Browsing by Author "Tadesse, Samuel (PhD)"
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Item Application of Marble Dust to Improve the Engineering Properties of Expansive Soils to be used as Road Bedding Material(Addis Ababa University, 2016-12) Mada, Tagel; Tadesse, Samuel (PhD)Expansive soils are characterized by volume change due to variation in moisture content. The cyclic wetting and drying process causes vertical and horizontal movement in expansive soils leading to failure of civil engineering structures found on such soils. The problematic nature of such soils can be improved by employing chemical stabilization techniques such as lime, cement and enzyme stabilization. However, as these techniques are expensive to developing countries such as Ethiopia, locally available low cost materials can be applied as alternative to improve the engineering properties of expansive soils. In the present research work, the performance of marble dust to improve the problematic nature of expansive soils is investigated. The study is carried out on a highly expansive soil section of selected road project. The natural subgrade soil obtained from the highly expansive section of the road is characterized for its engineering and strength properties and it is found to be highly expansive soil with low bearing capacity, high swell and characterized as A-7-5 according to the AASHTO classification and rated as poor (unsuitable) subgrade material. The expansive subgrade soil is blended with increasing percentage by weight (5% to 30%) and the improvements in engineering properties are studied and it is noted that it improves with increasing percentage of marble dust and with increased periods of curing though it is not significant as compared to specification requirements of several standards. With the higher percentage of marble dust (30%), the swelling potential of the natural soil changed from ‘High’ to ‘Medium’, LL reduced from 88% to 63%, PI reduced from 52% to 34%, CBR increased from 0.9% to 2.25% and the CBR swell reduced from 8.6% to 5.3%. Un-soaked CBR test is conducted on the natural subgrade soil and the 30% marble dust blended sample and it has been noted that the subgrade class improves for both indicating significant reduction in project cost as result of reduction in pavement thickness. Thus, marble dust can be recommended as an alternative stabilizing agent for expansive soils by itself or being blended with small percentage (1-3%) of effective stabilizing agents such as lime so that significant project cost reduction and minimal environmental degradation can be assured.Item Assessment of Road Pavement Failure Along Addis Ababa-Modjo Trunk Road(Addis Ababa University, 2015-03) Abate, Asnake; Tadesse, Samuel (PhD)Most of the roads constructed in Ethiopia fail prematurely before serving the design life due to various causes arising from many factors. One of these roads failed before reaching design life time is the Addis Ababa-Modjo Trunk Road. The Addis Ababa-Modjo road is approximately 50 km trunk road and very crucial for the country’s transportation and tourism sector as it is the main import export corridor to and from the capital, Addis Ababa. The road carries the highest daily traffic in the country. This road was constructed and opened to traffic in the year 2000. The design pavement life was estimated 15 years, however; pavement structure failure have been manifested since 2005, within the first 5 years after opening to traffic. From end of 2007 to date the Addis -Modjo trunk road is repeatedly under periodic maintenance. Considerable resources have been spent during this period for periodic maintenance but without solving the basic problem. This maintenance is not working as each maintained section is failing with in short period, hence, it needs finding the root causes of the failure to come up with appropriate solution. Field and laboratory investigations which include visual condition survey, Benkelman Deflection measurement, test pitting and pavement layer profiling, materials sampling and testing have been conducted in order to investigate causes of failure moreover, the past traffic data was collected and analysed. Finally based on the investigation, expansive subgrade soil, side drain problem, workmanship problems, use of substandard materials are found to contribute for the pavement failure. However, it is noted that the traffic load take the highest share for the cause of pavement failure. Proper treatment of expansive subgrade soil, use of quality construction materials, proper maintenance design based on the forecasted traffic are recommended as mitigation measures. Key Words: Pavement Failure, Condition Survey, Traffic Loading, Maintenance, Benkelman Beam, Deflection.Item Consolidation and Settlement behavior of Residual lateritic soils of Western Ethiopia (The case of Tongo-Begi-Mugi Road Project, Contarct-1, Tongo-Gidami)(Addis Ababa University, 2015-03) Adugna, Tiruneh; Tadesse, Samuel (PhD)Compressibility of soils is one of the basic Engineering properties of Soils, and it mostly occurs through the process of consolidation. Consolidation is a time dependent process in which expulsion of water from a soil mass occurs due to the application of stress on it. Consequently, there exist change in volume in the vertical direction of the soil mass and this difference in thickness results the settlement of the structures constructed above the soil. On the other hand, degree of consolidation and extent of settlement varies with types of soils. Therefore, on this study an effort was made to reach the unique behaviour of residual laterite soils with regard to consolidation and settlement properties focusing on the western Ethiopia which is rich of such soils. To achieve the intended objective