Nigerian Journal of Technology (NIJOTECH) Vol. 36, No. 4, October 2017, pp. 1016 – 1021 Copyright© Faculty of Engineering, University of Nigeria, Nsukka, Print ISSN: 0331-8443, Electronic ISSN: 2467-8821 www.nijotech.com http://dx.doi.org/10.4314/njt.v36i4.4 INVESTIGATION OF SHEAR STRENGTH PARAMETERS AND EFFECT OF DIFFERENT COMPACTIVE EFFORT ON LATERITIC SOIL STABILIZED WITH COCONUT HUSK ASH AND LIME C. C. Ikeagwuani1, D. C. Nwonu2,*, C. Eze3 and I. Onuoha4 1,2,3,4 DEPARTMENT OF CIVIL ENGINEERING, UNIVERSITY OF NIGERIA NSUKKA, ENUGU STATE NIGERIA Email addresses: [email protected], [email protected], 3 [email protected], [email protected] ABSTRACT This paper presented the results of the shear strength parameters and compaction characteristics of lateritic soil stabilized with a combination of Lime and Coconut husk ash (CHA) in various percentages using two compaction methods namely; British standard heavy (BSH) and British standard light(BSL). Undrained triaxial test was conducted to determine shear strength parameters of the stabilized soil with confining pressures of 69kN/m2, 138kN/m2 and 276kN/m2, after preliminary tests had been carried out to determine index properties of the soil. The test was conducted on a mixture of natural soil with 4%lime, which gave least plasticity index and percentages of CHA from 0- 12% by dry weight of soil. The BSL and BSH were applied on mixture of soil + 4% lime + percentages of CHA ranging from 4-20% by dry weight of soil. The most plausible improvement in maximum dry density was obtained by adding 4% lime + 12% CHA and 4% lime + 16% CHA using BSH and BSL respectively. The results also show significant improvement in angle of internal friction and cohesion of the soil at 6% and 8%CHA addition respectively. Keywords: Coconut husk ash; Compaction; Lateritic soil; Lime; Shear strength; Stabilization. 1. INTRODUCTION Although in its natural state, the extent of its usefulness The dwindling economic fortunes of most countries in geotechnical engineering application cannot be around the world particularly Nigeria has taken its toll ascertained. This is as a result of the fact that in greatly in the infrastructural development of the geotechnical design, variations prevalent in the natural country. The construction industry is more often than soil deposit and its properties is among the greatest not the most affected negatively due to its high threats encountered [2]. This poses some great involvement in the execution of most capital projects. challenges in determining the actual behaviour of soils The impact on the extremely scarce resources available under the action of imposed load. Among the soil for most construction works has been very devastating properties, it is the shear strength of the soil that resulting in the attendant inflation in the cost of most determines the ability of the soil to transmit load to the conventional construction materials. The need layers beneath. Whereas the maximum dry density therefore to evolve other relatively cheap but highly (MDD) achieved through compaction gives indication efficient alternative constructional materials cannot be of the strength of the compacted soil [3]. fully overemphasized. In the execution of construction projects on soils in 1.1 Shear Strength most tropical countries such as Nigeria, the most Shear strength of the soil can be seen as the magnitude naturally occurring and highly abundant soil is the of shear stress that will result in yielding of a soil mass lateritic soils. Laterite is a rock deposit principally of under load and is believed to exist due to interaction of sedimentary origin which is known to form due to particles brought about by cohesive and frictional weathering, and is one of the most readily available forces [4]. As such, the soil shear strength is measured raw materials for road construction in Nigeria [1]. in terms of cohesion and angle of internal friction of the Therefore, lateritic soils hold great potential with soil particles. The shear strength of the soil is therefore respect to offsetting the cost of construction projects. likely to be affected by any action than can impact on * Corresponding author, tel: +234 – 806 – 534 – 5122 INVESTIGATION OF SHEAR STRENGTH PARAMETERS AND EFFECT OF DIFFERENT COMPACTIVE EFFORT ON LATERITIC … C. Ikeagwuani, et al the cementation or interlocking of the soil particles [5]. with CHA. They discovered that the addition of CHA Furthermore, it is known that strength properties of greatly improved the geotechnical properties of the the soil are affected by soil composition, initial soil. Furthermore, it has been asserted by [4] that the condition, loading condition and its structure [6]. fines content of lateritic soil has a significant effect on Structure here would include factors like cementation its shear strength parameters, having done a research and voids that can affect particle arrangement within