INTRODUCTION Evaluation of Nonwoven Geotextile As a Filtration Layer for Internally Unstable Soils

10.2478/v10060-008-0042-1

Annals of Warsaw University of Life Sciences – SGGW Land Reclamation No 40, 2008: 107–114 (Ann. Warsaw Univ. of Life Sci. – SGGW, Land Reclam. 40, 2008)

Evaluation of nonwoven geotextile as a ﬁ ltration layer for internally unstable soils DARIUSZ WOJTASIK Department of Geotechnical Engineering, Warsaw University of Life Sciences – SGGW

Abstract: Evaluation of nonwoven geotextile building (Huang and Gao 2008). The as a fi ltration layer for internally unstable soil. use of this material, instead of mineral This paper presents the laboratory tested results fi lter, reduces earth work, increases evaluating the performance of three nonwoven geotextile material used as fi ltration layer to stabilization and the speed of installation. protect for three internally unstable soils. Test In many cases, it also decreases the load research was performed in apparatus ASTM-D- on the structures. -5101 (1990) which was modifi ed through installed A lot of studies and research have additional piezometers in distance 4 mm and 8 been carried out around the word in the mm above geotextile material tested. Applied piezometers ensure measurements pressure in last decades to evaluate the behavior of layer of soil situated near fabric. Laboratory geotextile either in the laboratory (Giroud test were performed for total hydraulic gradient 1982, Heerten 1983) or in the fi eld, and in range i = 1 to 10. Base on the test result the to defi ne design criteria (Calhoun 1972, relationship for the evaluation of the change soil Lawson 1987). The selection criteria of gradient ratio (soil layers 17 and 4 mm above the geotextile) is proposed. geotextile for specifi c fi lter application must consider three conditions (Fisher et Key words: geotextile, gradient ratio GR, hydraulic al. 1999): gradient, soil gradient ratio SGR. 1. Permeability-the geotextile must allow water to fl ow freely from soil situated INTRODUCTION near surface of the geotextile, 2. Retention-the geotextile must retain the Geotextiles are synthetic permeable majority protected of the soil particles, textile material used with soil, rock 3. Clogging-fl ow through the geotextile or any other geotechnical engineering must not be restricted such that excessive related material. Geotextiles are used pore pressures can develop. in soils to perform many functions such One of the tests used to determine the as: reinforcement, separation, drainage soil-geotextile system permeability and and fi ltration. They are used as fi lters clogging behavior is the gradient ratio in many applications such as e.g.: road test ASTM D-5101 (1990). The method drainage systems, agriculture drainage uses the critical point GR = 1 which and under geomembrances in retaining indicates that geotextile during test has pounds (Rollin 1986). In the 90s, about no effect on the hydraulic fl ow through 500 million m2 of geotextile was used the soil-geotextile system and the soil is annually only in North America in earth internally stable. The clogging in soil- 108 D. Wojtasik geotextile system is then when the values Experimental conditions and of gradient ratio are GR > 1. measurements The main objective of this paper is The tested soils were dried (under to present a series of laboratory tested 105°C for 24 h) and sieved with mesh results on internally unstable soils and 2 mm. The soil was placed around the nonwoven geotextile material. The geotextile material. In order to avoid and results are compared with those presented remove the air trapped in the tested soil by Haliburton and Wood (1982). and geotextile material, the water was delivered into the apparatus from bottom METERIAL AND METHODS to the top slowly in the beginning for 12 hours. Flow direction was then changed The characteristics and properties of the (i.e. from top to bottom). The temperature nonwoven geotextile material and the of the water was 20°C. When the water soils used in this study are given below. fl ow reached a stable (steady) condition, Geotextiles: Three K-500 geotextile the following measurements were taken material (Geo1, Geo2 and Geo3) were for each of the hydraulic gradients (i) at used in test. The values of apparent 1.0, 2.5, 5.0, 7.5 and 10.0. opening size and transsmisivity fl ow • temperature of water fl ow (T), obtained from the manufacturer. The • volume of fl ow (V), physical and hydraulic properties tested • time of fl ow (t), geotextiles showed in Table 1. • pressure of individual piezometer Soils: Tested soils are identifi ed as (∆h). slightly clayey sands (Fig. 1). Their physical and hydraulic properties are Experimental setup given in Table 2. The soils G2 and G3 The soil-geotextile testing system was were prepared as a mixed sand and carrying out by using the apparatus shown silt medium. Tested soils are internal in Figure 2. It is a modifi ed apparatus unstable according to the Kenney and from the ASTM D 5101-90 standard by Lau (1985) method the assessment of installing additional piezometers (6 and internal stability soils. 7) in order to obtain additional pressure

