What is the difference between normally consolidated and over consolidated clay?

Normally consolidated clays are these that are currently experiencing the maximum vertical overburden effective pressure they have ever experienced in their history. Over consolidated clays have experienced a higher overburden stress in the past.

What is over consolidated clay?

over-consolidated clay Clay that has been more compacted than would be expected from the existing overburden, e.g. it has been subjected to pressure from overburden that has subsequently been removed by erosion. Compare NORMALLY CONSOLIDATED CLAY.

What causes over consolidation?

Overconsolidation can occur in clays due to reasons such as; Self-weight of the soil which has eroded. Weight of continental ice sheet which has melted. Desiccation of layers close to the surface.

How can you decide whether a clay deposit at a site is normally consolidated or over consolidated?

If the current effective stress, s’, is equal (note that it cannot be greater than) to the preconsolidation stress, then the deposit is said to be normally consolidated (NC). If the current effective stress is less than the preconsolidation stress, then the soil is said to be over-consolidated (OC).

What is the meaning of over consolidation?

noun. Consolidation to an excessive degree; specifically the consolidation of soil to a greater degree than could have been produced by the present pressure of overburden.

What is an over consolidated soil?

The soil which had its load removed is considered to be “overconsolidated”. This is the case for soils that have previously had glaciers on them. The highest stress that it has been subjected to is termed the “preconsolidation stress”.

What is over consolidation soil?

The overconsolidation ratio (OCR) is a qualitative indicator of this densification or stiffening of the soil, and it is defined as the ratio of the maximum overburden stress ever experienced by the soil (i.e., with the ice sheet on top) to the present overburden stress (i.e., without the ice sheet).

Why normally consolidated soils have more strength then over consolidated soil?

This happens mainly due to glacier movement, fill placement, and groundwater change. On the other hand, normally consolidated soils are presently experiencing the largest pressure they have ever experienced. Due to this reason, normally consolidated soils tend to settle more than overconsolidated clays.

What does normally consolidated clay mean?

Clay that is compacted by exactly the amount to be expected from the pressure exerted by the overburden; clay which has never been overloaded.

What is the purpose of consolidation test?

Consolidation test is used to determine the rate and magnitude of soil consolidation when the soil is restrained laterally and loaded axially. The Consolidation test is also referred to as Standard Oedometer test or One-dimensional compression test.

What is over consolidation?

Overconsolidated soil may be defined as. “If the initial vertical effective stress of the soil sample is less than the preconsolidation stress, then the vertical effective stress in the field was once higher than its current magnitude, and the soil is called overconsolidated.” Or.

Why is the consolidation test considered to be one of the most important tests in geotechnical engineering?

Consolidation Test is used to determine the rate and magnitude of settlement in soils. The settlement values obtained by this test are due to primary consolidation only which is 90\% of the total consolidation. The results of consolidation test are very much helpful in the design of foundations.

What is the difference between over consolidated clay and normal clay?

Talking about over consolidated clays as clear from their name that they have larger shear strength than normal consolidated clays of the same composition. An OCC will expand during shearing while on the other hand NCC will further undergo consolidation whilst. Thus they devel0op negative pore pressure when tested under undrained condition.

What is the difference between normally consolidated soil and over consolidated soil?

If OCR=1 the soil is normally consolidated (NC), if OCR>1 the soil is over consolidated (OC). Soil deformation is higher in normally consolidated soil than it is over consolidated soil. To understand the reason for the above it is important to understand the concept of consolidation in soils mechanics.

How do you test for overconsolidation in soil?

An overconsolidated soil is reproduced in a triaxial test by an isotropic compression until a pressure pc, or K_0 consolidation, followed by unloading to a pressure p. The pressure pc is called the overconsolidation pressure and it stands for the highest pressure the soil has endured.

What are the factors that affect the shear strength of clay?

Shear strength of clays are greatly influenced by the following factors: Drainage conditions during testing. History of deposition of clays, i.e. over consolidated or normally consolidated clays. For the detailed study of the shear strength of clays they are classified into following sub classes: