P. K. Pradhan

Behavior of stabilized soil cushions under cyclic wetting and drying

Abstract The use of cushion below the base of foundation resting on expansive soil is very attractive from the view point of economy and overcoming the problems associated with construction of structures over expansive soil. Extensive studies on cohesive non-swelling soil (CNS) as a cushion show that it is not always effective with cycles of wetting and drying. With increase in the number of cycles, the CNS material has been shown to become less and less effective with time. Also, it is very rare to get CNS material in the nature. The present paper describes the possibility of using stabilized soil as a cushion material. The soil used as cushion in this investigation is not CNS, but its properties shows that it can be considered as a cohesive nonswelling soil. It has been observed that the soil cushion stabilized with lime and cement shows a substantial performance improvement in all the wetting and drying cycles and also in the key parameters i.e. highest swollen level, lowest shrunken level, equilibrium swollen and shrunken level, equilibrium band width, operating displacement, extreme displacement and operating middle level. Lime stabilized soil cushion is more effective than cement stabilized soil cushion.

Strength and compressibility characteristics of randomly distributed fiber-reinforced soil

Abstract This paper presents the laboratory investigation of engineering behavior of discrete fiber-reinforced soil. Locally available c - Φ soil (CL) is used as medium and two types of fibers (polypropylene and coir) with a constant aspect ratio (l/d = 75) are used as reinforcement. Soil is compacted with standard Proctors maximum density with low percentage of reinforcement (0 to 1% by weight of dry soil). Direct shear tests, unconfined compression tests and consolidation tests were conducted on un-reinforced as well as reinforced soil samples to investigate the strength and compressibility characteristics of fiber-reinforced soil. The test result reveals that the inclusion of fibers in soil increases both peak and residual shear strength and unconfined compressive strength of soil. From the consolidation test results it is observed that compression index as well as the coefficient of volume change decrease with increase in the fiber content. Further, the coefficient of consolidation increases with increase in fiber content. It is noticed that the optimum fiber content for achieving maximum strength is approximately 0.4% for polypropylene fibers and 0.8% for coir fibers by dry weight of the soil.

Parametric Investigation of Foundation on Layered Soil under Vertical Vibration

The paper presents the parametric investigation of foundation on layered soil underlain by a rigid base subjected to vertical vibration are found out using one-dimensional wave propagation in cone,based on the strength of material approach. The stiffness and damping co-efficient for a rigid massless circular foundation resting on layered half-space and homogeneous half-space, under vertical vibration are evaluated using various parameter such as, depth of the layer, material damping ratio, Poissons ratio. The static stiffness predicted by the model for different depth layer is evaluated using three value of Poissons ratio. The resonant frequency- amplitude and frequency-magnification are also studied varying the influencing parameter such as, mass ratio, Poissons ratio. Keyword- Cone model, Dynamic impedance, Circular foundation, one-dimensional wave propagation, Foundation vibration