SIST-TS CEN/TS 17445:2021
(Main)Geosynthetics - Standard test for the simulation of rainfall-induced erosion on the surface of a slope protected by geosynthetic erosion control products
Geosynthetics - Standard test for the simulation of rainfall-induced erosion on the surface of a slope protected by geosynthetic erosion control products
This specific test serves to determine the protective effect of different geosynthetics against water erosion by heavy rain. The test is performed in a laboratory apparatus and the results serve as a performance test.
Geokunststoffe - Prüfverfahren zur Simulation von durch Niederschlag hervorgerufener Erosion an geosynthetischen Erosionsschutzprodukten
Dieses Dokument legt ein Indexprüfverfahren zur Simulation von durch Niederschlag hervorgerufener Erosion auf einer durch geosynthetische Erosionsschutzprodukte geschützten Böschungsoberfläche fest.
Die Prüfung wird gewöhnlich an in einer festgelegten Atmosphäre konditionierten Messproben durchgeführt.
Die Prüfung ist auf die meisten Geokunststoffe anwendbar, aber besonders für geosynthetische Erosionsschutzprodukte geeignet.
Géosynthétiques - Essai normalisé de simulation de l’érosion induite par la pluie à la surface d’une pente protégée par des produits géosynthétiques de lutte contre l’érosion
Le présent document spécifie une méthode d’essai de référence pour la simulation de l’érosion induite par la pluie à la surface d’une pente protégée par des produits géosynthétiques de lutte contre l’érosion.
L’essai est normalement réalisé sur des éprouvettes conditionnées dans une atmosphère spécifiée.
L’essai s’applique à la plupart des géosynthétiques, mais convient particulièrement aux produits géosynthétiques de lutte contre l’érosion.
Geosintetika - Standardni preskus za simulacijo erozije, ki jo povzroči dež, na površini pobočja, zaščitenega z geosintetičnimi izdelki za nadzor erozije
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS CEN/TS 17445:2021
01-maj-2021
Geosintetika - Standardni preskus za simulacijo erozije, ki jo povzroči dež, na
površini pobočja, zaščitenega z geosintetičnimi izdelki za nadzor erozije
Geosynthetics - Standard test for the simulation of rainfall-induced erosion on the
surface of a slope protected by geosynthetic erosion control products
Geokunststoffe - Prüfverfahren zur Simulation von durch Niederschlag hervorgerufener
Erosion an geosynthetischen Erosionsschutzprodukten
Géosynthétiques - Essai normalisé de simulation de l’érosion induite par la pluie à la
surface d’une pente protégée par des produits géosynthétiques de lutte contre l’érosion
Ta slovenski standard je istoveten z: CEN/TS 17445:2021
ICS:
59.080.70 Geotekstilije Geotextiles
SIST-TS CEN/TS 17445:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TS CEN/TS 17445:2021
CEN/TS 17445
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
March 2021
TECHNISCHE SPEZIFIKATION
ICS 59.080.70
English Version
Geosynthetics - Standard test for the simulation of rainfall-
induced erosion on the surface of a slope protected by
geosynthetic erosion control products
Géosynthétiques - Essai normalisé de simulation de Geokunststoffe - Prüfverfahren zur Simulation von
l'érosion induite par la pluie à la surface d'une pente durch Niederschlag hervorgerufener Erosion an
protégée par des produits géosynthétiques de lutte geosynthetischen Erosionsschutzprodukten
contre l'érosion
This Technical Specification (CEN/TS) was approved by CEN on 11 January 2021 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 17445:2021 E
worldwide for CEN national Members.
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CEN/TS 17445:2021 (E)
Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 7
5 Apparatus . 7
5.1 Slope simulator . 7
5.2 Runoff and Sediment Collection System . 8
5.3 Rainfall simulator . 8
5.3.1 General. 8
5.3.2 Water source . 8
5.4 Disdrometer . 9
6 Soil . 9
7 Specimens . 9
8 Conditioning . 10
9 Calibration . 10
9.1 Setting the rainfall intensity gauges. 10
9.1.1 General. 10
9.2 Rainfall intensity calibration . 10
9.3 Disdrometer preparation . 10
9.4 Rainfall calibration . 11
9.5 Recording of data . 11
9.6 Calculation and expression of results . 11
9.7 Calculate the theoretical values. 12
9.7.1 Calculate the theoretical value. 12
9.7.2 Calculate the theoretical Kinetic Energy . 12
9.7.3 Calculate the terminal velocity vt . 12
9.8 Calibration check . 12
9.8.1 The apparatus shall be considered as satisfactorily calibrated if . 12
9.8.2 The apparatus is considered satisfactorily calibrated . 12
9.8.3 The apparatus is not considered satisfactorily calibrated . 12
9.9 Calibration Frequency . 13
10 Procedure . 13
10.1 Slope simulator preparation . 13
10.2 Rainfall simulator preparation . 14
10.3 Test Operation and Data Collection . 14
11 Test report . 15
11.1 Pre-Test Documentation . 15
11.2 The test report shall include the following information . 15
Annex A (informative) Typical apparatus . 25
Annex B (informative) Modifications to the standard procedure . 28
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Annex C (informative) Calculation and expression of results . 29
Annex D (informative) Evaluation of the C Factor of RUSLE (Revised Universal Soil Loss
Equation) . 31
Bibliography . 35
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European foreword
This document (CEN/TS 17445:2021) has been prepared by Technical Committee CEN/TC 189
“Geosynthetics”, the secretariat of which is held by NBN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
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CEN/TS 17445:2021 (E)
1 Scope
This document specifies an index test method for the simulation of rainfall-induced erosion on the
surface of a slope protected by geosynthetic erosion control products.
