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Erosion control for mudstone soil with ventilation and watertight resin
International Journal of Sediment Research 25 (2010) 194-201
Erosion control for mudstone soil with ventilation and watertight resin Chung-li HSU1, Shin-yi DAI2, Shiu-wen CHIANG3, and Chai-yin CHAN4
Abstract To accelerate the re-vegetation of exposed landslide areas, hydroseeding for soil and water conservation has been widely applied as one of the economically feasible ways. However, effect durations of different hydroseeding materials are different, the formulation density has a certain effect on plant growth and the addictives may exude. This paper presents laboratory experiments of soil erosion, exuding water quality and soil hardness by using a rainfall simulator with different conditions of slope, rainfall intensity and medication density. The results showed that soil erosion decreased significantly, suggesting a good erosion-resisting effect by the ventilation and watertight resin. No significant variation of the exuded water was observed during testing, which indicates that after gelling, the ventilation and watertight resin are unlikely to release chemical substances. It was found that high resin density will result in poor workability as well as high costs; adverse will cause the mudstone to fracture due to raindrops since cracks are common to soil surface. The weatherability after spraying and its effect on plant vegetation still need further investigation. Key Words: Ventilation and watertight resin, Hydro seeding, Mudstone, Soil erosion, Rainfall simulator
1 Introduction The mudstone area in southwest Taiwan covers a vast range, north from Guichong River near Hsinying and south to the Lushan near Kaohsiung Shoushan and Chinan Highway, with an area of 1,014km2. Mudstone contains a high level of alkali cations, resulting in the soil having high pH value (between 8 and 9) and unsound water retention. Moreover, since mudstone would swell and disintegrate. Once the slope is bare, it is unlikely to cover the vegetation spontaneously (Lee et al., 1994; Tien et al., 1994; Chen, 1994). Without effective soil and water conservation measures, artificial development would aggravate desertification and environment crisis. Hydroseeding for soil and water conservation is one of the economically feasible methods to rapidly revegetate the vast exposed landside. Good hydroseeding method pays special attention to its effects on ground adhesion, erosion prevention and rate of emergence. Effect durations and reaction effects to soil sorts, gradient and climate of different hydroseeding materials are different and the formulation density has effect on plant growth. All of the above effects should be quantified for further comparison (Carr and Ballard, 1980; Fohrer et al., 1999). 1
Assoc. Professor, Department of Soil and Water Conservation, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China, Corresponding Author, E-mail:[email protected] 2 Graduate student, Graduate Institute of Disaster Prevention on Hillslopes and Water Resources Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China 3 Graduate student, Department of Soil and Water Conservation, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China 4 Res. Assis., Department of Soil and Water Conservation, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China Note: The original manuscript of this paper was received in May 2009. The revised version was received in April 2010. Discussion open until June 2011. - 194 -
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
Methods of soil and water conservation vegetation engineering usually include grass planting, broadcast sowing, hydroseeding, and engineering cover, among which hydroseeding is faster and widely applicable (Simanton et al., 1984; Chiu and Yin, 1987; Figueiredo and Poesen, 1998; Lin and Huang, 2002; Kung and Lin, 2003). This study applied ventilation and watertight resin (KMCO-955) in mudstone areas to investigate its soil erosion-resisting effect through indoor experiments and field tests, and to determine if the ventilation and watertight resin used on landside could pollute the penetrated water and surface runoff. 2 Materials and methods (1) Properties of the ventilation and watertight resin Ventilation and watertight resin (KMCO-955) is a grade surface protective covering material that is introduced to Taiwan rather late. It mainly reacts and forms ventilation, watertight, and reticulated foam elastomeric, with interfacial activity action and good permeability to soil particles, and hardly cracked by vibration. Its basic properties are shown in Table 1. Table 1 Parameters Appearance Viscidity Proportion Gummed time
Basic characteristic of ventilation and watertight resin A Drug Yellowish 2000 CPS 1.05 1-2 min
B Drug Colorless 1-5 CPS 1
Besides covering straw or nonwoven to prevent erosion after filling additional soil and sowing seeds in the slop; also can be sprayed ventilation and watertight resin solution due to it has good operability and performance. (2) Properties of experimental soil Experimental soil samples were collected from the colluvial soil under the exposed mudstone grade surface in Tianliao Township Moon World, Kaohsiung County. The physical-chemical properties in mudstone area included greater pH value, high silt particle content, and high salt content. Besides, it’s hard as stones and its surface develops fish-scale crack in the dry state; but its surface would soften to extremely unstable slurry in the wet state. Under the alternating action of dryness and wetness, as well as rain erosion and leaching, the mudstone surface would fall off and flow away in a plate-like shape, thus forming an exposed and barren landform. Since the mudstone soil has very fine particles size and its infiltration rate is very low, the surface runoff would easily converge to rill flow, thus the soil would be seriously eroded. Mudstone soil contains high soluble salts, while these exchangeable sodium and chloride ions may likely to cause soil layer dispersion and make soil colloid suspend in water. In rainy seasons, the muddy water would be turbid and the soil would run off with the water flow (Vincent and Bissonnais, 2003; Rorke, 2006), thus affecting the landside steadiness and increasing the erosion degree. (3) Artificial rainfall simulator test Rainfall simulators for soil erosion have been extensively studies in the field and laboratory. The methods have played an important role in understanding soil erosion, and used to supply water at a constant pressure head, raindrop, intensity etc. (Bertrand and Parr, 1961; Nolan et al., 1997; Barthes and Roose, 2002; Shekl Abadi et al., 2003; Tejada and Gonzalez, 2006; Vahabi and Nikkami, 2008). In addition, small erosion plots in the lab allow the control of most influences, such as slope, soil texture, and moisture content, thus the influence of one specific factor can be investigated. Moreover, the relative effectiveness of various erosion control techniques can be assessed in a very efficient method (Vahabi and Nikkami, 2008). Artificial rainfall simulation could control the environment factor and test conditions easily, making it easier to analyze and compare the quality of treatment effects. Basic requirements of artificial rainfall simulator for indoor and outdoor use were rainfall uniformity, and fall distance and terminal velocity after raindrop forming (Singer and Blackard, 1978; Andraski et al., 1985; Tossell et al., 1987; Fan and Wu, 1996; Hsieh and Cheng, 1996; Singh et al., 1999; Wright et al., 2002). Artificial rainfall simulator applied in this study is shown in Fig. 1.
