ADVANCES in NATURAL and APPLIED SCIENCES

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1 ADVANCES in NATURAL and APPLIED SCIENCES ISSN: Published BY AENSI Publication EISSN: Special10(7): pages Open Access Journal Shear Modulus Of Soil Based On Surface Roughness Of Construction Materials 1 M. Murugan, 2 C. Natarajan and 3 K. Muthukkumaran 1 Associate Professor, Department of Civil Engineering, VV College of Engineering, Tamil Nadu, India. 2 Professor, Department of Civil Engineering, National Institute of Technology, Tamil Nadu, India. 3 Associate Professor, Department of Civil Engineering, National Institute of Technology, Tamil Nadu, India. Received 25 April 2016; Accepted 28 May 2016; Available 5 June 2016 Address For Correspondence: M. Murugan, Associate Professor, Department of Civil Engineering, VV College of Engineering, Tamil Nadu, India. Copyright 2016 by authors and American-Eurasian Network for Scientific Information (AENSI Publication). This work is licensed under the Creative Commons Attribution International License (CC BY). ABSTRACT The purpose of this paper is to estimate the initial shear modulus of soils based on the surface roughness of materials.interface shear modulus depends on soil type & gradation and surface roughness of specimens. By considering all the factors, a simple mathematical equation was arrived for interface shear modulus between soil and structural material.result indicates that interface shear modulus increases with the increment of the surface roughness of the specimens used in this study. The highest peak shear modulus is achieved when the surface is rough. This study is very important in the field of earthquake geotechnical engineering. KEYWORDS: Soil, Interface shear modulus, Initial shear modulus, surface roughness. INTRODUCTION Shear modulus is a most important property for evaluating the dynamic responses of soil structures at different sites. Seismic waves altered as they pass through soil layers, from bedrock to surface, change frequencies and amplitudes and these modifications result in different ground motion characteristics. Therefore, the effects of earthquakes in buildings and earthworks depend on the shear moduli of soil strata underlying the affected sites. In recent years many studies were performed to develop a general model to estimate shear modulus at small strain level. The initial shear modulus (G 0 ) is a very important parameter for seismic ground response analysis and also for a variety of geotechnical applications. A considerable number of empirical relationships have been proposed for estimating initial shear modulus for different kind of soils: [1,2,3]. Existing models for unsaturated soils are limited on empirical models for initial shear modulus [4,5] because the most of the literature experiments are included in investigating small strain behavior. 2.Soil Characteristics: Three different soils were selected. The index and engineering properties of these soils are presented in Table 1 to 3. The soils were classified according to IS: To Cite This Article: M. Murugan, C. Natarajan and K. Muthukkumaran., Shear Modulus Of Soil Based On Surface Roughness Of Construction Materials. Advances in Natural and Applied Sciences. 10(7); Pages:

2 387 M. Murugan et al., 2016/ Advances in Natural and Applied Sciences. 10(7) Special 2016, Pages: Table 1: Engineering properties of the sandy soils used in the study Soil Property Well graded sand Poorly graded sand Grain size analysis: Effective size, D 10 Coefficient of uniformity, C u Coefficient of curvature, C c Classification (unified) 0.36 mm SW 0.29 mm SP Specific gravity, G s Dry unit weight: Maximum, γ d(max) Minimum, γ d(min) kn/m kn/m kn/m kn/m 3 Table 2: Engineering properties of the gravel soils used in the study Soil Property Well graded gravel Poorly graded gravel Grain size analysis: Effective size, D 10 Coefficient of uniformity, C u Coefficient of curvature, C c Classification (unified) 2.52 mm GW 2.31 mm GP Specific gravity, G s Dry unit weight: Maximum, γ d(max) Minimum, γ d(min) kn/m kn/m kn/m kn/m 3 Table 3: Engineering properties of the SC soil used in the study % Passing Atterberg Limit Dry unit weight (kn/m 3 ) 4.75mm 425μ 75μ LL (%) PL (%) Ip γ d(max) γ d(min) Type of soil (IS 1498) SC 3. Surface Roughness Of Specimens: Three different types of specimens were used for this study; concrete, steel and timber with varying surface roughness. The specimens are shown in Fig. 1 to 3. Surface roughness of the material is one of the important factors that influence the shear strength parameters. Generally, Absolute roughness (R a ) is considered for calculating interface friction between two different materials. It is a measure of the surface roughness of a material. This roughness is generally expressed in units of length as the absolute roughness of the material. Surface roughness of specimens used in the study is given in the Table 4. Fig. 1: Concrete specimens used in this study

388 M. Murugan et al., 2016/ Advances in Natural and Applied Sciences. 10(7) Special 2016, Pages: 386-391 Fig. 2: Timber specimens used in this study Fig.

82 Epoxy coated concrete 0.44 Smooth surface timber 0.48 Medium surface timber 0. Rough surface timber 0.86 Epoxy coated timber 0.44 Smooth surface steel 0.51 Medium surface steel 0.

