Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Presentation to Illinois Mining Institute Authors: John E. Feddock, P.E., Senior Principal Mark S. Smith, GLS Business Unit Manager Phil Waters, Senior Supervisor - GLS Marion, Illinois • August 26, 2015 August 26, 2015

Abstract This presentation deals with the excavation of shafts and slopes for underground mines. Through properly located boreholes and the use of geophysical logging it is possible to identify and investigate ground control and the prediction of strata strength characteristics prior to excavation and avoid costly delays due to geologic and hydrologic changes that impede construction and increase costs. Through geophysical logging it is possible to predict compressive strength and tensile strength of strata, identify faults and fracture patterns, fissile shales in addition to water inflow and outflow zones and conductivity for controlling water during excavation.

What is Geophysical Logging ?

Geophysical Logging Services

Geophysical Logging Probes 0033 Density Probes 9051 Casing Collar Locator 9055 Deviation / Neutron Probes 9096 Gyro Deviation Probe 9041 Temperature-Fluid Conductvity-Res. Probes Downhole Cameras – three models for various applications 9035 Compensated Density Probe 9511 Induction Probe 9136 Density Temperature Deviation Probe 9721 EM Flowmeter 9804 Acoustic Televiewer Probe 0026 Three-arm Caliper/ Deviation/Temperature 9321 Full-wave Sonic Probe Discrete Interval Water Sampler

Core Photos

Standard Working Depth to 4,000 Feet Deeper upon request

The High-Resolution Density Probe Model No. 9030 Contains a very short spacing Americium source Records natural gamma, caliper, guard resistivity (in fluid) and open hole density Recording at 50 times per foot Purpose Provides for the identification of sedimentary strata by an estimate of its density and response to the nuclear source. The log can be interpreted to provide a general description of the type of strata.

Gamma-Density Log with Caliper and Resistivity Traces and Interpreted Geology

The Full Wave Sonic Tool Model No. 9320 Single transmitter and dual receiver Records 10 times per foot Sonic velocities are proportional to the compressional strength of the rock where the state of stress (σ) in a direction is proportional to the particle velocity (V) in that direction.

Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Elastic-wave (acoustic) methods Propagation paths for P, S, mud, and tube waves. (After Lobo, 1987) August 26, 2015

Sonic Log Traces

Trace of Acoustic Wave Train Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Trace of Acoustic Wave Train August 26, 2015

Focused Resistivity Century Model No. 0033 combination probe with natural gamma, density, guard resistivity and caliper. Uses a 4-inch current electrode centered within two guard electrodes Total length of 55 inches

Focused Resistivity Probe Schematic Electrode Guard Current 55 inches Guard Focused Resistivity Probe Schematic

Tensile Strength versus Guard Resistivity Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes   Tensile Strength versus Guard Resistivity August 26, 2015

Acoustic Televiewer Model No. 9804 Images the borehole sidewall using high-resolution sound waves (similar to sonogram) Picture displayed in both amplitude and travel time Digitizes 256 measurements around the boreholes Sample interval (0.005 meters/0.02 feet) Oriented directionally with magnetometers and inclinometers

Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Acoustic Televiewer August 26, 2015

Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Acoustic Televiewer : The circle produced by the intersection of a dipping plane and borehole is “unrolled” and appears as sine curve August 26, 2015

Televiewer Log - Amplitude Televiewer Log – Travel Time Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes           Televiewer Log – Travel Time Televiewer Log - Amplitude 45º Fracture dipping North 10º East August 26, 2015

Interpretation of a Highly Fractured zone over 8 feet Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Televiewer Log Trace Interpretation of a Highly Fractured zone over 8 feet August 26, 2015

Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes From the log we can Plot Stereographs and Rose diagrams for wedge and plane failure analysis August 26, 2015

Down Hole Video Camera Use Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Down Hole Video Camera Use Presenter’s Notes: Geophysical equipment is highly mobile. The truck shown is configured for off the road use and packs all of the equipment and tools for a full suite of downhole logs as well as down hole camera video capture. August 26, 2015

Geological Logging Systems’ latest camera systems have: Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Geological Logging Systems’ latest camera systems have: Internal rotating and external fixed lighting Ring lighting (not shown) that gives an unobstructed downward view. Pan-tilt-zoom model for large shaft –mine void use. Very low lux sensitivity that allows horizontal scan viewing into large openings such as mine voids, tunnels, etc. Rugged stainless steel construction, hermetically sealed with internal nitrogen charge. Explosion proof with up to a 2500-psi pressure rating, Viewing distances from fractions of inches out to 70 feet or more depending upon lighting and void conditions. A 5,000-foot depth capacity as mounted in a four wheel drive Ford F-350 with off-road capabilities Various models for use in boreholes from 3 inches in diameter up to large shafts and 6 inch boreholes into mine voids. August 26, 2015