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
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Fig. 1
Artificial rainfall simulator
The velocities of water supply, spraying and screen shaking was checked and revised constantly to make the raindrop distribute uniformly on the treated soil sampling. The fall distance of the whole set instrument was increased by 2 meters to make the raindrop velocity as close to the terminal velocity as possible (higher than 80%). Lastly, the test process was kept from wind interference and close to a clean water source, in order to avoid needle jam and ensure the test flow. (4) Infiltration water quality test To find out the effect of infiltrated matters on soil and water quality after applying ventilation and watertight resin solution during testing, TENCO Model 113 and pH Model 620D were applied for measurement and comparison to examine the quality change of this material penetration water. (5) Soil hardness test In order to find out whether the ventilation and watertight resin would change the landside soil hardness, this study compared and tested the in-place two adjacent landsides with a soil hardness tester. (6) Research workflow The main focuses of this study included indoor soil sampling and implantation, rainfall erosion simulation, infiltration water quality test, and outdoor actual spraying test. The research flow is shown in Fig. 2.
Fig. 2 Flowchart of this study
(7) Experimental layout The plastic container applied in this study for soil sample (42cm×30cm×15cm) contained naturally tamped (watered and placed outdoor for more than 2 weeks) weathered mudstone soil, as shown in Fig. 3. - 196 -
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
Then artificial rainfall simulator was used to simulate the effects of different chemic concentrations (1%, 5%, 10%, 20%) on the mudstone soil erosion at different slopes (20°, 30°, 40°) and under different rainfall intensities (20mm/hr, 30mm/hr, 40mm/hr). The effects were compared with the control test.
Fig. 3
The size of experimental soil sample
(8) Duncun’s multiple range analysis Duncun’s multiple range test (DMRT) is an effective statistic method for multiple comparison procedure developed by David B. Duncan in 1955. DMRT belongs to the general class of multiple comparison procedures that use the studentized range statistic to compare sets of means. DMRT is especially protective against false negative (Type II) error at the expense of having a greater risk of making false positive (Type I) errors. DMRT is commonly used in agronomy and other agricultural research. The steps for calculating DMRT are a. Do the single factor ANOVA test first, to make sure this is worth doing. b. Yi is rank the treatment averages, and MSE is the standard error square of Yi. c. The overall standard deviation (St). St = (MSE/n) / 2 d. Look up in the r table for the r value. (It depends on the degrees of freedom of the number of treatments and the number in each treatment, and α value.) e. Calculate the statistic value Rp. Then p are the group sizes such as 2, 3, etc. Rp = r [from table] × St f. Compare each treatment R value, for example: 1 vs. 2, 2 vs. 4, etc., by subtracting. g. Compare Rp values. If the calculated subtraction R is greater than the table value Rp, then there is a significant difference between the mean pairs. 3 Results and discussion (1) Relationship between rainfall intensity and erosion The results showed that, under rainfall intensities of 20mm/hr, 30mm/hr and 40mm/hr, the relationship between erosion and test slope can be obtained (Tables 2 to 4). The erosions of soil samples treated by ventilation and watertight resin in different matching are less than that of the control group. Moreover, the erosion decreased with an increase of the matching ratio. Further statistical analysis is needed to explore whether the difference between them is significant. The significance between each factor was checked by using Duncan’s multiple range test based on the obtained data (Tables 5 and 6). As shown in Table 5, the erosions of all slopes belong to the same subset, indicating no significant difference of treated soil erosion affected by slope variation. According to Tables 2 to 4, the erosion of soil treated by ventilation and watertight resin showed no significant increase as the slope increased. Therefore, applying ventilation and watertight resin in different slopes has good protective effect. Table 6 shows the relationship between different matching and erosion. The control group and matching 1% belong to the same subset, indicating that there is no significant difference of soil erosion treated by 1% matching and untreated one. However, there is significant difference between other matching and International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
