Semi-empirical procedures for evaluating liquefaction potential during earthquakes

Granted that good site control is exercised in carrying out the standard penetration test the energy delivered to the sampler, and therefore the blow count obtained in any given sand deposit at a particular effective overburden pressure, can still vary to a significant extent depending on the method of releasing the hammer, on the type of anvil and on the length of rods (if less than 10 m). For consistency it is essential to correct the observed blow count N to the value which would have been measured using a specified rod energy. A recommended value, which should be recognized internation- ally, is 60% of the free-fall energy of the standard hammer weight and drop. The corrected blow count is then designated as N60 and the normalized value (N1)60 at unit effective pressure (1 kg/cm2 or 100 kPa) may be regarded as a basic characteristic of the sand. Factors controlling the rod energy ratio are examined in detail and methods of deriving N60 values are developed. An examination of selected field and laborat...

Standard penetration test procedures and the effects in sands of overburden pressure, relative density, particle size, ageing and overconsolidation

This paper reports findings from an experimental study that aimed to investigate the undrained behaviour of sand in non-symmetrical cyclic loading, and to clarify the role of initial static shear in liquefaction resistance. The testing programme, conducted on a standard sand under triaxial conditions, covers a broad range of initial states in terms of relative density, confining stress and initial shear stress ratio (α). Three distinct failure modes have been identified from the tests: flow-type failure, cyclic mobility and plastic strain accumulation. Of these, flow-type failure, characterised by abrupt runaway deformations without any prior warning, is the most critical, and pertains to sand in the loose state. The tests also demonstrate that the presence of initial static shear stress is beneficial to the liquefaction resistance of loose sand at low α levels, but it becomes detrimental at high α levels. In this connection the concept of threshold α is proposed, together with the use of a no-stress-reve...

/pdf/cyclic-behaviour-and-resistance-of-saturated-sand-under-non-5764iyefkn.pdf

Cyclic behaviour and resistance of saturated sand under non-symmetrical loading conditions

https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=1462&context=cengin_fac

A 3D Model for Earthquake-Induced Liquefaction Triggering and Post-Liquefaction Response

The Groningen gas field is one of the largest in the world and has produced over 2000 billion m3 of natural gas since the start of production in 1963. The first earthquakes linked to gas production in the Groningen field occurred in 1991, with the largest event to date being a local magnitude (ML) 3.6. As a result, the field operator is leading an effort to quantify the seismic hazard and risk resulting from the gas production operations, including the assessment of liquefaction hazard. However, due to the unique characteristics of both the seismic hazard and the geological subsurface, particularly the unconsolidated sediments, direct application of existing liquefaction evaluation procedures is deemed inappropriate in Groningen. Specifically, the depth-stress reduction factor (rd) and the magnitude scaling factor relationships inherent to existing variants of the simplified liquefaction evaluation procedure are considered unsuitable for use. Accordingly, efforts have first focused on developing a framework for evaluating the liquefaction potential of the region for moment magnitudes (M) ranging from 3.5 to 7.0. The limitations of existing liquefaction procedures for use in Groningen and the path being followed to overcome these shortcomings are presented in detail herein.

/pdf/addressing-limitations-in-existing-simplified-liquefaction-4n60u78fcd.pdf

Addressing limitations in existing ‘simplified’ liquefaction triggering evaluation procedures: application to induced seismicity in the Groningen gas field

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Papers

Undrained cyclic shear strength of a dense niigata sand

Cyclic Undrained Triaxial Strength of Sand by a Cooperative Test Program

依夫 牧原

Papers

Undrained cyclic shear strength of a dense niigata sand

Cyclic Undrained Triaxial Strength of Sand by a Cooperative Test Program

依夫牧原