Dynamic Cone Penetration Test

Transportation Engineering Laboratory, IITG

EXPERIMENT NO. NAME OF THE EXPERIMENT: DYNAMIC CONE PENETRATION TEST AIM OF THE EXPERIMENT: To determine the in situ CBR value of undisturbed soil using dynamic cone penetrometer. TEST DESCRIPTION: In this test the Dynamic Cone Penetrometer tip is driven in to the undisturbed soil or compacted material by using the sliding hammer. The total penetration for a given number of blows is measured and recorded in mm/blow which is then used to find in- situ CBR strength. It is typically used to assess material properties of soil down to a depth of 1000 mm. The correlation of penetration per blow (DCP) is derived from the following equation recommended by the US Army Corps of EngineersCBR value=

292 ( DCP)1.12

for DCP in mm / blows

APPARATUS USED: 1) Handle: The handle is located at the top of the device and is used to hold the DCP shafts plumb and to limit the upward movement of the hammer. 2) Hammer: The hammer is generally of 8 kg weight with a freefall of 575 mm and is used to transfer energy to the cone tip. 3) Upper shaft: It is a 16 mm diameter steel shaft on which the hammer moves. 4) Anvil: It serves as the lower stopping mechanism for the hammer and 5) 6) 7) 8)

connects the upper and lower shafts. Lower shaft: It is a 16 mm diameter steel shaft and 1000 mm long. Cone: The cone measures 20 mm in diameter with 600 apex angle. A vertical graduated scale capable of reading increments of 1mm An optional sliding attachment for use with a separate scale

Page 1 of 3

Transportation Engineering Laboratory, IITG

9) A rotary hammer drill or coring apparatus capable of drilling a minimum diameter hole of 25 mm 10) Thread locking compound

Fig.1 DCPT sketch

Fig.2 The

Dynamic Cone Penetrometer

RELEVANT CODES: ASTM D6951/D6951M-09: Standard Test Method for Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications, American Society for Testing and Materials

PROCEDURE: Checking of the equipment: Before the test begins, the DCP device is inspected for damaged parts especially the coupler, the handle, the drive rod and replaceable point tip. All the joints should be securely tightened. Basic operation: The operator holds the device by the handle in a vertical and lifts and releases the hammer from the standard drop height. The recorder measures and records the total penetration for a given number of blows or the penetration per blow.

Page 2 of 3

Transportation Engineering Laboratory, IITG

Initial Reading: The DCP is held vertically and the tip seated such that the top of the widest part of the tip is flush with the surface of the material to be tested. An initial reading is obtained from the graduated drive rod or a separate vertical scale/measuring rod. When testing materials underlying a bound layer, a coring apparatus is used to provide an access hole to the layer to be tested. Testing Sequence: i.

Dropping the Hammer: The DCP device is held in a vertical or plumb position. The operator raises the hammer until it makes only light contact with the handle. The hammer shall not impact the handle when being raised. The hammer is then allowed to free-fall and impact the anvil coupler assembly. The number of blows and corresponding

ii.

penetrations are recorded. Depth of Penetration: It will vary with application. A penetration less than 900 mm will generally be adequate for typical highway

iii.

applications. Refusal: If after 5 blows, the device has not advanced more than 2 mm or the handle has deflected more than 75 mm from the vertical position, the test shall be stopped, and the device moved to another test location.

PRECAUTIONS:  All the while the shaft should be kept vertical  Wear safety shoes  Care should be taken while handling with the hammer

Page 3 of 3