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control group or 1% matching, indicating that the ventilation and watertight resin has anti-erosion effect. Moreover, the treatment effect is more significant as the matching increases. The results showed that the anti-erosion effect was not obvious until the medication matching reached 5%, and the erosion at matching 1% was several times higher than that at 5%, indicating that 5% matching should be recommended for economical and convenient outcome (higher matching leads to difficulty in uniform spray, and poor workability). Since the slope increase causes more soil erosion, medication matching should be increased properly for steeper slopes. Table 2 Slope 20° 30° 40°
0% 17.9 25.3 29.2 Table 3
Slope 20° 30° 40°
0% 69.0 77.6 99.8 Table 4
Slope 20° 30° 40°
0% 83.5 94.5 153.8
Soil erosion with 20mm/hr rainfall Experimental matching 1% 5% 12.4 2.8 14.9 10.2 26.3 11.9
10% 2.6 5.3 6.8
20% 1.9 3.0 6.3
Soil erosion with 30mm/hr rainfall Experimental matching 1% 5% 47.5 12.0 68.2 18.3 80.3 31.3
10% 3.4 18.7 19.6
20% 2.6 6.4 6.9
Soil erosion with 40mm/hr rainfall Experimental matching 1% 5% 58 15.1 67.1 37.7 137.2 65.9
10% 13.3 29.3 38.7
20% 13.5 14.3 26.0
Table 5 Duncun’s multiple range test result for Slope and soil erosion compared Subset with α= 0.05 Slope Number 1 20° 15 23.7013 30° 15 32.7117 40° 15 49.3193 Significant 45 0.072 Table 6 Duncun’s multiple range test result for Cementation ratios and soil erosion compared Subset with α= 0.05 Experimental matching Number 1 2 20% 9 8.9789 10% 9 15.2922 5% 9 22.7956 1% 9 56.8732 0% 9 72.2806 Significant 45 0.335 0.254
(2) Penetration water quality variation The most sensitive pH value and conductivity were measured in this study to find out whether the ventilation and watertight resin could dissolve chemical matters and affect the soil or environment. During test runs, the water-quality variation through infiltration cultivation was investigated. The results showed that, after the soil sample was treated for 30 days, pH value and conductivity were not significantly different from those before cultivation, as shown in Table 7. The variation amplitude for pH value was 0.77, and that for conductivity was 0.56, both about 11% of the absolute value. Such results - 198 -
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
suggested that, should this ventilation and watertight resin be applied on the grade surface for a long term, the soil sample property would not change and other relevant reactions or matters penetration due to the resin decomposition or chemical matters penetration would not occur. Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
pH 6.21 6.45 6.25 6.31 6.49 6.57 6.62 6.68 6.80 6.84 6.93 6.86 6.94 6.98 6.90
Table 7 Permeates water quality variation Conductivity Day 4.69 16 4.69 17 4.52 18 5.01 19 4.45 20 4.79 21 4.76 22 4.86 23 4.57 24 4.84 25 4.68 26 4.73 27 4.75 28 4.81 29 4.61 30
pH 6.89 6.87 6.91 6.87 6.83 6.85 6.82 6.91 6.86 6.89 6.88 6.93 6.98 6.87 6.92
Conductivity 4.74 4.69 4.97 4.68 4.78 4.65 4.91 4.88 4.87 4.98 4.79 4.86 4.70 4.69 4.96
(3) Soil hardness variation Field soil hardness variation test sites were situated on two adjacent steep landside slopes about 60 degree of mood word badland at Kaohsing County Tainliau Townshipn, one was sprayed ventilation and watertight resin, the other remained undisturbed, as shown in Fig. 4. Measured results of surface hardness were compared and analyzed. Before testing, this place had not rained for more than 2 weeks and the landside surface presented obvious dried cracks. This test was carried out by using a Yamanaka’s soil hardness tester and the results are shown in Table 8.
