Indian Journal of Science and Technology, Vol 9(39), DOI: 10.17485/ijst/2016/v9i39/94160, October 2016
ISSN (Print) : 0974-6846 ISSN (Online) : 0974-5645
Determination of Correlation between Laboratory based Electrical Resistivity and Bulk Density of Compacted Laterite Soil Muhammad Burhan Memon, Syed Baharom Azahar* and Waqar Hussain Qazi Department of Civil and Environmental Engineering, Universiti Teknologi PETRONAS, 32610 Seri Iskandar, Perak, Malaysia;
[email protected],
[email protected],
[email protected]
Abstract Objectives: The principal objective of this study is to contribute towards the possible replacement of the conventional techniques by implying geoelectrical technique which is an attractive tool for depicting sub surface soil profile to study the relationship between Laboratory Electrical Resistivity (LER) and Bulk Density (BD) of compacted laterite soil. Methods/Statistical Analysis: This research study is based on laboratory investigation of laterite soil properties and its relationship with electrical resistivity values. Findings: Beside some inconsistencies observed, the present study also reveals some significant results by showing a decreasing trend between electrical resistivity and BD for 40 soil samples. Application/Improvement: Laterite soil engineering properties are usually investigated through borehole sampling by employing heavy machinery, which affects the cost of the project and took too much time in the completion of the projects. Therefore an alternative, quick and less cost involved method is needed for soil investigation. Electrical resistivity technique is one of the most popular method which can be used for detailed soil investigation as being a cost effective, time saving and less effort involved method.
Keywords: Borehole Sampling, Bulk Density, Correlations, Laterite Soil, Laboratory Electrical Resistivity
1. Introduction
Soil engineering properties are acquired through borehole sampling which offers an accurate testing of subsurface soil profile but on the contrary, it involves much effort, cost, time, and fatigue. Geophysical methods are mainly comprised of electrical resistivity, seismic refraction, magnetic, radiometric, electromagnetic and ground penetration radar techniques. Beside other geophysical methods, the electrical resistivity technique is the most popular and preferable technique that is being used in the field of geotechnical engineering for the aim of soil investigation as being a cost- effective, time-saving and less fatigue involved method1. Various studies have been carried out by many researchers to understand the behavior of electrical
* Author for correspondence
resistivity with distinct soil properties such as soil moisture and salinity for agricultural purpose, hydrogeological properties of the soil, hydraulic conductivity of aquifers, subsurface water movement, detect water seepage through earth dam, assessing foundation stability, foundation structure of old buildings etc2–10. Also, there are studies which has been carried out on laterite soil only without considering the electrical resistivity measurements. An improved lateritic soil was used as a base material in highway pavement construction in order to prevent the application of crushed rocks which result in environmental problems11. The LER study on the sandbox to correlate electrical resistivity with moisture content and BD of clayey silt and silty sand was conducted1,12. A curvilinear correlation is observed between electrical resistivity and moisture
Determination of Correlation between Laboratory based Electrical Resistivity and Bulk Density of Compacted Laterite Soil
content. The study reported that the greater percent of moisture content in soil reduces the electrical resistivity value. A similar relation has been evaluated for electrical resistivity and BD. Previous studies rendered same results13,14. It is also recommended that the geophysical and geotechnical methods together can be used to depict meaningful contribution for the geotechnical engineers. The investigation of electrical properties of lateritic soil using electrical conductivity or resistivity measurements on a self-developed testing device was conducted15. The attempt was made to understand the behavior of resistivity with soil engineering properties. Correlation of water content, saturation, dry density, temperature, and soil structure with electrical resistivity has been developed. It was found that water content decreases with the increase in resistivity and similar relationship was observed for degree of saturation and dry density with resistivity. It has witnessed that the increment in temperature causes the electrical resistivity to be lowered. The variation in wet-dry cycle shows that the resistivity rapidly increased in the first 3 cycles whereas no significant variation was observed during 4th and 5th cycle. The concept related to electrical resistivity and unit weight correlation was also discussed by Memon MB et al. This research work aims to evaluate the relationship of electrical resistivity with BD of compacted laterite soil. This research study is carried out under laboratory conditions with the aim to correlate the BD values with electrical resistivity measurements.