The test is normally carried out on specimens conditioned under a specified atmosphere.
The test is applicable to most geosynthetics, but is especially suited to geosynthetic erosion control
products.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 13286-2, Unbound and hydraulically bound mixtures - Part 2: Test methods for laboratory reference
density and water content - Proctor compaction
EN ISO 9862, Geosynthetics - Sampling and preparation of test specimens (ISO 9862)
EN ISO 10318-1, Geosynthetics - Part 1: Terms and definitions (ISO 10318-1)
EN ISO 11074, Soil quality - Vocabulary (ISO 11074)
EN ISO 14688-1, Geotechnical investigation and testing - Identification and classification of soil - Part 1:
Identification and description (ISO 14688-1)
ISO 554, Standard atmospheres for conditioning and/or testing - Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 10318-1, EN ISO 14688-1,
EN ISO 11074, and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp/ui
3.1
disdrometer
laser-optical source that produces a parallel light-beam
Note 1 to entry: The instrument determines the size and fall speed of rain drops by measuring the signal
reduction caused by the drop falling through the light-beam; the amplitude and duration of the reduced signal is
used to estimate the drop size and fall speed, respectively
3.2
test series
test repetitions including at least one test with and without geosynthetic specimens placed in the test
box
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3.3
N
total number of detected raindrops
3.4
n
i
number of detected raindrops in the size class i
3.5
D [mm]
mean
mean drop diameter
3.6
D [mm]
i
drop diameter at the middle of the size class i
3.7
D [mm]
spherical equivalent diameter of the raindrops
3.8
v [m/s]
mean
mean fall velocity
3.9
n
j
number of detected raindrops in the fall velocity class j
3.10
v [m/s]
j
fall velocity at the middle of the fall velocity class j
3.11
R [mm/h]
rainfall intensity
3.12
R(Di) [mm/h]
rainfall intensity for a given drop size class i
3.13
2
A [m ]
disdrometer detection area
3.14
2
KE [J/(m mm)]
kinetic energy of the simulated rain
3.15
−6 3
ρ (10 kg/mm )
water density
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3.16
D [mm]
LP
expected value of mean drop diameter according to Laws and Parsons (1943)
3.17
2
KE [J/(m mm)]
e
expected kinetic energy according to Renard et al. (1997)
3.18
vt (m/s)
terminal velocity of rain drops in still air
4 Principle
The specimen is placed on an inclined steel box filled with the specified soil, simulating a slope. Above
the slope simulator, a rainfall simulator produces a rainfall of controlled characteristics for the specified
duration; the quantity of soil that is eroded by the rainfall is collected, dried, and weighted. The amount
of eroded soil is an index value of the ability of the product to protect a slope against rainfall induced
erosion.
The apparatus shall be able to produce a rainfall with the required characteristics in terms of:
— the rainfall intensity R;
— the mean drop diameter D ;
mean
— the mean drop velocity vmean;
— the kinetic energy KE.
5 Apparatus
5.1 Slope simulator
The slope simulator is made by a rigid box, as shown in Figure 1.
The box shall have minimum dimensions of 1,0 m width x 2,0 m length x 0,10 m depth, with a tolerance
of ± 5 mm.
The base of the box shall not allow free vertical drainage through the soil profile and out of the box,
while containing the soil in the box.
The lower part of the box shall be adapted to separate surface runoff water from water filtrating
through the soil (see Figure 2).
The slope of the box is set at a standard inclination of 1V/2H, that is at an angle β equal to 26,6° from
the horizontal.
The box shall be capable to vary the inclination from horizontal position up to desired inclination (see
Figure 2).
NOTE The box can be vertically positioned such that the centre point of the surface is at approximately
1,00 m over the ground surface, as shown in Figure 2.
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5.2 Runoff and Sediment Collection System
The runoff and eroded soil collection system includes a collection apparatus and holding tanks.
The collection apparatus shall be fabricated to collect direct runoff flow and infiltration flow separately
into the holding tanks, as shown in Figure 2, using either a geomembrane deflector fixed continuously
across the entire bottom edge of the plot or any other suitable method. The infiltration flow may fall
freely into its holding tank, or a specific collection and diversion system can be arranged.
The collecting tanks shall be shielded from the rainfall, that is no rainfall shall fall directly into the tanks.
A nonwoven geotextile with characteristic opening size less than or equal to 75 µm shall be placed
above the tanks for collecting the eroded soil while allowing water to flow into the tanks, as shown in
Figure 2. The geotextile pieces shall be dried and weighted before testing.
5.3 Rainfall simulator
5.3.1 General
The rainfall simulator shall be designed in order to achieve the required characteristics of the rainfall,
i.e. rainfall intensity R; mean drop diameter D ; mean drop velocity v ; kinetic energy KE.
mean mean
Figure 3 and Figures A.1, A.2 and A.3 show a typical rainfall simulator layout.
NOTE 1 Rainfall simulator typically includes a suspension system, pipes, sprinkler nozzles and pressurized
systems giving a range of raindrop sizes, replicating as closely as possible natural rainfall with valves and pressure
gauges for control.
