Investigation on Some of the Engineering Properties of Soils Found in Haromaya Town, Ethiopia
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Date
2016-04
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Addis Ababa University
Abstract
As construction expands to news frontiers, frequent problems are being faced in the civil engineering structures such as cracking and break-up of pavements, highway,embankments, roadways, building foundations, slab-on-grade members and, channel and reservoir linings, irrigation systems, water lines, sewer lines. The problems are either due to not understanding of the behavior of the soil or lack of information on the engineering properties of the soil. Therefore, to obtained information on type, characteristics and distributions of soil, geotechnical investigations should be done on soil and rock underlying (and sometimes adjacent to) the site of the proposed structures.
The objective of this research is to investigate the engineering properties of soil found in Haromaya town. To achieve this objective ten sampling areas were selected. From the selected sampling areas, pits were excavated to a maximum depth of three meters and both disturbed and undisturbed samples were collected. Laboratory tests were done on the collected samples.
The laboratory test result indicates that the natural moisture content for CH soil ranges from 13.5-33.5%, specific gravity ranges from 2.7-2.84, Liquid Limits ranging from 52-72%, Plastic Limit ranges from 21.3-28.4% and plasticity index ranges from 25.9-45.5%, free swell ranges from 35-75%. The natural moisture content test results showed that for CL soil ranges from 11.5-27.6%, specific gravity ranges from 2.7-2.75, Liquid Limits ranging from 32-44.9%, Plastic Limit ranges from 8.25-22% and plasticity index ranges from 14.7-28%, free swell ranges from 30-75%. The natural moisture content test result indicates that for SM soil ranges from 10.5-25%, specific gravity ranges from 2.65-2.74, free swell ranges from 20-30%. The natural moisture content test results showed that for expansive soil ranges from 29-35.9%, specific gravity ranges from 2.75-2.8, Liquid Limits ranging from 86.4-87.3%, Plastic Limit ranges from 23-23.8% and plasticity index ranges from 63.3-63.4% free swell ranges from 105-113%.
The grain size analysis test results showed that the dominant proportion of soil particles on the research area was clay and sand. For the CH soil a clay content ranging from 36.1-65.75%, silt fraction 18.3-36.7%, sand fraction 6.88- 39.6% and gravel content from 0.0-6.9%. For the CL soil clay content ranging from 49.6-65.4%, silt fraction 19.9-34.1%, sand fraction 7.99-24% and Investigation on some of engineering properties of soils found in Haromaya town 2016 Geotechnical engineering AAiT/AAU X
gravel content from 0.0-8.6%. Clay content for SM soil ranging from 1.6-10.3%, silt fraction 5.2-21.1%, sand fraction 67.7- 84.3% and gravel content from 0.9-9.0%. For the expansive soil clay content ranging from 50.2-50.5%, silt fraction 21.9-32.2%, sand fraction 9.7-10.0% and gravel content from 7.7-18.5%.
From the compaction test results the maximum dry density (MDD) of Haromaya soil ranges from 1.39 to 1.52 g/cm3 and the optimum moisture content lies between 13 to 23.4 percent.
According to the Unified Soil Classification System, the soil is categorized as CH (high plastic clay soil), CL (low to medium plastic clay soil) and SM (silty sand). The AASHTO Classification System shows that most of soils of study areas categorized on A-7-6 and A-6 therefore those soils have poor quality for use as subgrade.
The unconfined compressive strength test result for CH soil ranges from 132.2kN/m2 - 273.4kN/m2 this indicates that consistency of the soil of the study area ranges between stiff to very stiff. The direct shear test result indicates that areas near Lake Haromaya are cohesionless soil material with angle of internal friction, ϕ = 27.30 and cohesion, C = 2.35 (kN/m2).
One-dimensional consolidation test result shows that the area under investigation is over consolidated in its natural state having compression index ranging from 0.13-0.33, pre-consolidation pressure 90-150kPa, swelling pressure ranging from 14-110kPa and over consolidation ratio ranges from 1.41-2.54.
Therefore it was found out that area Haromaya soil is mostly covered with red clay soil. Those materials are generally considered the poorest performers with regard to roadway construction, but can be utilized as sub-grade material.
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civil engineering