2. Material and Methods Laboratory geophysical and geotechnical tests were carried out on disturbed laterite soil samples acquired from distinct field locations near Perak state, Malaysia. Soil sample was obtained by digging a burrow pit of approximately 0.3 to 0.5 meters depth using harrow and shovel. Soil material was then transferred into polyethene bags and tightened with cable ties. Soil samples taken to the laboratory were firstly air-dried, crushed and undersized followed by soil mixing of 3 kg soil mass with initially 10, 15, 20, 25 and 30% of distilled water added based on the nature of the soil tested. An increment of 5% of water was added after the soil was mixed thoroughly and compacted based on initial water addition. Prior to the compaction process, a thick plastic bag with binding tape was used as a lining material along the internal
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sides of the mold in order to prevent mold steel from affecting resistivity values. Soil material was compacted using automatic compactor machine into three equal layers; each layer exhibited 27 number of blows. Once the third and uppermost layer was compacted, the mold was taken outside from the machine and straightened using straightener which was then subjected to BD calculations. This procedure was repeated five times for five equal increments of water added in the soil mixer until the BD value lowered twice. Altogether 40 laterite soil samples were obtained and tested. LER measurements were taken on the mold by connecting the two disc electrodes at both sides of the cylindrical soil sample after the soil was mixed and compacted in three equal layers at every increment of water content. The procedure implemented was in accordance with BS 1377: Part 3: 1990. Five readings of resistivity were performed and LER measurements were carried out using a simple multimeter and DC power source. Potential difference of an average 60V was applied and resulting current was recorded for each sample. Electrical resistivity values were obtained by using Equation (1) and (2).
(1)
(2)
Where, V represents voltage (volts). I represents current (amperes). R represents resistance (ohms). A represents cross-sectional area of soil sample in mold in m2. L represents length of the soil sample in mold in meters. ρ represents resistivity(ohms meter).
3. Results and Discussion 3.1 Soil Samples Analysis
Overall 40 laterite soil samples procured from different field locations were tested and analyzed under laboratory environment. Correlation of BD values calculated from each number of sample tested was successfully developed with LER values by using Simple Regression Analysis
Indian Journal of Science and Technology
Muhammad Burhan Memon, Syed Baharom Azahar and Waqar Hussain Qazi
(SRA) in MS Excel 2013. Established correlations revealed quite a strong relationship between resistivity and BD measurements for laterite soil samples with the maximum R-square value of 0.957. Results showed a nonlinear relationship between resistivity and BD. Correlations indicate that as the BD increases, a decrement in resistivity value will be observed. The procured relationship may be due to the presence of water in soil pores which causes increment in the BD of soil and thus declined resistivity by facilitating the movement of current without causing any hindrance. Apart from some significant results, there were few soil samples which showed inconsistent relationship and found that due to the increase in BD the resistivity also increased and after reaching at some point resistivity again started to decline. This might be when the water content was added to the soil during mixing then some water might dry out due to some heat released by mixer blade which causes the soil to be dried and resistant therefore results in the higher resistivity. Relationship of electrical resistivity with BD for 40 soil samples is illustrated from Figures 1 to 8.
Figure 3. to 15.
Relationship of LER with BD from sample 11
Figure 4. to 20.
Relationship of LER with BD from sample 16
Figure 1. Relationship of LER with BD from sample 1 to 5. Figure 5. Relationship of LER with BD from sample 21 to 25.
Figure 2. to 10.
Relationship of LER with BD from sample 6
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Figure 6. Relationship of LER with BD from sample 26 to 30.
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Determination of Correlation between Laboratory based Electrical Resistivity and Bulk Density of Compacted Laterite Soil
LER study have been successfully discussed to find its relation for the BD of compacted laterite soil. Moreover, results obtained so far can contribute towards the better understanding of the resistivity phenomenon to replace the borehole sampling for geotechnical properties of laterite soil.
5. References Figure 7. to 35.
Relationship of LER with BD from sample 31
Figure 8. Relationship of LER with BD from sample 36 to 40.
