What is the over consolidation ratio?
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).
Can the 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 normal and over consolidated soil?
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).
Is over consolidation good?
But that is not the case actually. Overconsolidation is almost always a good thing. Except in Cut slopes where overconsolidated soils are less desirable.
What is the use of Oedometer test?
Oedometer tests are performed by applying different loads to a soil sample and measuring the deformation response. 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 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 is the difference between compaction and consolidation?
Compaction is the compression of soil by the expulsion of air from the voids of the soil. Consolidation is the compression of soil by the expulsion of water from voids of the soil.
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.
How do you calculate over consolidation 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 normal consolidation?
The condition that exists if a soil deposit never has been subjected to an effective pressure greater than the existing pressure, and if the deposit is completely consolidated under the existing overburden.
What does over consolidate mean?
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.
How do you calculate over-consolidation ratio?
What is over consolidation ratio?
The ratio of pre consolidation stress to the initial vertical effective stress is known as over consolidation ratio. OCM remains same throughout the data but OCR varies as a function of depth.
What is The overconsolidation ratio (OCR) of soil?
The overconsolidation ratio (OCR) allows characterising the stress history of soils. This parameter can be computed from the preconsolidation stress, σ ′ p, and the overburden vertical effective stress for a given soil, σ ′ z, as In principle, values of OCR < 1 are associated with a underconsolidated state for the soil.
What is The overconsolidation ratio in OCR?
An average value of K01 / K00 = 1.6 yields an overconsolidation ratio OCR according to Eq. (4.7) and Fig. 4.15 in the range of 2.5–4.0. This overconsolidation effect, which is generally neglected, is important for the analysis of many geotechnical problems.
What is overconsolidation ratio in geotechnical engineering?
In geotechnical engineering, generally a parameter called the overconsolidation ratio (OCR) is used to indicate the stress history of a soil deposit. Value of OCR can be determined by conducting an odometer test using an undisturbed soil sample.
