Comparison of suction and oedometer methods for the measurement of swell pressure

In this paper, a thermocouple psychrometric technique is used to measure soil suction and assess the reliability of a swell pressure prediction method. Kaolinite-bentonite clay mixtures were prepared to obtain expansive soils with a wide range of plasticities. Suction measurements using thermocouple psychrometers and constant volume swell tests in oedometers were made on statically compacted :specimens. Soil suction-water content relationships were evaluated. The results indicate a linear relationship between the logarithm of initial soil suction and swell pressure measured in the oedometer. it has been shown that the method proposed by Johnson & Snethen for the prediction of swell pressure using suction measurements overestimates the ultimate swell pressure

Swelling and shrinkage behaviour of expansive soil blended with lime and fibres

Expansive soils are considered to be highly problematic because of their capacity to significant volume change. They swell during the rainy season as they absorb water and shrink when water evaporates from them during the summer season. Because of this dual swell-shrink behaviour, an expansive soil causes severe distress to many civil engineering structures. Several mitigating techniques are adopted to counteract the problems posed by the expansive soils, either by modifying the properties of the soil by adopting stabilization techniques using lime, cement, fly ash, calcium chloride etc. or by adopting special foundation technique such as construction of belled piers, under-reamed piles, etc. In recent years polymeric fibres have also been used to stabilize the soil as well as to improve the strength of the expansive soils. Hence in the present study lime and fibres have been used in different proportions to study the swelling and shrinkage behavior of expansive soils. Swell tests were performed by varying the fibre content and lime with expansive soils. Tests were also conducted by blending fibres and lime together with expansive soils. In a similar way, shrinkage tests were also performed for the various proportions. The test result show that swelling tends to decrease slightly with an increase in the fibre content, whereas shrinkage tends to decrease significantly upon addition of fibres. Both swelling and shrinkage tends to decrease significantly with increasing lime content. The optimum content of fibre was found to be 2%. So the expansive soil specimens blended with 2% fibres and with varying lime content was tested. It is found that blending 2% fibres and 15% lime together in expansive soils is considered to be more effective in controlling the swelling and shrinkage behaviour