Probe Mackintosh Test

Probe Mackintosh test Objective • Collecting a disturbed soil sample for grain-size analysis and soil classification • Determine sub-surface stratigraphy and identity materials present • Evaluate soil density and in-situ stress conditions • Estimate geotechnical parameters Theory The main purpose of the test is to provide an indication of the relative density of granular deposit, such as sands and gravels from which it is virtually impossible to obtain undisturbed samples. The great merit of the test and the main reason for its widespread use is that it is simple and inexpensive. The soil strength parameters which can be inferred are approximate, but may give a useful guide in ground conditions where it may not be possible to obtain borehole samples of adequate quality like gravels, sands, silts, clay containing sand or gravel and weak rock. The usefulness of SPT results depends on the soil type, with fine-grained sands giving the most useful results, with coarser sands and silty sands giving reasonably useful results, and clay and gravelly soils yielding results which may be very poorly representative of the true soil conditions. This test method provides a disturbed soil sample for moisture content determination, for identification and classification purposes, and for laboratory tests appropriate for soil obtained from a sampler that will produce a large shear strain disturbance in the sample. Soil deposits contained gravels, cobbles or boulders typically result in penetration refusal and damage to equipment. This test method is used extensively in a great variety of geotechnical exploration projects. Many local correlations and widely published correlation which relate blow count, or N-value, and the engineering behavior of earthworks and foundations are available. Apparatus • Boring Rods • Rod Couplings • Lifting tools • Penetration Cone • Hammer • Wrench • Ruler • Marking tools

Procedure 1. Equipments for the test are assembled. The cone diameter is measured in SI unit. 2. The boring rods and hammer are joint using the rod coupling. Grease is sweep up for an easy dissembles later. 3. Distance of 0.3 m is measured and marked on the rod start from the tip of the cone. 4. The equipment is set up on the ground. 5. The hammer is pulled until it reached the maximum. The hammer is dropped freely to driven the cone into the soils. 6. The sum of the number of blows for penetration of 0.3 m is recorded in the data sheet. 7. The hammer is taken off on the last 0.3 m of each rod and joined the existing rod with another rod and lastly the hammer. The blow is continued and stopped when: • The blow is more than 400 for 0.3 m penetration • The depth reached 15 m 8. Pull the rods using lifting tools after the penetration reached the requirement. 9. The equipment is dissembled and cleaned before storing.