of the research, papers, journals and different books have been scrutinized under literature review, samples from the research area were collected, and then laboratory tests for index properties and primary consolidation have been carried out using disturbed and undisturbed samples respectively. From the test results, it has been observed that index properties of lateritic soils greatly are affected by pretest treatment and manipulation, and in the case of consolidation and settlement behaviours, laterite soils at intermediate and high stress levels depict very similar behavior to transported soils, but at the initial phase the lateritic soils behave as if overconsolidated due to their cementation bond whereas transported soils show overconsolidation due to the past stress historyItem Cost and Time Effect of Using Sub Grade ANSS Chemical Stabilizer on Road Construction (A Case Study of Addis Ababa City, Road Construction on Expansive Soil)(Addis Ababa University, 2016-01) Hailu, Helen; Tadesse, Samuel (PhD)Road connectivity is one of the key components for development in a city as well as in a nation, as it promotes access to economic and social services, generating increased income and employment. However, the construction of such economically vital sector is the most expensive and time taking public project undertaken by the government. Conventional pavement design and construction practices require high quality materials to fulfill minimum construction standards which will be transported from long distances from the project site under construction which is costly. In addition, natural resources are degraded and environmentally affecting the quarry areas which has significant environmental effect, and this way of construction takes longer time to complete the project. In many of road projects it is very difficult to obtain suitable construction materials for sub grade with in economical hauling distances. One of the proven technologies to reduce cost and time of road construction is enabling use of marginal materials by using stabilization of soil. Stabilization can be derived from chemical, electrical, mechanical or thermal means. In this study chemical stabilizer are considered. Chemical stabilizers can generally be categorized in to two broad categories: conventional and unconventional stabilizers. Conventional stabilizers such as cement lime, fly ash, and bituminous products have been intensely researched, and their fundamental stabilization mechanisms have been identified. Unconventional soil stabilizers are additives consist of a variety of chemical agents that are diverse in their composition and in the way they interact with the soil. In this research ANSS (Anyway Natural Soil Stabilizer) which is categorized as unconventional chemical stabilizers used to analyze the effect of stabilizer on engineering properties of expansive soils. A case study has been made on Addis Ababa City roads which are constructed on expansive soils are taken. In the laboratory, the native soil were combined with different dosages of the stabilizer 2%,4%, 6% and 8% to find out the optimum dosage of stabilizer. From the laboratory test results it is confirmed that 6%is an optimum dosage of stabilizer for the typical expansive soil in the study area. Using this optimum dosage of chemical stabilizer cost and time comparison have been made with the conventional way of construction. xv As it has been observed from the analysis, treated expansive soil with 6% of the chemical stabilizer improves the bearing capacity and Plasticity of the soil to a required level and it saves around 30% of the cost and 42% of the time of road construction in a the city which is constructed in a conventional way, however the performance duration of the stabilizer shall be studied further in the future, as the road which have been done with same technology shall be evaluated after some service years.Item Developing Correlation Between Dynamic Cone Penetration Index And Undrained Shear Strength of Soils that are Found In Debre Markos Town(Addis Ababa University, 2015-11) Andualem, Gedeyon; Tadesse, Samuel (PhD)Determination of the in-situ engineering properties of foundation materials has always been a challenge for practicing engineers in developing countries. Especially in a country like Ethiopia, where construction of small scale buildings like residential, warehouses, health centres, which are thought to solve the problem of the society in general, is growing in a fast rate. Debre- Markos is one of the fastest developing towns in Ethiopia, which is exposed to rapid civil engineering works like high-rise buildings, and large residential buildings, banks, etc. Since the municipality (sub-city) does not force the designers to conduct soil investigation for buildings less than G+4, designers depend on simple visual inspection and then use the minimum recommended presumptive bearing capacity by EBCS.Even some designers or companies do not conduct soil investigation for building greater than G+4. Some of these predictions may lead to unexpected failures of structure or uneconomical design. To avoid such problems, this research introduces the use of Dynamic Cone Penetration (DCP) which is a simple test device that is inexpensive, portable, and easy to operate and understand. In this thesis, field tests were conducted by locally manufactured dynamic cone penetration equipment from available materials. Laboratory tests needed to classify the soil and study the parameters that affect the dynamic cone penetration index and undrained shear strength of soil were also conducted. The data has been categorised in to two categories, correlation between undrained shear strength and dynamic cone penetration index has been developed. In addition correlation