How do you calculate Preconsolidation 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, .

What is Preconsolidation pressure of a soil sample?

Casagrande (1932, 1936) defined preconsolidation pressure, up’ as the maximum past vertical effective stress applied to the soil and correlated it to the change in slope of a curve of void ratio versus logarithm of the vertical effective stress a,’ obtained from a one- dimensional consolidation test.

How do you calculate recompression index?

The recompression index is calculated by taking the slope in the recompression curve. Compute I it using the below expression. 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.

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 ′ .

What is void ratio formula?

The formula for bulk density is (mass of dry soil) / (total volume of soil), 1 – (bulk density/particle density) for porosity, and (volume of pores) / (volume of solids) for void ratio.

How do you calculate soil OCR?

OCR is evaluated by the formula: OCR = σ’ / σ’. If OCR≤1, the soil is considered to be normally consolidated, when OCR> 1 – it is overconsolidated.

What is swelling index of soil?

The swell index which is the slope of the rebound curve of void ratio versus the logarithm of the effective pressure curve is used to estimate the consolidation settlement of over-consolidated fine grained soils.

What is coefficient of consolidation?

The coefficient of consolidation is the parameter used to describe the rate at which saturated clay or other soil undergoes consolidation, or compaction, when subjected to an increase in pressure. It is measure in square centimeters per second or square inches per minute.

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.

How do you calculate water content?

The amount of water is determined by subtracting the dry weight from the initial weight, and the moisture content is then calculated as the amount of water divided by the dry weight or total weight, depending on the reporting method.

How do you calculate Voidage?

Divide the volume of the container into the volume of water added. For example, if the container has a volume of 2 liters (2000 milliliters) and you added 500 milliliters of water, you have 500/2000 = 0.25. The voidage is therefore 0.25. Express the voidage as a percentage by multiplying by 100.

What is the OCR equal to?

The OCR is defined as the ratio of the maximum past effective consolidation stress and the present effective overburden stress. OCR is a function for undrain shear strength ratio (Su/p′), which is equal to 0.22 in the case of normally consolidated clay with a shear stress angle equal to 26 degrees.

Which is the best description of preconsolidation pressure?

Preconsolidation pressure. Preconsolidation pressure is the maximum effective vertical overburden stress that a particular soil sample has sustained in the past.

Why is preconsolidation pressure important in geotechnical engineering?

Preconsolidation pressure. 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.

How to calculate preconsolidation pressure of undisturbed soil?

Tomás et al. used this method to calculate the preconsolidation pressure of 139 undisturbed soil samples to generate preconsolidation pressure maps of the Vega Baja of the Segura (Spain). Using a consolidation curve, intersect the horizontal portion of the recompression curve and a line tangent to the compression curve.

How is preconsolidation pressure defined in Tavenas method?

The pre-consolidation pressure is defined as the intersection point of two fitted lines. Tavenas Method, (1979) assumed the linear relationship between strain energy and effective stress for the recompression part used directly from the laboratory recompression curve without considering the under – reloading portion of the test.