Journal of Sustainable Development Vol. 6. No. 1 DETERMINATION OF SOIL CHARACTERISTICS OF EROSION SITES AND EARTH FILL IN ROAD MAINTENANCE AND CONSTRUCTION IN SOUTHEAST NIGERIA TOLUBANWO, S. E.1; IJIOMA, C. I2 AND KADURUMBA, C. H.1 1. National Root Crops Research Institute, Umudike, Abia State, Nigeria. 2. Department of Agricultural Engineering, Federal University of Technology, Owerri, Imo State, Nigeria ABSTRACT Southeast Nigeria has the worst scenario in gully and erosion menace as well as very bad road network. A technical characterization of soil type in Amaifeke, Ihioma and Okwudor all in Orlu of Imo State, Nigeria was carried out. The objective was to determine suitable soil with highest properties that can be used in earthfill. From the analysis carried out, Amaifeke soils exhibited highest cohesion, liquid and plastic limits of 10KN/m2; 56 and 23% respectively, than 5KN/m2; 41 and 20% for Ihioma soils and 3.5KN/m2; 29 and 18.2% for Okwudor soils. It is equally important to note that irrespective of percentage slope and compactive energy imposed on the site, soil loss was consistently least in Amaifeke site. The results therefore showed that in Orlu Zone, Imo State, Amaiefeke is the best site to collect soil for earthfill when compared to soils from Okwudor and Ihioma in raod construction and erosion/gully control. Keywords: Soil characteristics, Erosion, Earth fill, Road maintenance INTRODUCTION their stability, shear strength, infiltration capacity with fine particle are resistant to Most soils in the South East Nigeria are more of detachment because of their cohesiveness. Evans coastal soils and like most within the acids sand (1980) examined erodobility in terms of clay areas in Nigeria, have been subjected to cycles of content, while (Okagbue, 1987) compiled the degradation due to man’s activities and opinions of several authors as the causes of gully ecological problems (Tolubanwo, 2005). The erosion. resultant effect of this is that the soils are highly weathered due to high rainfall in the area above The extent of erosion is not just proportional to 2000mm/annum which washes away particles the steepness of the slope, but rises rapidly as of the loss solis (Chukwu, 1999). This leads to rill slope increases. MOWD (1992) showed that erosion, which ultimately depends and become excessive quantities of fertile soils have been gully. Gully erosion is a major problem in part washed from cultivated steep slope (>6%). It is of Imo State, especially in Orlu area (Ijioma, very important to note that soils from erosion- 1988) and generally in the Southeast Nigeria prone areas, especially the lateritic soil are (Okagbue, 1987). It has degraded the soil which widely used as subgrades and earth fill results in structural failure. Gully erosion is materials in engineering construction works responsible for the destruction of transportation without fully subjecting the areas to erosion and communication systems, degradation of tests. This practice often leads to regular arable land, contamination, and more than 2,500 structural failures during and after rainstorms gullies are active in the Southeast Nigeria (Tolubanwo, 2005). A technically (Egboka, 2004). characterization of soil in Orlu zone, Imo State of Southeast Nigeria was therefore undertaken The problem of gully erosion in Imo State has to assess the qualities of these soils for earthfill been identified as a major environmental purposes in controlling erosion as well as in problem. Ijioma (1988) examined the compactive road maintenance/construction. energy for erosion control on earthfill materials at Ohafia and found that it has significant effect on the compacted soil with regard to soils loss. He then recommended that similar tests be carried out at different locations and to relate 54 Journal of Sustainable Development Vol. 6. No. 1 MATERIALS AND METHOD of the soils was determined by the use of flame photometer. This study was conducted at three sites: Okwudor, Ihioma and Amaifeke all in Imo State, Southeast Nigeria. The parameters of the site are RESULTS AND DISCUSSION as follows: Okwudor (050 48’N; 070 01’E); Ihioma (050 41’N; 070 02’E) and Amaifeke (050 47’N; 070 The physical analysis of the three burrowed sites 01’E). The soils are typical of the acid sands is presented in Table 1. Results showed that derived from false-beded stand stones and Okwudor, Ihioma and Amaifeke soils are sandy coastal plain sands (Fdalr, 1990). The physical (Fdalr, 1990). The percentage finer particles of laboratory tests were carried out on the soil Okwudor are 1.9%, Ihioma 2.3% and Amaiefeke samples, before the soils were tilled into the test 3.5%. The internal friction and cohesion force for channel (1.2m X 1.6m X 0.7m) to a depth of the three soils are also shown in Table 1. 