Findings of current research study are verfied with previous studies for example12,17 carried out LER study on sand box to correlate moisture content and BD of clayey silt and silty sand and found a curvilinear correlation between electrical resistivity and BD. Therefore, it is suggested that the geophysical and geotechnical techniques for soil testing together can be used to depict meaningful contribution for the geotechnical engineers in the foundation, design and construction of roads and buildings.
4. Conclusion Electrical resistivity and BD correlations have been successfully established for compacted laterite soil samples. The results obtained from the analysis indicate strong relationship between LER and BD. Despite of good relation for some soil samples, few samples revealed some inconsistent results, which needs to be verified through conducting more tests in the future. However, based on the analyzed results, it could be concluded that the
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1. Hazreek Z, Aziman M, AzharA, Chitral W, Fauziah A, Rosli S. The behaviour of laboratory soil electrical resistivity value under basic soil properties influences. IOP Conference Series: Earth and Environmental Science, IOP Publishing; 2015. p. 1–10. 2. Jiao-Jun Z, Hong-Zhang K, Gonda Y. Application of Wenner configuration to estimate soil water content in pine plantations on sandy land. Pedosphere. 2007; 17(6):801–12. 3. Liu X, JiaY, Zheng J, Shan H, Li H. Field and laboratory resistivity monitoring of sediment consolidation in China’s Yellow River estuary. Engineering Geology. 2013; 164:77– 85. 4. Corwin D, Lesch S. Apparent soil electrical conductivity measurements in agriculture. Computers and Electronics in Agriculture. 2005; 46(1):11–43. 5. Lesmes DP, Friedman SP. Relationships between the electrical and hydrogeological properties of rocks and soils. Hydrogeophysics, Springer; 2005. p. 87–128. 6. Purvance DT, Andricevic R. On the electrical-hydraulic conductivity correlation in aquifers. Water Resources Research. 2000; 36(10):2905–13. 7. Arora T, Ahmed S. Characterization of recharge through complex vadose zone of a granitic aquifer by time-lapse electrical resistivity tomography. Journal of Applied Geophysics. 2011; 73(1):35–44. 8. Cho I-K, Yeom JY. Crossline resistivity tomography for the delineation of anomalous seepage pathways in an embankment dam. Geophysics. 2007; 72(2):31–8. 9. Cardarelli E, Cercato M, Filippo DG. Assessing foundation stability and soil-structure interaction through integrated geophysical techniques: A case history in Rome (Italy). Near Surface Geophysics. 2007; 5(2):141–7. 10. Zeid NA, Balducci M, Bartocci F, Regni R,Santarato G. Indirect estimation of injected mortar volume in historical walls using the electrical resistivity tomography. Journal of Cultural Heritage. 2010; 11(2):220–7. 11. Jaritngam S, Somchainuek O, Taneerananon P. An investigation of lateritic soil cement for sustainable pavements. Indian Journal of Science and Technology. 2012 Nov; 5(11):1–4. 12. Abidin MHZ, Saad R, Ahmad F, Wijeyesekera DC, Yahya AS. Soil moisture content and density prediction using laboratory resistivity experiment. International Journal of Engineering and Technology. 2013; 5(6):731–5. 13. Siddiqui FI, Osman S. Integrating geo-electrical and geo-
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technical data for soil characterization. International Journal of Applied Physics and Mathematics. 2012; 2(2):104. 14. Tezel O, Ozcep F. Relationships of electrical resistivity and geotechnical parameters. Proc of Conf on Earth Sciences and Electronics; Istanbul, Turkey. 2003.p. 1250–68. 15. Bai W, Kong L, Guo A. Effects of physical properties on electrical conductivity of compacted lateritic soil. Journal of Rock Mechanics and Geotechnical Engineering. 2013; 5(5):406–11.
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16. Memon MB, Osman SBABS, Qazi WH. Effects of shear strength properties on electrical resistivity of compacted laterite soil: A conceptual model. ARPN Journal of Engineering and Applied Sciences. 2016; 11(6):3663–7. 17. Hazreek ZAM, Aziman M, AzharATS, Chitral WD, Fauziah A, Rosli S. The behaviour of laboratory soil electrical resistivity value under basic soil properties influences. IOP Conference Series: Earth and Environmental Science; 2015. p. 1–10.
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