International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 9, September 2013)

Determination of Compaction Characteristics of Maiduguri Soil F. A. Adeniji1, B. G. Umara2, J. M. Dibal3, K. A. Otobo4 1,2,3

Department of Agricultural and Environmental Resources Engineering, Faculty of Engineering, University of Maiduguri, P.M.B. 1069, Maiduguri. Borno State Nigeria 4 Graduate student Being the quantitative measure of wetness of a soil mass the moisture content of the soil, it is an important property that controls its compactive behavior and potential flooding [2]. Significant improvement in structural failure and environmental control could therefore be achieved when the MDD and OMC of a soil are known and incorporated in planning and construction, and in selection of tractors sizes and the appropriate soil moisture contents to handle. In geotechnical engineering, mechanical compaction is one of the most common and cost effective means of stabilizing soils. An extremely important task of geotechnical engineers is the performance and analysis of field control tests to assure that compacted fills are meeting the prescribed design specifications. Design specifications usually state the required density (as a percentage of the “maximum” density measured in a standard laboratory test), and the water content. In general, most engineering properties, such as the strength, stiffness, resistance to shrinkage, and imperviousness of the soil, will improve by increasing the soil density. The maximum dry density (MDD) and optimum moisture content, as defined below, are determined by establishing the moisture-density relationship of a material when prepared and compacted with a hammer at different moisture contents. The maximum density of a material for a specific compactive effort is the highest density obtainable when the compaction is carried out on the material at varied moisture contents [3]. The optimum moisture content (OMC) for a specific compactive effort is the moisture content at which the maximum density is obtained. It is the water content that results in the greatest density for a specified compactive effort. Compacting a material at water contents higher than (wet of) the OMC results in a relatively soil structure that is weaker, more ductile, less pervious, softer, more susceptible to shrinking; and compacting dry soil (at moisture lower than the OMC) does not achieve the specified degree of densification [4]. This explains why soils liquefy when their moisture contents exceed their OMC, possibly due to flooding, thereby loosing load carrying capacity. This illustrates the significance of determining MDD and OMC of any structural material.

Abstract--Compaction is one of the efficient ways to improve the strength and stiffness properties of soils, such as elasticity modulus and shear modulus. Moreover, compaction decreases soil settlement, improves bearing capacity and the stability of sloped embankments. An optimum water content is required to provide the best path to enter energy into soil and compact it. A constant value of energy applied to a particular type of soil, at optimum water content, leads to a maximum dry unit weight. The aforementioned parameters MDD , OMC) are not unique for various types of soils and vary with the type of soils and the compaction energy. This study was carried out to gain the understanding of the relationship between moisture content and bulk density of Maiduguri sandy loam soil, collected from the University research farm. The particle size distribution analysis of the soil was carried out using the dry sieving analysis method. The soil was loaded in the cylinder and compacted at different moisture contents and its dry bulk density determined. The plot of bulk density versus moisture content was drawn to obtain the soil’s compaction curve, yielding its optimum moisture content and maximum dry density for the soil as 15% and 1645kg/rn3 respectively. Keywords-- Maximum dry density, optimum moisture content, sandy loam soil, Maiduguri, semi-arid environment

I. INTRODUCTION Water logging and structural failure have been a common social and environmental predicament confronting Maiduguri and environs, particularly during the rainy seasons. This is strongly attributed to the reaction of the soil to variation in moisture contents under the weights of the structures. A precise means of alleviating this dilemma became one of the main concerns of structural engineers, town planners, and environmentalists in Maiduguri and environs. Also, farmers recorded depression in crop yields as consequence of soil compaction by tractors. The soil in the study area is predominantly used in crop production and often as structural material, such as road and dam fill up; and, most importantly as the base upon which buildings are founded. Maximum dry density (MDD) is generally one of the most important factors determining soil’s capacity to bear a load, and the behavior of a soil mixture is influenced more by its moisture content than by the other reasons [1].

