Subgrade K Value

The k-value used for floor-slab design reflects the response of the subgrade under temporary elastic conditions and small deflections usually 125 mm 005 in or less. In general the more resistant to deformation a subgrade is the more load it can support before reaching a critical deformation value.

Equivalent Modulus Of Subgrade Reaction Based On K Of Soil Load P Download Table

-L L N A O O Q N A A B H A.

Subgrade k value. Selection of the subgrade modulus k which is recommended by Broms to be taken as the average value within a depth equal to 08f3L. Crude but will get you in the ballpark. It is determined using Plate load test.

This test is used for the design of pavement structures and raft foundations. This is hardly a surprise as by definition the modulus of subgrade reaction Ks is a constant for the entire footing and the program used Ks as its soil property. Measurements of entirely different characteristics of a soil.

An approximate empirical relationship between the modulus of subgrade reaction K s. That the subgrade k value could be backcalculated from deflections of the slab surface rather than from load tests on the subgrade 56. In the SI unit system it is expressed as kNm 2 m.

Coefficient of subgrade reaction Winkler foundation E. Here k is the modulus or coefficient of subgrade reaction p is the pressure and s is the deformation of soil settlement. The magnitude of k typically ranges from about 100 to 250 pci sometimes higher depending on the subgrade materials and conditions.

According to IRC Value of K should be measured at the 125 mm settlement. K sf value of modulus of subgrade reaction for the full-size foundation. It is also known as Modulus of subgrade reaction.

Although there are other factors involved when evaluating subgrade materials such as swell in the case of certain clays stiffness is the most common characterization and thus CBR k-value and resilient modulus are discussed here. Basically it is the actual bearing pressure of the mat divided by the anticipated settlement. If values larger than 90MNm 3 need to be adopted either for the 300mm plate or for the actual foundation then actual plate load tests and further site investigations.

What is the average total load. The k-value can be determined by field tests or by correlation with other tests. E s can be derived from the results of triaxial tests.

The basic equation is. 02 The C modulus of subgrade reaction test usually known as K-valur. The constant conversion factor of 194 as suggested in the AASHTO Guide for Design of Pavement Structures 1993 is no longer used.

Additionally the modulus of subgrade reaction used for design effective modulus of subgrade reaction can be enhanced by using a. You can calculate the K yourself. B side dimension of square base used in the plate load test.

K pressure settlement. Values of K s may also be assessed by relating them to the intrinsic parameters of the soil such as elastic modulus E s and California bearing ratio CBR Vesic 1961 Bowels 1997. There is no direct laboratory procedure for determining k-value.

Since the settlement will be larger in the center of the mat assuming the mat is somewhat flexible the k value will be lower in the center and higher at the edgescorners. Arlington Road Tests In the early 1930s the Bureau of Public Roads conducted extensive field tests to investigate concrete pavement behavior. Hence the k value varies depending on the location with the mat.

CBR modulus of subgrade reaction k and elastic resilient modulus. K s the coefficient of subgrade reaction. Ks the value of subgrade reaction for 03 03 1 ft wide bearing plate.

Thus any k s values produced using this method for the actual foundation cannot exceed 90MNm 3. The modulus of subgrade reaction k is used as a primary input for rigid pavement design. The conversion from resilient modulus of the subgrade to k-value was updated in the fall of 2011 to better reflect published test results.

Its value is in the range of 005 to 015. It estimates the support of the layers below a rigid pavement surface course the PCC slab. What is K value in pavement design.

You cannot estimate K with only allowable bearing pressure. If 2000psf and 1 settlement then K 14pci. The modulus of subgrade reaction k is used as a primary input for rigid pavement design.

The Modulus of subgrade reaction is often referred as the K value. Soil compressibility and bearing capacity values normally used to predict and limit differential settlements. 16 Winkler subgrade K value etc.

In our paper we will use either subgrade reaction or the shortened K for our discussions. P E K J ê Δ. Soil elastic properties both the initial response and the long-term response due to soil consolidation from the sustained loading.

It is expressed as. It is also important to note that the software default Ks value 10858 kNm 2 m was exactly the same as the constant ratio calculated in Table 1. Because it has been suggested that the load deflection relationship is highly nonlinear the value of this average k is obviously dependent on the magnitude of the lateral load.

Test is essenti111 y a plate bearing test. It is not a fundamental soil property as it is a function of. Subgrade materials are typically characterized by 1 their resistance to deformation under load in other words their stiffness or 2 their bearing capacity in other words their strength.

What settlement do you expect at the center and the edges and the corners. Winkler first proposed the subgrade reaction in 1867 Ref. In foundation design as distinct from pavement design the value of K is the secant modulus of the graph over the estimated working range of bearing s pressure p as indicated in Figure 2.

B width of footing. The coefficient of subgrade reaction is measured and expressed as load intensity per unit of displacement. It is pressure sustain by a sample of soil under a rigid plate of std diameterunit settlement measured at a specified pressure.

03 Like all other soil strength tests K-value test will not provide a representative measurement ofsuhgradc strength unless performed under. This upper bound value of SPT produces a maximum K SPT03 value of 90MNm 3.

Subgrade Reaction Modulus Required For Design Of Mat And Slab On Grade Geotechsimulation

Modulus Of Subgrade Reaction Pavement Interactive

Some Different Formulii To Calculate The Modulus Of Subgrade Reaction Download Table