Comparison of Geotechnical Properties of Laterite, Kaolin and Peat

This paper compares some geotechnical properties of Kaolin, Laterite and Peat. Laterite was collected from Bukit Banang while Peat sample was collected from Parit Nipah, both locations were in Batu Pahat, Johor. Meanwhile, kaolin that was used in this research was manufactured kaolin. These soil samples were subjected to routine laboratory analysis and resulting data were analyzed statistically using a correlation analysis. A laboratory testing program consists of “Basic properties test” to obtain general information on the materials (e.g Natural moisture content, Atterberg Limit, Specific gravity, grain size analysis, chemical composition and pH) and “Geotechnical properties tests” to measure specific properties that characterize soil behaviour for design and constructability assessments (e.g Standard Proctor Test, Unconfined Compressive Strength and CBR).The results showed that the Natural/initial moisture content for laterite, peat and kaolin is 22.54%, 480.61% and 0.22% respectively. Meanwhile Specific gravity for each soil was in the range 1.50-2.79.It was also found that the pH of all soil is acidic which lay in the range of 3.76-5.95.The UCS for the optimally compacted sample of laterite is 445.77 kPa, kaolin is 199.23 kPa and for peat is 58.70 kPa. This paper summarizes the result of analysis performed on all tests conducted. Based on the results, the geotechnical property of the soil is a highly dependent with the type of soil and therefore, determining the soil characterization and the soil strength should be considered during the planning phase of any earthwork construction operation.


Introduction
Geotechnical engineering is a speciality of Civil Engineering which deals with the properties, behaviour and use of earth materials (soil and rocks) in engineering works [1]. In most geotechnical engineering projects and problems, site characterization and property evaluation are the two most important elements. Thus, running through every aspect of the work is the need for sufficient understanding of what soils are and the principles that govern their importance. Soils are naturally occurring, highly complex materials with variable ingredients and properties. Since there are so many types of soils, it is important to describe and classify them in terms that exude their characteristics clearly and concisely [2].
A lot of studies have been done by previous researchers to find out more about the different of physical and engineering behaviour of different types soils. Particle size analysis is important for characterizing a variety of physical properties and affect porosity and permeability, and they are also related to the geotechnical properties of sediment [3]. Determination of soil conditions is the most important in civil engineering works. The geotechnical properties of soil such as its grain-size distribution, plasticity, compressibility, and shear strength can be assessed by proper laboratory testing [4]. This paper discusses the comparisons of geotechnical properties of compacted laterite, kaolin and peat.

Materials and Methods of Testing
Natural sample of Laterite (obtained from Bukit Banang, Batu Pahat) and Peat (obtained from Parit Nipah, Batu Pahat) was obtained manually from a borrow pit at a depth of about 1.5 m. The kaolin used in this research is manufactured Kaolin from the K&M Kaolin Malaysia Sdn Bhd. The collected and manufactured soil was subjected to laboratory tests in order to determine its basic and geotechnical properties. The test conducted included Natural Moisture Content, Atterberg Limits, Particle Size Analysis, Compaction (Standard proctor test), Unconfined Compressive Strength test (UCS) and California Bearing Ratio (CBR). These tests were conducted based on B.S 1377-1990.

Results and Discussions
Soil properties Soil classification test were perform based on BS 1377 (1990). The detailed results were summarized in Table 1 below.  Table 1 indicated that Coefficient of uniformity (Cu) for laterite, kaolin and peat is 105.26, 6.143 and 76.92 while coefficient of curvature (Cc) is 0.213, 1.329 and 0.0787 respectively. Meanwhile, the Plasticity index for investigated soil is 30.9% (laterite), 33.57% (kaolin) and 162.115% (peat). By using USCS classification, laterite was classified as CL, both kaolin and Parit Nipah peat was classified as CH and Pt. All of the investigated soil is characterize as acidic and peat has the higher amount of organic content than laterite and kaolin.

Compaction Test
The compaction curve presented in Fig.1 and Fig.2 was determined using the standard Proctor method. The value of maximum dry densities (MDD) and optimum moisture contents (OMC) for the soils has been summarized in Table 2. Moisture Density relationship Standard proctor tests were carried out on Laterite, Kaolin and Parit Nipah Peat. The difference can be allocate by some extended from the differences in the grain size distribution. Soil compactability determined by soil texture, soil water, organic matter content, soil aggregation and compaction effort [5]. At a lower water contents, the soil is stiff and the soil grains offer more resistance to compaction. The dry density achieved depends upon the type of soil. A well graded soil attains a higher dry density that a poorly graded soil. The susceptibility to compaction increases as soil organic matter content decrease. Due to lower specific gravity and higher water holding capacity, dry unit weight of peat is lower than inorganic soils.

Unconfined Compressive Strength Test
Unconfined compression strength (UCS) test were carried out on Laterite, Kaolin and Parit Nipah Peat .The results are shown in Fig. 3 and Table 3. Meanwhile Fig. 4 shows the failure patterns of the samples.  content, the greater the soil strength. Soils that have higher water content have weak soil strength.
Since the samples was compacted, soil texture also affects soil strength, this is because soils with a broad distribution of particle size are considered the most compactable although fine textured soils have been found to compact to relatively high densities [6]. Soils with a broad distribution particle sizes resisted strength more than soil with fine material. Bulk density is the third factor affecting soil strength as bulk density of a given soil increases soil strength also increases

California Bearing Ratio (CBR) Tests
The CBR test was carried out for both unsoaked and 4 days soaked samples, as required. For the unsoaked condition, CBR tests were carried out immediately. The relation of CBR value with respect to different soil properties are presented in Table 4.  Unsoaked CBR samples gives higher value compared to soak CBR for all types of soil. This is due to unsoaked soil specimen was partially saturated and having high suction pressure leads to high pressure between clay particles results high CBR value. It can be concluded that the CBR value of a given soil is controlled by the densification (the CBR value of the soil is dependent on the relative dry unit weight) [7]. The factors affecting CBR value are soil texture, moisture, and density. The testing procedure employed will depend on the type of material being tested. Granular soils were not greatly affected by swelling during the soaking period, and, therefore, the surcharge weights are not significant during this part of test [8]. In contrast, claylike soils, which are greatly affected by swelling pressures, will yield CBR values depending upon the weight of the surcharges used during the soaking period.

Conclusion
Analysis of data obtained from the study indicated that the geotechnical properties were influenced by different types of soil. This is because all the types of soil due to different water content, soil texture and bulk density. The behaviour and strength of soil is largely determined by the size of its particles and the migration of water through the soil skeleton. A change in water content influenced a change in the soil strength. Understanding the behaviour of various soils is an important concern to the engineer. A geotechnical property of soil is utmost important in designing from a buildings foundation to a highway overpass. So it is important for engineer to know how various soils behave in solving geotechnical problems.