The sprinkler nozzles can be single full-cone nozzles, with spray angle of 120°, in order to model natural
raindrop size and distribution. At least one nozzle is necessary to cover the plot of 1 m x 2 m.
NOTE 2 Additional nozzles can be required to ensure uniform rainfall on the whole test plot.
NOTE 3 A flow control valve and a pressure gauge, capable of maintaining a uniform operating pressure and
the set rainfall intensity can be located on the inlet pipe.
A first estimation of rainfall uniformity and full plot coverage shall be carried out, and tests shall be
performed to adjust the distance between the rainfall generating system and the centre of the slope.
NOTE 4 The use of one mesh (or more meshes, if required) can provide a better distribution of the drops, and
can also increase their size and kinetic energy (Peixeira Carvalho, 2004). The meshes can be made of plastic,
stainless steel, aluminium or any other suitable material. When meshes are used, the vertical distance between the
mesh and the nozzles is 200 mm. Anyway this distance can be adapted to get the required mean drop size and
kinetic energy.
NOTE 5 In order to reduce the height of the installation, experience has shown that with suitable adjustment
the distance between the nozzles or the lowest mesh and the centre point of the specimen placed on the soil in the
slope simulator can be reduced to a typical minimum of 2,50 m, provided that the required characteristics of the
rainfall are met.
5.3.2 Water source
Any water source is suitable provided that it does not contain deleterious materials (like suspended
solids, sand, dust) which could impair the operation of the rainfall simulators.
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5.4 Disdrometer
The simulated rainfall intensity and the speed and size of the drops shall be measured with a Laser
Precipitation Monitor (LPM) or disdrometer.
NOTE Other methods or instruments can be used, provided that their performance match that of the
disdrometer.
The instrument itself, or a computer connected to it and featured with a specific software, shall be able
to provide statistics (distribution, mean value, variance, etc.) of the raindrops size and velocity, and
calculation of the rainfall intensity and the kinetic energy achieved on the horizontal measuring plane of
the disdrometer.
Other methods are acceptable as long as they give at least the required parameters of rainfall intensity,
mean drop diameter, mean drop velocity, kinetic energy KE with the prescribed accuracy.
6 Soil
The test soil shall be defined as a very erodible soil.
The soil mix for the standard test shall be:
— clay (particle size less than or equal to 0,002 mm): 10 % to 14 %;
— silt (particle size in the range 0,002 mm to 0,050 mm): 24 % to 28 %;
— sand (particle size in the range 0,050 to 2,0 mm): 58 % to 62 %.
The target gradation curve for this soil type is shown in Figure 4.
The target plastic index (PI) for the soil shall be approximately 4.5.
The test soil shall be placed in the box in two lifts of 50 mm each and compacted to 90 % of Standard
Proctor density in accordance with test method EN 13286-2.
NOTE Other soil types can be used for non-standard tests, as stated in Annex B.
7 Specimens
A minimum of three specimens shall be tested for each rainfall intensity.
If the erosion protection characteristics of the geosynthetic have previously been established, then for
control purposes it can be sufficient to determine the soil loss on one specimen only.
Take specimens randomly from the sample in accordance with EN ISO 9862.
Specimens shall be cut in 1,0 m x 2,0 m dimensions, or according to the length and width of the rigid
box, with the machine direction placed down the slope or across the slope in accordance with the
manufacturer recommendation.
If the material to be tested is known to have different characteristics on each faces (example a flat face
and a waving face), specimens shall be placed in the slope simulator in accordance with the
manufacturer recommendation.
Specimens shall be placed above the soil that fills the slope simulator.
NOTE Specimens can be either placed without filling or filled with the same soil used in the box and in
accordance with the manufacturer recommendation. The filling conditions are reported in the report.
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8 Conditioning
The test specimens shall be conditioned at standard atmosphere for testing (20 ± 2) °C and (65 ± 5) %
relative humidity as defined in ISO 554.
The specimens can be considered to be conditioned when the change in mass in successive weightings
made at intervals of not less than 2 h does not exceed 0,25 % of the mass of the test specimen.
Conditioning and/ or testing at the standard atmosphere may only be omitted when it can be shown
that results obtained for the same specific type of product (both structure and material type) are not
affected by changes in temperature and humidity exceeding the limits. This information shall be
included in the test report.
Specimens shall be conditioned after cutting, and shall be placed on a horizontal surface in order to
minimize bowing and curling.
9 Calibration
9.1 Setting the rainfall intensity gauges
9.1.1 General
The apparatus is set for calibration of the rainfall intensity as shown in Figure 5.
9.1.2 Place the rainfall simulator (the nozzles, and optionally the meshes) at the prescribed height
above the slope simulator.
9.1.3 Place the box of the slope simulator horizontally, empty, with the top surface approximately.
1,0 m above the floor.
NOTE A horizontal plane of 1 m x 2 m minimum, like a table, with the top surface approximately. 1,0 m above
the ground level, can be used as well.
9.1.4 Place minimum 18 rainfall intensity gauges (e.g. calibrated glasses or an equivalent system)
uniformly in the box, as shown in Figure 5.b.
9.2 Rainfall intensity calibration
9.2.1 Start the rainfall, with the expected intensity, and apply for 30 min, recorded to the nearest
second.
9.2.2 For each rainfall intensity measure the distribution of rainfall intensity in the rain gauges.
9.2.3 If such spatial distribution is not correct according to the criteria set in 9.8, fine tune the water
pressure, flow rate, position of nozzles, and mesh type and position. Repeat until the measured rainfall
intensity is satisfactory.