Down hole and Side Views from Camera Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Down hole and Side Views from Camera Immersed Side View of Borehole Wall Presenter’s Notes: Date 2003 Upper left hand image, depicts a down the hole view. The lower left hand image, depicts a side view of the borehole wall. The camera is submerged at this point. The lower right hand image depicts a side view of a water inflow into the borehole. The camera is submerged at this point. Immersed Side View of Borehole Wall Showing Water Inflow “Cloud” August 26, 2015

Down hole Views from Camera Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Down hole Views from Camera Down Hole View Down Hole View with ring light August 26, 2015

Down hole and Side Views from Camera Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Down hole and Side Views from Camera Down hole view of Borehole and Pilot Hole Presenter’s Notes: Date: 2003 Down hole videos, in either dry or wet holes, can be used to detect problems. Here, an eleven-inch diameter hole drifted away from its pilot hole. A piece of PVC piping was found lodged in the pilot hole. Close-up view of Item Lost in Pilot Hole Down hole view of Item Lost in Pilot Hole August 26, 2015

Shaft and Mine Void Inspection Camera Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Shaft and Mine Void Inspection Camera Imersed Side View of Borehole Wall Presenter’s Notes: Date 2003 Upper left hand image, depicts a down the hole view. The lower left hand image, depicts a side view of the borehole wall. The camera is submerged at this point. The lower right hand image depicts a side view of a water inflow into the borehole. The camera is submerged at this point. Old Mine Void thru 6 inch borehole Wide angle in Photo above. Zoomed in on Pillar 60 feet away, on right. August 26, 2015

Now that we have all of this data what do we do with it? Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Now that we have all of this data what do we do with it? ? August 26, 2015

Information Available Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Information Available Knowledge of fractures and bedding planes allows prediction of possible unstable rock conditions in the shaft walls or the slope roof. Prediction of rock strengths are an indicator of weak rock strata and provides information for rock bolting or secondary support. In sedimentary rock, porosity is inversely proportional to the modulus of elasticity and the wave velocity, giving an indicator for water bearing strata. Ground water information gives the ability to predict potential water inflow and the design of water rings in shafts or effective grouting plans. In sedimentary rocks sonic wave velocities can be treated as if they are isotropic, but in metamorphic and igneous rocks tectonic stress can have a large effect on sonic wave velocities. August 26, 2015

Different Rock Types can create Difficult Mining Conditions Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Different Rock Types can create Difficult Mining Conditions Interbedded Sandstone and Shale (Stack rock) can result in very difficult mining conditions especially during construction of shafts and slopes. Weak or incompetent strata is difficult to predict from only core logs. When it occurs weak or incompetent strata allows for overbreak during blasting and/or rock falls during excavation. August 26, 2015

Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes A Slope with an overbreak problem involved a Geology Assessment and Interpretation of Rock Stability August 26, 2015

Slope Logging Activities Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Slope Logging Activities Three bore holes were located near the base of the slope but the two holes near the top of the slope were located plus or minus 1600 feet away from the center line of the slope. Core for three of the holes were logged 50 feet above the coal seam, while the rest of the hole relied on drillers logs. Although two of the five holes had geophysical logs for sonic, density, gamma ray, and caliper performed by Geological Logging Systems (GLS), subsidiary of Cardno, only one had agreement with geologists log. Using the geologists and sonic logs, an RMR rating was subjectively estimated for seven zones along the line of the slope . Zones of weak roof were identified and a recommended bolt length was estimated so that excavation of the slope could continue safely. August 26, 2015

Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes The outcome was favorable but delays occurred when weak strata interfered with the normal excavation cycle and forced an assessment of possible future adverse geology. The sonic, density and gamma logs provided the opportunity to predict the weak rock areas and identify the necessary reinforcement such that the excavation cycle could proceed with minimal interference. August 26, 2015

Geophysical Logging in Planning & Minimizing Costs in Shafts and Slopes Recommendations Drill core holes on or near the center line of shafts, and at the bottom or radius of the slope, slightly lower than the midpoint, and between the slope collar and the upper quarter point. For example if a slope will have an inclined length of 1700 feet, core holes should be located ~400 feet, ~1000 and ~1700 feet from the collar. Geophysical logging of each hole should include: density, gamma ray, and caliper density, and caliper logs for geologic interpretation, acoustic televiewer, sonic, and resistivity logs for fracture analysis and rock strength evaluation, and temperature log to identify water zones. The geophysical information can be used to predict: unstable or weak strata that will require blasting precautions and/or roof support, water bearing strata that may require enhanced water control by grouting, or installation of water rings and dewatering holes. August 26, 2015

THANK YOU Mining and Mineral Services Resource/Reserve Evaluations Geotechnical Evaluations (Subsidence) Geophysical Logging Hazard Prediction Field Exploration Water Resources Management Probable Hydrologic Consequences Evaluations Mine design and Plant Evaluations