work which showed that an increase in fines content the soil [6]. Hence, a method of improving the structure reduces and increases the angle of internal friction and of the soil to augment its strength properties would be cohesion of the soil respectively. the use of admixtures to induce cementation of soil Based on the works of the aforementioned researchers, particles and filling of existing voids within the soil a combination of fine particles of CHA and lime could mass. Stabilizing agents like lime, etc are widely have a significant effect on the shear strength applied in soil stabilization to improve the soil parameters and compaction characteristics of the properties. natural lateritic soil. Hence, this research work is an investigation to determine the shear strength 1.2 Compaction parameters and effect of different compactive effort on Compaction is a mechanical form of soil stabilization lateritic soil stabilized with a combination of coconut that is widely applied in executing construction husk ash and lime. This work therefore aims to projects. Compaction is very pertinent to soil determine the combination that will produce the stabilization and the MDD obtained through maximum cohesion, angle of friction and optimum compaction is directly related to the strength of the MDD for the stabilized soil. compacted soil [3]. Furthermore, the soil type, addition of admixtures, compactive effort and moisture content 2. MATERIALS affects the dry density of soil achieved by compaction 2.1 Soil Sample [7]. The lateritic soil used for this work was obtained from a borrow pit of about 2m depth in a single location at 1.3 Brief Review about 1 kilometer from the green house gate of the Since the advent of soil stabilization technology, lime University of Nigeria Nsukka in Enugu state. Nsukka is stabilization has been the most widely used for the said to lie at latitude of 6°51’24”N and longitude of stabilization of weak soils. However, due to its soaring 7°23’45”E according to the geographical map of Nigeria cost implications, it is often added with other relatively [12]. The soil was dug out of the borrow pit with the aid cheap additives for soil stabilization. One of such of a shovel and this can be described as a disturbed additives is Coconut Husk Ash (CHA), a product of sampling method. The sample was collected and sealed combustion of coconut husk, which is a major in polyethene bags to prevent ingress of moisture that agricultural waste from tropical regions. CHA has can change the moisture content of the natural soil. The proved to be very efficient in soil stabilization because collected soil sample was taken to the soil mechanics of its siliceous, aluminous and iron oxide content [8]. laboratory section of the Department of Civil The combination of lime and CHA as stabilizing agents Engineering, University of Nigeria Nsukka were the soil in this research work was to offset the cost required for tests were conducted. lime stabilization. In recent times, some researchers have worked on combination of different stabilizing 2.2 Lime agents for the stabilization of lateritic soil. Two The lime that was used for the soil stabilization in this researchers [9] worked on combination of stabilizing research work was quicklime. Its principal sources are agents in which they used coconut shell, leaf and husk rocks, mainly chalk and limestone. The primary for stabilization of lateritic soil. Their result showed chemical composition of these rocks is calcium that the combination of coconut shell, leaf and husk ash carbonate, which is then chemically altered to produce improved the strength properties of the soil. Three the highly caustic material known as quicklime [12]. researchers [8], recently worked on the compressibility characteristics of lateritic soil stabilized with a 2.3 Coconut Husk combination of lime and CHA. They discovered that a The coconut husk used was the outer part of a coconut combination of 4% lime and 5% coconut husk ash usually discarded by consumers or used as tinder for improved the compressibility characteristics of the making fire in villages. It was obtained close to the natural soil. Some other researchers [10] [11], have house of a coconut dealer at Onuiyi, Nsukka town in also worked on the stabilization of poor lateritic soil Nsukka local government area. Nigerian Journal of Technology, Vol. 36, No. 4, October 2017 1017 INVESTIGATION OF SHEAR STRENGTH PARAMETERS AND EFFECT OF DIFFERENT COMPACTIVE EFFORT ON LATERITIC … C. Ikeagwuani, et al 3. METHODOLOGY 3.2.3 Atterberg’s Limits 3.1 Production of Coconut Husk Ash. The liquid limit and plastic limit were determined in The coconut husk ash used for this work was produced the laboratory using the Cassagrande apparatus, and by burning the collected coconut husk in a furnace at the tests were conducted in accordance with the the Department of Metallurgical and Materials specification in [13].