Un-treatment Treatment
The status of experimental area
Yamanaka’s soil hardness tester Fig. 4
Location of treatment and un-treatment for spray the ventilation and watertight resin
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
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Table 8 Measured results by using Yamanaka’s soil hardness tester Measuring soil hardness (mm) Average Standard error T-test value 33 34 28 34 36 Treatment area 32.6 2.6750 33 35 30 34 29 0.9491 32 33 30 34 27 Un-treatment area 31.5 2.5055 34 34 28 31 32 PS. When α = 0.05 the critical t value is 1.7341 and less than this test vales, thus reject null hypothesis. Project
Table 8 shows the soil hardness of ventilation and watertight resin plot was 28 to 36mm, with an average value of 32.6mm; while that of the untreated plot was 27 to 34mm, and average value was 31.5mm. The statistics analysis indicates insignificant, obviously, using ventilation and watertight resin has less affected on soil hardness. Moreover, through on-site investigation, cracks on mudstone surface still existed that were easy to erode. The anti-erosion mechanism of this ventilation and watertight resin was a reactant of foam elastomeric, directly blocks the raindrop instead of reacting with the soil. Therefore, during foaming, it did not penetrate deep into the soil. This spray was only for testing, and the depth was very thin. However, since the cracks on the mudstone surface covered a wide range, the resin was unable to penetrate deep into the landslide soil to improve the hardness or strength of subsurface soil layers. (4) Analysis of results The test results showed no significant variation of the exuded water quality during testing, which apparently indicated that after gelling, the ventilation and watertight resin did not release much chemical matters to affect exuding water quality or soil property. However, further tests and researches are needed to confirm whether it would release relevant matters to change water quality or affect soil properties. During actual spraying, since the reaction time of ventilation and watertight resin was very short, when the resin density was too high, it had poor workability and could be uneconomical; thus, the uniformity should be considered. When the resin density was too low, mudstone still had problems of easily cracking when dry, and the breaking off of the protecting layer during high-intensity rainfall. Moreover, the issues such as ventilation and watertight resin, low leakage and high ventilation, weather-resistant degree, combination with the hydroseeding, and the effects on subsequent growth should be further tested and discussed. 4 Conclusions Statistics analyses showed that the soil samples for exuding water quality, soil erosion with different conditions of slope, rainfall intensity and medication density: (1) The soil erosion of ventilation and watertight resin amended soils are less than the controlled group. Moreover, the erosion decreases as the matching of ventilation and watertight resin increases, nonetheless the effect of slope is insignificant. (2) The anti-erosion effect treated by low medication density is insignificant, and that adding matching density of higher than 5% is better. (3) For all treatments and during the experimental period the pH value and conductivity were no significant difference. Hence, this ventilation and watertight resin didn’t cause the sample soils or water quality to react or change. (4) Comparing the hardness average value of the experimental plot, the amended plot increased slightly than the control plot, but the statistics analysis showed insignificant. Obviously, this reagent has less affected on soil hardness. References Andraski B. J., Daniel T. C., Lowrey B., and Mueller D. H. 1985, Runoff results from natural and simulated rainfall for four tillage systems. Trans. ASAE, Vol. 28, No. 4, pp. 1219–1225. Barthes B., and Roose E. 2002, Aggregate stability as an indicator of soil susceptibility to runoff and erosion; Validation at several levels. Catena, 47, pp. 133–149. Bertrand, A. R., and Parr, J. F. 1961, Design and operation of the Purdue sprinkling infiltrometer. U.S.D.A. Res. Bulletin No. 723. Lafayette, IN. Carr, W.W., and Ballard, T.M. 1980, Hydroseeding forest roadsides in British-Columbia for erosion control. Journal Soil Water Conservation, Vol. 33, pp.33–35. - 200 -
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Chen S. T. 1994, The engineering geological characteristics of the mudstones in southwestern Taiwan. Sino-Geotechnics, Vol. 48, pp. 25–33 (in Chinese). Chiu C. Y., and Yin C. Y. 1987, Greening experiment on landslide of mudston. Journal of National Pingtung Agriculture College, Vol. 28, pp. 115–131 (in Chinese). Duncan, D. B., 1955, Multiple range and multiple F tests. Biometrics, Vol. 11, pp. 1–42. Fan J. C., and Wu M. F. 2001, Effect of soil strength, texture, slope steepness and rainfall intensity on interrill erosion of some soils in Taiwan. D. E. Stott, R. H. Mohtar and G. C. Steinhardt(eds). pp. 588-593. Figueiredo T., and Poesen J. 1998, Effects of surface rock fragment characteristics on interrill runoff and erosion of a silty loam soil. Soil & Tillage Research, Vol. 46, No. 1, pp. 81–95. Fohrer N., Berkenhagen J., Hecker M. J., and Rudolph A. 1999, Changing soil and surface conditions during rainfall: Single rainstorm/subsequent rainstorms. CATENA, Vol. 37, No. 3–4, pp. 355–375. Hsieh C. H., and Cheng J. D. 1996, Performance of a small-scale rainfall simulator. Journal of Soil and Water Conservation by National Chung-Hsing University, Vol. 28, No. 2, pp. 63–70 (in Chinese). Kung J. S., and Lin H. D. 2003, A study of vegetation for slope stability of ecological engineering methods. Professional Engineer Journal by Taipei Professional Civil Engineers Association, Vol. 31, pp. 60–68 (in Chinese). Lee D. H., Chi Y. Y., and Tien K. G. 1994, Characteristics and protective measure of the mudstones slope. Sino-Geotechnics, Vol. 48, pp. 35–47 (in Chinese). Lin S. H., and Huang C. J. 2002, An investigation of vegetation engineering methods on