What is the significance of Preconsolidation pressure and how its value is determined?
Preconsolidation pressure is the maximum effective vertical overburden stress that a particular soil sample has sustained in the past. This quantity is important in geotechnical engineering, particularly for finding the expected settlement of foundations and embankments.
Who found the method of determination of Preconsolidation pressure?
14. Who founded the method of determination of pre-consolidation pressure? Explanation: Casagrande in 1936 gave the empirical method for finding the per-consolidation pressure.
How do you calculate Preconsolidation pressure?
Draw the bisector line between the previous horizontal and tangent lines, and draw the NCL; The vertical stress corresponding to the point of intersection between the bisector line and the NCL represents the preconsolidation pressure, σ ′ p .
What is Preconsolidation pressure PC?
1. Introduction. The preconsolidation stress pc, is the maximum effective stress to which the soil has been exposed may result from loading . Geological evidence of past loadings should be used to estimate the order of magnitude of preconsolidation stresses before laboratory tests are performed.
What is recompression index?
The recompression index is used to find the consolidation settlement for over consolidated clay. If the sum of existing stress and overburden and incremental stress in the soil is smaller than or equal to the preconsolidation stress, then the expression for computing the settlement is as below.
How do you calculate Overconsolidation ratio?
The OCR can be computed by the following equation:(8) OCR = 2 1 1.95 M + 1 q t – u 2 σ v 0 ′ 1 / Λ where M is the slope of the critical state line in a p′–q plot (where p′ is the mean effective stress and q is the deviator stress) defined as, M = 6 sin ϕ ′ 3 – sin ϕ ′ . In Eq.
What is Virgin compression?
During virgin compression, the additional voids ratio sustained by soil structure is inversely proportional to the current mean effective stress. This principle implies that the virgin compression.
What is Preconsolidation pressure of a soil sample?
Is recompression index same as swelling index?
The stress is applied to the soil again. Here, the term C r is recompression index, Δe is the change in void ratio and is change in effective stress in log scale. It is otherwise called as swelling index. The recompression index is used to find the consolidation settlement for over consolidated clay.
What is the excess pore pressure called?
excess hydrostatic pressure
Excess pore pressure is also known as excess hydrostatic pressure or hydrodynamic pressure.
What does OCR 1 mean?
Soils with an OCR = 1 are called normally consolidated (NC) and unaged (which means the soil layer is young and has not experienced more load than what it supports presently), while an OCR from 1 to 1.3 can still indicate NC soil, but usually soil that is older.
Can Overconsolidation ratio be less than 1?
The overconsolidation ratio, OCR, is the ratio of σp to σ o, and nu- merically represents the state of consolidation: an OCR equal to 1 is a normally consolidated sediment, an OCR greater than 1 shows over- consolidation, and an OCR less than 1 shows underconsolidation.
What is the preconsolidation pressure and why is it important?
The preconsolidation pressure allows determining the value of the overconsolidation ratio, OCR.
What is the relationship between shear strength and preconsolidation pressure?
The two parameters both reflect the clay’s structure and state of stress, and hence empirical correlations for undrained shear strength normalized with respect to preconsolidation pressure are widely used to assess soil behavior.
How does temperature affect preconsolidation pressure of soil?
The preconsolidation pressure of soils is markedly dependent of temperature with reference to the temperature variations associated with the geothermal operation of energy geostructures (it decreases for the same initial void ratio with an increase in temperature).
How does sample disturbance affect pre-consolidation pressure?
Pre-consolidation pressure is affected not only by sample disturbance, but also by load durations and load increment ratios during testing [10], [11]. Al-Zairjawi [2] carried out experimental study and he concluded that the values of бc decreased as load durations and load increment ratios increased.