Pile Foundation Failure

Pile foundations are widely used both onshore and offshore to transfer heavy structural loads to copetent load bearing soil strata or bedrock.

eotechnical engineers are called upon to design deep foundations hen the shallo layers of soils beneath the building are either unable to support the loads iposed by the superstructure on the shallo foundations or if the shallow layers may become unstable due to the cyclic shear stresses induced by the earthquake loading. Under such circumstances it is imperative to look for pile foundations that transfer the load fro the superstructure to ore fir and stable soil strata at deeper levels or onto bedrock. In this chapter the seismic design of pile foundations is considered in the light of the EC 8 Part 5 (2003) provisions as well as some of the current research findings. It is perhaps helpful if some of the well-known examples of failures of pile foundations during or following an earthquake loading are considered first.

9.1.1 Examples of pile foundation failures following earthquake loading

Although pile foundations are widely used in the regions of high seismicity around the world, there are a number of examples where the pile foundations have failed during strong earthquake events. Such failures can cause either collapse of the superstructure or excessive settlements and rotations.

During the 1964 Niigata earthquake the Showa Bridge collapsed as shown in Figure 9a. Figure 9b shows one of the piles that was extracted during the post earthquake investigation, while Figure 9 c shows the schematic diagram of the collapsed spans.

The Showa bridge collapse was attributed to many causes. For example, Hamada (1992) proposed that lateral spreading of the soil following liquefaction (see Figure 9c) caused large displacements at the pile heads and resulted in the dislodging of the spans. Bhattacharya et al (2005a) have proposed that buckling of the piles in liquefied sands could have caused the collapse of the Showa Bridge. The Showa Bridge collapse is not a unique event. here have been any other failures involving pile foundations.

Pile Failure Earthquake Liquefaction

Figure 9.1 a) Collapse of the Showa bridge b) Excavated pile, after Hamada, 1992 c) Collapsed spans of the Showa bridge, after Takata et al., 1965

Figure 9.1 a) Collapse of the Showa bridge b) Excavated pile, after Hamada, 1992 c) Collapsed spans of the Showa bridge, after Takata et al., 1965

More recently the harbour master's building at Kandla Port suffered a rotation of about 11o from the vertical following the Bhuj earthquake of 2001 as shown in Figure 9.2. The pile foundations supporting this building have suffered differential settlement. Similarly Tokimatsu et al (1997) describe the failure of a three-storey building supported on pile foundations during the 1995 Kobe earthquake as shown in Figure 9.3. They suggest that the failure of the quay wall allowed the seaward movement of the soil that caused the pile foundations to fail. Lateral spreading of soil subjects the pile to additional loading. he piles need to be adequately designed to sustain these additional lateral loads.

Piles Failure
Figure 9.2 Rotation of a tall masonry building on pile foundations during the Bhuj earthquake (Madabhushi et al. 2005)

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Earthquake Pile Deep Foundation Failure

Sandy silt Sandy gravel

Figure 9.3 Failure of piles in a three-storeyed building in 1995 Kobe earthquake (Tokimatsu et al. 1997)

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Responses

  • juhana
    How to calculate settlements of piles?
    9 years ago
  • tytti
    How does a bridge fail during liquefaction eurocodes?
    8 years ago

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