How To Calculate The Modulus Of Subgrade Reaction

Friday, November 5, 2021

The modulus of subgrade reaction ks is a function of the contact pressure and allowable settlement on an unit area of soil. So you could employ the above equation in determining the Soil Subgrade Modulus.

Modulus Of Subgrade Reaction That Varies With Magnitude Of Displacement Of Cohesionless Soil Semantic Scholar

This method is used to calculate the modulus of subgrade reaction of the ground on the basis of the results of tests carried out using the Ménard pressuremeter.

How to calculate the modulus of subgrade reaction. Ks qδ - 1 Where. If ks is an area spring like a spread footing under vertical load units are kPamm or. Kyi is the spring constant at ith node.

In simple Modulus of subgrade reaction is a measure of the grounds ability to resist immediate elastic deformation under load. The sub grade reaction at any point along the beam is assumed to be proportional to the vertical displacement of the beam at that point. It estimates the support of the layers below a rigid pavement surface course the PCC slab.

In this paper 1 the relation between the values of deformation modulus measured by different soil investigation methods was obtained from the results of a comparison study2. It estimates the support of the layers below a rigid pavement sur. Here k modulus or coefficient of subgrade reaction.

This paper proposes an experimental formula to estimate the modulus of horizontal subgrade reaction k to be used in design practice for analyzing the lateral deflection of a pile at the top and the ground surface. There is no direct laboratory procedure for determining k-value. This is for an area spring.

In particular the modulus of subgrade reaction is estimated on the basis of the following factors. It is a stiffness parameter that is commonly used to define the support conditions of footings and mat foundations. It is defined as the pressur.

23 K-value- If the assumption that the reaction of the subgrade is proportional to the deflection is entirely correct thecurve in Fig. The modulus of reaction corresponds to the safe bearing. Modulus of subgrade reaction is defined as the pressure per unit deformation of the subgrade at specific pressure or deformation.

The 80 pci would have both the reduction of wide area loading and the reduction for long-term soil consolidation. If ks is a discrete spring like a single pile under vertical load units are kNmm or kipsinch. Kyi Ks x Tai Eqn 2 where.

Hence the modulus of sub grade reaction k s for the soil is given by k s Pδ where P is the ground bearing pressure at a point along the beam and δ is. The k-value can be determined by field tests or by correlation with other tests. The program first calculates the tributary area for each node of the footing and then multiplies the modulus of subgrade reaction by the corresponding tributary area for each node to get the linear spring constant at each node.

1 should be straight line and the slope ofthis line should give the modulus ofsub grade reaction measured in MPacm kgf ICDllcm. P ky 1 where k is the subgrade modulus. For a uniformly loaded flexible foundation contact pressure remains uniform throughout the foundation but settlement decreases from the center towards the edge so qs or modulus of subgrade reaction increases from the center towards the edge Figure 2.

The 80 psi would be 35 80 pci230 pci X 100 of the plate subgrade reaction value. K 40 x SF x qa where SF is factor of safety considered in bearing pressure calculation and qa is allowable soil bearing capacity. As discussed above modulus of subgrade reaction is the ratio between the contact pressure q and its corresponding settlement s.

Contact pressure divided by vertical displacement. The modulus of subgrade reaction k is used as a primary input for rigid pavement design. On the opposite hand the safe bearing capacity is that the maximum pressure which.

Its also referred to as Pressure per unit settlement. E Also by reversing the steps presented in section 5 the CBR value can be predicted using the results of the field plate load test. P applied pressure and s deformation of soil settlement.

It is expressed as kps. In other word the soil is assumed to obey Hooks law. There are many methods to find the modulus of subgrade reaction using the bearing capacity or standard penetration valueSPT in addition to testing methods.

Mathematically this is expressed as. The modulus of subgrade reaction k is used as a primary input for rigid pavement design. For each node of the footing and then multiplies the modulus of subgrade reaction by the corresponding tributary area for each node to get the linear spring constant at each node.

The coefficient of subgrade reaction is expressed in load intensity per unit of displacement. For our example the equivalent modulus of subgrade reaction was determined to be 80 pci. The modulus of subgrade reaction ks also called the coefficient of subgrade reaction of soil is the ratio between the pressure against a flat surface on soil and the settlement at that point.

The theory of subgrade reaction assumes that the unit soil reaction p with respect to a laterally loaded pile increases linearly with the lateral deflection y as expressed in the fol lowing equation. Methods of obtaining the subgrade reaction are given in the book foundation analysis and design by Bowles. The modulus of subgrade reaction k s which is otherwise difficult to determine at depths more than 1 or 2 m below the Ground Level can also be assessed.

Modulus of subgrade reaction or coefficient 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. The springs were assigned at each 01 m interval in foundation with modulus of subgrade reactions 7500 kNm 2 m and 24000 kNm 2 m. A simplified empirical equation is given to calculate the subgrade reaction.

Once a subgrade modulus is known the behavior of a.

Modulus Of Subgrade Reaction Pavement Interactive