earthquake induced landslides. Sino-Geotechnics, Vol. 92, pp. 27–36 (in Chinese). Mbagwu J. S. C., and Auerswald K. 1999, Relationship of percolation stability of soil aggregates to land use, selected properties, structural indices and simulated rainfall erosion. Soil and Tillage Research, Vol. 50, pp.197–206. Nolan, S. C., van Vilet, L. J. P., Goddard, T. W., and Flesch, T. K. 1997, Estimating storm erosion with a rainfall simulator. Canadian Journal of Soil Science, Vol. 77, No.5, pp. 669–676. Rorke B. B. 2006, Soil erodibility and processes of water erosion on hillslope. Geomorphology, Vol. 32, No. 3–4, pp. 385–415. Shekl Abadi M., Khademi H., and Charkhabi A. H. 2003, Runoff and sediment yield in soils developed on different parent materials in the Golabad watershed Ardestan. Journal of Science and Technology of Agriculture and Natural Resources, Vol. 7, No. 2, Summer 2003, pp. 85–101. Simanton J. R., Rawitz E., and Shirley E. D. 1984, Effects of rocks fragments on erosion of semiarid rangeland soils. SSSA Special Publication (Soil Science Society of America), No. 13, pp. 65–72. Singer M. J., and Blackard J. 1978, Effect of mulching on sediment in runoff from simulated rainfall. Soil Sci. Soc. Am. J., Vol. 42, No. 3, pp. 481–486. Singh R., Panigrahy N., and Philip G. 1999, Modified rainfall simulator infiltrometer for infiltration, runoff and erosion studies. Agricultural Water Management, Vol. 42, No. 2, pp. 167–175. Tejada M., and Gonzalez J. L. 2006, The relationships between erodibility and erosion in a soil treated with two organic amendments. Soil and Tillage Research, Vol. 91, pp.186-198. Tien Y. M., Chang H. W., and Wang Z. C. 1994, Evaluating the effectiveness of the mudstone slope stabilization with technical treatments. Sino-Geotechnics, Vol. 48, pp. 83–94 (in Chinese). Tossell R. W., Dickinson W. T., Rudra R. P., and Wall G. J. 1987, A portable rainfall simulator. Can. Agric. Eng., Vol. 29, No. 2, pp. 155–162. Vahabi J., and Nikkami D. 2008, Assessing dominant factors affecting soil erosion using a portable rainfall simulator. International Journal of Sediment Research, Vol. 23, pp.376-386. Vincent A. M. C., and Bissonnais Y. L. 2003, Runoff features for interrill erosion at different rainfall intensities, slope lengths, and gradients in an agricultural loessial hillslope. Soil Science Society of America Journal, Vol. 67, No. 3, pp. 844–851. Wright J. A., Smith J., Gundry S. W., and Glasbey C. A. 2002, A spatial rainfall simulator for crop production modeling in Southern Africa. Mathematical and Computer Modelling, Vol. 35, No. 13, pp. 1459–1466(8).
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
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Erosion control for mudstone soil with ventilation and watertight resin Chung-li HSU1, Shin-yi DAI2, Shiu-wen CHIANG3, and Chai-yin CHAN4
Abstract To accelerate the re-vegetation of exposed landslide areas, hydroseeding for soil and water conservation has been widely applied as one of the economically feasible ways. However, effect durations of different hydroseeding materials are different, the formulation density has a certain effect on plant growth and the addictives may exude. This paper presents laboratory experiments of soil erosion, exuding water quality and soil hardness by using a rainfall simulator with different conditions of slope, rainfall intensity and medication density. The results showed that soil erosion decreased significantly, suggesting a good erosion-resisting effect by the ventilation and watertight resin. No significant variation of the exuded water was observed during testing, which indicates that after gelling, the ventilation and watertight resin are unlikely to release chemical substances. It was found that high resin density will result in poor workability as well as high costs; adverse will cause the mudstone to fracture due to raindrops since cracks are common to soil surface. The weatherability after spraying and its effect on plant vegetation still need further investigation. Key Words: Ventilation and watertight resin, Hydro seeding, Mudstone, Soil erosion, Rainfall simulator
1 Introduction The mudstone area in southwest Taiwan covers a vast range, north from Guichong River near Hsinying and south to the Lushan near Kaohsiung Shoushan and Chinan Highway, with an area of 1,014km2. Mudstone contains a high level of alkali cations, resulting in the soil having high pH value (between 8 and 9) and unsound water retention. Moreover, since mudstone would swell and disintegrate. Once the slope is bare, it is unlikely to cover the vegetation spontaneously (Lee et al., 1994; Tien et al., 1994; Chen, 1994). Without effective soil and water conservation measures, artificial development would aggravate desertification and environment crisis. Hydroseeding for soil and water conservation is one of the economically feasible methods to rapidly revegetate the vast exposed landside. Good hydroseeding method pays special attention to its effects on ground adhesion, erosion prevention and rate of emergence. Effect durations and reaction effects to soil sorts, gradient and climate of different hydroseeding materials are different and the formulation density has effect on plant growth. All of the above effects should be quantified for further comparison (Carr and Ballard, 1980; Fohrer et al., 1999). 1
Assoc. Professor, Department of Soil and Water Conservation, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China, Corresponding Author, E-mail:[email protected] 2 Graduate student, Graduate Institute of Disaster Prevention on Hillslopes and Water Resources Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China 3 Graduate student, Department of Soil and Water Conservation, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China 4 Res. Assis., Department of Soil and Water Conservation, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, China Note: The original manuscript of this paper was received in May 2009. The revised version was received in April 2010. Discussion open until June 2011. - 194 -
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
