# PLATE LOAD TEST – its 7 [ Procedure steps, Equations & advantages]

Plate load test was conducted on subgrade, base and surface course layer and due to this test and for performing the plate load test, the plate is placed at the desired depth and then the load is applied and settlement under load is recorded.

To determine the ultimate bearing capacity of soil at that depth the total load up to that point is calculated and divided by the area of the plate and then to determine the safe bearing capacity the ultimate bearing capacity is divided by a safety factor. ### Equipments Of Plate Load Test:

1. Test plate
2. Hydraulic jack and pump
3. Reaction truss or reaction beam
4. Pressure gauge
7. Spirit level, plumb bob, tripod, etc.

### Procedure Of Plate Load Test:

There are following steps in the procedure of plate load test such as;

#### Step 2:

A small hole is created at the center of the pit and the size of the hole must be the same as the size of the steel plate and the level of the actual foundation should correspond to the level of the bottom of the hole. The hole is created that the ratio of depth to width of the hole is equal to the actual foundation depth and width.

Step 3:

As a load-bearing plate a mild steel plate is used and the size of this plate may vary from 300mm to 750mm and the thickness of this plate should be at least 25mm. the plate can be circular or square, for circular footing circular plate is used and for square footing square plates are used.

Step 4:

Step 5:

Step 6:

To record the settlement at least two dial gauges should be placed at diagonal corners if the plate and apply seating load and note the initial readings. Then the load is applied through the hydraulic jack and from pressure gauge the applied load is noted.

Step 7:

From dial gauge the settlement is observed for each increment and load should be observed after 1, 10, 20 and 60 minutes after increasing load settlement, in tabular form readings are noted. Then under new load readings are noted and until the maximum load is applied increment and data collection is repeated.

### Calculation Of Bearing Capacity From Plate Load Test:

The load settlement curve is drawn after collection of the field data and in this where the load applied is plotted on x-axis and settlement in y-axis so the ultimate load for plate is obtained and is the corresponding load for the settlement. On the graph points are plotted and at one point curve are broken and the corresponding load at that breakup point is considered to be the ultimate load. From the ultimate load ultimate bearing capacity can be calculated and then to determine the safe bearing capacity of soil the ultimate bearing capacity is divided by a suitable factor of safety.

### Equation For Calculation of Bearing Capacity Of Clayey Soil:

qu(f) = qu(p)

As qu(f) is the ultimate bearing capacity and

qu(p) is the ultimate load for a plate.

### Equation For Calculation Of Bearing Capacity Of Sandy Soil:

qu(f) = qu(p) x Bf / Bp

Where

qu(f) is the ultimate bearing capacity

qu(p) is the ultimate load for plate

Bf is the width of the pit and Bp is the size of the plate.

So,

Safe bearing capacity = ultimate bearing capacity / factor of safety.

### Equations For Foundation Settlement Calculation From Plate Load Test:

#### For Clayey Soil:

sf = sp x Bf/Bp

Where

sf is settlement of foundation

sp is settlement of plate

Bf is the width of the pit and Bp is the size of the plate.

#### For Sandy Soil:

(sf) = sp [{Bf(Bp + 0.3)}/{Bp(Bf + 0.3)}]2

Where

sp is settlement of plate

Bf and Bp are widths of plate and foundation.

1. To understand the foundation behavior under loading the condition, the plate test helps in it.
2. For a certain load, evaluation of bearing capacity of soil at a certain depth and prediction of settlement.
3. Shallow foundation can be calculated.
4. Efficient cost and time.
5. Reliable and easy to perform.