# Plate Load Test to Calculate Bearing Capacity and Settlement of Soil

## What is Plate Load Test?

Plate load test is done at site to determine the ultimate bearing capacity of soil and settlement of foundation under the loads for clayey and sandy soils. So, plate load test is helpful for the selection and design the foundation. To calculate safe bearing capacity suitable factor of safety is applied.

## Apparatus for Plate Load Test on Soil

• Mild Steel plate
• Hydraulic jack
• Reaction beam or reaction truss
• Dial gauges
• Excavating tools

## Calculation of Bearing Capacity from Plate Load Test

From the results obtained in plate load test, a logarithmic graph is drawn between loads applied to the corresponding settlement. Load is taken on x-axis and settlement is on y-axis. From the graph, we can find out the value of ultimate load for the plate, which is equal to the corresponding settlement of 1/5th of plate width. The curve breaks at one point, the load corresponding to that break point is considered as ultimate load for plate. From this ultimate load for plate we can determine the value of ultimate bearing capacity and safe bearing capacity of soil for foundation.

### Bearing Capacity Calculation for Clayey Soils

Ultimate bearing capacity = ultimate load for plate I.e. qu(f) = qu(p)

### Bearing Capacity Calculation for Sandy Soils

Ultimate bearing capacity = ultimate load for plate x {Width of pit (Bf) / Size of Plate (Bp)} qu(f) = qu(p) x Bf / Bp Finally, safe bearing capacity = ultimate bearing capacity / factor of safety The factor of safety ranges from 2 to 3.

## Calculation of Foundation Settlement from Plate Load Test

We can also calculate settlement for given load from plate load test as follows

### Foundation Settlement Calculation on Clayey Soils

Settlement of foundation (sf) = sp x Bf/Bp

### Foundation Settlement Calculation on Sandy Soils

Settlement of foundation (sf) = sp [{Bf(Bp + 0.3)}/{Bp(Bf + 0.3)}]2 Where Bf and Bp are widths of foundation and plate. Â  Read More What are the Needs and Functions of Pile Foundation? Soil Stabilization Methods with Different Materials Soil Tests Required for Shallow and Raft Foundations Pile Load Capacity Calculation for Single Pile and Group Piles