Methods of soil and water conservation vegetation engineering usually include grass planting, broadcast sowing, hydroseeding, and engineering cover, among which hydroseeding is faster and widely applicable (Simanton et al., 1984; Chiu and Yin, 1987; Figueiredo and Poesen, 1998; Lin and Huang, 2002; Kung and Lin, 2003). This study applied ventilation and watertight resin (KMCO-955) in mudstone areas to investigate its soil erosion-resisting effect through indoor experiments and field tests, and to determine if the ventilation and watertight resin used on landside could pollute the penetrated water and surface runoff. 2 Materials and methods (1) Properties of the ventilation and watertight resin Ventilation and watertight resin (KMCO-955) is a grade surface protective covering material that is introduced to Taiwan rather late. It mainly reacts and forms ventilation, watertight, and reticulated foam elastomeric, with interfacial activity action and good permeability to soil particles, and hardly cracked by vibration. Its basic properties are shown in Table 1. Table 1 Parameters Appearance Viscidity Proportion Gummed time
Basic characteristic of ventilation and watertight resin A Drug Yellowish 2000 CPS 1.05 1-2 min
B Drug Colorless 1-5 CPS 1
Besides covering straw or nonwoven to prevent erosion after filling additional soil and sowing seeds in the slop; also can be sprayed ventilation and watertight resin solution due to it has good operability and performance. (2) Properties of experimental soil Experimental soil samples were collected from the colluvial soil under the exposed mudstone grade surface in Tianliao Township Moon World, Kaohsiung County. The physical-chemical properties in mudstone area included greater pH value, high silt particle content, and high salt content. Besides, it’s hard as stones and its surface develops fish-scale crack in the dry state; but its surface would soften to extremely unstable slurry in the wet state. Under the alternating action of dryness and wetness, as well as rain erosion and leaching, the mudstone surface would fall off and flow away in a plate-like shape, thus forming an exposed and barren landform. Since the mudstone soil has very fine particles size and its infiltration rate is very low, the surface runoff would easily converge to rill flow, thus the soil would be seriously eroded. Mudstone soil contains high soluble salts, while these exchangeable sodium and chloride ions may likely to cause soil layer dispersion and make soil colloid suspend in water. In rainy seasons, the muddy water would be turbid and the soil would run off with the water flow (Vincent and Bissonnais, 2003; Rorke, 2006), thus affecting the landside steadiness and increasing the erosion degree. (3) Artificial rainfall simulator test Rainfall simulators for soil erosion have been extensively studies in the field and laboratory. The methods have played an important role in understanding soil erosion, and used to supply water at a constant pressure head, raindrop, intensity etc. (Bertrand and Parr, 1961; Nolan et al., 1997; Barthes and Roose, 2002; Shekl Abadi et al., 2003; Tejada and Gonzalez, 2006; Vahabi and Nikkami, 2008). In addition, small erosion plots in the lab allow the control of most influences, such as slope, soil texture, and moisture content, thus the influence of one specific factor can be investigated. Moreover, the relative effectiveness of various erosion control techniques can be assessed in a very efficient method (Vahabi and Nikkami, 2008). Artificial rainfall simulation could control the environment factor and test conditions easily, making it easier to analyze and compare the quality of treatment effects. Basic requirements of artificial rainfall simulator for indoor and outdoor use were rainfall uniformity, and fall distance and terminal velocity after raindrop forming (Singer and Blackard, 1978; Andraski et al., 1985; Tossell et al., 1987; Fan and Wu, 1996; Hsieh and Cheng, 1996; Singh et al., 1999; Wright et al., 2002). Artificial rainfall simulator applied in this study is shown in Fig. 1.
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
- 195 -
Fig. 1
Artificial rainfall simulator
The velocities of water supply, spraying and screen shaking was checked and revised constantly to make the raindrop distribute uniformly on the treated soil sampling. The fall distance of the whole set instrument was increased by 2 meters to make the raindrop velocity as close to the terminal velocity as possible (higher than 80%). Lastly, the test process was kept from wind interference and close to a clean water source, in order to avoid needle jam and ensure the test flow. (4) Infiltration water quality test To find out the effect of infiltrated matters on soil and water quality after applying ventilation and watertight resin solution during testing, TENCO Model 113 and pH Model 620D were applied for measurement and comparison to examine the quality change of this material penetration water. (5) Soil hardness test In order to find out whether the ventilation and watertight resin would change the landside soil hardness, this study compared and tested the in-place two adjacent landsides with a soil hardness tester. (6) Research workflow The main focuses of this study included indoor soil sampling and implantation, rainfall erosion simulation, infiltration water quality test, and outdoor actual spraying test. The research flow is shown in Fig. 2.
Fig. 2 Flowchart of this study
(7) Experimental layout The plastic container applied in this study for soil sample (42cm×30cm×15cm) contained naturally tamped (watered and placed outdoor for more than 2 weeks) weathered mudstone soil, as shown in Fig. 3. - 196 -
International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
Then artificial rainfall simulator was used to simulate the effects of different chemic concentrations (1%, 5%, 10%, 20%) on the mudstone soil erosion at different slopes (20°, 30°, 40°) and under different rainfall intensities (20mm/hr, 30mm/hr, 40mm/hr). The effects were compared with the control test.
