Laboratories and Test Facilities

Rock Mechanics Laboratory

The EMI rock mechanics laboratory includes 5 MTS test frames, of which capacities range from 20,000 to 1,000,000 lbs. The MTS machines are used for measuring many of the physical properties of rock. They are driven by, and digitally record the data via, a computer controlled closed servo loop. Typical physical property tests include: Unconfined Compressive Strength (UCS), Brazilian Tensile Strength (BTS), Triaxial Compressive Strength, and Punch Penetration Response. Much additional equipment, for determining parameters such as abrasivity, elastic constants, petrographic analysis and total hardness, exist at EMI facilities.



All physical property testing is performed under strict quality control guidelines of ASTM and/or ISRM established test procedures

Unconfined Compressive Strength (UCS)

UCS is one of the most basic parameters of rock strength, and the most common determination performed for boreability predictions. It is measured in accordance with the procedures given in ASTM D2938, with the length to diameter ratio of 2 by using NX-size core samples. 3 to 5 UCS determinations are recommended to achieve statistical significance of the results. If the sample length to diameter ratio was greater or less than 2, ASTM recommends a correction factor that is applied to the UCS value determined from testing. UCS measurements are made using an electronic-servo controlled MTS stiff testing machine with a capacity of 220 kips. Loading data and other test parameters are recorded with a computer based data acquisition system, and the data is subsequently reduced and analyzed with a customized spreadsheet program. The unconfined compressive strength of the specimen is calculated by dividing the maximum load at failure by the sample cross-sectional area:

Indirect (Brazilian) Tensile Strength

Indirect, or Brazilian, tensile strength (BTS) is measured using NX-size core samples cut to an approximate 0.5 length-to-diameter ratio, and following the procedures of ASTM D3967. BTS measurements are made using an electronic-servo controlled MTS stiff testing machine with a capacity of 220 kips. Loading data and other test parameters are recorded with a computer based data acquisition system, and the data is subsequently reduced and analyzed with a customized spreadsheet program. BTS provides a measure of rock toughness, as well as strength.

In bedded/foliated rocks, particular attention needs to be given to loading direction with respect to bedding/foliation. The rock should be loaded so that breakage occurs in approximately the same direction as fracture propagation between adjacent cuts on the tunnel face. This is very important assessment in mechanical excavation by tunnel boring machines.

Cerchar Abrasivity Index

This test measures rock abrasivity for determining cutter wear and costs. A series of sharpened steel pins of a known hardness alloy steel are pulled across a freshly broken surface of the rock. The average dimensions of the resultant wear flats are related directly to cutter life in field operation. The geometry of the planned excavation then allows calculation of the expected cutter wear per unit distance of cutter travel. This test can be performed on irregular rock pieces an inch across. The rock sample is fixed in a holder with the fresh surface facing upward. A conical 90° hardened steel pin, fastened in a 15 lb. (7.5 kg) head, is set carefully on the fresh surface and drawn 0.4 in. (1 cm) across it in 1 second. This is repeated for a total of five pins The tips of the pins then are examined under a reticular microscope and two perpendicular diameters of the resulting wear flat are recorded for each pin.

Punch Penetration Test

In this test, a standard conical indenter is pressed into a rock sample that has been cast in a confining steel ring. The load and displacement of the indenter are recorded with a computer system. The slope of the force-penetration curve indicates the excavatibility of the rock, i.e., the energy needed for efficient chipping. This is affected by the stiffness, brittleness, and porosity of the sample.

Acoustic Velocities and Dynamic Elastic Constants

This non-destructive measurement is performed in accordance with the procedures recommended by ASTM D2845, usually on core samples prepared for UCS testing. The velocities of compressive and shear ultrasonic waves through the core sample are measured and used to calculate the elastic modulus and Poisson’s ratio. This method indicates the competency of the rock. Other factors such as anisotropy affect the results, however, and a minimum of five measurements is recommended. From the waves’ velocities and the sample bulk density, the dynamic elastic modulus and dynamic Poisson’s ratio are then calculated.