9.3 Disdrometer preparation
9.3.1 Check that the disdrometer is correctly working, according to its operating instructions.
9.3.2 Place the disdrometer in position, with the laser beam at approx. 1 m above the floor.
9.3.3 Three measurements with the disdrometer positioned vertically below the nozzle and laterally
to it shall be taken, as shown in Figure 6.
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9.4 Rainfall calibration
9.4.1 Start the rainfall, with the expected intensity as calibrated at 9.2.
9.4.2 Measure rain drop diameters, drop velocity and kinetic energy with the disdrometer in the
three positions, for one minute each, or according to the sampling time of the disdrometer.
9.4.3 If the values of mean drop diameter, mean fall velocity, and mean kinetic energy are not correct
according to the criteria set in 9.8, fine tune the water pressure, flow rate, position of nozzles, and mesh
type and position. Repeat until the measured values are satisfactory.
9.5 Recording of data
Record the following for each calibration test:
— rainfall height in each rain gauge;
— number of rain drops in each class of drop diameter set in the disdrometer regulations;
— drop speed in each class of drop diameter set in the disdrometer regulations;
— kinetic energy in each class of drop diameter set in the disdrometer regulations.
9.6 Calculation and expression of results
9.6.1 For the three disdrometer measurements plot the raindrop diameter distribution versus the
raindrop velocity distribution and the kinetic energy distribution. Figure 9 shows examples of such
plots.
9.6.2 From data measured and recorded by the rain gauges and the disdrometer, make the following
calculations:
— the mean drop diameter, D [mm];
mean
— the mean fall velocity, v [m/ s];
mean
— the mean rainfall intensity, R [mm/h];
2
— the kinetic energy KE [J/(m mm)].
Formulas for calculating D , v , R, KE are reported in Annex C.
mean mean
NOTE Disdrometer software usually performs such calculations automatically.
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9.7 Calculate the theoretical values
9.7.1 Calculate the theoretical value
Calculate the theoretical value of the mean drop diameter D according to Laws and Parsons (1943)
LP
formula:
0,182
D = 1,238 ∙ R (1)
LP
where
D is the theoretical mean drop diameter (mm)
LP
R Is the mean rainfall intensity (mm/h)
9.7.2 Calculate the theoretical Kinetic Energy
2
Calculate the theoretical Kinetic Energy KE [J/(m mm)] according to Renard et al. (1997) formula:
e
−4 -0,05 ∙R
KE = 0,29 ∙ 10 ∙ [1 – 0,72 ∙ e ] (2)
e
where
2
KE is the expected Kinetic Energy [J/(m mm)]
e
R is the mean rainfall intensity (mm/h)
9.7.3 Calculate the terminal velocity v
t
Calculate the terminal velocity v as function of the mean diameter D from the chart in Figure 7.
t mean
9.8 Calibration check
9.8.1 The apparatus shall be considered as satisfactorily calibrated if
— the variation between the maximum and minimum rainfall intensity measured by the rain gauges is
less than 30 % of the prescribed value;
— the mean rainfall intensity R is equal to the prescribed rainfall intensity ± 5 %;
— the mean drop diameter D is equal to the theoretical value D ± 30 %;
mean LP
— the mean drop velocity v is equal to the terminal velocity v ± 30 %;
mean t
— the kinetic energy KE is equal to the theoretical kinetic energy KE ± 10 %.
e
9.8.2 The apparatus is considered satisfactorily calibrated
When the apparatus is considered satisfactorily calibrated according to the criteria in 9.8.1, record the
regulations of inlet pressure and flow rate to the nozzles, position of nozzles and meshes, and all other
regulation data for replicating the same conditions for subsequent tests.
9.8.3 The apparatus is not considered satisfactorily calibrated
If the apparatus cannot be considered as satisfactorily calibrated according to the criteria in 9.8.1,
modify the regulations of inlet pressure and flow rate to the nozzles, position of nozzles and meshes,
etc., and repeat the calibration procedure until a satisfactorily calibration is obtained
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9.9 Calibration Frequency
The rainfall simulation calibration for any rainfall intensity (e.g. 100 mm/h) can be used for a maximum
of 10 sets of tests with that rainfall intensity or after a maximum of 1 year, whichever comes first.
10 Procedure
10.1 Slope simulator preparation
10.1.1 The soil shall be previously air-dried and sieved (high frequency mechanical sieve) using a
4,75 mm aperture square-hole mesh in order to breakdown all aggregates, and all vegetative material
and unusual coarser particles shall be removed.
Afterwards, the soil shall be mechanically mixed to guarantee homogeneity for the series of tests to
achieve a uniform depth of 0,1 m when placed in the box.
Lay the test soil in the box in two lifts of identical thickness, and compact to 90 % of standard Proctor
density in accordance with test method EN 13286-2.
To obtain a plane surface, a sharp, straight-edged blade that cou
...