between parameters that affect the DCPI and undrained shear strength of soil has also been developed. It has been found out that parameters like unconfined compression strength& liquidity index have influence on the Dynamic Cone Penetration Index (DCPI). These research work revealed that Undrained shear strength can be estimated by UCS= -209.5*ln (DCPI) +800.5 for red clay soils of Debre Markos and UCS= -7.1661*(DCPI) +416.82 for black clay (expansive) soils of Debre Markos in general. These correlations were used to develop bearing capacity equation based on the bearing capacity theory. The equation found were qult= - 538.625ln (DCPI) +12058.086+h for red clay soils of Debre Markos, qult= -18.423*(DCPI) +1071.64+h for black clayey (expansive) soils of Debre Markos. The results are expected to have wide application in the construction sectorItem Effect Of Sample Height on Stress- Strain Behaviour of Undrained Shear Strength of Addis Ababa Red Clay Soil Using Ucs Test(Addis Ababa University, 2016-10) Merga, Soressa; Tadesse, Samuel (PhD)In this work, the effect of sample height (H/D) on the stress-strain behavior of undrained shear strength of red clay soil in Addis Ababa from a depth of 1.5m and 3m below the ground surface using unconfined compression test was assessed. In most scientific and technical standards, (H/D) of between 2 and 3 is generally accepted. This acceptance is based on the smooth slope of the change in shear strength of the soil at various (H/D) ratios and considering plate effect. But, there was no discussion about the failure pattern developed within the selected specimens size was full fill the assumptions made about stress-strain properties of soils. Therefore, this thesis investigated the effect of the specimen’s size on the stress-strain behavior and undrained shear strength of red clay soil in Addis Ababa by testing undisturbed and compacted cylindrical specimens at different moisture content with four various H/D ratios ( i.e. 1, 1.5, 2, and 2.5), while the specimens’ diameter was constantly used as 38mm. The test results indicated that the length of stress-strain curve increases with decreasing specimen’s height. The specimens with H/D = 1 attained its peak strength at large axial strains and strain at failure is too small as specimen’s H/D increased to 2 and 2.5. But, the range is not too much in both undisturbed and remoulded samples. The unconfined compressive strength and undrained shear strength of the sample also decreases with increasing H/D ratios. In addition, the failure pattern develops(ed) with the various specimens height changes from non-uniform to uniform as H/D ratio of the specimens decreases. For the H/D = 1, the shear failure plane and deformation are uniformly distributed with in the entire of specimens height and as the specimens H/D ratio increases, the deformation and shear failure distribution are localized to some portions of the specimens height. This indicates as sample height is one of the factor which causes non-uniform stress-strain distribution with in clay soils. Generally, based on the uniformity of the failure mechanism developed with in the specimens height and the assumption made during calculation of axial strain, the specimens with H/D = 1 is preferable and based on axial strain ranges at which the sample attain its peak strength, sample with H/D = 1 to H/D = 2 is preferable. Accordingly for red clay soil sample in Addis Ababa it is possible to use sample with H/D = 1 to H/D = 2and further study was needed on the effect of end platen to highly recommend.Item Evaluation of Weathered Rock Material for Embankment Dam Construction (The Case of Zarema May Day Dam)(Addis Ababa University, 2016-03) Alemayehu, Bisrat; Tadesse, Samuel (PhD)In the construction of many embankment dams rock materials plays a vital role. These rock materials exist at every parts of the world at different stages of weathering which is from residual soil up to fresh intact rock. GW soils (well graded gravels) are the best free draining shell material. Nevertheless, several problems associated with these materials when they are found at highly weathered condition which creates more fines. The most common problems due to these are pore water development in the dam body, shear strength decrement and failure of the shoulder section of the dam. In this thesis, evaluation has been conducted on weathered rock materials at different level using several laboratory tests to determine their suitability for use in embankment dam construction. The laboratory test includes grain size analysis, Atterberg limits, permeability, compaction, specific gravity, Los-Angeles abrasion test and direct shear test. Also field Schmidt hammer test had been conducted. The test result on several samples indicate that as the weathered rock samples produce more fines, the permeability and shear strength of rock decreases. But in recent embankment dam engineering technology there is an approach to design and construct the dam based on the available material on the site without extensive processing. This means accommodating easily accessible materials surrounding the site based on the strength of materials. Also provide technical procedures to following appropriate construction and techniques starting from quarrying up to placement of the material. From samples collected SN-10 is desirable for core of the dam. And SN-1, SN-2 and SN-3 are best to be inner shell and transition filter from the core to the outer shell. Sample no SN-6 and SN-8 are best to be outer shell because they have high hydraulic conductivity (greater than 10-4 cm/s) and helps to stabilize the dam by dissipating pore water pressure. As well as SN-4, SN-7 and SN-9 are better material for inner shell.Item Examining Atterberg Limits for Expansive