LiquefactionPotential

The liquefaction Potential is the maximum Cyclic Shear Stress Ratio that the layer of soil can whitstan

Liquefaction Potential

The Cyclic Limit Shear Stress Ratio induced by external load is usually correlated to the SPT normalized blow count data

Nataraja and Gill's

For wave loading the correlation, proposed by 5 , can be expressed as a function of the normalized blow count:

\frac{\tau_{lim}}{ \sigma_{v}^{'}}=0.009 \cdot N_{1}

The following have to be highlighted on using this relation

• this relation has been primarly developed for earthquake induced liquefaction and then scaled for the wave induced one
• Nataraja and Gill (1983) reported that the Cyclic shear Stress Ratio (CSR) decrement is approximately 40-20% from Nc = 10 to Nc = 100, but the CSR between the number of cycles (N_{c}) at 100 and 1,000 have no significant differences. Thus, for wave-induced seabed liquefaction liquefaction potential of seabed could adopt the CSR related number of equivalent stress cycles liquefaction potential of seabed could adopt the CSR related number of equivalent stress cycles, N_{eq} for the number of wave load cycles N_{c} = 100.

Meyerhof

Using the equation stated at Soil Parameters Estimation Topic, the liquafaction potential can be expressed as a function of the relative density using the 1 and pressure in KPa

\frac{\tau_{lim}}{ \sigma_{v}^{'}}=0.009 \cdot C_{N} \cdot ( a + b \cdot \frac{\sigma_{v}^{'}}{98} )\cdot D_{R}^{2}

The use of different expressions for C_{N}, ( 4 ), can lead at different values for the CSR. The more suitable seems to be:

C_{N} =\frac{2}{1.2+\cdot \frac{\sigma_{v}^{'} }{ \sigma_{ref} } }

C_{N} =\sqrt{ \frac{\sigma_{v}^{'} }{ \sigma_{ref} } }

Seed and Cetin

A more updated SPT based correlation between CSR and normalized blow count is presented, in a grfical form in ref. 6

Reference

[1] Meyerhof, G.G. 1957. Discussion on Research on determining the density of sands by penetration testing. Proc. 4th Int. Conf. on Soil Mech. and Found. Engrg., Vol. 1: 110.

[4] ROBERT E. K., JAMES K. M., Arias Intensity Assessment of Liquefaction Test Sites on the East Side of San Francisco Bay Affected by the Loma Prieta, California, Earthquake of 17 October 1989”, http://walrus.wr.usgs.gov/geotech/arias/

[5] M.S. Nataraja, H. S. Gill, . Ocean Waves-Induced Liquefaction Analysis. Journal of Geotechnical Engineering, April 1983 Vol. 109 No4.

[6] R. B. Seed, K. O. Cetin, et alii, RECENT ADVANCES IN SOIL LIQUEFACTION ENGINEERING:A UNIFIED AND CONSISTENT FRAMEWORK, 26th Annual ASCE Los Angeles Geotechnical Spring Seminar, Keynote Presentation, H.M.S. Queen Mary, Long Beach, California, April 30, 2003.

-- RobertoBernetti - 17 Feb 2010