Point Load Test

The Point Load Strength test is intended as an index test for the strength classification of rock materials. It may also be used to predict other strength parameters with which it is correlated, for example the unconfined compressive and the tensile strength. It is measured in accordance with the procedures recommended in ASTM D5731, usually with NX-size core samples. The testing machine consists of a loading frame, which measures the force required to break the sample, and a system for measuring the distance between the two platen contact points. Rock specimens in the form of either core, cut blocks, or irregular lumps are broken by application of concentrated load through a pair of spherically truncated, conical platens

Thin Section Petrographic Analysis

The thin section petrographic analysis provides useful information about microscopic features of rock, which might significantly impact its boreability behavior. Numerous field case histories exist where the TBM failed to achieve its expected performance because of one or more unusual characteristics exhibited by the rock formation, which could not have been foreseen unless petrographic analysis data were available. These “unusual” features include grain suturing/interlocking, certain alignment/orientation of hard minerals, tight matrix, micro fractures, etc.

Schmidt Hammer

This test measures the rebound hardness of a rock specimen by the rebound of an impacting piston striking rock, which is held by a steel anvil. The piston is driven by a set of springs within the hammer, which store and release energy while pressing the hammer on the sample by hand. The test was originally developed as a quick measure of compressive strength of concrete and later was extended to estimate the hardness of rock.

Abrasive Mineral Content and Moh's Hardness

Cutter life also can be estimated from the relative percentages of minerals of several Moh’s hardness classes (>7, 6, 4 to 5, and <4). This is determined by hand-lens examination of fresh rock surfaces. The higher the percentage of harder minerals, the more abrasive the rock and the shorter the cutter life.

Static Elastic Constants

This determination can be performed during UCS testing, and consists of measuring and recording the axial/lateral deformation history of the sample in addition to its load history. It is measured in accordance with the procedures given in ASTM D3148.

Triaxial Strength Testing

This type of test simulates the behavior of rock underground, because it applies significant confining pressure to the sample during loading. It is performed according to ASTM D2664. Five tests are conducted, each at a different confining pressure. The resulting sample strengths are plotted on a stress difference versus axial strain curve, and on a Mohr circle, to determine the failure criteria for the rock type.

Additional Tests

In addition to the tests described above, the following tests can be performed on request, with costs determined on a case by case basis: Direct shear test (ASTM 5607) Moisture content (ASTM D2216) Permeability Porosity Rock Quality Designation, RQD (ASTM D6032) Mineral identification by X-ray diffraction Slake durability index Sieve Analysis (ASTM D2487)
Linear Cutting Tests


Linear cutting tests provide a direct measure of rock cuttability under simulated field conditions. The LCM measures the forces acting on an individual cutter while cutting actual rock. Data from this test provides input for performance prediction, machine specification, cutterhead balancing and optimization for cutting geometry. These full-scale tests eliminate the uncertainties of the rock, which may not be identified by physical property testing.Linear Cutting Machine

The normal force recorded by the LCM is used to calculate necessary effective mass and thrust required of the machine.  This is important to ensure that the machine is able to provide the necessary thrust, so the cutters can effectively penetrate the rock.  The rolling/drag force is directly related to the torque requirement of an excavator, and is used to calculate the specific energy requirement. Specific energy is defined as the amount of energy required to excavate a unit volume of rock.  Using the specific energy (hp-hr/yd3), achievable production rates are calculated for a machine with a known horsepower available on the cutterhead.  Lower specific energy means that a given machine will produce more material, or that a smaller/less expensive machine may be used to produce the required amount of material.  The side force may be used along with normal force and rolling force to balance the cutterhead design.

The LCM features a large stiff reaction frame on which the cutter is mounted.  A triaxial load cell, between the cutter and the frame, monitors forces and a linear variable displacement transducer (LVDT) monitors travel of the rock sample.  The rock sample is cast in concrete within a heavy steel box to provide the necessary confinement during testing.  A servo controlled hydraulic actuator forces the sample through the cutter at a preset depth of penetration, width of spacing and constant velocity.  During the cut, the triaxial load cell measures the normal, rolling, and side forces acting on the cutter.  After each cut the rock box is moved sideways by a preset spacing to duplicate the action of the multiple cutters on a mechanical excavator.

In field excavation, the individual cutters on the machine always operate on a rock surface damaged from the previous cutting action.  This condition is duplicated in the laboratory by thoroughly conditioning the rock surface before testing began.  This is accomplished by making several passes of cuts before data is collected.

LCM test equipment can be used to test different type of cutters and bits as shown in the following photos.



