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This loss of soil structure causes it to lose its strength (the ability to transfer shear stress), and it may be observed to flow like a liquid (hence 'liquefaction'). Although the effects of soil liquefaction have been long understood, engineers took more notice after the 1964 Alaska earthquake and 1964 Niigata earthquake.
This phenomenon of soil behaviour can be included in the Hardening Soil model by means of a dilatancy cut-off. In order to specify this behaviour, the initial void ratio, e i n i t {\displaystyle e_{init}} , and the maximum void ratio, e m a x {\displaystyle e_{max}} , of the material must be entered as general parameters.
The first equation determines the magnitude of the deviatoric stress needed to keep the soil flowing continuously as the product of a frictional constant (capital ) and the mean effective stress ′. The second equation states that the specific volume ν {\displaystyle \ \nu } occupied by unit volume of flowing particles will decrease as the ...
The above equation works well for a horizontal tube, but if the tube was inclined so that point b was a different elevation than point a, the equation would not work. The effect of elevation is accounted for by replacing the pore pressure by excess pore pressure, defined as: =
The effects of soil liquefaction, seen after 2011 Canterbury earthquake In geology , soil liquefaction refers to the process by which water-saturated, unconsolidated sediments are transformed into a substance that acts like a liquid, often in an earthquake. [ 6 ]
Use of SPT data for direct prediction of liquefaction potential suffers from roughness of correlations and from the need to "normalize" SPT data to account for overburden pressure, sampling technique, and other factors. [4] Additionally, the method cannot collect accurate data for weak soil layers for several reasons:
Temperature variations are most extreme at the surface of the soil and these variations are transferred to sub surface layers but at reduced rates as depth increases. Additionally there is a time delay as to when maximum and minimum temperatures are achieved at increasing soil depth (sometimes referred to as thermal lag).
When a structure is subjected to an earthquake excitation, it interacts with the foundation and the soil, and thus changes the motion of the ground. Soil-structure interaction broadly can be divided into two phenomena: a) kinematic interaction and b) inertial interaction. Earthquake ground motion causes soil displacement known as free-field ...