What is the subgrade modulus of soil?

Modulus of subgrade reaction is the reaction pressure sustained by the soil sample under a rigid plate of standard diameter per unit settlement measured at a specified pressure or settlement. IRC specifies that the K value be measured at 1.25 mm settlement.

How do you find subgrade modulus?

Modulus of subgrade reaction is defined as the pressure per unit deformation of the subgrade at specific pressure or deformation. It is expressed as k=p/s. Here, k = modulus or coefficient of subgrade reaction; p = applied pressure and s = deformation of soil settlement.

What is K value of soil?

K factor is soil erodibility factor which represents both susceptibility of soil to erosion and the rate of runoff, as measured under the standard unit plot condition. Soils high in clay have low K values, about 0.05 to 0.15, because they resistant to detachment.

What is the elastic modulus of sand?

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Soil Es (tsf)
clay shale 1000 – 2000
loose sand 100 – 250
dense sand 250 – 1000
dense sand and gravel 1000 – 2000

What is a good modulus of subgrade reaction?

The value of k is in terms of MPa/m (pounds per square inch per inch of deflection, or pounds per cubic inch – pci) and ranges from about 13.5 MPa/m (50 pci) for weak support, to over 270 MPa/m (1000 pci) for strong support.

What is subgrade modulus in safe?

The modulus of subgrade reaction ks is a function of the contact pressure and allowable settlement on an unit area of soil. It is also known as Pressure per unit settlement. On the other hand, the safe bearing capacity is the maximum pressure which the soil can carry safely without risk of shear failure.

What is bulk modulus of soil?

Change of size: bulk modulus As the mean stress increases materials compress (reduce in volume). The bulk modulus K’ relates the change in stress to the volumetric strain.

What is modulus of soil reaction?

The Modulus of Soil Reaction (E’) represents the stiffness of the embedment soil placed on the sides of buried flexible pipe. E’ is used to estimate the deflection of the pipe due to dead and live loads over the pipe. E’ varies with the type of embedment soil and with the degree of compaction.

How do you find the safe subgrade modulus?

k = 40 x SF x qa, where SF is factor of safety considered in bearing pressure calculation and qa is allowable soil bearing capacity. So, you could employ the above equation in determining the Soil Subgrade Modulus. In above reply you are using factor of safety while calculating the sub grade modulus.

What is CBR formula?

C.B.R. = (PT/PS) X 100 4. The C.B.R. values are usually calculated for penetration of 2.5 mm and 5 mm. Generally the C.B.R. value at 2.5 mm will be greater than at 5 mm and in such a case/the former shall be taken as C.B.R. for design purpose.

What is the modulus of subgrade reaction of sand?

Typical values of modulus of subgrade reaction Soil description Modulus of subgrade reaction (kN/m2/m) Humus soil or peat 5000 – 15000 Recent embankment 10000 – 20000 Fine or slightly compacted soil 15000 – 30000 Well compacted sand 50000 – 100000

What is the subgrade modulus for a rigid plate?

Typical subgrade modulus for a rigid plate 12 inch in diameter. As noted in the table the subgrade reaction modulus varies in a wide range for each soil type. It is highly recommended to follow either of approaches 1 or 2 as described in this article to determine subgrade reaction modulus.

Which is the best value for soil subgrade modulus?

Bowles equation (120xqa) give me the subgrade modulus value is about 22pci which is very less then as suggested above (50 pci) so which value is best approach to design this raft/mat footing on grade.

Is the lateral subgrade modulus a function of depth?

However, the lateral subgrade modulus i a function of depth for cohesion­ less soils (1). McClelland and Focht (2) also howed that soil responses to lateral loading are dependellt on depth and pi.le deflection. A representative value of the lateral subgrade modulus may be assumed for a particular problem (3).