TABLE 1. Properties of tested geotextile material, K-500 Properties Parameters values Physical Geo1 Geo2 Geo3 Thickness for the applied load 2 kPa, g [mm] 5.15 5.19 5.31 2 Mass per unit area, μA [g/m ] 526.4 521.1 515.8 Apparent opening size, O90 [mm] 0.06 0.06 0.06 Hydraulic –4 –4 –4 Hydraulic conductivity (Cross-plane fl ow), kv [m/s] 5.8 × 10 5.6 × 10 5.4 × 10 2 –3 –3 –3 Transmissivity (In-plane fl ow), kh [m /s] 2.7 × 10 2.7 × 10 2.7 × 10 Evaluation of nonwoven geotextile as a fi ltration... 109

Fractions

Clay Silt Sand Gravel Cobl. 100 90 Soil G1 80 Soil G2 70 60 Soil G3 50 40 30 Percentagepassing d, [%] 20 10 0 0.001 0.01 0.1 1 10 100 Grain size d, [mm] FIGURE 1. Grain size distribution of tested soil

TABLE 2. Physical and hydraulic properties of tested soils Properties Parameters values Physical Slightly Clayey Sand G1 G2 G3 Fractions Sand [%] 83 82 70 Silt [%] 8 14 25 Clay [%] 9 4 5 Coeffi cient of uniformity, Cu [-] 37.5 5 6 Coeffi cient of curvature, Cc [-] 12.4 2.1 1.2 Size (diameter) d90 [mm] 0.47 0.21 0.21 d60 [mm] 0.30 0.14 0.12 d10 [mm] 0.008 0.03 0.02 3 Density of dry soil, ρd [t/m ] 1.96 1.70 1.79 Hydraulic 4.9 ×10–4 2.8 ×10–4 6.3 ×10–5 Permeability coeffi cient, k [m/s] measurements in layer of soil situated – zone 6–8 (geotextile and 8 mm near geotextile material. The following layer of soil between piezometers piezometer readings were taken in 6 to 8), individual zones. – zone 4.5–8 (geotextile and 25 mm • for soil-geotextile: layer of soil between piezometers – zone 7–8 (geotextile and 4 mm 4 and 5 to 8). layer of soil between piezometers • for soil: number 7 to 8), 110 D. Wojtasik

– zone 6–7 (4 mm layer of soil within ⎛ + ⎞ hh45− the distance from 4 to 8 mm above ⎜ hL84⎟ ⎝ 2 ⎠ geotextile between piezometers 6 GR = = 25 ⎛ + + ⎞ and 7), hhhh23− 45 ⎜ ⎟ L24− – zone 4.5–6 (17 mm layer of soil ⎝ 2 2 ⎠ within the distance from 8 to 25 Δ hL45. − 8 4 mm above geotextile between = Δh −−L piezometers 4, 5 and 6), 223.. 45 2 4 (1) – zone 2.3–4.5 (50 mm layer of soil where: within the distance from 25 to Δh4.5–8 = is the difference manometer 75 mm above geotextile between readings between average reading of piezometers 2 and 3 as well as 4 4 and 5 piezometers and 8 piezometer and 5. [mm], The following equation (1) is used Δh2.3–4.5 = is the distance in manometer to calculate the gradient ratio in soil- readings between average reading of 2 geotextile system: GR (ASTM D-5101) and 3 piezometers and average reading = GR25 (see Fig. 4 for deﬁ nition sketch). of 4 and 5 piezometers [mm]. The relationship for the evaluation of the change gradient ratio (for the soil