SLOVENSKI STANDARD
kSIST-TS FprCEN/TS 17445:2019
01-december-2019
Geosintetika - Standardni preskus za simulacijo erozije, ki jo povzroči dež, na
površini pobočja, zaščitenega z geosintetičnimi izdelki za nadzor erozije
Geosynthetics - Standard Test for the Simulation of Rainfall-Induced Erosion on the
surface of a slope protected by Geosynthetic Erosion Control Products
Geokunststoffe - Prüfverfahren zur Simulation von durch Niederschlag hervorgerufener
Erosion an geosynthetischen Erosionsschutzprodukten
Géosynthétiques - Essai normalisé de simulation de l’érosion induite par les
précipitations de la surface d’une pente protégée par des produits de contrôle de
l’érosion géosynthétiques
Ta slovenski standard je istoveten z: FprCEN/TS 17445
ICS:
59.080.70 Geotekstilije Geotextiles
kSIST-TS FprCEN/TS 17445:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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kSIST-TS FprCEN/TS 17445:2019
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kSIST-TS FprCEN/TS 17445:2019
FINAL DRAFT
TECHNICAL SPECIFICATION
FprCEN/TS 17445
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
October 2019
ICS 59.080.70
English Version
Geosynthetics - Standard Test for the Simulation of
Rainfall-Induced Erosion on the surface of a slope
protected by Geosynthetic Erosion Control Products
Geokunststoffe - Prüfverfahren zur Simulation von
durch Niederschlag hervorgerufener Erosion an
geosynthetischen Erosionsschutzprodukten
This draft Technical Specification is submitted to CEN members for Vote. It has been drawn up by the Technical Committee
CEN/TC 189.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a Technical Specification. It is distributed for review and comments. It is subject to change
without notice and shall not be referred to as a Technical Specification.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TS 17445:2019 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 6
5 Apparatus . 6
6 Soil . 8
7 Specimens . 8
8 Conditioning . 9
9 Calibration . 9
10 Procedure . 12
11 Test report . 13
Annex A (informative) TYPICAL APPARATUS . 24
A.1 Examples of apparatus . 24
A.2 Miscellaneous equipment . 26
Annex B (informative) Modifications to the Standard Procedure . 27
B.1 Modifications to the standard procedure . 27
Annex C (informative) Calculation and expression of results . 28
C.1 Calculation and expression of results . 28
Annex D (informative) Evaluation of the C Factor of Rusle (Revised Universal Soil Loss
Equation) . 30
D.1 Procedure for evaluating the C Factor of RUSLE . 30
Bibliography . 34
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European foreword
This document (FprCEN/TS 17445:2019) has been prepared by Technical Committee CEN/TC 189
“Geotextiles”, the secretariat of which is held by NBN.
This document is currently submitted to the Vote on TS.
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1 Scope
This document specifies an index test method for the simulation of rainfall-induced erosion on the
surface of a slope protected by geosynthetic erosion control products.
The test is normally carried out on specimens conditioned under a specified atmosphere.
The test is applicable to most geosynthetics, but is especially suited to geosynthetic erosion control
products.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 13286-2, Unbound and hydraulically bound mixtures. — Part 2: Test methods for laboratory reference
density and water content — Proctor compaction
EN ISO 9862, Geosynthetics — Sampling and preparation of test specimens
EN ISO 10318-1, Geosynthetics — Part 1: Terms and definitions
EN ISO 11074, Soil quality — Vocabulary
EN ISO 14688-1, Geotechnical investigation and testing — Identification and classification of soil — Part
1: Identification and description
ISO 554, Standard atmospheres for conditioning and/or testing — Specifications
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 10318-1, EN ISO 14688-1,
EN ISO 11074, and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
disdrometer
laser-optical source that produces a parallel light-beam
Note 1 to entry: The instrument determines the size and fall speed of rain drops by measuring the signal
reduction caused by the drop falling through the light-beam; the amplitude and duration of the reduced signal is
used to estimate the drop size and fall speed, respectively
3.2
test series
test repetitions including at least one test with and without geosynthetic specimens placed in the test
box
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3.3
N
total number of detected raindrops
3.4
n
i
number of detected raindrops in the size class i
3.5
D [mm]
mean
mean drop diameter
3.6
D [mm]
i
drop diameter at the middle of the size class i
3.7
D [mm]
spherical equivalent diameter of the raindrops
3.8
v [m/s]
mean
mean fall velocity
3.9
n
j
number of detected raindrops in the fall velocity class j
3.10
v [m/s]
j
fall velocity at the middle of the fall velocity class j
3.11
R [mm/h]
rainfall intensity
3.12
R(Di) [mm/h]
rainfall intensity for a given drop size class i
3.13
2
A [m ]
disdrometer detection area
3.14
2
KE [J/(m mm)]
kinetic energy of the simulated rain
3.15
3
−6
ρ (10 kg/mm )
water density
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3.16
D [mm]
LP
expected value of mean drop diameter according to Laws and Parsons (1943)
3.17
2
KE [J/(m mm)]
e
expected Kinetic Energy according to Renard et al. (1997)
3.18
v (m/s)
t
terminal velocity of rain drops in still air
4 Principle
The specimen is placed on an inclined steel box filled with the specified soil, simulating a slope. Above
the slope simulator, a rainfall simulator produces a rainfall of controlled characteristics for the specified
duration; the quantity of soil that is eroded by the rainfall is collected, dried, and weighted. The amount
of eroded soil is an index value of the ability of the product to protect a slope against rainfall induced
erosion.
The apparatus shall be able to produce a rainfall with the required characteristics in terms of:
• the rainfall intensity R;
• the mean drop diameter D ;
mean
• the mean drop velocity v ;
mean
• the kinetic energy KE.
5 Apparatus
5.1 Slope simulator
The slope simulator is made by a rigid box, as shown in Figure 1.
The box shall have minimum dimensions of 1,0 m width x 2,0 m length x 0,10 m depth, with a tolerance
of ± 5 mm.
