The practical effect of increasing the density of the construction site due to pile driving on reducing its liquefaction potential

Document Type : Research Paper

Authors

1 Dam and powerhouse developing manager of K.W.P.A, IRAN. and PhD. Graduated. Department of Civil Engineering, Payame Noor University, north unit , Tehran, Iran. E-mail: kia551@yahoo.com

2 Assistant Professor, Department of Civil Engineering, Payame Noor University, Tehran, Iran.

3 Assistant Professor, Department of Civil Engineering, Payame Noor University, Tehran, Iran

Abstract

In this research, Seed and Idris method based on the SPT test number was used to evaluate the liquefaction potential of the sand layers for river navigation at the Khorramshahr dam and shipping lock construction site. For fine-grained layers, the methods of Wong, Andrew and Martin and Seed and Idris. have been used. For level 1 and level 2 earthquakes (with return periods of 75 and 475 years), the limit to ensure against the risk of liquefaction is assumed to be 1.5 and 1.1. For each pile, the number of blows to penetrate each meter of their length is calculated. Normaly, the compression caused by striking the the first series of piles has increased the number of blows required to penetrate the second series of piles . The ratio of the increase in the number of blows necessary to penetrate each pile of the second series of relativity to the first series has been calculated. The obtained increase rate is assumed to be equal to the increase of SPT number. Calculations to determine the seafty factor against liquefaction have been done again with new SPT numbers. The application of the proposaled method shows the reduction of the levels and depths of liquefaction caused by the density of layers due to the penetration of piles. In the example used (Mard dam and its ship) , the relative increase of SPT number was nearly 20 percent. Therefore, the proposed method has reduced the liquefaction zones, ranges by 8%. In addition, in the areas that have been diagnosed as low liquefaction potential in the studies but had a low confidence factor, a 9.5% increase in the confidence factor against liquefaction has also occurred. By increase the SPT number, The proposed method can increase the accuracy of liquefaction calculations in sites.

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History

  • Receive Date: 29 December 2024
  • Revise Date: 16 February 2025
  • Accept Date: 18 February 2025

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