Soils(Addis Ababa University, 2006-12) Kassahun, Habtamu; Tadesse, Samuel (PhD)Expansive soils have been responsible for many structural damages that result in great financial losses in many parts of the world including Ethiopia. Proper understanding of the properties of the soil helps to understand the actual causes of failure of structure. The main objective of this research work is to examine Atterberg limits by giving emphasis on the range at which a reduction of water content will not cause a decrease in the volume of the soil mass, i.e. shrinkage limit. In addition to this an attempt has been made to define the maximum moisture content corresponding to the maximum swelling and the effect of initial moisture content on the swell pressure of expansive soils. To achieve the research objective, disturbed and undisturbed samples of both Expansive and red clay soils were collected from Addis Ababa. The red clay soil was used as a methodology control of Atterberg limits .The following laboratory and field test were conducted to attain the purpose of this work Free swell and linear shrinkage Atterberg limits Swelling measurement with and without seating load Artificial flooding of test pit and moisture content Measuring of volume at various stages of desiccation ( Drying process) Re wetting of the completely dry pat Swell pressure measurement by varying initial moisture content Laboratory test results on both clay samples show that the volume change of expansive soil is more significant than that of red clay soil. The volume change on expansive soil is mainly due to the swell property of the soil and this volume change is sufficient enough to develop distress on structures. The investigation of swell measurement and moisture content of undisturbed soil samples showed that the moisture content after a complete swelling is found with in the range of liquid x limit and plastic limit. In addition to this high moisture content soils experience less uplift, but the pressure required to maintain a constant volume is not altered.Item Influence of Molding Water Content on the Engineering Properties of Lime Stabilized Expansive Soil(Addis Ababa University, 2015-09) Demissu, Brook; Tadesse, Samuel (PhD)Expansive soil is considered defective due to the large volume change it undergoes for any moisture fluctuation. There are several engineering solutions to the problems these soils pose to the structures built on them. At times when removing the defective soil is uneconomical or impractical, stabilizing the soil with lime has proven to be effective. Past researches on lime stabilization of expansive soils identified many factors influencing the stabilization process. However, all the factors that contribute to best results are not yet obtained. Common practice in lime stabilization is to compact the mixture of soil and lime at optimum moisture content (moisture content at maximum dry density). If the soil is expansive, at maximum dry density, large amount of expansive clay minerals (montmorillonite) will fill a given volume. On the other hand, using the dry side of the optimum moisture content may affect water dependent reactions that takes place during lime stabilization. If one uses the wet side of the optimum moisture content to mix the soil with lime, the clay mineral will absorb more water and go through large volume change. Therefore, the optimum amount of water required for lime stabilization of an expansive soil must be determined through laboratory experiments. This research tends to identify the properties of an expansive soil. Lime is then added in proportions of 0%, 2%, 4%, and 6% to the soil sample. After a series of laboratory tests the optimum amount of lime that obtains desirable effect on engineering properties of the soil is determined to be 6%. Then, the stabilized soil property at the wet and dry side of the optimum moisture content has been investigated. The results of the research have shown that molding water content does not affect the swelling pressure. However, unconfined compressive strength improves significantly on soil specimens ix prepared on the wet side of optimum moisture content of soil-lime mixture. The improvement in compressive strength on the wet side of optimum moisture content is found to be dependent on the curing time.Item Investigating the Strength Characteristics of Laterittic Soil Blended with Marble Dust(Addis Ababa University, 2016-11) Assefa, Blen; Tadesse, Samuel (PhD)The purpose of this study is to investigate the strength characteristics of a stabilized lateritic soil with marble dust. The sample of the residual lateritic soil used in the study is taken from Mekanejo area. The soil is classified as A-7-5 according to AASHTO classification. The material could possibly termed true laterite, since silica-sesquioxide ratio is Less than 1.33. An attempt has been made in the study to improve the index and engineering properties of the lateritic soil by stabilization using an industrial waste, marble-dust. This method is both low-cost and ecofriendly. Accordingly, the lateritic soil was treated with marble-dust of 4%, 8%, 12%, 16% and 20% by dry weight of soil, and various tests have been carried out on the marble-stabilized soil to assess alterations in its strength characteristics. The lateritic soil responded very well to the marble-dust treatment, as exhibited in improvement of its strength, and its increased resistance to softening by water. 