The base of the box shall not allow free vertical drainage through the soil profile and out of the box,
while containing the soil in the box.
The lower part of the box shall be adapted to separate surface runoff water from water filtrating
through the soil (see Figure 2).
The slope of the box is set at a standard inclination of 1V/2H, that is at an angle βequal to 26,6 deg. from
the horizontal.
The box shall be capable to vary the inclination from horizontal position up to desired inclination (see
Annex A).
NOTE The box can be vertically positioned such that the centre point of the surface is at approximately
1,00 m over the ground surface.
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5.2 Runoff and Sediment Collection System
The runoff and eroded soil collection system includes a collection apparatus and holding tanks.
The collection apparatus shall be fabricated to collect direct runoff flow and infiltration flow separately
into the holding tanks, as shown in Figure 2, using either a geomembrane deflector fixed continuously
across the entire bottom edge of the plot or any other suitable method. The infiltration flow may fall
freely into its holding tank, or a specific collection and diversion system can be arranged.
The collecting tanks shall be shielded from the rainfall, that is no rainfall shall fall directly into the tanks.
A nonwoven geotextile with characteristic opening size less than or equal to 75 µm shall be placed
above the tanks for collecting the eroded soil while allowing water to flow into the tanks, as shown in
Figure 2. The geotextile pieces shall be dried and weighted before testing.
5.3 Rainfall simulator
5.3.1 General
The rainfall simulator shall be designed in order to achieve the required characteristics of the rainfall,
i.e. - rainfall intensity R; mean drop diameter D ; mean drop velocity v ; kinetic energy KE.
mean mean
Figure 3 shows a typical rainfall simulator layout.
NOTE 1 Rainfall simulator typically includes a suspension system, pipes, sprinkler nozzles and pressurized
systems giving a range of raindrop sizes, replicating as closely as possible natural rainfall with valves and pressure
gauges for control.
The sprinkler nozzles can be single full-cone nozzles, with spray angle of 120°, in order to model natural
raindrop size and distribution. At least one nozzle is necessary to cover the plot of 1 m x 2 m.
NOTE 2 Additional nozzles can be required to ensure uniform rainfall on the whole test plot.
NOTE 3 A flow control valve and a pressure gauge, capable of maintaining a uniform operating pressure and
the set rainfall intensity can be located on the inlet pipe.
A first estimation of rainfall uniformity and full plot coverage shall be carried out, and tests shall be
performed to adjust the distance between the rainfall generating system and the centre of the slope.
NOTE 4 The use of one mesh (or more meshes, if required) can provide a better distribution of the drops, and
can also increase their size and kinetic energy (PeixeiraCarvalho, 2004). The meshes can be made of plastic,
stainless steel, aluminium or any other suitable material. When meshes are used, the vertical distance between the
mesh and the nozzles is 200 mm. Anyway this distance can be adapted to get the required mean drop size and
kinetic energy.
NOTE 5 In order to reduce the height of the installation, experience has shown that with suitable adjustment
the distance between the nozzles or the lowest mesh and the centre point of the specimen placed on the soil in the
slope simulator can be reduced to a typical minimum of 2,50 m, provided that the required characteristics of the
rainfall are met.
5.3.2 Water Source
Any water source is suitable provided that it does not contain deleterious materials which could impair
the operation of the rainfall simulators.
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5.4 Disdrometer
The simulated rainfall intensity and the speed and size of the drops shall be measured with a Laser
Precipitation Monitor (LPM) or disdrometer.
NOTE Other methods or instruments can be used, provided that their performance match that of the
disdrometer.
The instrument itself, or a computer connected to it and featured with a specific software, shall be able
to provide statistics (distribution, mean value, variance, etc.) of the raindrops size and velocity, and
calculation of the rainfall intensity and the kinetic energy achieved on the horizontal measuring plane of
the disdrometer.
Other methods are acceptable as long as they give at least the required parameters of rainfall intensity,
mean drop diameter, mean drop velocity, kinetic energy KE with the prescribed accuracy.
6 Soil
The test soil shall be defined as a very erodible soil.
The soil mix for the standard test shall be:
• clay (particle size less than or equal to 0,002 mm): 10 to 14%,
• silt (particle size in the range 0,002mm to 0,050 mm): 24 to 28%,
• sand (particle size in the range 0,050 to 2,0 mm): 58 to 62%.
The target gradation curve for this soil type is shown in Figure 4.
The target plastic index (PI) for the soil shall be approximately 4.5.
The test soil shall be placed in the box in two lifts of 50 mm each and compacted to 90 % of Standard
Proctor density in accordance with test method EN 13286-2.
NOTE Other soil types can be used for non-standard tests, as stated in Annex B.
7 Specimens
A minimum of three specimens shall be tested for each rainfall intensity.
If the erosion protection characteristics of the geosynthetic have previously been established, then for
control purposes it can be sufficient to determine the soil loss on one specimen only.
Take specimens randomly from the sample in accordance with EN ISO 9862.
Specimens shall be cut in 1,0 m x 2,0 m dimensions, or according to the length and width of the rigid
box, with the machine direction placed down the slope or across the slope in accordance with the
manufacturer recommendation.
If the material to be tested is known to have different characteristics on each faces (example a flat face
and a waving face), specimens shall be placed in the slope simulator in accordance with the
manufacturer recommendation.
Specimens shall be placed above the soil that fills the slope simulator.