3 388 M. Murugan et al., 2016/ Advances in Natural and Applied Sciences. 10(7) Special 2016, Pages: Fig. 2: Timber specimens used in this study Fig. 3: Steel specimens used in this study Table 4: Surface roughness of specimens Steel specimens Smooth surface concrete 0.62 Medium surface concrete 0.88 Rough surface concrete 1.82 Epoxy coated concrete 0.44 Smooth surface timber 0.48 Medium surface timber 0. Rough surface timber 0.86 Epoxy coated timber 0.44 Smooth surface steel 0.51 Medium surface steel 0.76 Rough surface steel 0.92 Epoxy coated steel 0.44 Surface roughness, R a (μm) 4. Experimental Results: Interface friction angle was determined by conducting direct shear test. Fig. 4, 5 and 6 shows the effect of surface roughness of specimens on the initial shear modulus (G) for 0.2 N/mm 2 normal stress.

4 389 M. Murugan et al., 2016/ Advances in Natural and Applied Sciences. 10(7) Special 2016, Pages: Shear modulus (N/mm 2 ) 75 Well graded sand 55 Poorly graded sand Surface roughness (μm) Fig. 4: Effect of surface roughness of specimens on initial shear modulus (G) between sandy soils and specimens 85 Shear modulus (N/mm 2 ) Well graded gravel Poorly graded gravel Surface roughness (μm) Fig. 5: Effect of surface roughness of specimens on initial shear modulus (G) between gravel soils and specimens Shear modulus (N/mm 2 ) Surface roughness (μm) Fig. 6: Effect of surface roughness of specimens on initial shear modulus (G) between SC soil and specimens

5 390 M. Murugan et al., 2016/ Advances in Natural and Applied Sciences. 10(7) Special 2016, Pages: An Empirical Model For Predicting The Interface Shear Modulus Based On Surface Roughness: The experimental result shows that the interface shear modulus depends on soil type & gradation and surface roughness of specimens. By considering all the factors, a simple mathematical equation was arrived for the interface shear modulus between soil and structural material. The mathematical equation is valid only for surface roughness of specimens between 0.44 to 1.82 μm. Shear modulus between soil and structural material, G = a + b (R a ) where, R a = Surface roughness of structural material (μm) a & b are constants depends on soil type & gradation. The values of a & bwere obtained from the experimental results and tabulated in Table 5. Table 5: Constants a & b Type of soil Constants a b Well graded sand Poorly graded sand Well graded gravel Poorly graded gravel Sandy clay A scatter plot was drawn between the actual shear modulus (experimental value) and the predicted shear modulus (predicted from the developed mathematical equation) for all type of soils. From the scatter plot it was observed that the R 2 value for all the soil lies above Therefore, the developed equation is suitable for shear modulus prediction with less error. Fig. 7 shows the scatter plot between actual shear modulus and predicted shear modulus for well graded sandy soil. Measured shear modulus (N/mm 2 ) 80 R² = Obtained shear modulus (N/mm 2 ) Fig. 7: Scatter plot between actual shear modulus and predicted shear modulus for well graded sandy soil Conclusion: Examining the data, it could be seen that, the shear modulus at the interface increases with increase in surface roughness of specimens. The highest peak shear modulus is achieved when the surface is rough. Interface shear modulus also based on the type of soil and soil gradation. This study is very important in the field of earthquake geotechnical engineering to evaluate the performance of soil under dynamic loads. REFERENCES 1. Hardin, B.O. and W.L. Black, "Closure to vibration modulus of normally consolidated clays". Journal of Soil Mechanics and Foundations Division, ASCE, 95(SM6): Iwasaki, T. and F. Taksuoka, "Effects of Grain size and grading on dynamic shear moduli of sands". Soils and Foundations, 17(3): Biarez, J., A. Gomes Correia, H. Liu and S. Taibi, "Stress-strain characteristics of soils interesting the serviceability of geotechnical structures". 2nd International Symposium on Pre-failure Deformation Characteristics of Geomaterials, Torino (in press).

6 391 M. Murugan et al., 2016/ Advances in Natural and Applied Sciences. 10(7) Special 2016, Pages: Mancuso, C., R. Vassallo and A. d Onofrio, Small strain behavior of a silty sand in controlledsuction resonant column torsional shear tests. Canadian Geotechnical Journal, 39: Biglari, M., C. Mancuso, A. d Onofrio, M.K. Jafari and Shafieem, 2010b. A. Modelling the initial shear stiffness of unsaturated soils as a function of the coupled effects of the void ratio and the degree of saturation. Computers and Geotechnics, DOI: /j.compgeo

International Journal of Scientific & Engineering Research, Volume 7, Issue 5, May ISSN

International Journal of Scientific & Engineering Research, Volume 7, Issue 5, May-2016 36 EXPERIMENTAL STUDY OF THE BEHAVIOUR OF INTERFACES BETWEEN CARBON FIBRE REINFORCED POLYMERS AND SC SOIL S. Subburaj