Original Cerchar abrasiveness index tester (OCAI 70) – ASTM D The OCAI accurately determines the rock abrasivity index (CAI) employed for the. ASTM D Standard Test Method for Laboratory Determination of Abrasiveness of Rock Using the CERCHAR Method Link. Two standards exist for this test method: the French. standard AFNOR NF P () and ASTM. D (). The test is widely.
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The main difference between the two methods is in the duration of the test.
Advances in d762 of underground excavation, in particular the use of the tunnel boring machine TBMnecessitates knowledge of rock abrasiveness. CAI is used to assess the abrasiveness of rock for mechanical excavation. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Cerchar Abrasivity test –
The Cerchar abrasiveness index. The abrasivity of rock and soil is a factor of significant importance for excavation in tunnelling, underground construction, mining or quarrying. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Work Item s – proposed revisions of this standard. There are two equipment design to run the test: Pricing information and quote request on Geotechgate.
ASTM D | Testing Services | Cerchar Abrasivity Index (CAI)
Both devices include the following main parts: Can you edit this page? Users of these practices are cautioned that compliance with Practice D does not in itself assure reliable results. While, in the West design, the rock sample moves under a stationary pin.
The test is then carried out by relative displacement of the pin on the rock surface across 10 mm at given time intervals. Link to Active This link will always route to the current Active version of the standard.
ASTM D7625 – 10
The device is rigid and also fixed to avoid any lateral movement. Rock abrasiveness testing for tunnelling. CAI tests were originally carried out on natural broken surfaces.
The test method consists of measuring the wear on the tip of steel stylus with a cone shape and known Rockwell Hardness, caused by scratching against a freshly broken or saw cut rock surface for a prescribed 10 mm distance using one of the two test apparatus.
Abrasiveness expresses a behavioral characteristic of rock rather than a fundamental physical or mechanical property.
CERCHAR abrasivity test
The Cerchar- Abrasivity-Index CAI is then calculated from the measured diameter of the resulting wear flat on the pin:. The Cerchar- Abrasivity-Index CAI is then calculated from the measured diameter of the resulting wear flat on the pin: In heterogeneous rock types such as conglomerates, coarse grained granite or schistose rock, suitable fresh test surfaces are not achieved by mechanical breakage using a hammer.
The testing principle is based on a steel pin with defined geometry and hardness that is scratches the surface of a rough rock sample over a distance of 10 mm under static load of 70 N.
Cerchar Abrasivity test equipment The testing principle is based on a steel pin with defined geometry and hardness that is scratches the surface of a rough rock sample over a distance of 10 mm under static load of 70 N.
Note 1—The quality of the result produced by these practices is dependent upon the competence of the personnel performing it and the suitability of the equipment and facilities used.
The CAI values obtained for both testing velocities 1 are estimated to be equal. No other units of measurement are included in this standard. However, there are situations where stylus with different Rockwell Hardness can be used Therefore, this test method includes discussions on stylus with different Rockwell Hardness. There are two equipment design to run the test:.
It should have a diamater of at least 6 mm and the length should be such at the visibile part of th epin is at least 15 mm. The rock sample is placed in the equipment and firmly clamped using a rigid vice. Free quote for buying vane shear test equipment: The dead load is then placed on the top of the pin and the pin is carefully lowered to the rock surface.
It allows to determine an index called CERCHAR Abrasicity Index CAI for the rock’s abrasivity which can be used for evaluate the wear of excavation equipment in different application such as mining, tunnelling and drilling. Reliable results depend on many factors; Practice D provides a means of evaluating some of those factors.
Send us an email to editor geotechdata. Agencies that meet the criteria of Practice D are generally considered capable of competent and objective testing and sampling. Rock abrasiveness governs the performance of disc cutters, the rate of its replacement and therefore subsequent tunnel costs.
After the test, th epin is carefully removed and the tip flat wear is measured. Copyright – Geotechdata. Abraison can be defined as wearing or tearing away of particles and material from the solid surface.