Papers by Keyword: Subgrade

Abstract: This study assessed the effect of potassium hydroxide on geotechnical properties of Biomass fuel ash stabilized lateritic soil. In-situ tests were conducted on the original soil sample for identification and classification purposes. The soil sample was classified as A-2-6. Thereafter, the soil sample was mixed with both Biomass fuel ash and Potassium hydroxide at percentages of 0, 5, 10, 15 and 0, 3, 6, 9 respectively. These were later subjected to various tests such as natural moisture content, specific gravity, sieve analysis, Atterberg limit and compaction .The result showed that the addition of Biomass fuel ash increases the Plastic limit but decreases the plasticity index of the lateritic soil. Similarly, the addition of potassium hydroxide increases the plastic limit while the plasticity index decreases.The addition of Biomass fuel ash increases the optimum moisture content while the maximum dry density decreases. Similarly, the addition of potassium hydroxide increases the optimum moisture content however the maximum dry density decreases. It could be concluded that both Biomass fuel ash and Potassium hydroxide perform satisfactorily as stabilizing agents for stabilizing lateritic soil especially for subgrade and sub base purposes in road construction

Abstract: At present, the introduction of only organic or inorganic binder is not always sufficient for the practical application of stabilized soils. The research investigated the effect of the stabilizing additives Chimston, Baustab and Dorstab on changing a number of parameters over time, such as: average density, water saturation, ultimate compression and tensile strength, and frost resistance. All the researched parameters were determined at intermediate and target age — 7, 14 and 28 days respectively. Tests to assess the effectiveness of various stabilizing additives in strengthening loamy soil have shown the feasibility of using Baustab and Chimston-3 additives (in the dosage of 2%). Introduction of additives into the soil composition allowed obtaining soil with high strength characteristics and higher frost resistance as compared to the control composition. Composition No.2 has the compressive strength of 5.1 MPa and the tensile strength of 1.6 MPa. Composition No.7 has the limit of compression strength of 5.4 MPa, and the limit of tensile strength of 1.27 MPa. Thus, both compositions have the strength grade M40. Such soil will be subject to minimal subsidence and loss of strength.

Abstract: By using repeated load triaxial test method, test results of permanent strain of fine sand were obtained. The main factors affecting permanent strain of fine sand samples are water content, degree of compaction and deviator stress. Permanent strain of sand is less sensitive to moisture when compared to clay and silt. Well compacted fine sand subgrade is less affected by the change of water content, which illustrates a more stable long-term performance. Analyze from meso-structure, the ellipsoid shaped particle is less stable than sphere shaped one under the effect to repeated load. Fine sand with smaller amount of ellipsoid shaped particle would have better dynamic behaviors. Predicting models of permanent strain with basic soil physical properties were established using regression analysis.

Abstract: Railway and highway subgrade is considered to be one of the most vulnerable elements of transport structures. Undoubtedly, its failure may cause serious delays or even traffic interruption. Moreover, subgrade reliability is affected by various material, technological, climatic, as well as, soil-related and geological factors. This paper presents the results of a structural analysis with impact matrix cross-reference multiplication applied to a classification (MICMAC) technique applied for the identification of the most essential factors based on the intensity of their influence on each other. By doing so, an opinion survey was undertaken through expert consultations with industry and academic representatives in the field of construction materials, design, construction and operation of railways and roads in order to increase the subgrade effectiveness and reliability. Based on the outcomes of the derived structural analysis, it can be concluded that the following factors are the most influential: strength, water and physical properties of the top subgrade layer material; optimal subgrade soil moisture monitoring during its maintenance; and construction management of subgrade. Targeted control of the mentioned factors in general, and the top subgrade layer properties in particular, mainly depends on the properties of applied materials. This condition is generic, regardless of a region where railways and roads are being operated.

Abstract: Roads are the most important component for the economic and social development of any country. India has a total road network of more than 6 million kilometers, which carry around 90% of passenger traffic and 65% of freight traffic. More than 20% land area of India is covered with soils having low California bearing ratio (CBR) and shear strength values. The pavement constructed over such soils will lead to rapid increase in construction and maintenance costs. This study presents a laboratory investigation about the combined effect of geotextile and geogrid reinforcement, placed in layers at various depths from top of specimen, on the strength behaviour of poor subgrade soil. Heavy compaction, soaked CBR and unconfined compressive strength (UCS) tests are conducted. The test results indicate significant improvement in CBR and UCS values for all geosynthetic reinforced cases, whereas ductility and rupture strength remains almost constant as compared to virgin soil. Scanning electron microscopy (SEM) analysis shows significant bonding between soil particles and fibers of geogrid, causing stress transfer from soil to reinforcing material and hence preventing soil from overstressing. It is concluded that combination of geogrid and geotextile can be used effectively for reinforcing poor subgrade soil.

Abstract: This paper determines deformation law of the new and old subgrade differential settlement by studying on subgrade deformation characteristics and control methods, mainly by using the method of numerical simulation under certain conditions. By comparing the subgrade differential settlement before and after preloading, it is confirmed that preloading treatment can be used to prevent the road structure from the effect of differential settlement during and after highway widening construction process.

Abstract: The present article describes the use of computational models to perform quantitative assessment of the environmental effects over the design period to ensure reliable operation of transport facilities, built with traditional materials. The peculiarities of forming moisture accumulation in road pavement materials and subgrade are given, as well as the climatic factors, which have an important role in change of the material properties of pavement.

Abstract: An analysis based on questionnaire was conducted to study the technology of highway subgrade disaster prevention and maintenance. A serial of questions related to the subgrade maintenance management, maintenance technique, and existing problems were consulted with 39 experts from local highway administrations, highway management and maintenance centers, highway construction Co. Ltd, road maintenance companies in Guangdong Province. The investigation and analysis results provide a valuable scientific reference for further formulating “the technical specification of the highway subgrade maintenance”.

Abstract: With different fine aggregate, gradation type, oil stone ratio, asphalt type specimen molding and molding method and calculate the porosity of the specimen. The experimental results show that the using basalt coarse aggregate and fine aggregate forming specimen, specimen porosity significantly larger, all are beyond the scope of regulatory requirements; If using basalt coarse aggregate and limestone fine aggregate forming specimens, specimen porosity is small, both meet regulatory requirements. The main reason is basalt fines aggregate bulk volume density is too large and not easily compacted. Recommendation: we’d better use of basalt coarse aggregate and limestone fine aggregate forming specimen, try to avoid using basalt aggregate thickness of molded specimen. If the region lacks limestone fines, we should detect the special type of basalt fine aggregate firstly. If the indicators of basalt fines are in line with the requirement, you can use, if the indicators do not meet regulatory requirement, you can not use.

Abstract: Direct shear tests by laboratory to study the red sandstone aggregate mixture under the action of water intensity decay law, got red sandstone aggregate mixture, fill high subgrade compaction experimental study, tests showed that dynamic compaction compacted earth and rock mix fill embankment feasible, Rayleigh Wave test results show that the effect of dynamic compaction compaction good.