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Indian Institute of Science (2000)

Collapse Behaviour Of Red Soils Of Bangalore District

Revanasiddappa, K

Titre : Collapse Behaviour Of Red Soils Of Bangalore District

Auteur : Revanasiddappa, K

Organisme de soutenance : Indian Institute of Science

Grade : Doctoral PhD 2000

Résumé partiel
Collapse phenomenon is exhibited by two types of residual soils. The first category of collapsing residual soils is believed to be transported soils that have undergone post-depositional pedogenesis. The second category of collapsing residual soils is highly weathered and leached soils formed by in-situ weathering of parent rock. Residual red soils occur in Bangalore District of Karnataka State. Physical and chemical weathering of the gneissic parent rock formed the residual soils of Bangalore District. The red soils of Bangalore District are generally moderate to very highly porous (porosity range 35-50%). These soils are also unsaturated owing to presence of alternate wet and dry seasons and low ground water table. Moderately to highly porous, unsaturated red soils occur in Pernambuco State of Brazil. These residual soils formed by weathering of gneissic rock significantly collapse on wetting under external pressures. Kaolinite is predominant clay mineral in the red soils of Bangalore and Pernambuco Districts. Similarities exist in the mode of soil formation, clay mineralogy, porosity and degree of saturation (Sr) values of the red soils from Pernambuco State, Brazil, and Bangalore District. Given the collapsible nature of red soils from Pernambuco State, Brazil, the red soils from Bangalore District also deserve to be examined for their potential to collapse in the compacted and undisturbed conditions. The roles of initial dry density, compaction water content, clay content and flooding pressure (the external stress at which a laboratory specimen is inundated is termed as flooding pressure in this thesis) in determining the collapse behaviour of compacted soils are well recognized. However, the influences of above parameters on the collapse behaviour of compacted red soil specimens from Bangalore District are lacking. Such studies are essential as they help to identify the critical compaction parameters (dry density and water content), soil composition, and applied stress level that needs to be controlled by the fill designer in order to minimize wetting-induced collapse. The importance of matric suction in the collapse behaviour of unsaturated soils is well recognized. Yet, the influence of matric suction in the collapse behaviour of compacted soils has only been indirectly examined by varying the compaction water content/degree of saturation of the soil specimens. The climate of Bangalore District is characterized by alternate wet and dry seasons which affects the soil microstructure and the matric suction. Both these parameters have a significant influence on collapse behaviour of unsaturated soils. Cyclic wetting and drying is expected to have a significant bearing on the collapse behaviour of residual soils and is therefore examined. The red soil deposits of Bangalore District are important from foundation engineering view point as they are subjected to structural loading. Owing to the presence of alternate wet and dry seasons and low ground water table, red soil deposits of Bangalore District are more often than not unsaturated. These foundation soils would however be susceptible to increase in moisture content from causes such as infiltration of rainwater, leakage of pipes or watering of lawns and plants.

Mots clés : Soil Mechanics ; Red Soils – Bangalore ; Residual Soils – Bangalore ; Soil – Behaviour ; Red Soil - Collapse Behaviour

Présentation

Page publiée le 17 octobre 2013, mise à jour le 16 février 2021