Pile on liquafiable soilPresented by khope mekrisuh

MT/14/GTE/02

IntroductionSoil liquefaction during strong earthquakes

resultscomplete loss of strength stiffness in the liquefied soillarge lateral ground movementTwo type of displacement-1. cyclic and 2. unilateral (both due to

spreading of liquefied soils and demage large properties)

Two types of lateral loadskinematic loads due to lateral ground movement inertial loads due to vibration of the structure

Pile foundations are commonly used to transfer axial loads from a superstructure to the ground

Piles are used to support structures in areas of seismic risk especially where the soils can liquefy due to the seismic shaking

pile foundations in liquefiable soil are susceptible to damage or failure

the structures in liquefied soil occurs tilting and settlement

settlement of a pile due to Axial compression of pileSlip between soil-pile interfaceSettlement of the soil mass as a whole

The piles supporting the building passed through liquefiable soils.

Fig 1 (a) Tilting of Customs Tower House (b) Schematic diagram of failure of (a) 

(c) Tilting of Pile-supported building (d) Schematic diagram of failure of (c).

PROBLEM DEFINITIONEngineers need to design a piled foundation

where the soil profile is layered and one of the layers may liquefy

For Case I and Case II in figure 2, due to the loss of shaft resistance in the liquefied layer, the pile will settle but sudden collapse or failure may be avoided if the pile is sufficiently embedded in the non-liquefiable layer below the liquefiable layer

For Case III and Case IV, where the pile rests on liquefiable soil deposits, settlement or tilting of the structure is inevitable. Structural failures such as plastic hinges etc

A SIMPLE FRAMEWORK TO PREDICT SETTLEMENTA simple schematic diagram of a pile-

supported building in two stages

Fig: Load transfer curve

Fig. Load-movement and load transfer characteristics of an axially loaded pile

DISCUSSION AND CONCLUSIONS

when the reduction in soil strength is about 30%, the pile will lose it bearing capacity and will tilt or sink

the settlement of a pile due to loss of effective stress owing to liquefaction

Thank you

Reference Reference Bhattacharya, S. (2003). Pile instability during earthquake

liquefaction.Hideaki, K. (1966).Soils and Foundations. Ishihara, K. and Yoshimine, M. (1992). Evaluation of settlements in

sand deposits following liquefaction during earthquakes, Soils and Foundations.

Zhou, S. G. (1981). Advances in Geotechnical Earthquake Engineering and Soil Dynamics.

Cubrinovski, M., Kokusho, T. & Ishihara, K. 2006. Soil Dynamics and Earthquake Engineering,

Kramer, S.L. 2008. Performance-Based Earthquake Engineering: opportunities and implications for geotechnical engineering practice. ASCE Geotechnical Special Publication.

Bhattacharya, S and Madabhushi, S.P.G. (2008), A critical review of the methods for pile design in seismically liquefiable soils, Bulletin of Earthquake Engineering.