Fig. 3
The size of experimental soil sample
(8) Duncun’s multiple range analysis Duncun’s multiple range test (DMRT) is an effective statistic method for multiple comparison procedure developed by David B. Duncan in 1955. DMRT belongs to the general class of multiple comparison procedures that use the studentized range statistic to compare sets of means. DMRT is especially protective against false negative (Type II) error at the expense of having a greater risk of making false positive (Type I) errors. DMRT is commonly used in agronomy and other agricultural research. The steps for calculating DMRT are a. Do the single factor ANOVA test first, to make sure this is worth doing. b. Yi is rank the treatment averages, and MSE is the standard error square of Yi. c. The overall standard deviation (St). St = (MSE/n) / 2 d. Look up in the r table for the r value. (It depends on the degrees of freedom of the number of treatments and the number in each treatment, and α value.) e. Calculate the statistic value Rp. Then p are the group sizes such as 2, 3, etc. Rp = r [from table] × St f. Compare each treatment R value, for example: 1 vs. 2, 2 vs. 4, etc., by subtracting. g. Compare Rp values. If the calculated subtraction R is greater than the table value Rp, then there is a significant difference between the mean pairs. 3 Results and discussion (1) Relationship between rainfall intensity and erosion The results showed that, under rainfall intensities of 20mm/hr, 30mm/hr and 40mm/hr, the relationship between erosion and test slope can be obtained (Tables 2 to 4). The erosions of soil samples treated by ventilation and watertight resin in different matching are less than that of the control group. Moreover, the erosion decreased with an increase of the matching ratio. Further statistical analysis is needed to explore whether the difference between them is significant. The significance between each factor was checked by using Duncan’s multiple range test based on the obtained data (Tables 5 and 6). As shown in Table 5, the erosions of all slopes belong to the same subset, indicating no significant difference of treated soil erosion affected by slope variation. According to Tables 2 to 4, the erosion of soil treated by ventilation and watertight resin showed no significant increase as the slope increased. Therefore, applying ventilation and watertight resin in different slopes has good protective effect. Table 6 shows the relationship between different matching and erosion. The control group and matching 1% belong to the same subset, indicating that there is no significant difference of soil erosion treated by 1% matching and untreated one. However, there is significant difference between other matching and International Journal of Sediment Research, Vol. 25, No. 2, 2010, pp. 194–201
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control group or 1% matching, indicating that the ventilation and watertight resin has anti-erosion effect. Moreover, the treatment effect is more significant as the matching increases. The results showed that the anti-erosion effect was not obvious until the medication matching reached 5%, and the erosion at matching 1% was several times higher than that at 5%, indicating that 5% matching should be recommended for economical and convenient outcome (higher matching leads to difficulty in uniform spray, and poor workability). Since the slope increase causes more soil erosion, medication matching should be increased properly for steeper slopes. Table 2 Slope 20° 30° 40°
0% 17.9 25.3 29.2 Table 3
Slope 20° 30° 40°
0% 69.0 77.6 99.8 Table 4
Slope 20° 30° 40°
0% 83.5 94.5 153.8
Soil erosion with 20mm/hr rainfall Experimental matching 1% 5% 12.4 2.8 14.9 10.2 26.3 11.9
10% 2.6 5.3 6.8
20% 1.9 3.0 6.3
Soil erosion with 30mm/hr rainfall Experimental matching 1% 5% 47.5 12.0 68.2 18.3 80.3 31.3
10% 3.4 18.7 19.6
20% 2.6 6.4 6.9
Soil erosion with 40mm/hr rainfall Experimental matching 1% 5% 58 15.1 67.1 37.7 137.2 65.9
10% 13.3 29.3 38.7
20% 13.5 14.3 26.0
Table 5 Duncun’s multiple range test result for Slope and soil erosion compared Subset with α= 0.05 Slope Number 1 20° 15 23.7013 30° 15 32.7117 40° 15 49.3193 Significant 45 0.072 Table 6 Duncun’s multiple range test result for Cementation ratios and soil erosion compared Subset with α= 0.05 Experimental matching Number 1 2 20% 9 8.9789 10% 9 15.2922 5% 9 22.7956 1% 9 56.8732 0% 9 72.2806 Significant 45 0.335 0.254
(2) Penetration water quality variation The most sensitive pH value and conductivity were measured in this study to find out whether the ventilation and watertight resin could dissolve chemical matters and affect the soil or environment. During test runs, the water-quality variation through infiltration cultivation was investigated. The results showed that, after the soil sample was treated for 30 days, pH value and conductivity were not significantly different from those before cultivation, as shown in Table 7. The variation amplitude for pH value was 0.77, and that for conductivity was 0.56, both about 11% of the absolute value. Such results - 198 -
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suggested that, should this ventilation and watertight resin be applied on the grade surface for a long term, the soil sample property would not change and other relevant reactions or matters penetration due to the resin decomposition or chemical matters penetration would not occur. Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
pH 6.21 6.45 6.25 6.31 6.49 6.57 6.62 6.68 6.80 6.84 6.93 6.86 6.94 6.98 6.90
Table 7 Permeates water quality variation Conductivity Day 4.69 16 4.69 17 4.52 18 5.01 19 4.45 20 4.79 21 4.76 22 4.86 23 4.57 24 4.84 25 4.68 26 4.73 27 4.75 28 4.81 29 4.61 30
pH 6.89 6.87 6.91 6.87 6.83 6.85 6.82 6.91 6.86 6.89 6.88 6.93 6.98 6.87 6.92
Conductivity 4.74 4.69 4.97 4.68 4.78 4.65 4.91 4.88 4.87 4.98 4.79 4.86 4.70 4.69 4.96
(3) Soil hardness variation Field soil hardness variation test sites were situated on two adjacent steep landside slopes about 60 degree of mood word badland at Kaohsing County Tainliau Townshipn, one was sprayed ventilation and watertight resin, the other remained undisturbed, as shown in Fig. 4. Measured results of surface hardness were compared and analyzed. Before testing, this place had not rained for more than 2 weeks and the landside surface presented obvious dried cracks. This test was carried out by using a Yamanaka’s soil hardness tester and the results are shown in Table 8.