NOTE Specimens can be either placed without filling or filled with the same soil used in the box and in
accordance with the manufacturer recommendation. The filling conditions are reported in the Report.
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8 Conditioning
The test specimens shall be conditioned at standard atmosphere for testing (20 ± 2) °C and (65 ± 5) %
relative humidity as defined in ISO 554.
The specimens can be considered to be conditioned when the change in mass in successive weightings
made at intervals of not less than 2 h does not exceed 0,25 % of the mass of the test specimen.
Conditioning and/ or testing at the standard atmosphere may only be omitted when it can be shown
that results obtained for the same specific type of product (both structure and material type) are not
affected by changes in temperature and humidity exceeding the limits. This information shall be
included in the test report.
Specimens shall be conditioned after cutting, and shall be placed on a horizontal surface in order to
minimize bowing and curling.
9 Calibration
9.1 Setting the rainfall intensity gauges
9.1.1 General
The apparatus is set for calibration of the rainfall intensity as shown in Figure 5.
9.1.2 Place the rainfall simulator (the nozzles, and optionally the meshes) at the prescribed height
above the slope simulator.
9.1.3 Place the box of the slope simulator horizontally, empty, with the top surface approximately.
1,0 m above the floor.
NOTE A horizontal plane of 1 m x 2 m minimum, like a table, with the top surface approximately. 1,0 m above
the ground level, can be used as well.
9.1.4 Place minimum 18 rainfall intensity gauges (e.g. calibrated glasses or an equivalent system)
uniformly in the box, as shown in Figure 5.b.
9.2 Rainfall intensity calibration
9.2.1 Start the rainfall, with the expected intensity, and apply for 30 minutes. Recorded to the nearest
second.
9.2.2 For each rainfall intensity measure the distribution of rainfall intensity in the rain gauges.
9.2.3 If such spatial distribution is not correct according to the criteria set in 9.8, fine tune the water
pressure, flow rate, position of nozzles, and mesh type and position. Repeat until the measured rainfall
intensity is satisfactory.
9.3 Disdrometer preparation
9.3.1 Check that the disdrometer is correctly working, according to its operating instructions
9.3.2 Place the disdrometer in position, with the laser beam at approx. 1 m above the floor.
9.3.3 Three measurements with the disdrometer positioned vertically below the nozzle and laterally
to it shall be taken, as shown in Figure 6.
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9.4 Rainfall calibration
9.4.1 Start the rainfall, with the expected intensity as calibrated at 9.2.
9.4.2 Measure rain drop diameters, drop velocity and kinetic energy with the disdrometer in the
three positions, for one minute each, or according to the sampling time of the disdrometer.
9.4.3 If the values of mean drop diameter, mean fall velocity, and mean kinetic energy are not correct
according to the criteria set in 9.8, fine tune the water pressure, flow rate, position of nozzles, and mesh
type and position. Repeat until the measured values are satisfactory.
9.5 Recording of data
Record the following for each calibration test:
— Rainfall height in each rain gauge,
— Number of rain drops in each class of drop diameter set in the disdrometer regulations,
— drop speed in each class of drop diameter set in the disdrometer regulations,
— kinetic energy in each class of drop diameter set in the disdrometer regulations.
9.6 Calculation and expression of results
9.6.1 For the three disdrometer measurements plot the raindrop diameter distribution versus the
raindrop velocity distribution and the kinetic energy distribution. Figure 9 shows examples of such
plots.
9.6.2 From data measured and recorded by the rain gauges and the disdrometer, make the following
calculations:
— The mean drop diameter, D [mm];
mean
— The mean fall velocity, v [m/ s];
mean
— The mean rainfall intensity, R [mm/h];
— The kinetic energy KE [J/(m2 mm)].
Formulas for calculating D , v , R, KE are reported in Annex C.
mean mean
NOTE Disdrometer software usually performs such calculations automatically.
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9.7 Calculate the theoretical values
9.7.1 Calculate the theoretical value
Calculate the theoretical value of the mean drop diameter D according to Laws and Parsons (1943)
LP
formula:
0.182
D = 1.238ˑR (1)
LP
where
D is the theoretical mean drop diameter (mm)
LP
R Is the mean rainfall intensity (mm/h)
9.7.2 Calculate the theoretical Kinetic Energy
2
Calculate the theoretical Kinetic Energy KE [J/(m mm)] according to Renard et al. (1997) formula:
e
-0.05ˑR
−4
KE = 0.29ˑ10 ˑ [1 - 0.72 ˑ e ] (2)
e
where
KE 2
e is the expected Kinetic Energy [J/(m mm)]
R is the mean rainfall intensity (mm/h)
9.7.3 Calculate the terminal velocity v ,
t
Calculate the terminal velocity v as function of the mean diameter D from the chart in Figure 7.
t mean
9.8 Calibration check
9.8.1 The apparatus shall be considered as satisfactorily calibrated if
— the variation between the maximum and minimum rainfall intensity measured by the rain gauges is
less than 30% of the prescribed value;
— the mean rainfall intensity R is equal to the prescribed rainfall intensity ± 5%;
— the mean drop diameter D is equal to the theoretical value D ± 30%;
mean LP
— the mean drop velocity v is equal to the terminal velocity v ± 30%;
meann t
— the kinetic energy KE is equal to the theoretical kinetic energy KE ± 10%.
e
9.8.2 The apparatus is considered satisfactorily
When the apparatus is considered satisfactorily calibrated according to the criteria in 9.8.1, record the
regulations of inlet pressure and flow rate to the nozzles, position of nozzles and meshes, and all other
regulation data for replicating the same conditions for subsequent tests.
