Issue 7

Abdoullah Namdar et alii, Frattura ed Integrità Strutturale, 7 (2009) 73-79; DOI: 10.3221/IGF-ESIS.07.06 73 Bearing capacity of mixed soil model Abdoullah Namdar DOS in Geology, Manasa Gangotri, Mysore University, Mysore, India, 570006; sina_a_n@yahoo.com Mehdi Khodashenas Pelkoo Amirkabir University, Dept of Mining Engineering, Tehran, Iran A BSTRACT . The main objective of this research is the improvement of red soil by the addition of construction materials. This method could provide a scientific way to create a soil foundation with sufficient stability against geo-technical problems or instabilities. Laboratory tests have been conducted to characterize the behavior of red soil when amended with different types of gravels, soils and sand under compacted conditions with Optimum Moisture Content (OMC). Safe bearing capacity of all models have been calculated to identify the best and worst soil mixed model. K EYWORDS . Red soil; shear stress; soil improvement; bearing capacity I NTRODUCTION oil mixing to stabilize soft or loose soils is considered a fairly new technology in the United States. This technique has been applied to improve and stabilize cohesive and cohesion-less soils under static loads. Successful applications include liquefaction mitigation, steel reinforced retaining walls, groundwater cutoff walls, and stabilization of contaminated soils. Applications of this technology have recently expanded to settlement control of soils, slope stabilization and the formation of composite gravity structures. Design for these applications requires the unconfined compressive strength, elastic modulus and shear strength of the soil and soil-cement columns must be determined or estimated. On a recent project in Honolulu, Hawaii, loose soils were sufficiently stabilized with a 23% treatment ratio, and at a site in Lakeland, Florida, a very soft and compressible clay layer was sufficiently stabilized with only a 12% treatment ratio. In slope stability applications, soil mixing improves the overall shear strength of the soil to adequately increase the factor of safety, and also the soil-cement columns can force the potential failure surface deeper. Lastly, soil mixing has been applied to construct in-situ gravity structures where its composite action design assumption was confirmed with an instrumented test wall, and used in two recent commercial applications [1]. Another soil-cement mixing method uses jet grouting as a technique to improve the bearing capacity of sub-base foundation. This method reduces total settlement and increases shear strength of the soil foundation [2]. Soil amendment is one of the economic techniques to improve soil bearing capacity and it guarantees achievement of safe soil bearing capacity in any situation with minimum time consumption. Wide ranges of soils have shown improved soil characteristics based on application of the technique of soil mixing. In this regard, laboratory testing plays a critical role in assessing soil properties. This investigation is invaluable in terms of providing recommendations concerning site improvement. Several laboratory experiments are required for developing the soil-mixing model necessary for reliable field application (a rational assessment selecting soil property for improvement of soil bearing capacity should include a logical investigation in laboratory testing method for accurate interpretation of results providing feasible data in field application). The research presented is the state of-the-practice for soil foundation bearing capacity over a wide range of soil foundation improvements. S