Un-treatment Treatment
The status of experimental area
Yamanaka’s soil hardness tester Fig. 4
Location of treatment and un-treatment for spray the ventilation and watertight resin
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Table 8 Measured results by using Yamanaka’s soil hardness tester Measuring soil hardness (mm) Average Standard error T-test value 33 34 28 34 36 Treatment area 32.6 2.6750 33 35 30 34 29 0.9491 32 33 30 34 27 Un-treatment area 31.5 2.5055 34 34 28 31 32 PS. When α = 0.05 the critical t value is 1.7341 and less than this test vales, thus reject null hypothesis. Project
Table 8 shows the soil hardness of ventilation and watertight resin plot was 28 to 36mm, with an average value of 32.6mm; while that of the untreated plot was 27 to 34mm, and average value was 31.5mm. The statistics analysis indicates insignificant, obviously, using ventilation and watertight resin has less affected on soil hardness. Moreover, through on-site investigation, cracks on mudstone surface still existed that were easy to erode. The anti-erosion mechanism of this ventilation and watertight resin was a reactant of foam elastomeric, directly blocks the raindrop instead of reacting with the soil. Therefore, during foaming, it did not penetrate deep into the soil. This spray was only for testing, and the depth was very thin. However, since the cracks on the mudstone surface covered a wide range, the resin was unable to penetrate deep into the landslide soil to improve the hardness or strength of subsurface soil layers. (4) Analysis of results The test results showed no significant variation of the exuded water quality during testing, which apparently indicated that after gelling, the ventilation and watertight resin did not release much chemical matters to affect exuding water quality or soil property. However, further tests and researches are needed to confirm whether it would release relevant matters to change water quality or affect soil properties. During actual spraying, since the reaction time of ventilation and watertight resin was very short, when the resin density was too high, it had poor workability and could be uneconomical; thus, the uniformity should be considered. When the resin density was too low, mudstone still had problems of easily cracking when dry, and the breaking off of the protecting layer during high-intensity rainfall. Moreover, the issues such as ventilation and watertight resin, low leakage and high ventilation, weather-resistant degree, combination with the hydroseeding, and the effects on subsequent growth should be further tested and discussed. 4 Conclusions Statistics analyses showed that the soil samples for exuding water quality, soil erosion with different conditions of slope, rainfall intensity and medication density: (1) The soil erosion of ventilation and watertight resin amended soils are less than the controlled group. Moreover, the erosion decreases as the matching of ventilation and watertight resin increases, nonetheless the effect of slope is insignificant. (2) The anti-erosion effect treated by low medication density is insignificant, and that adding matching density of higher than 5% is better. (3) For all treatments and during the experimental period the pH value and conductivity were no significant difference. Hence, this ventilation and watertight resin didn’t cause the sample soils or water quality to react or change. (4) Comparing the hardness average value of the experimental plot, the amended plot increased slightly than the control plot, but the statistics analysis showed insignificant. Obviously, this reagent has less affected on soil hardness. References Andraski B. J., Daniel T. C., Lowrey B., and Mueller D. H. 1985, Runoff results from natural and simulated rainfall for four tillage systems. Trans. ASAE, Vol. 28, No. 4, pp. 1219–1225. Barthes B., and Roose E. 2002, Aggregate stability as an indicator of soil susceptibility to runoff and erosion; Validation at several levels. Catena, 47, pp. 133–149. Bertrand, A. R., and Parr, J. F. 1961, Design and operation of the Purdue sprinkling infiltrometer. U.S.D.A. Res. Bulletin No. 723. Lafayette, IN. Carr, W.W., and Ballard, T.M. 1980, Hydroseeding forest roadsides in British-Columbia for erosion control. Journal Soil Water Conservation, Vol. 33, pp.33–35. - 200 -
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