Modulus of Subgrade Reaction
(Plate Bearing K-Value — IRC 37)

In-situ determination of the modulus of subgrade reaction (K-value) of soil or granular sub-base using a 750mm diameter plate — the primary pavement design parameter for rigid pavement thickness design per IRC 58.

Overview

What is the Modulus of Subgrade Reaction (K-Value) Test?

The Modulus of Subgrade Reaction (K-value) is determined by loading a 750mm diameter rigid plate on the prepared subgrade or sub-base surface and measuring the pressure required to produce 1.25mm of deformation. K-value directly enters the IRC 58 rigid pavement design as the foundation strength parameter — higher K-value means stiffer subgrade and thinner PQC.

Conducted as per IS 9214 and AASHTO T222, K-value testing is mandatory for NHAI rigid pavement design. Global Lab conducts K-value tests using 750mm dia plates with calibrated load cells and dial gauges, providing the design K-value for IRC 58 pavement thickness calculations.

IRC 58 Design Parameter

K-value directly used in IRC 58 rigid pavement thickness chart.

750mm Standard Plate

Standard plate size per IS 9214 / IRC 37 for pavement design.

Corrected K-Value

K-value corrected for plate size and subgrade saturation per IRC 58 guidelines.

Reaction Beam Setup

Heavy loaded truck or kentledge provides reaction against applied plate load.

NABL Certified Reports

All results on NABL-accredited letterhead per IS 9214 for NHAI submission.

Combined with CBR

K-value correlated with laboratory CBR for complete subgrade characterisation.

Test in Action

Modulus of Subgrade Reaction (K-Value) Test — Site Images

750mm Plate Setup on Subgrade

Hydraulic Jack and Load Cell Assembly

K-Value Pressure-Settlement Curve Plotted

Test Procedure

How the Modulus of Subgrade Reaction (K-Value) Test is Conducted

1

Surface Preparation

Subgrade or sub-base surface prepared, trimmed and levelled at test location. Loose material removed.
2

Plate & Jack Setup

750mm dia plate placed on prepared surface. Hydraulic jack and load cell positioned between plate and reaction beam/loaded truck.
3

Gauge Installation

Three dial gauges or LVDTs positioned at 120° around plate perimeter to measure average settlement.
4

Load Application

Load applied in increments. Settlement recorded after stabilisation. K-value reading taken at 1.25mm settlement.
5

K-Value Calculation & Report

K = pressure / settlement at 1.25mm (MPa/m or kg/cm²/cm). Corrected for saturation per IRC 58. NABL report within 3 days.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 9214	Method of Determination of Modulus of Subgrade Reaction (K-Value) of Soils in Field	K-Value	Indian Standard
IRC 58	Guidelines for the Design of Plain Jointed Rigid Pavements for Highways	Rigid Pavement	IRC
AASHTO T222	Standard Method of Test for Non-Repetitive Static Plate Load Test of Soils	Plate Load	AASHTO
IRC 37	Guidelines for the Design of Flexible Pavements	K-Value Reference	IRC

Applications

Where is the CAPO Test Used?

Subgrade K-value determination for NHAI rigid pavement thickness design

Sub-base K-value verification after WBM, GSB or DLC layer construction

Ground improvement effectiveness — comparing K-value before and after improvement

Industrial floor slab sub-base assessment for heavy machinery loading

Airport pavement subgrade K-value for rigid apron and taxiway design

Bus rapid transit (BRT) and urban road rigid pavement design

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsNHAI-accepted K-value certificates for IRC 58 pavement design.

IRC 58 Design FormatK-value reported in format directly usable in IRC 58 design charts.

Combined Pavement TestingK-value + Plate load + Field density as complete pavement sub-grade QC.

Pan-India Highway CoverageGeotechnical teams at all 7 locations for NHAI project sites.

Fast 3-Day ReportComplete K-value test and NABL report within 3 days.

DLC + PQC Mix DesignFull pavement design package: subgrade K-value + DLC + PQC mix design.

Modulus of Subgrade Reaction(Plate Bearing K-Value — IRC 37)