in the production of the
protective walls 5 is the fact that sand as a mineral
aggregate in applications near the coast is of course
available in practically unlimited quantities.
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List of designations
1 Dyke body
2 Foundation
3 Banquette
4 Dyke crown
Protective wall
6 Slope
7 Base
a Angle of inclination
(3 Slope angle
dW Wall thickness
hW Height
lW Length
