J. T. Shahu

Pasternak Model for Oblique Pullout of Inextensible Reinforcement

AbstractAn analysis is presented for evaluation of the pullout capacity of sheet reinforcement subjected to oblique pullout force considering that the subgrade soil is represented as a two-parameter linear-elastic Pasternak model and the reinforcement as inextensible. Use of the Pasternak model makes the oblique pullout analysis more realistic. The orientation of the reinforcement at the pullout end is found to be different from the direction of the pullout force and depends on the shear modulus of the subgrade soil. A parametric study is carried out to evaluate the effect of various factors, such as the modulus of the subgrade reaction, shear modulus of the subgrade, angle of interface shear resistance, and the obliquity of the pullout force on the magnitude and direction of the reinforcement force and the end displacement. For the first time, oblique pullout results have been compared with direct measurements of the reinforcement inclination in the vicinity of the failure surface available in the litera...

Analysis of Extensible Reinforcement Subject to Oblique Pull

A rational analysis of extensible sheet reinforcement subjected to an oblique end force has been presented that properly accounts for complex soil-reinforcement interaction and involves stress-deformation relationship implicitly. The results can be used for internal design of geosynthetic reinforced soil walls against pullout failure and tension failure. The pullout force and the end displacement at pullout for an extensible reinforcement are found to be almost the same as those for an inextensible reinforcement if the ratio of the reinforcement stiffness to the axial pullout capacity J* is greater than 15. With decrease in J* below 15, the maximum strain increases, the pullout failure becomes irrelevant, the tension failure dominates and the maximum allowable oblique force decreases. A minimum stiffness of about 25 times the axial pullout capacity is required to avoid the tension failure before the pullout provided the failure strain is 0.1. The predicted results have been calibrated against the finite-element analysis of pullout tests and detailed back analyses of published test data on model reinforced walls constructed with a wide range of extensible materials. The present analysis gives better predictions of the critical height against the pullout and the tension failure in model reinforced soil walls constructed with extensible reinforcements as compared to that of Rankines method.

Analysis of reinforced soil wall considering oblique pullout of reinforcement resting on two-parameter Pasternak subgrade

Conventional methods of analysis and design of reinforced soil walls consider only axial direction of the pullout force and do not consider complex soil- reinforcement interaction and obliquity of the pullout force. However, kinematics of failure of the walls suggests that the failure surface intersects the reinforcement obliquely thus causing an oblique pullout of the reinforcement. Consequently, the reinforcement deforms downward and mobilizes additional normal and shear stresses at the soil-reinforcement interface. Thus, the pullout capacity of the reinforcement may be considerably different compared to the axial one. In this paper, a new analysis is presented for the design of reinforced soil walls considering that the reinforcement is subjected to an oblique pullout force and resting on a two-parameter Pasternak subgrade. The contribution of shear stiffness of the subgrade has been incorporated in the analysis by assuming a Pasternak shear layer resting on a set of Winklers springs. Thus, use of Pasternak model as subgrade makes the analysis more realistic. A modified factor of safety is defined, evaluated, and compared with the conventional one to establish the suitability and applicability of the present analysis in the design of reinforced soil walls. A parametric study is also conducted to study the effect of various geometrical and material properties on the stability of reinforced soil walls.