International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 08 Issue: 02 | Feb 2021 www.irjet.net p-ISSN: 2395-0072 © 2021, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 752 Correlation of Compression Index with Index Properties of Soil Samples from Several Places in Chattogram, Bangladesh. Sabrin Ara 1,* , Mohammad Salah Uddin 2 and Md. Nurul Hasan Showkat 3 1 Lecturer, Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet, Bangladesh. 2 Graduate Student, Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet, Bangladesh. 3 Student, Department of Civil Engineering, Port City International University, Chattogram, Bangladesh. ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - In Engineering application, physical properties (liquid limit, plastic limit, plasticity index) and mechanical property (Compression Index, Cc) of soil have been found to be imperative to determine. As the soil properties fluctuate from place to place and mostly unpredictable, it is essential to inspect the properties of soil for different locations. Again, performing laboratory experiments to determine the value of Cc is cumbersome and it triggers at developing a predictive equation for compression index in terms of the index properties. This study is an initiative to determine the index properties and Compression Index (Cc) of soil samples taken at several locations in Chattogram city and their correlation. Undisturbed soil samples were taken at eight different points for the desired laboratory tests. Specific Gravity test have been conducted to report more detail information of the soil samples. Moisture content of the soil samples have also been measured as water content interfere with the soil properties. From the results it is observed that, the value of Compression Index (Cc) increases with the increase in liquid limit. Correlation test between this two parameters conforms the relationship. Key Words: Liquid limit, Plastic limit, Plasticity Index (PI), Compression Index (Cc), Disturbed and undisturbed soil sample, Correlation. 1. INTRODUCTION This Soil is a complex system [1] which although does not give birth to life, is considered as the incubator for the living world [2]. It is a heterogeneous mixtures of air, water, mineral particles, organic ingredients, and living organisms [3, 4]. Properties of soil and their influences on the strength and sustainability of the structure needs to be assessed to avoid any unavoidable errors in effort and materials costly construction work. In Geotechnical Engineering, Atterberg limit (liquid limit LL, plastic limit PL) test is olden concept of testing soils in the era of advanced testing methods still it plays an important role in evaluation of cohesive soil properties i.e. how cohesive soil behavior (physical properties) changes with water content. Liquid limit helps to estimate the water content at which the soil initiates to flow and the plastic limit test is the assessment of the alteration of the soil sample to brittleness or ductility [5, 6]. On the other hand, the compression index (Cc) (mechanical property) supports to guess the amount of settlement that will take place in the respective area. Correlation of Plasticity index (difference between Liquid Limit and Plastic Limit) with compression index is essential to be examined to study how plasticity index will affect compressibility of soil. But it is highlighted that this approach is not anticipated as a substitute for completer site exploration, sampling and testing [7]. Undisturbed soil samples help to determine more accurate data while disturb samples may lead to some errors as the soil condition (both soil structure and moisture content) is not protected. Collection of undisturbed soil samples is quite challenging due to certain constraints like time, cost or diversity of soil deposits. In this paper attempt was made to generate a correlation of the compression index with the index properties with a view to reducing the experimental time and budget for the similar type of soil samples. 1.2 Background Studies As determination of compression index by Oedometer test is more expensive and time consuming compared to the determination of plasticity index by Atterberg Limit test, former researchers have made correlation of compressibility characteristics with index properties [8]. Researchers have used different parameters like liquid limit [9,10] natural moisture content [11], void ratio [12] to correlate with compression index to lessen the challenges of conducting laboratory test. Zaman, M. W. et al. [7] studied various correlations of the index properties with compression index of soil samples with an intention to reduce experimental time and cost and to predict the soil type. Widodo, S. and Ibrahim A. [13] performed a research on the correlation of compression index (Cc) with the index properties, void ratio and liquid limit. In a study of Ibrahim NM et al. [14] it is shown that when the value of plasticity index (PI) increases, the compression index (Cc) will also be increased. Jain VK, Dixit M and Chitra R [15] performed experiments on 44 soil samples and concluded that plasticity index and compression index have significant level of correlation while Vinod and Bindu [16] conducted their research on 18