Water Inlet

h 1

h 3 h 2 1

h 5 h 4

h 6 2 3

h 7

L 2-4 4 5 h 8 6 7 L 4 L 6 L 7 g „O” Ring Piping Barier Soil 8 Nonwoven Geotextile „O” Ring Gasket Support Screen

Water Outlet

FIGURE 2. Experimental setup hn is the manometer reading for nth manometer [mm], Ln = is the distance between piezometer nth and the bottom of geotextiles [mm], L2–4 = is the distance between piezometers 2 to 4 [mm], g – thickness of geotextile [mm]. Evaluation of nonwoven geotextile as a fi ltration... 111 layers 17 and 4 mm above the geotextile) RESULTS is proposed: The permeability coeffi cient of geotextile ⎛ + ⎞ hh45− material measured was slightly higher ⎜ hL646⎟ − ⎝ 2 ⎠ (infl uence of structure material) than SGR = = 17 ⎛ + + ⎞ the value provided by the manufacturer. hhhh23− 45 ⎜ ⎟ L24− During the fi ltration process, the ⎝ 2 2 ⎠ maximum difference of the permeability ΔhL = 45. − 6 446− coeffi cients was obtained in the most Δ internal unstable soil G1. Permeability hL23..−− 45 2 4 coeffi cient decreased about 15 times –3 –4 (2) from kgeo = 5.8 × 10 to 4.0 × 10 m/ − ()hhL6767− s. In soils G2 and G3, it decreased by 4 SGR = = 4 ⎛ + + ⎞ and 6 times, respectively. The change of hhhh23− 45 ⎜ ⎟ L24− gradient ratio for individual hydraulic ⎝ 2 2 ⎠ gradient is shown in the Figures 3, 4 ΔhL = 67−− 67 and 5. Δ Tested results showed that gradient h23..− 45524L − ratio value in soil-geotextile system (3) (GR25) decreased in comparison with where: gradient ratio in soil (SGR17 and SGR4). Δh4.5–6 = is the difference manometer The largest difference was found in readings between average reading of the soil layer immediately above the 4 and 5 piezometers and 6 piezometer geotextile material. Tested results [mm], also showed that signifi cant clogging L4–6 is the distance between piezometers occurred in the 17-mm soil layer situated 4 to 6 [mm], in distance from 8 to 25 mm above L6–7 is the distance between piezometers geotextile material. Figure 6 gives 6 to 7 [mm]. the comparisons of the tested results

2.0 SGR17

1.5 GR25

1.0

SGR4 GR orGR [-] SGR 0.5

0.0 12345678910 Gradient i [-] FIGURE 3. The change of gradient ratio and soil-gradient ratio under hydraulic gradient from 1 to 10 in soil G1 (ﬁ nes – 17%) 112 D. Wojtasik

2.0

SGR17 1.5 SGR4 GR25 1.0

GR or SGR [-] orSGR GR 0.5

0.0 12345678910 Gradient i [-] FIGURE 4. The change of gradient ratio and soil-gradient ratio under hydraulic gradient from 1 to 10 in soil G2 (ﬁ nes – 18%)

4.0 SGR17 SGR 3.0 4

GR25 2.0 GR or SGR [-] or SGR GR 1.0

0.0 12345678910 Gradient i [-] FIGURE 5. The change of gradient ratio and soil-gradient ratio under hydraulic gradient from 1 to 10 in soil G3 (ﬁ nes – 30%)