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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 9, September 2013) Bulk density and total porosity are the most frequently used physical quantities to characterize the state of soil compaction [3]. Sridharan and Nagaraj [5] showed that there exists a definite relationship between the soil moisture content and the dry density of a compacted soil and that, for a specific amount of compaction energy used, and there is a particular moisture content at which a particular soil attained its maximum dry density. Figure 1 shows a typical sketch of the relationship between moisture content and dry density of a soil at particular compaction energy. On agricultural point of view, considerable research has been conducted to gain an understanding and to quantify the effects of soil compaction on crop growth [6; 7]. Emphasis has been placed on the importance of bulk density because it is greatly related to soil organic matter, air capacity, available water, and other properties that are vital to survival of crop. Availability of data on MDD and OMC will help in selecting tractor and machinery sizes to be used on agricultural farms to guard against over compacting agricultural soils to avert the loses in crop yields. On the other hand, it is an essential tool in design of structures, such dams. Therefore, it is desirable to obtain the values of MDD and OMC of natural soils. Despite this important feature, there have been little published data on MDD and OMC of soils in Maiduguri and environs. The objectives of the study were to determine the relationship between bulk density and moisture content; and to determine the optimum moisture content and maximum dry density of Maiduguri sandy loam soil.

300-500 mm and the average daily temperature ranging from 22 – 35 oC, with mean of the daily maximum temperature exceeding 40oC [8]. It has mainly sandy loam soils.

II. MATERIALS AND METHODS

Particle Size Analysis (PSA) Bulk density was observed to have been increasing steadily with moisture content until such a point where an increase in moisture content does not result in an increase in bulk density as in Figures 1 and 2. The Figure also shows that (MDD) relates to OMC in quadratic function. The coefficient of determination (R2) of 0.7732 indicates a strong degree of agreement between MDD and OMC.

Soil Sample Collection The soil samples were collected from the University Research Farm (URF) in nylon bags at five different places at a radius of 2-3 km and transported to the laboratory. A specially constructed sieve was used to separate samples from foreign materials such as plastics, bottles, plant residues, and all other visible materials. The soil is locally used for structural fills, road bases, as well as agriculture. Experimental Procedure The samples were then bulked and analyzed for particle size distribution following the procedure of [9] to determine the gradation of the soil. The soil was then subjected to manual compaction using a 16 kg rammer at a drop height of 1000 mm. The rammer has a central hollow pipe of mass 7 kg and height 1500 m. Each layer was compacted by giving 25 blows of freely falling rammer. The geometric dimensions of the soil were recorded before and after each compaction, from which the bulk density was then computed. This procedure was repeated at varying the moisture content in an ascending order until the soil sample was too wet to be compacted. Moisture Content was determined gravimetrically using triplicate representative samples from the compacted soils. III. RESULTS AND D ISCUSSION

Study Site The study was in conducted 2012 at the Agricultural and Environmental Resources Engineering laboratory, University of Maiduguri (13° 05E and 110 05E; and 345m above mean sea level). Maiduguri and its immediate environs is dry, within a semi-arid climate, savannah or tropical grasslands vegetation, light annual rainfall of about

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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 9, September 2013)

DRY DENSITY

MAXIMUM DRY DENSITY 100% COMPACTION

OPTIMUM MOISTURE CONTENT MOISTURE CONTENT Fig. 1: Sketch of the relationship between moisture content and dry density of a compacted soil

1800 MAXIMUM DRY DENSITY (Kg/m3)

1600 1400 1200 1000 800 600 400 200 0 0

5

10

15

20

25

MOISTURE CONTENTS (%) (W/W) Fig. 2. Relation between soil dry density and moisture content

But the negative value the first slope (-2.4253) and the skewed nature of the curve on the left hand side means the soil is only moderately graded and not fully well graded.

This implies some corrective measures need to be applied to the soil in its present form before it can reliably be used for any structural construction [3]. It also points that the soil contains substantive percentage of organic matters and many fine grained soils.

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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 9, September 2013) Table 1 Determination of Particle Size Distribution

Mass of sample collected = l00 g S/N

Sieve diameter (mm) 4mm 2mm 1mm 850μm 710 500 425 300 250 150 63 Pan

1 2 3 4 5 6 7 8 9 10 11 12

Mass retained (g)

Mass passing (g)

% retained

% Passing

1.56 3.20 2.78 1.22 0.85 2.57 0.84 1.19 7.53 24.31 36.81 15.90

98.44 95.24 92.46 91.24 90.39 87.82 86.98 85.79 78.26 53.95 17.14 1.24

1.56 3.20 2.78 1.22 0.85 2.57 0.84 1.19 7.53 24.31 36.81 15.90

98.44 95.24 92.46 91.24 90.39 87.82 86.98 85.79 78.26 53.95 17.14 1.24

Table 2 Bulk Density and Moisture Content Relationship with Compaction Under 5 Blows.

