Dynamic probe super heavy test is a simple, economical test for percussively testing strength in soil and rock. It is similar to a Standard Penetration Test (SPT) but with different drop weight and heights.
The test equipment consists of a 90° sacrificial or retained cone, a series of extension rods and a hammer with variable mass and drop height. It can be used to generate correlations with other tests and geotechnical parameters.
What is Dynamic Probing?
Dynamic probing is a common method of ground investigation which can be used as an alternative to Standard Penetration Testing (SPT) in certain situations. The test involves driving a rod with an oversize point at its base into the ground with a uniform hammer blow. The number of blows for every 100mm of driving is recorded and the results plotted against depth.
The test can be used to locate boundaries between different strata of differing density or driving resistance and the test can also help to identify voids or cavities within the ground. However, it is important to note that the results of the test do not indicate the composition or properties of the soil, nor can any soil samples be retrieved.
MCD offer two types of dynamic probe equipment; light and super heavy, both based on the dimensions of the sacrificial cone and mass/drop height of the hammer. DPSH test readings are converted to Dynamic Probing Point Resistance (DPPRT) values which can be used to estimate Ultimate Compressive Strength (UCS) using established correlations.
DPSH Equipment
DPSH is an efficient and cost-effective geotechnical investigation method used to determine the strength of soils and soft rock in-situ. It is quick and easy to setup and can be completed on-site within 10 minutes per test. The rig can also be used to locate areas of made ground, solution features, tunnels and other underground voids and cavities.
The equipment is simple, relatively inexpensive and robust which allows a greater number of tests to be conducted in a day than would be possible with a shell and augur rig. Additionally, the system is portable which means that testing can be undertaken in locations where access may not be feasible with a larger rig.
Our GRIZZLY instrumented DPSH meets EN ISO 22476-2: Geotechnical investigation and testing – Field testing – Part 2 – Dynamic probing – Heavy (DPSH) and Light (DPL). It’s powered by a constant energy, heavyweight dynamic cone penetrometer that can be used to test to depths of up to 10-15 m in suitable soils.
DPSH Test Procedure
We provide a comprehensive site investigation service using a range of testing methods including trial pitting, cable percussion boring, rotary core drilling, dynamic probing and window sampling. We have a range of rubber tracked or wheeled probes that are ideally suited to site investigations where access is limited and a lighter piece of equipment is required.
The DPSH test can be used to compare the strength of a soil in a continuous manner or to establish a profile of resistance with depth. The test involves driving a 90o sacrificial or fixed cone into the ground and counting the number of blows per 100mm penetration of the rod string. The results are then correlated to the Standard Penetration Test (SPT) by assuming that the hammer weight and drop height of the SPT and the probe have similar dimensions.
The DPSH can be used in conjunction with the light and medium mass DPSH tests or with the heavy hammer to provide a continuous log of soil resistance across a site. The resulting blow counts are plotted as a graph and can be imported into our ‘Stratigraphy’ software for interpretation.
DPSH Results
DPSH is a specialized evaluation technique for subsurface conditions. It involves driving a solid 90o cone at the end of a rod string into the ground using a uniform hammer strike and recording blow counts for each 100mm of penetration. The results are plotted and correlated to standard penetration test (SPT) data. Our rigs are capable of measuring to depths of 10-15m, depending on the soil type.
Compared to the SPT, which measures only the force and displacement of the tip during a single test point, DPSH provides continuous information about the force and energy of the tip during its penetration into the soil. Therefore, a deeper understanding of the mechanism of advancement can be gained through this method.
The equivalence of DPSH results to SPT N values and undrained shear strengths has been a controversial subject in the geotechnical industry. It is generally agreed that the equivalence is not linear and that there is a threshold amount of energy needed to produce penetration (known as Th). Consequently, a different calculation method must be used for determining the actual value of energy at the rods (EntHRUcone).