20% marble dust is the optimum quantity in terms of improving plasticity index, maximum dry density and soaked and unsoaked CBR properties but for unconfined compressive value, the optimum marble dust content is 8%. The addition of marble-dust to the lateritic soil has beneficial effects on its engineering properties, including reduction in plasticity, improved workability, increased strength, more resistance to moisture effect, and enhanced durability. Besides, a trial pavement design revealed that lateritic subgrade stabilization results in thinner pavement structures, and hence reduces costs of road constructionItem Investigation into Some of the Engineering Properties of Soils Found in Ziway Town ,Ethiopia(Addis Ababa University, 2015-02) Tesfaye, Bezza; Tadesse, Samuel (PhD)Investigation of the ground conditions is used for the economical design of the sub structural elements. It is also necessary to obtained sufficient information on type, characteristics and distributions of a soil and rock underlying sites of proposed structures for feasibility and economic studies for a proposed project. The objective of this thesis is to investigate the engineering properties of soil found in Ziway town. To achieve its objective disturbed and undisturbed samples from different parts of the town were collected and laboratory tests were done on the collected samples. Grain size analysis tests revealed that, starting from few centimeters below the ground level to the depth of investigation which is three meters, the soil in Ziway town is mostly silts and silty sand. In which for silt soils of ziway town has clay content ranging from 6.72 to 10.93%, silt fraction 51.45 to 73.03%, sand fraction 15.16 to 40.4%, and gravel content from 0.84 to 1.88% and for silty sand soils clay content ranging from 0.66 to 4.41%, silt fraction 17.15 to 42.18%, sand fraction 52.06 to 81.3%, and gravel content from 0.89 to 1.6% Within the depth of exploration, the specific gravity of the town ranges from 2.40 to 2.62. These values are low compared with Arora, 2003, this is because the soils are light weighted. From the consistency limit test results, liquid limit ranges from 27–37 %, plastic limit from none plastic to limit ranges from 23 – 29% and plastic index from ranges 0-8%. Compaction tests carried out on samples collected from the study area revealed that the maximum dry density (MDD) ranges from1.22 to 1.55 g/cm3 and the optimum moisture content ranges from 22.6 to 35.8 percent. Shear strengh parameters from the graph of shear stress vesrsus displacement and maximum shear stress vesrsus applied vertical load respectively gives cohesion(C) and angle of internal friction (Φ). From those results the cohesion ranges from 2.90 to 20.15kPa and the angle of internal friction ranges from 19.80-28.40.Item Investigation into Some of the Engineering Properties of Soil in Woldiya Town(Addis Ababa University, 2014) Abebe, Tadesse; Tadesse, Samuel (PhD)Woldiya is a hillside market town, capital of the Semien Wollo Zone, and Woreda in Northern Ethiopia. Located North of Dessie and Southeast of Lalibela in the Amhara Region. This town has a latitude and longitude of 11°50′N, 39°36′E and an average elevation of 2112 meters above sea level. A lot of civil engineering structures are under construction; however, nothing has been done on the investigation of soil with respect to the intended urban development plan. Therefore, the objective of the research is to investigate some of the engineering properties of soils found in Woldiya town. The engineering behavior of soils formed under temperate or tropical conditions is determined by certain physical characteristics designated as engineering properties. In practice the determination of all the engineering properties of soils is expensive and time consuming. Whereas, Index properties are simpler and cheaper engineering characteristics which are indicative of some engineering properties and essential parameters for soil classification. To achieve the aim of the thesis disturbed and undisturbed samples from different parts of the town were collected and laboratory tests were done. The index property investigation in this study includes; natural moisture content, specific gravity, particle size distribution, Atterberg limits and free swell tests. Furthermore, the consolidation and shear strength characteristics of soil in the town were studied. The grain size analysis test result showed that the dominant proportion of soil particle in the research area is fine-grained soils, which have clay content ranging from 6-50%, silt faction 40-63% sand fraction 2- 20% . The result of Atterberg Limit test on the soil in the research area showed a liquid limit ranging from 34- 97%, plastic limit ranging from 28-35% and plastic index from 5-63%.The specific gravity ranges from 2.65-3.0. Free swell test conducted on the samples collected shows range from 39-130%. The shear strength of a soil mass is the internal resistance per unit area that the soil mass can offer to resist failure and sliding along any plane inside it. Shear strength is the principal engineering property which controls the stability of a soil mass under loads. It governs the bearing capacity of soils, the stability of slopes in soils , the earth pressure against retaining structure and many other problem. Disturbed and undisturbed samples were collected during the driest season. The soil was very stiff, when try to do unconfined compression test it shows crumble before the run of the test. Because of this reason it is impossible to do unconfined compression test in this thesis. Even though, unconfined compression test is not done, direct shear test was done to show the shear strength of soil in the town. The cohesion and IX internal friction of the representative samples of test pit four and five are (64.83kPa,17.850) and (91.56kPa,19.650) respectively. According to the Unified Soil Classification System, the soil is categorized mainly as clay soils and partially silts soils. The AASHTO Classification System shows that the usual types of significant constituent materials of the