Earthquakes - Geotechnical Engineering Investigation - page 946

TABLE 11.10
Estimated Susceptibility of Sedimentary Deposits to Liquefaction during Strong Seismic Shaking a

Type of Deposit Generai Distribution Likelihood That Cohesionless Sediments,

of Cohesionless When Saturated, Would Be Susceptible

Sediments in to Liquefaction (by Age of Deposit)

Deposits

500 Year Holocene Pleistocene Prepleistocene

Continental Deposits
River channel Locally variable Very high High Low Very Low

Floodplain Locally variable High Moderate Low Very low

Alluvial fan and plain Widespread Moderate Low Low Very low

Marine terraces and plains Widespread Low Very low Very low

Delta and fan-delta Widespread High Moderate Low Very low

Lacustrine and playa Variable High Moderate Low Very low

Colluvium Variable High Moderate Low Very low

Talus Widespread Low Low Very low Very low

Dunes Widespread High Moderate Low Very low

Loess Variable High High High Unknown

Glacial till Variable Low Low Very low Very low

Tuff Rare Low Low Very low Very low

Tephra b Widespread High High ? ?

Residual soils Rare Low Low Very low Very low

Sebka c Locally variable High Moderate Low Very low

Coastal Zone
Delta Widespread Very high High Low Very low

Estuarine Locally variable High Moderate Low Very low

Beach
High wave energy Widespread Moderate Low Very low Very low

Low wave energy Widespread High Moderate Low Very low

Lagoonal Locally variable High Moderate Low Very low

Fore shore Locally variable High Moderate Low Very low

Artificial
Uncompacted fill

Variable Very high

Compacted fill Variable Low

a

From Youd, T. L. and Perkins, D.M., Proc. ASCE, J. Geotech. Eng. Div., 104, 433-446, 1978. With permission.

b

Tephre — coastlines where slopes consist of unconsolidated volcanic ash or bombs.

c

Sebkha —flat depression, close to water table, covered with salt crust, subject to periodic flooding and evap-
oration. Inland or coastal.

Groundwater conditions : To be susceptible, the stratum must be below the groundwater
level and saturated, or nearly so, without the capacity to drain freely.
Relative density : D'Appolonia (1970) suggested that liquefaction might occur where D R
values were as high as 50% during ground accelerations

0.1 g , but for sands with D R in

the range of 75% or greater, liquefaction was unlikely.
Boundary drainage conditions and soil stratigraphy : These factors affect the rate of pore
pressure increase.
Initial effective overburden pressure : Also known as depth effect, this pressure influences
susceptibility.
Duration, amplitude and period of induced vibrations : These factors influence liquefaction
potential. It appears that liquefaction does not occur for 0.1 g or less.

Soil Conditions
Susceptible soils: From a study of four case histories, Seed (1975) concluded that liquefac-
tion occurs in relatively uniform, cohesionless soils for which the 10% size is between 0.01