0.22m. The beds were compacted in lifts using Amaiefeke soil has the highest cohesive force, 39Kg roller compacter. Three compactive 10KN/m2 than Okwudor and Ihioma soils with energies (95.7, 191.3 and 382.6 KJ/m3) strength cohesion of 3.5 and 5.0KN/m2 respectively. of the soils were determined. Ring samples were Consequently, the soils at Amaifeke are likely to used to collect soil from the channel to have highest resistance to erosion since cohesive determine the dry density. The holes were force varies directly with resistance erosion refilled and recompacted at first set of tests were (Morgan, 1990). Similarly, Amaifeke has the performed at 1.5% slope, number of passes (NP) highest liquid and plastic limits among the soils =5 and number of lift (NL) =4. The discharge for suggesting its potential to resist soil erosion than the test was from Otamiri Rivers. Water was other soils. Also, Okwudor and Ihioma soils introduced to the channel by pumping waters more dispersive in waters and hence very from Otamiri Rivers through the design flow susceptible to erosion force than Amaifeke soil. tank. The flow was maintained constant. The Table 2 shows the quantity of soil loss relation of detached sediments were deposited on the soil loss relation to percentage slope. Quantity of flume or transported to the sedimentation tank. soil lost varied directly as percentage slope These sediments were collected at the end of the increased, confirming the report of MOWD test and electric conductance bridge was used to (1992) and (Morgan, 1990). Table 3 shows the indicate the commencement of soil detachment. effect of compactive energy on soli loss across The washed soils were transferred into locations. It was observed that compactive containers and weighed prioir to drying energy of 383.6JKJ/m3 had the least soil loss was overnight in the oven. The weights of the dry also least in Amaifeke irrespective of the soils were determined. The above process was compactive energy imposed. This confirmed the repeated using 10passes, 20passes on slopes of 3, report that compactive energy 382.6KJ/m3 5 and 9% respectively. The sodium (Na+) content reduced the erodibility of soils (Ijioma, 1988). Table 1. Selected Results of the physical parameters at the three burrow site in Orlu Zone Parameters Okwudor Ihioma Amaifeke Liquid limit (%) 39.0 41.0 56.0 Plastic limit (%) 18.2 20.5 23.9 Plastics index (%) 20.5 20.8 31.1 Sand (%) 98.1 98.1 97.4 Fine (Silt+Clay) (%) 1.9 1.9 2.6 Cohesion (KN/m3) 3.5 5.0 10.0 Angle of internal friction 42.5 40.5 39.5 Specific Gravity 2.68 2.67 2.61 Moisture content (%) 12.2 11.2 16.7 Dry density (Kg/m3) 2038.6 2063.7 1935.7 Dispersion ratio 0.60 0.47 0.32 55 Journal of Sustainable Development Vol. 6. No. 1 Table 2: Effect Percentage Slope on Soil Loss (Kg/m2) Slope (%) 1.5 3.0 5.0 9.0 Location Soil Loss (Kg/m2) Mean S.E Okwudor 1.59 2.07 3.60 8.88 4.03 2.36 Ihioma 1.09 1.37 1.89 3.88 2.06 0.89 Amaifeke 0.12 0.18 0.32 0.52 0.28 0.13 Mean 0.93 0.21 0.74 4.43 - - SE 0.28 0.90 1.27 2.42 0.00 0.00 Table 3: Effect of Compactive energy (KJ/m3) on soil Loss (Kg/m2). Compactive Energy (KJ/m3) 95.7 191.3 382.6 Soil Loss (Kg/m2) Location Mean SE Okwudor 4.13 4.00 3.95 4.03 0.05 Ihioma 2.15 2.03 1.98 2.05 0.0189 Amaifeke 0.40 0.29 0.18 0.29 0.0242 Mean 2.23 2.11 2.02 SE 1.077 1.067 1.09 - - CONCLUSION due to compactive energy than Ihioma and Okwudor soils.It is therefore recommended for Amaifeke site is a better choice for soil earthfill erosion control and in road rehabilitation/ purpose than soil from Okwudor because of its construction in the Southeast Nigeria with high high cohesive strength, higher plastic and liquid rate of erosion problems and very bad road limits. The soil is also least susceptible to losses network. REFERENCES Chukwu, G.O. (1999); Estimation of water requirements of soya bean and groundnut in the Southeastern Nigeria; Journal of Sustainable Agric and Environment; 1 (1):150-154. Egboka, B. (2004); “Gully erosion in Alaigbo” Osondu Newsletter, Online edition, vol.4. http://www.osondu.com/abec/erosionindex.htm 56 Journal of Sustainable Development Vol. 6. No. 1 Evans, R. (1980); Mechanics of water erosion and their spatial and temporal controls,109-128. Fdalr; (1990); Deatil Soil Map of Nigeria, Federal Ministry of Agriculture, Abuja. Ijioma, C.I.(1985); Compactive Energy for Erosion and Earthfill Materials at Ohafia, Imo State of Nigeria, Proceeding of the International Symposium on Erosion in S.E.