Woldiya soil are clayey soil. Finally one-dimensional consolidation tests were done and have compression index ranging from 0.28-0.4, recompression index ranging from 0.05-0.07, coefficient of consolidation ranges from 0.031-0.039cm2/sec.Item Investigation into Some of The Engineering Properties of Soils Found in Woliso Town(Addis Ababa University, 2014-12) Haile, Biruk; Tadesse, Samuel (PhD)Investigation of the ground conditions is used for the economical design of the sub structural elements. It is also necessary to obtain sufficient information on type, characteristics and distributions of soil and rock underlying a site for proposed structures. The overall aim of this study is to come up with reliable results for some of the engineering properties of soils found in Woliso town in order to understand clearly the nature of the soil so that suitable foundation can be recommended for better design and construction of civil engineering structures in the town. To achieve these objective disturbed and undisturbed samples from different parts of the town were collected and laboratory tests were done on the collected samples. The undisturbed samples were taken from the test pits by mechanically driving a Shelby tube. For all tests the apparatus and the procedures used for analysis were done according to American Society for Testing Materials (ASTM) standard. The natural moisture content of soil in the study area ranges from 25.5% - 66%. Expansive and non-expansive soils were investigated in the study area. The average specific gravity of the expansive soils is 2.68 and a non-expansive soil is 2.74. The grain size analysis test result showed that the dominant proportion of soil particle in the research area is clay. For expansive soils the clay content ranging from 55 - 80%, silt ranging from 13.8 – 28.2%, sand ranging from 4.5 – 9.7% and gravel ranging from 0.1 – 11.4% and for non-expansive soils the clay content ranging from 42.5 – 85%, silt ranging from 12.8 – 51.1%, sand ranging from 2.2 – 7.5% and gravel ranging from 0 – 0.4% . Atterberg Limit test results in the research area showed a liquid limit of expansive soils ranging from 70.5 - 126%, plastic limit ranging from 31.2 - 44% and plasticity index ranging from 39.3 – 81.7% and for non-expansive soils the liquid limit ranging from 56.2 – 61.1%, plastic limit from 30.3 – 34.4% and plasticity index ranging from 26.2 – 29.7%. According to Unified Soil Classification System, expansive and non-expansive soils in the study area are categorized as highly plastic inorganic clay and silt soils respectively. The unconfined compressive strength of the soils in the study area ranges from 75 -540kN/m2 and undrained shear strength ranges from 37.5 - 270 kN/m2. Unconfined compressive strengths show that the approximate consistencies of the soil ranges from medium to hard. One-dimensional consolidation test showed that the area under investigation is over consolidated in its natural state, have compression index ranging from 0.11-0.62, coefficient of consolidation from 1.25-17.17 (x10-3)cm2/min, coefficient of permeability from 0.15-10.63 (x10-8 cm/sec).Item Investigation into Some of the Engineering Properties of Soils in Adet Town(Addis Ababa University, 2015-07) Aynekulu, Tadesse; Tadesse, Samuel (PhD)The purpose of this study is to investigate soils engineering properties and prepare soil map of Adet town. Samples from ten test pits were used for this study. Both disturbed and undisturbed samples were retrieved from the open test pits dug manually. Laboratory tests performed on disturbed soil samples included natural moisture content, specific gravity, Atterberg limits, free swell as well as grain size analysis. Oedometer consolidation tests, swelling pressure test and unconfined pressure tests were also carried out by performing tests on undisturbed samples. Reconnaissance survey and laboratory test results revealed that the soils in the town are mainly two types. The first one which covers the northern part of the town is black clay soil which has a characteristics of specific gravity ranging from 2.62 to 2.67, liquid limit of 77-86%, plasticity index of 42-51% , clay fraction of 56-71%, free swell values of 67-100%, compression index of 0.266, recompression index of 0.047,preconsolidation pressure of 250kPa,coefficient of permeability ranging from 10-8 to 10-11 cm/sec and swelling pressure of 125kPa. The second type that is found in most parts of the town is red soils which are classified as clay and inorganic silts according to Unified Soil Classification System. These red soils have characteristics of specific gravity ranging from 2.70 to 2.85, liquid limit of 47-72%, plasticity index of 14-39%, clay fraction of 21-90%, compression index of 0.19-0.299, recompression index of 0.023- 0.029,pre consolidation pressure ranging from 150 to300 kPa, coefficient of permeability ranging from 10-8 to 10-10 cm/sec and free swell values of 27-67.5%.Item Investigation of Soil Erosion Resistance Along Adama-Iteya Road Section (Case Study)(Addis Ababa University, 2016-03) Hlefome, Lemma; Tadesse, Samuel (PhD)Various studies have shown that the physical and chemical properties of soil are major cause of soil erosion and the formation of erosion gully. This study was intended to investigate erosion resistance of the soil and cause of erosion gully along the Adama–Iteya road section. The assessment was achieved by conducting different physical and chemical laboratory tests on collected soil samples along the study area. The test results of the soil along the study area shows that, it is highly susceptible to water erosion. Grain size of the soil in the study area is uniform and poor graded fine sand and silty soil. These soils are small in size compared to sands and do not bind