S/N

1 2 3 4 5 6 7 8

Moisture Content (MC) (%)

Mass of Soil (kg) Wet

Dry

1.15 2.90 5.48 9.59 10.40 15.04 17.76 20.11

3.90 3.90 3.90 3.90 3.90 3.90 3.90 3.90

3.86 3.79 3.69 3.53 3.49 3.31 3.21 3.12

Thickness of Soil (m) Before Compaction 0.1550 0.1520 0.1515 0.1499 0.1491 0.1398 0.1391 0.1280

After Compaction 0.1490 0.1410 0.1335 0.1219 0.1190 0.1094 0.1121 0.1260

The soil is therefore better as an agricultural rather than a structural material. Generally, from the results shows that the Maiduguri sandy loam soil has dry bulk densities of 1409.77, 1462.74, 1504.15, 1575.86, 1595.97, 1646.46, 1558.29, and 1347.51 kg/m3 corresponding to moisture contents of 1.15, 2.90, 5.48, 9.59, 10.40, 15.04, 17.76, and 20.11% (w/w) respectively. The maximum dry density (MDD) of the soil is 1645kg/m3 and the optimum moisture content (OMC) is 15.5 %.

Volume of Soil (m3) Before Compaction 2.85 x10-3 2.79 x10-3 2.78x10-3 2.75x10-3 2.74x10-3 2.57 x10-3 2.56 x10-3 2.35x10-3

Difference (m3)

After Compaction 2.74 x10-3 2.59 x10-3 2.45x10-3 2.24x10-3 2.19x10-3 2.01 x10-3 2.06 x10-3 2.32x10-3

1.10 x10-4 2.00 xl0-4 3.30x10-4 5.l0xl0-4 5.50.x l0-4 5.60 x l0-4 5.00 x l0-4 3,00x l0-5

Bulk Density (kg/rn3) Wet

Dry

1424.38 1505.20 1589.75 1741,04 1783.47 1939.97 1893.24 1684.39

1409.77 1462.74 1504.15 1575.86 1595.97 1646.49 1558.29 1347.51

IV. CONCLUSION Increasing moisture content of the sandy loam soil studied, results in an increase in bulk density with compaction up to the optimum moisture content of about 15.5 %, after which any increase in moisture content resulted in a decrease in bulk density from the maximum of 1645kg/m3 at optimum moisture content. Overall, however, the soil is better used for crop production than as a structural material.

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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 9, September 2013) [6]

REFERENCE [1]

[2] [3]

[4] [5]

Imhoff, S., A. P. Da Silva, and D. Fallow 2004. Susceptibility to compaction, load support capacity, and soil compressibility of Hapludox. Soil Sci. Society of America J. 68: 17-24. Osula, D. O. A. 1996: A comparative evaluation of cement and lime modification of laterite. Eng. Geol. 42, 71–81. Alavi, A. H., Gandomi, A. H., Mollahassani, A. Heshmati, A. A. and Rashed, A. 2010 . Modeling of maximum dry density and optimum moisture content of stabilized soil using artificial neural networks. J. Plant Nutr. Soil Sci. 173, 368–379 Borys M., Mosiej K. 2006. Regulations for evaluation of technical conditions and safety of flood banks, IMUZ Falenty. 321 Sridharan, A., Nagaraj, H. B. 2005: Plastic limit and compaction characteristics of fine-grained soils. Ground Improvement. 9, 17–22

[7]

[8]

[9]

Ohu, J.O., Folorunso, O.A. 1989. The effect of machinery traffic on the physical properties of a sandy loam soil and on the yield of sorghum in northeastern Nigeria. Soil Till. Res. 13, 399–405. Ohu, J.O., Folorunso, F.A., Adeniji, F.A. 1989. Critical moisture content as an index of soil compactibility of agricultural soils in Borno state of Nigeria. In: Soil Technology, Vol. 2, pp. 211–219. Arku, A.Y., S.M. Musa, A.L.E. Mofoke and J. M. Dibal. 2012. ReExamining Raw Effluents from Nigerian Bottling Company Maiduguri for Crop Irrigation. Journal of Applied Phytotechnology in Environmental Sanitation. 1(1):43-49. Tilligkeit, J.E. 2012. The spatial distribution of K-factor values across a toposequence and a soil survey map unit. Unpublished M. Sc thesis, Faculty of California Polytechnic State University, San Luis Obispo. 54p

Corresponding author: J.M. Dibal. [email protected], [email protected]

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