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9.8.3 The apparatus is not considered satisfactory
If the apparatus cannot be considered as satisfactorily calibrated according to the criteria in 9.8.1,
modify the regulations of inlet pressure and flow rate to the nozzles, position of nozzles and meshes,
etc., and repeat the calibration procedure until a satisfactorily calibration is obtained
9.9 Calibration Frequency
The rainfall simulation calibration for any one rainfall intensity (e.g. 100 mm/h) can be used for a
maximum of 10 sets of tests with that rainfall intensity or after a maximum of 1 year, whichever comes
first.
10 Procedure
10.1 Slope simulator preparation
10.1.1 The soil shall be previously air dried and sieved (high frequency mechanical sieve) using a
4,75 mm aperture square-hole mesh in order to breakdown all aggregates, and all vegetative material
and unusual coarser particles shall be removed.
Afterwards, the soil shall be mechanically mixed to guarantee homogeneity for the series of tests to
achieve a uniform depth of 0,1 m when placed in the box.
Lay the test soil in the box in two lifts of identical thickness, and compact to 90% of standard Proctor
density in accordance with test method EN 13286-2.
To obtain a plane surface, a sharp, straight-edged blade that could ride on the top edge of the sidewalls
of the box may be used to remove excess soil. In any case the surface of the soil shall be plane and
smooth.
The bulk density of the soil depends greatly on the degree of compaction; therefore the same mass of
3
soil shall be used each time the box is filled (with approx. density of 16 kN/m for air-dried soil).
To ensure identical initial conditions (e.g. in terms of soil moisture, soil compaction, soil surface
roughness) for the different runs, the soil material in the box shall be entirely removed and replaced
with new air dried soil before each test.
10.1.2 Fix the geosynthetic specimen on the surface of the soil. The geosyntheticshall be fixed with
(see Figure 8):
— A system of clamping on the top of the plot, which shall prevent the specimen to slip down the
slope.
— 5 staples (Ø4 mm, 50 mm x 50 mm), staggered as in Figure 8, or as recommended by the
manufacturer, in order to ensure contact between the specimen and the soil and to avoid bowing
and curling of the specimen.
10.1.3 Place the box centered below the rainfall simulator. Incline the box at 1V/2H, with the center
point of the top surface at approx. 1,0 m above the floor.
10.1.4 Place the tanks for collecting runoff water and infiltration water. A nonwoven geotextile with a
characteristic opening size ≤ 75 µm shall be placed above the tanks for collecting the eroded soil while
allowing water to flow into the tanks, as shown in Figure 2. The geotextile pieces shall be dried and
weighted before testing.
10.1.5 Wet the plot using the rainfall simulation system with low rainfall intensity (5 mm/h) for 20
minutes. Determine the moisture content for the soil with a soil moisture gauge.
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10.1.6 Take photographs or videotapes, or both, of the covered plot prior to testing.
10.2 Rainfall simulator preparation
Set the inlet water pressure and flow rate to the nozzles for the selected rainfall intensity, and all other
settings, according to those established during calibration.
10.3 Test Operation and Data Collection
10.3.1 Be prepared to collect the following test data: operating pressure; nozzles activated; time
rainfall began; time runoff from the plot began; time rainfall stopped; time runoff stopped; final volume
of water in the holding tanks.
10.3.2 Perform minimum one test on a control plot (bare soil) and minimum one test with specimen in
place, for each rainfall intensity.
10.3.3 Perform testing at the desired intensity for 30 min.
10.3.4 Rainfall intensities shall be 100 mm/h as reference.
10.3.5 After the end of the rainfall sequence, continue to collect water in the holding tanks until runoff
ceases.
10.3.6 Measure runoff volume and infiltration volume in litres with a maximum tolerated error of
0,01 l. Runoff and infiltration volumes can be evaluated by continuously measuring the weight of water
in the tanks, correcting for the unit weight of water – soil mix at the end of water collection.
10.3.7 Collect the geotextiles containing the eroded soil from test plot in the runoff and infiltration
holding tanks. Dry geotextiles and soil in the oven at 105 °C. Weigh geotextile and soil together, then
subtract the weight of the geotextile to obtain the weight of soil.
10.3.8 If the water in the tanks shows turbidity or suspended solids, determine the weight of soil that
passed through the geotextile and remained in the tanks. Dry the suspended soil in oven and weigh the
dried soil to 0,1 g accuracy. Add this weight to the weight collected in the geotextiles.
10.3.9 Record general observations regarding the condition of the tested specimen at the end of the
data collection (e.g. any notable deformations or tears in the sample).
10.3.10 Carefully, remove the specimen from the test plot with as little disturbance of the soil as
possible. Note general observations regarding the condition and erosion patterns (rills, etc.). Take
photograph or videotape, or both, to record the condition of the soil.
NOTE Markers can be used to identify any rilling patterns for the pictorial documentation.
11 Test report
11.1 Pre-Test Documentation
11.1.1 Test folder for each test cycle containing: test conditions; geotechnical and soil conditions;
product type; specimens description and placing procedure; photo documentation.
11.1.2 General visual conditions of the plot to be tested; plot treatment; photographs or videotape, or
both, and any supplemental information that is not included in the following sections but is felt to
...
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