together like clays and are subject to the most erosion. The test result indicates that the soils along the study area are non plastic. The non plastic and cohensionless properties of the soil in the area is account for the formation of gully erosion. The maximum dry density values of the soil are generally low and it indicate that the natural deposits are loose and account for the high void ratio and the high void ratio of the soil will generate high flow velocities, high seepage pressure and account high internal erosion potential. The chemical test results of the soil samples along the study area shows it has contain relatively high percent sodium concentration and it will be easily eroded. An integrated approach including watershed management strategies, Construction of ditches (concrete or masonry) at appropriate locations and filling the gully with high plastic reddish clay soil, and a long term re-vegetation strategy are recommended for mitigation and controlling soil erosion and gulling in the study areaItem Investigation on Engineering Properties of Soils Found in Dangila(Addis Ababa University, 2014-12) Addis, Ephrem; Tadesse, Samuel (PhD)The town of Dangila, having adequate land area for expansion will have a high potential for future development. Due to rapid development of the town and appearance of construction works, the characteristics of the soil are important to be investigated. The aim of this present research is to investigate the engineering properties i.e. index properties, compressibility characteristics and shear strength properties of soils of natural soils. A laboratory research was conductedto determine such properties. The USCS classification reveals that Dangila soils are classified as MH or CH. The PI values lie between 24.8 and 44.9. The Specific gravity results range between 2.61 and 2.9. For the Consolidation tests, Coefficient of Consolidation varies between 0.94x 10-3 and 3.6x10- 03cm2/sec,While the Coefficient of Permeability ranges between1.8x10-09 and9.89x10- 08cm/sec.The compression indexes of undisturbed samples are calculated and the values of Cc and Cs are in the range of 0.13 - 0.22 and 0.019 - 0.033 respectively.The values of unconfined compressive strength lie from 140 to 200 kN/m2, at corresponding moisture content of 30 to 34 %. With those values, it is possible to evaluate classification indices and estimate relevant engineering properties necessary for foundation design. Key words: Natural soils; index and compressibility characteristics, shear strength properties, classification indices, foundation designItem Investigation on Some of Engineering Properties of Soils Found in Ambo Town, Ethiopia(Addis Ababa University, 2014-11) Hunde, Behaylu; Tadesse, Samuel (PhD)Soil investigation program is necessary to provide information for design and construction and environmental assessment. Ambo is located at a distance of 112kms from Addis Ababa. Ambo is serving as the main town of west shoa zone of Oromia region. In the town many constructions were under taken, but without detailed geotechnical investigation. Therefore, the objectives of this research is to investigate some of engineering properties of soils found in the town by conducting different types of laboratory tests and to prepare soil map of Ambo town using information and data collected from field observation, laboratory tests and secondary data. This research is useful in providing necessary data or information that can be used in designing civil engineering structures in Ambo town. Inorder to meet the objectives of this research, 21 disturbed samples and 9 undisturbed samples were collected at different areas and brought to soil laboratory of Addis Ababa institute of Technology for conducting different tests such as: moisture content, specific gravity, Atterberg limits, grain size analysis, free swell, unconfined compressive strength and one dimensional consolidation tests. Laboratory tests carried out on disturbed and undisturbed samples revealed that the natural moisture content ranges from 23.4-42.1%,specific gravity of the soils ranges from 2.51-2.78,Atterberg limits of soils of the study area has liquid limits ranging from 62-114%, plastic limit ranges from 30-47% and plasticity index ranges from 30-83%.The results of grain size analysis showed that soils of Ambo town have clay content ranging from 28-67.6%, silt content from 22.8-54.4%, sand from 1.1-13.2% and gravel from 0-15.3%.Free swell index of Ambo soils ranges from 35-155%. Soils of the study area are classified according to AASHTO and USCS.AASHTO classification shows that soils of the study area are A-7-5, which means clay soil with poor quality as a subgrade material. USCS indicates two main types of soils, which are: IX CH, high plastic clay soils and MH, high plastic silt soils. The results of unconfined compressive strength test shows that UCS of Ambo soils range from 112-545 kN/m2. Consolidation test results indicate that CH soil has preconsolidation pressure 225 kPa, swelling pressure 80kPa and over consolidation ratio 3.9. For MH soil, preconsolidation pressure 150kPa, swelling pressure 100kPa and over consolidation ratio 3.03 is obtained.Item Investigation on Some of Engineering properties of Soils found in Sebeta Town(Addis Ababa University, 2015-11) Mekbib, Selamawit; Tadesse, Samuel (PhD)Sebeta is one of the areas identified as an industry zone. Therefore, lots of constructions are undertaken by various local and foreign investors. These constructions have both light and heavy structures. The purpose of this study is to identify the engineering properties of soils located in the town. The investigation was made on active areas for new building construction and a total number of thirteen locations were identified at different