The MTS 815 load frame is capable of delivering 600,000
lbs. of force and is completely servo-controlled with a MTS
458 Controller.
Several triaxial cells are used with this load frame. The load
frame is typically used to apply axial force for triaxial compression
experiments, but can also be used to apply axial loads to large,
unconfined samples such as cement test cylinders, cubic samples of rock, acousitic emmision test blocks, etc..
A doctoral dissertation research project utilized the 815 loading frame for uniaxial loading of cubic
samples of various rock types. Rock cubes were instrumented with strain gages and peizo-electric
crystals for measurement of changes in the rock due to application of load. Shown are the
instrumentation required for the strain gages, acoustic velocity measurement, and computer based data
acquisition system.
Graduate students are shown preparing a triaxial cell for use with the MTS 815.
MTS
819
The MTS
819 load frame is capable of either tensile or compressive
loading while simultaneously applying torsional loads to a rock
core sample. The apparatus has an operational range of 50
kips force in the tension and compression modes and
20,000 inch pound torsional force. Hydraulic grips are available to accommodate
samples up to 2 inch in diameter. The system has a MTS 458
controller for servo-operation of the system. The load frame has been used with
appropriate additional fixtures for direct tension test, Brazilian tension tests,
unconfined compession experiments, uniaxial tests, triaxial tests, torsional test
of hollow rock cylinders, fracture toughness tests, and fracture growth in plates.
Triaxial tests with confining vessel are performed for small size samples at any
confining pressure or NX size samples ( 2 1/8 inch diameter 4 1/4 inch length)
with low strength or low confining pressures.
A portable pressure and flow control system
has been configured for use with any loading system in the laboratory. The system utilizes ISCO syringe
pumps with pressure rating of 10,000 psi to apply confining pressure and provide precision control of
fluid flow when evaluating effect of fluid contact on mechanical properties of formation material.
All confining vessels in the laboratory are
currently configured to allow use of strain gages or acoustic measurement in the vessels. Shown on the
819 loading frame is a cell base under use without the wall for acoustic velocity measurement on a
sample during uniaxial loading.
MTS
815 Rig
The MTS
815 rig has an integral triaxial cell incorporated
into its design. The load frame has a 600,000 lb. capability.
Two hydraulic intensifiers supply 20,000 psi for the confining
and pore pressure systems. The cell has recently been refurbished
and now has four pore pressure ports (for axial and lateral
permeability determinations during triaxial tests) and 15
electrical feedthroughs (4 pins each) to 60 wires.
This cell can accommodate rock core samples up to 4 inch in
diameter and 8 inch in length and is servo-controlled by the
MTS TestStar II system.
Sample deformation measurements in the MTS
815 rig are performed using a MTS circumferential extensometer for determination of lateral change of
the sample. Length change of the sample are measured using a MTS axial extensometer. Graduate students
are shown inspecting the installation of the extensometers on a sample prior to testing.
Triaxial
Cells
This is
one of several triaxial cells in the laboratory. This particular
cell can test rock samples in sizes from 1 inch diameter, 2 inch
length to 2 1/8 inch diameter, 4 1/4 inch length and subject
them to pore and confining pressures up to 10,000 psi. In this photograph
the shell of the triaxial cell is sitting beside the baseplate.
A rock core sample is mounted on the baseplate with a circumferential
extensometer. Axial deformations are measured via two LVDTs
clamped to the upper platen. The cell has band heaters which
allow experiments to be conducted at temperatures up to 300°C.
Additional testing performed in the equipment include testing of
unconsolidated materials up to 3 inch diameter, 6 inch length with
various confining pressures has been performed without circumferential
measurements, triaxial testing of 1 1/2 diameter rock sample with
acoustic velocity measurement, and other various tests.
A second triaxial cell is setup with 6 fluid pressure ports and
7 electrical feedthrus. This cell is used in testing the effect
of fluid contact on rock strength while simultaneously measuring acoustic
velocity during the experiment.
MTS
810
The laboratory also has a 55 Kip capacity
MTS 810 load frame with an integral MTS TestStar II controller. The apparatus was acquired
and setup for long term tests on weak rocks (such as Shales). The role of this load frame
has been expanded to include use for instructional purposes in graduate and undergraduate
courses instructed by PMI faculty for unconfined sample testing.
The system has a separate SBEL Model 10 triaxial cell which has been modified with up
six fluid pessure ports for various fluid flow configurations to evaluate effect of
different fluids on rock strength and electrical feed thrus for acoustic velocity
measurement.
GAIS
The
Geomechanical Acoustic Imaging System (GAIS) consists of five
technologies:
1. an ultrasonic tomography system;
2. an acoustic emission system for both parametric and full
waveform AE acquisition;
3. a multichannel acoustic system for compressional and shear
wave velocity acquisition;
4. a high capacity load frame and triaxial cell; and,
5.a data acquisition and command & control system.
The
acoustic systems are arrayed around one of the largest triaxial
compression systems in the world. The load frame has a capacity
of 3,000,000 lbs and an integral triaxial cell with a capability
of 20,000 psi pore and confining pressures. The system can
accommodate samples as large as 6 inches in diameter and 20
inches in length.
The above photograph shows a 6 inch diameter sample being prepared for loading into the test chamber of
the system.
The control
system was upgraded by installation of a MTS TestStar IIM digital controller.
Microscope Analysis
The laboratory
has recently added a microscope and camera system which allows petrographic analysis of samples
submitted for uniaxial or triaxial testing with capability of storing photographs for later retrieval.