10 9 1 8 7 [-] n 6

SGR 5 GR25 = 3 n , n , 4 SGR17 SGR GR 3 4 i=10

2 GR25 1 0 0 5 10 15 20 2527 30 35 40 Fines content F [%] FIGURE 6. The change of gradient ratio depending on fi nes content in soils Curve 1: reported by Hali- burton and Wood (1982) Evaluation of nonwoven geotextile as a fi ltration... 113 obtained in this study with quantify the with internal unstable soil with fi ne clogging potential geotextiles in contact content (d < 0.05 mm) of 27%. with soil-silt content by Halliburton and Wood (1982). Fabric should defi nitely not be used in critical design applications REFERENCES where soil-geotextile system gradient ratio (GR ) exceeds 3.0 ASTM D-5101 (1990): Standard Test Method 25 for Measuring the Soil–Geotextile System From Figure 6, it can be seen that Clogging Potential by the Gradient when the criteria proposed by Haliburton Ratio. and Wood (1982) is used, the GR25 value CALHOUN C.C. 1972: Development (within the range of external hydraulic of design criteria and acceptance gradient i = 1 to 10) in the tested soils specifi cations for plastic fi lter cloth. USAGE. Waterways Experimental did not exceed the limit of GR25 = 3. Station, Vicksburg. However, soil gradient ratio SGR17 for soil G3 (with 30% of fi nes) exceeds this FISHER G.R., MARÉ A.D, HOLTZ R.D. 1999: Infl uence of Procedural Variables limit when the hydraulic gradient (i) was on the Gradient ratio Test. Geotechnical larger than 2.5 (Figure 5). The results Testing Journal, Vol. 22, No 1, 22–31. show that the all three geotextile material GIROUD J.P. 1982: Filter criteria for can be used as the fi ltration layer for geotextiles. 2nd Int. Conf. On Geotextiles, any soil with fi nes (d < 0.05 mm) 27% Geomembranes and Related Products, content. Las Vegas, 103–108. HALIBURTON T.A., WOOD P.D. 1982: Evaluation of the U.S. Army Corps of Engineers Gradient Ratio Test for CONCLUSIONS Geotextile Performance. 2nd Int. Conf. On Geotextiles. Las Vegas, Nevada, 97–101. 1. Permeability coeffi cient under HEERTEN G. 1983: Filtereigenschaften von different hydraulic gradient during Geotextillien für den Erd – und Wasserbau. long time test (about 2100 h) was Wasser und Boden, 348–353. changed decrease from initial value HUANG HSU-YEH., GAO XIAO: 2008: to fi nished about 4 to 15 times. Geotextiles (www.engr.utk.edu/mse/ 2. During fi ltration process-clogging Textiles/Geotextiles.htm) KENNEY T.C., LAU D. 1985: Internal phenomena was very intensive in 17 stability of granular fi lters. Canadian mm layer situated in distance from 8 Geotechnical Journal, Vol. 22, No 2, to 25 mm above geotextile material. 215–225. 3. Nonwoven geotextile K-500 based on LAWSON C.R. 1987: Use of Geotextile for formula soil gradient ratio (SGR17) Subsurface Drainage in South East Asian according to the Haliburton and Context. International Symposium on Wood criterion (1982) can cooperate Geosynthetics, Kyoto, Japan, 145–165. 114 D. Wojtasik

ROLLIN A.L. 1986: Filtration opening size niny. Badania laboratoryjne przeprowadzono of Geotextiles. ASTM Standardization przy zewnętrznych gradientach hydraulicznych News, 50–52. w zakresie i = 1÷10. Na podstawie uzyskanych badań została zaproponowana zależność ocenia- jąca zmiany stosunku gradientów w gruncie (17 Streszczenie: Ocena nietkanej geowłókniny jako mm warstwa gruntu znajdująca się w odległości warstwy fi ltracyjnej w kontakcie z gruntami we- 8–25 mm gruntu powyżej geowłókniny) w ukła- wnętrznie niestabilnymi. W artykule przedstawio- dzie grunt-geowłóknina na podstawie zewnętrz- no wyniki laboratoryjnych badań trzech nietka- nego gradientu hydraulicznego oraz zawartość nych geowłóknin, wykorzystanych jako warstwa frakcji drobnych w gruncie. fi ltracyjna ochraniająca trzy wewnętrznie niesta- bilne pisaki gliniaste. Badania przeprowadzono w aparacie według normy ASTM D-5101 (1990), MS. received November 2008 który poddano modyfi kacji poprzez zainstalowa- nie dodatkowych piezometrów w odległości 4 Author’s address: i 8 mm powyżej badanego materiału syntetycz- Dariusz Wojtasik nego. Zastosowane piezometry podczas badań Katedra Geoinżynierii SGGW umożliwiły odczyt ciśnienia w warstwie gruntu 02-776 Warszawa, ul. Nowoursynowska 159 znajdującej się w bliskiej odległości od geowłók- Poland e-mail: [email protected]