sites. Pit excavation method was used to collect samples. From the samples specific gravity, particle size distribution, Atterberg limits and free swell ; unconfined compression strength and one dimensional oedometer tests were conducted. Based on laboratory test results and site observation the soils in the town were grouped in to five categories. From the test results it is concluded that some part of the town is covered by expansive soils especially around rolling areas. Yet, a small part of the town is rocky. Besides, the findings indicated that around depth of 1.5m 10% MH, 31% CH, 39% Expansive and 20% Rock whereas 18% MH, 19% Expansive, 33% CH, 10% CL and 20% Rock at depth of 3m were found. Moreover majority of the built up area have soil of high plasticity and great amount of clay particles.Item Investigation on The Engineering Properties of Soil Found in Burayu Town(Addis Ababa University, 2015-11) Hirpasa, Wubshet; Tadesse, Samuel (PhD)Soil is the ultimate foundation material which supports the structure. The proper functioning of the structure will, therefore, depend on the engineering properties of the underlying soil. The objectives of this research is to investigate the engineering properties of soils found in the town by conducting different types of laboratory tests and to prepare soil map of Burayu town.This research is useful in providing necessary data or information that can be used in designing civil engineering structures in Burayu town. Laboratory tests carried out on disturbed and undisturbed samples revealed that the natural moisture content ranges from 30.8-33.7%,specific gravity of the soils ranges from 2.70-2.82%. Results of Atterberg limits tests show that of soils of Burayu town have liquid limits ranging from 66.1-72.1%, plastic limit ranges from 30.6–34.1 % and plastic index from 35.5–39.8%.This indicate that soils of the study area is highly plastic. The grain size distribution indicates all soil samples have clay material more than 50%. Therefore clay type of soil is dominantly located in the study area. The free swell test result indicates that soils of the study area are nonexpansive which means degree of swell of the soils is non-swelling. The degrees of activity of most of the study area soils are Inactive with maximum Activity index of 0.74. Soils of the study area are classified according to USCS and AASHTO.USCS indicates one main type of soils, which is highly plastic clay soil (CH). According to AASHTO classification soils of the study area is A-7-5, which means clay soil with poor quality as a subgrade material. The Compaction test result showed that maximum dry density (MDD) of the study area ranges from 1.31 to 1.38 g/cm3 and the optimum moisture content (OMC) ranges 30.4 to 35.0%. The unconfined compressive strength test result and liquidity index indicates the soil consistency of the study area fall in hard state. Finally the consolidation test result shows that the soil exists naturally in a condition of over-consolidated, which has O.C.R >1, therefore the soil had been subjected to a pressure in excess of the present pressure.Item Investigation Some of the Engineering Properties of Soil in Merawi Town(Addis Ababa University, 2015-02) Minichle, Eyasu; Tadesse, Samuel (PhD)Merawi, Mecha wereda capital Town, which is located 540 km from Addis Ababa in North West direction on the main high way road of Addis Ababa to Bahir Dar and 30 km away from Bahir Dar in the South West direction. It was founded in 1935E.C which situated at latitude 11o24`56.36``N, longitude 37o09`33.03``E and an average elevation of 2010m above sea level. A lot of civil engineering structures are under construction; however, so far nothing has been done on the investigation of soil with respect to the intended town development plan. There are no previously done researches around Merawi. The objective of the research is to investigate some of the engineering properties of the soils in Merawi Town, where development has a promising future. Investigations have been made on the properties of the soils in the town for this research. The research is intended to investigate some of the engineering properties of soils in the Town. After visiting the Town, six representative test pit points were selected and from each test pit disturbed and undisturbed samples were taken to perform laboratory tests. As it was observed, the depth of the soil coverage is uniform in each test pit. The number of test pits taken were limited because of that the soil in the entire area of the town is more or less similar. From reconnaissance survey it has been observed that the Town is covered by red clay soil. After collecting representative disturbed and undisturbed samples from proposed open test pits by direct manual excavation, laboratory tests were carried out including specific gravity, natural moisture content, Atterberg limit, unconfined compression, consolidation, free swell, sieve analysis and hydrometer tests. AAU AAiT SCEE GEOTECHNICAL ENGINEERING STREAM Page ix The laboratory test results show that the soil in the Town has clay fraction ranges 63.6% to 91.3% which is fine clay soils. Based on index property test results, the soil under investigation was classified as clay soil using Unified and AASHTO soil classification systems. The specific gravity of the soil ranges from 2.70 to 2.76. From the Atterberg Limit results the soil is highly plastic clay and the activity grouped as inactive. The soil has free swell between 14.5% and 20% which indicates that the soil is not expansive soil. The unconfined compressive strength of the soil ranges between 63.7kN/m2 and 117.8kN/m2 and the consistency index of the soil ranges between 50% to 93.7% which indicates that the soil natural consistency is soft to stiff clay soil.