CEN/TS 17445:2021

SLOVENSKI STANDARD
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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.

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
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

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.
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
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
A [m ]
disdrometer detection area
3.14
KE [J/(m mm)]
kinetic energy of the simulated rain
3.15
−6 3
ρ (10 kg/mm )
water density
3.16
D [mm]
LP
expected value of mean drop diameter according to Laws and Parsons (1943)
3.17
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.
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.
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.
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.
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
...