What is the undrained shear strength of sand?
Triaxial compression, triaxial extension, and simple shear test data on clean sand were examined and it was revealed that the undrained shear strength ratio could be related to the relative density of the material provided that the initial stress, p(i)’, was less than 500 kPa.
How do you calculate undrained shear strength?
The principal stress difference (deviator stress) (P1 – P3) is computed as the axial piston load divided by the corrected area of the sample and plotted as a function of the axial strain. The undrained shear strength (su) is defined as one-half of the peak value of (P1 – P3).
What is undrained shear strength used for?
= Su (or sometimes cu), the undrained strength. It is commonly adopted in limit equilibrium analyses where the rate of loading is very much greater than the rate at which pore water pressures, that are generated due to the action of shearing the soil, may dissipate.
What is undrained shear strength ratio?
Undrained Shear Strength Ratio Ladd and Foott (1974) and Mesri (1975) show that the undrained shear strength can be normalized with respect to the effective overburden stress. The resulting ratio, Su /v0, where v0 is the effective overburden stress, is termed the undrained shear strength ratio.
What affects undrained shear strength?
The increase in undrained shear strength with axial strain rate can be attributed to a reduction in the magnitude of excess pore water pressure, with similar reductions in magnitude for all the degrees of saturation considered.
What is the difference between cohesion and undrained shear strength?
Based on analysis that undrained shear strength coincides with 50 percentile of distribution data meanwhile undrained compressive strength is around twice of cohesion for testing using unconfined pressure. This relationship is the most familiar equation.
Are cohesion and undrained shear strength the same?
Value of undrained shear strength without confining pressure is equal to unconfined compressive strength. This value is theoretically twice as big as cohesion.
Why does undrained strength increase with depth?
Undrained shear strength is not a fundamental soil parameter. It generally varies over depth as a function of insitu confining stress at a given depth. Note that larger confining stress reduces void ratio over the historical time. By the decrease of void ratio, undrained shear strength increases.
What is undrained analysis?
If the soil is normally consolidated clay, the short-term (undrained) analysis governs due to development of positive pore water pressure. If the soil is overconsolidated clay, the long-term (drained) analysis governs due to development of negative pore water pressure in the short-term.
Is undrained shear strength the same as cohesion?
What is the importance of undrained shear strength in geotechnical engineering?
The undrained shear strength (cu) is considered one of the most basic para- meter characterizing soils in engineering practice. The particular importance of cu is in the case of clayey soil. This parameter also is the basis for the classification of soil according to the ISO standard.
Does undrained shear strength vary with depth?
Undrained shear strength is not a fundamental soil parameter. It generally varies over depth as a function of insitu confining stress at a given depth.