What is the unit of modulus of subgrade reaction?

What is the unit of modulus of subgrade reaction?

Modulus of Subgrade Reaction (Ks) This term is measured and expressed as load intensity per unit of displacement. For the English unit system, it is often expressed in kip/in2/in; in the SI system it is expressed as kN/m2/m.

What is the unit of K in pavement design?

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 K30 value of soil?

The values of K30 ranged from 183.3 to 478.5MN/㎥ and average value was 249.0MN/㎥. The all test result satisfied the minimum requirement value, 110MN/㎥, of the specification to control the compaction quality.

What is stiffness modulus of subgrade reaction?

The Subgrade Modulus, also known as the Modulus of Subgrade Reaction, is a stiffness parameter typically used in defining the support conditions of footings and mat foundations, such as that shown on Figure 1. The parameter is expressed in units of [Force]/[Length]3. Mat foundation for a building under construction.

What is subgrade modulus in staad?

Subgrade modulus has units of force per length^3. So, the spring will have units of force/length. The problem with using this method is that, for irregularly-shaped or large slabs with. many nodes, computing the influence area for each node can become quite tedious.

Is code for modulus of subgrade?

IS 9214: Method of determination of modulus of subgrade reaction (K-value) of soils in field.

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 calculate subgrade modulus from soil bearing capacity?

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.

What is soil stiffness?

In general, soil stiffness is determined by soil shear strength. The higher the soil stiffness is, the more fatigue damage may occur in the riser pipe, since vibration frequency and stress ranges will be higher. Secant soil stiffness is generally higher than tangent soil stiffness.

Is Youngs modulus and Elastic Modulus same?

Young’s modulus, also referred to as elastic modulus, tensile modulus, or modulus of elasticity in tension is the ratio of stress-to-strain and is equal to the slope of a stress–strain diagram for the material.

What is the modulus of subgrade reaction?

Westergaard’s Modulus of Subgrade Reaction (k) is used in this procedure to express the supporting capability of the subgrade soil. It represents the load in pounds per square inch on a loaded area, divided by the deflection in inches of that loaded area, psi/inch.

What is the relationship between Westergaard’s equation and the resisting section?

Westergaard’s gives a relation for equivalent radius of the resisting section in cm in the equation . The cement concrete slab is assumed to be homogeneous and to have uniform elastic properties with vertical sub-grade reaction being proportional to the deflection.

How do you find the k-value of a subgrade reaction?

The k-value can be determined by field tests or by correlation with other tests. There is no direct laboratory procedure for determining k-value. The modulus of subgrade reaction came about because work done by Westergaard during the 1920s developed the k-value as a spring constant to model the support beneath the slab (Figure 1). Figure 1.

What is the typical value of subgrade modulus of soil?

On large projects it may be feasible to construct a test section and perform plate load tests on top of the subbase. Typical values of subgrade modulus range between 100-400 pci for coarse grained soils and 25-150 pci for fine grained soils.