What does a dynamic cone penetrometer do?
What does a dynamic cone penetrometer do?
The Dynamic Cone Penetrometer (DCP) is used to determine underlying soil strength by measuring the penetration of the device into soil after each hammer blow.
What did the penetrometer tell you?
The penetrometer works by dropping a cone onto a test subject under the influence of gravity and measuring the depth of the resulting hole to calculate consistency.
How do you calculate DCP?
Say, one conducted single-mass DCP test on a site. The average single-mass DCP value is measured to be 6.5 mm per blow. Then, the dual-mass DCP value is 1.61 x 6.5 = 10.5 mm per blow. The R-value will be 330.66(10.5)–0.924 = 38.
How do you use a penetrometer?
The penetrometer rod should be driven in the soil at a rate of approximately 1 inch per second. As you push the penetrometer into the soil, record the depth at which the 300 psi level is exceeded, using the gradients on the penetrometer rod. This level is the top of the compacted zone.
Can one use the dynamic cone penetrometer to predict the allowable bearing pressure?
Since its development, the DCP has been widely used as a simple, but effective means of determining the in-situ stiffness of subgrade materials, and can be used to determine the load bearing capacity of the soil.
What is the CBR value of soil?
CBR is the ratio expressed in percentage of force per unit area required to penetrate a soil mass with a standard circular plunger of 50 mm diameter at the rate of 1.25 mm/min to that required for corresponding penetration in a standard material. The ratio is usually determined for penetration of 2.5 and 5 mm .
What is dynamic cone test?
Dynamic Cone Penetration (DCP) testing is used to measure in-situ soil’s strength and the thickness and location of subsurface soil layers. It is similar to CPT in that a metal cone is advanced into the ground to characterize soil behavior continuously.
What units does a penetrometer use?
The penetrometer indicates consistency, shear strength, and approximate unconfined shear strength. It has a direct-reading scale—in tons/sq ft, or kg/sq cm, which corresponds to equivalent unconfined compressive strength.
How do you measure soil strength?
The ease of pushing a 2.4mm diameter smooth metal rod into the soil with the palm of the hand gives an estimate of soil strength. The best time to carry out the measurement of soil strength is when the soil is at field capacity. This is when the soil moisture tension is approximately 10kPa.
What is the relationship between DCP and CBR?
Results of correlation study between the cone penetrometer laboratory tests and CBR laboratory tests indicate a consistent and definable relationship. DCP penetration can be used to predict CBR values with relatively high accuracy for soils ranging from sand with gravel to clay.
How do I know if my soil is compacted?
The most common signs of compacted soil are:
- Puddling of water in low areas of your lawn.
- Water running quickly away from high areas of your lawn.
- Trees with shallow roots.
- Thin, patchy areas of grass.
- Bare dirt areas where not even weeds will grow.
- Heavy clay soil.
- Soil so hard a shovel can’t pierce it.
How do you measure soil bearing capacity?
Determining Bearing Capacity on Site You can get a pretty good idea of the soil bearing capacity in the trench bottom using a hand penetrometer. This pocket-sized device is a spring-loaded probe that estimates the pressure the soil can resist and is calibrated to give readings in tons per square foot.
What is a good CBR result?
What are the typical CBR values? The harder the material, the higher the CBR value. A CBR value of 2% is usually found for clay, high-quality sub-base will have CBR values between 80% and 100%, and some sands may have values around 10%.
What is a good CBR value for subgrade?
To understand the impact of CBR (subgrade strength) on the pavement, let’s look at some typical CBR values. A clayey soil generally has a low CBR value (less than 8). Sands are more granular and drain better and will generally have CBR values between 15 and 35. Gravel will have the best CBR values, generally 25 and up.
How do you calculate CBR from DCP?
This study resulted in the relationship between CBR values from the results of the CPT and DCP tests shown in the following equation: CBR (DCP) % = 0.2552 CBR(CPT) + 2.6306 and CBR (DCP) % = 0.617 CBR(CPT).
How do you test soil for compaction?
Soil compaction occurs below the surface, so it’s hard to spot. The best way to test is to probe the soil with a compaction tester to a depth of 36″ to 48″. The testing rod should move down through the soil with steady, even pressure, Hard, compacted soils resist penetration with the rod.
What is C value of soil?
Cohesion (c) This is almost zero for dry loose sandy soils and can rise to over 100 kN/m2 for hard dry clay soils. Friable (moist) sandy loam soils are typically in the range 5 to 15 kN/m2 and moist plastic clay soils 10 to 40 kN/m2.