PILES ON SLOPING GROUND

Abstract

Present era of fast development requires accommodation of large population under one single roof. Therefore, the reliability of multi-storey buildings against the natural calamities like earthquakes is of serious concern. In order to ensure the safety of the buildings and its occupants, properly justified and reliable analysis method and design philosophy should be adopted. From the past earthquakes, it has been observed that the structures which were not properly analyzed, designed and constructed considering earthquake loads did not perform well. Therefore, approximate analyses methods for seismic loads do not seem to be sufficient for the safety of structures. Hence, non-linear beahviour (i.e., degradation in strength and stiffness) need to be incorporated in the analyses of the structures under earthquake loading. Structures like, bridge abutment on steep river slope, open type berthing structure, electric/telephone poles on high way/ railway embankment and approach to water intake tower in river /sea are constructed in sloping ground and these structures are subjected to lateral load due to the lateral soil movement of unstable slope. Lateral movement of these unstable slopes results in large lateral force on pile supported structures. The behavior of soil slope and pile foundation passing through the unstable slopes is a complex soil-structure interaction problem. Though the behavior of pile under lateral load is well known for level ground surface, its behavior on sloping ground is not studied in detail. To understand the behavior of piles in slope have used PLAXIS 3D software. In PLAXIS 3D the soil is modeled as the Mohr-Coulomb model and pile is modeled as linear elastic model. The model in case of static loading is validated analytically using the IS code method, the results obtained were quite comparable with a max error of 5.9%. The model in case of dynamic loading has been validated using linear analytical software i.e. DEEPSOIL v6.01, the results obtained were under the limits of error. The lateral capacity of pile gets considerably reduced when the applied horizontal force in the direction of slope. No well-defined guidelines are available to estimate the lateral capacity of such piles on slope. In this report, for static conditions it has been presented the effect of sloping ground due to the lateral soil movement and the results are compared with level ground. For the dynamic conditions different parameters are considered to study the behavior of pile on sloping ground. Different earthquake time histories have been iii applied to study the response of pile under various conditions. It has been inferred from the study that with increasing slope angle lateral load capacity decreases due to decrease in initial confining pressure. In case of static loading, when the position of pile is shifted from crest of slope to 2D distance towards the slope the percentage decrease in lateral load capacity is 37.25%. In case of static loading when the diameter is increased from 0.2m to 0.6m than the increase in lateral load is 91.58%.