How do you find the Preconsolidation pressure on a graph?
Estimation of the “most probable” preconsolidation pressure Using a consolidation curve, intersect the horizontal portion of the recompression curve and a line tangent to the compression curve. This point is within the range of probable preconsolidation pressures.
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.
What is Preconsolidation pressure How is it determined?
In 1936, Casagrande proposed the classical method to determine preconsolidation stress using an empirical construction from the e − log σ curve, where e is the void ratio and σ is the vertical effective stress. The effective pressure corresponding to point T is expressed as preconsolidation pressure (σc).
Who founded the method of determination of Preconsolidation pressure Mcq?
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. He selected a point in the graph that has the minimum radius and drew tangents to it.
How do you do Casagrande method?
In the Casagrande cup method, the soil paste is placed in the Casagrande cup, and a groove is made at the center of it (see procedure below). The limit is defined as the moisture content, in percent, required to close a distance of 0.5 inches along the bottom of a groove after 25 blows in a liquid limit device.
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.
What are the factors influencing shear strength of soil?
The shear strength of cohesionless materials is essentially controlled by five factors: (a) mineralogical composition, (b) size and gradation of the individual particles, (c) shape of the individual particles, (d) void ratio or dry density, and (e) confining pressure.
Why is the Oedometer test performed?
An oedometer test is a kind of geotechnical investigation performed in geotechnical engineering that measures a soil’s consolidation properties. The results from these tests are used to predict how a soil in the field will deform in response to a change in effective stress.
What is Casagrande method?
A method for determining the liquid limit of a soil. A paste of soil and water is put in a shallow cup, the paste is cut into two parts with a deep groove and the cup is then dropped repeatedly in a standard manner until the groove has closed owing to the flow of the paste.
How is Preconsolidation calculated?
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, .
How do you do liquid limits?
Liquid limit is measured by placing a clay sample in a standard cup and making a separation (groove) using a spatula. The cup is dropped till the separation vanishes. The water content of the soil is obtained from this sample. The test is performed again by increasing the water content.