The Drill Test Fixture (DTF) is used for performance evaluation of drill bits and cutterheads up to 3-ft (0.9-m) in diameter. The DTF has the ability to bore axially with the drill string, as well as slew, or cutting perpendicular to the drill string. The DTF is instrumented to measure all operational parameters, as well as vibrations generated by the cutting action. These measurements are digitally recorded with a computer based data acquisition system. The testing of a full-scale cutterhead provides an accurate measure of qualifying the dynamic effects of cutting and an economic proving ground for new bits and cutterheads.

EMI’s laboratory drill rig can perform drilling and boring tests up to 3-ft (0.91 m) in diameter. Its capacity is 100,000 lbs (445 kN) of thrust and 150 hp (112 kW). Cutterhead rotational speed is variable up to 60 rpm.

The machine performs both mechanical and water jet-assisted drilling tests. The cutting action of a roadheader or drum shearer can be simulated by moving the rock sample sideways with a hydraulic actuator. A computer-based data acquisition system monitors and records all drilling parameters during testing.

The DTF can also be used to test tri-cone bits, coring bits, and new-designed bits such as drill bits equipped with mini-disc cutters. The off-center drive system also allows for installation of a swivel unit. In addition to basic drilling parameters, cutter forces and pipe stresses can also be measured and recorded during testing.


32inch Microtunneling Cutterhead

36inch Drum Cutterhead

36inch Drum Cutterhead2

36inch Roadheader Cutterhead


Another unique test fixture at EMI is the Laboratory Tunnel Boring Machine (LTBM). It is used to test the performance of full-scale cutterheads up to 6 feet (2 m) in diameter. It is mounted on a swivel frame so that any orientation can be tested, from straight up to straight down, in wet or dry conditions. The LTBM data acquisition system is computer based for high resolution and accuracy. Individual cutters can be instrumented to measure actual cutter forces during boring.


A six-foot diameter, computer-controlled rotary cutting machine with removable cutters and cutterhead performs tunnel, raise and shaft boring investigations. The machine is pivoted on an anchor frame so that it can be tilted to any desired direction. The machine is used in laboratory studies to develop design guidelines to optimize tunnel, raise and shaft boring performance. All machine operative functions are servo-controlled and run by a computer system. The capacity is one million pounds of thrust and 200,000 foot-pounds torque with cutterhead speed variable up to 55 rpm. Instrumentation includes monitoring of individual cutter forces in three directions, as well as measuring all machine parameters during cutting. The machine can also be fitted with water jets to perform water jet-assisted mechanical cutting tests. The machine can also be used to run dust suppression and muck removal tests.














LTBM Rotating

LTBM Cutting


A 5-foot diameter, single-cutter rotary machine tests full-scale cutter bits (disc, pick, etc.) for performance and wear evaluations over long periods of time. Water jets may also be incorporated into the system to perform jet-assisted mechanical cutting tests.



The rotary drill facility permits laboratory testing and evaluation of various roof drills and bits, using an Epiroc COP1240 rotary hammer drill. The equipment includes a commercial-scale roof drill mounted on a multi-position drill boom assembly, and a heavy structural frame for holding the rock sample. The unit can also be fitted with water jets to perform water jet drilling tests.

Epiroc COP1240


Water jet equipment is available for high-speed drilling and slotting in rocks. A drill unit is mounted on a mobile self-contained chassis with a multi-position boom to enable precise positioning and angling of drill holes. A modified machining mill is used for water-jet slotting of straight and curved curfs These water-jet test stands are set up to provide a wide range of pressures and flow rates.

Water Jet

EMI has extensive laboratory test and
computing facilities for conducting
various rock and soil tests and fullscale
cutting and drilling tests. Data
collected during the testing processes
is then analyzed by computer models.
The laboratory facilities are continually
expanded to accommodate new
research programs requiring the design
and construction of specialized equipment.

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New Testing and Developments


SIntef   Sintef   Sintef

Soil Abrasion

Objective: To develop a device for direct measurement of abrasion of soil and rock fragments to predict wear on various excavation / drilling equipment.

Accomplished: A new device for testing is designed and fabricated, various types of soil and rock fragments were tested in dry, wet, and saturated conditions, elevated pressures examined, impacts of mixing of various foams and mud  were tested, various types/hardness of steel/carbides tested. New Index introduced.

SA Vessel  SA Schematic

Miniature Linear Cutting Machine

A new system is being developed that will allow for small cuts and scratching of samples as small as 6 inches. The new system operates much in the same manner as the full-size Linear Cutting Machine.

Mini LCM

Space Resources and Mining

NASA Overview