Attachment 005 FLH Rock Identification Guidelines_2025.pdf

Federal Lands Highway

Rock Description, Characterization, and Reporting Guidelines

FLH Rock Characterization Guidelines August 2025 i

TABLE OF CONTENTS

1 INTRODUCTION

1.1 PURPOSE AND INTENT

1.2 REFERENCED PROCEDURES

2 EXPLORATION AND SAMPLE IDENTIFICATION

2.1 EXPLORATION NAME AND NUMBER CONVENTION

2.2 SAMPLE COLLECTION AND LABELS

3 ROCK DESCRIPTION

3.1 ROCK TYPE

3.1.1 IGNEOUS ROCKS

3.1.2 SEDIMENTARY ROCKS

3.1.3 METAMORPHIC ROCKS

3.2 ROCK STRENGTH

3.3 ROCK COLOR

3.4 WEATHERING

3.5 GRAIN SIZE AND SHAPE

3.6 STRATIFICATION AND DIP ANGLE

3.7 SLAKING

3.8 VESICULARTY

4 DISCONTINUITY PROPERTIES DECSRIPTION

4.1 DISCONTINUITY TYPES AND DESCRIPTIONS

4.2 DISCONTINUITY SPACING

4.3 DISCONTINUITY CONDITION

4.4 DISCONTINUITY ANGLE RANGE AND ORIENTATION

4.5 DISCONTINUITY SEPARATION AND APERTURE

4.6 DISCONTINUITY SURFACE ROUGHNESS AND JRC

5 OTHER PROPERTY DESCRIPTORS

5.1 ROCK CORE RECOVERY

5.2 ROCK QUALITY DESIGNATION

5.3 FRACTURE FREQUENCY

5.4 ROCK CORING RUN TIME

5.5 VOIDS

5.6 REMARKS

5.7 GROUNDWATER OBSERVATIONS

6 FIELD: ROCK EXPLORATION LOGS

6.1 DEFINING AND DELINEATING STRATIFICATION

ii

6.2 POORLY INDURATED AND TRANSITIONAL MATERIALS

6.3 ORDER OF DESCRIPTORS

6.4 ROCK CORE LOGGING EXAMPLES

7 REPORT: ROCK EXPLORATION LOGS

7.1 DATA AND SAMPLE REVIEW AND LABORATORY TESTS

7.2 FIELD ROCK EXPLORATION LOG MODIFICATIONS

8 REFERENCES

1 INTRODUCTION

This guide outlines the standard practice for field identification and classification of rock on Federal Lands Highway (FLH) projects. The intent of this guide is to produce consistent and uniform field descriptions for rock by FLH personnel and consultants working on FLH projects.

1.1 PURPOSE AND INTENT

The purpose of performing geotechnical investigations is to characterize the in situ subsurface conditions underlying a site. Some common methods used to collect rock data include boreholes, test pits, exposed outcrop mapping, and geophysics, among others, and each can be performed with variable types of equipment and sampling tools. Typically, no single method will collect all the needed data due to various limitations, and assumptions and interpretations will be necessary to properly characterize a site.

The intent of these guidelines pertains specifically to describing rocks based on direct field observations of exploration surface walls, slope cuts, and physical rock samples collected by advancing and/or driving samplers. Determining in situ subsurface conditions from boreholes can be particularly challenging due to, for example, the drill rig type, drill method, sample intervals, sample recovery, sampler type and size, etc., which can eliminate, limit, or preferentially collect materials.

Two important notes to consider:

• The field identifications in the exploration logs should not solely be an assessment of the collected materials in a sample and should consider the above discussed variables, along with drill action and other observations, that are included as detailed notes.

• The exploration logs with the detailed notes should be carried forward to assist in:

o Selecting appropriate samples for and the types of laboratory tests, and o Digitalization of the exploration for report presentation.

1.2 REFERENCED PROCEDURES

Rock characterization for engineering purposes consists of two basic assessments identified in the 1978 and 1981 International Society of Rock Mechanics (ISRM) publications; one based on the intact rock properties of the rock, and the other based on the discontinuity features. Together, the intact rock and the discontinuity properties define the overall rock mass.

• Intact Rock Properties – This assessment is based on the character of the intact rock (hand specimens and rock core) in terms of its genetic origin, mineralogical make-up, texture, strength, and degree of chemical alteration and/or physical weathering.

• Discontinuity Properties – This assessment is based on the engineering characteristics

(orientation, spacing, etc.) of the bounding discontinuities (bedding, joints, foliation planes, shear zones, faults, etc.) within the rock mass.

Both assessments are essential to engineering characterization of the rock mass and are the basis for rock slope design and excavation, tunnel design and excavation, foundation design on rock, rock anchorage, and characterization of rock quarries.

Several other rock mass classification systems for engineering purposes and standard guides are presented in ASTM International (ASTM) D 5878 and ASTM STP 984.

Unless otherwise directed, FLH requires contractors and consultants to use the guidance presented in this document following the 1978 and 1981 ISRM publications.

2 EXPLORATION AND SAMPLE IDENTIFICATION

Exploration naming conventions and sample labels should adhere to the following guidelines.

2.1 EXPLORATION NAME AND NUMBER CONVENTION

Identify each exploration with an alphanumeric identification (ID) that includes the two-digit year the exploration was completed followed by a dash and then a two-digit sequential number. Letters used in the ID should either describe the exploration type, instrumentation(s) installed, or location of the boring. Use the same total numerical digits in all exploration identifications for each project (i.e., BH24-01 and BH24-10).

The following abbreviations are recommended:

BH Conventional boring CP Cone penetrometer test hole

IT Multiple instruments MW Monitoring well/open standpipe

PM Pressuremeter test hole SA Shape array

SG Subgrade boring SI Slope inclinometer casing

TD Time domain reflectometer TM Thermistor

TP Test pit VW Vibrating wire piezometer

Example Boring IDs are listed and described below:

BH24-01 indicates boring number 1 drilled in 2024 with no instrumentation

SG24-22 indicates subgrade boring number 22 drilled in 2024

VW24-04 indicates boring number 4 drilled in 2024 with a vibrating wire piezometer installation

SI24-22 indicates boring number 22 drilled in 2024 with slope inclinometer casing installation

TP24-01 indicates test pit number 1 excavated in 2024

TM24-01 indicates boring number 1 drilled in 2024 with thermistor installation

INST24-01 indicates boring number 1 drilled in 2024 with multiple instrument installations, i.e., slope inclinometer casing and vibrating wire piezometer

2.2 SAMPLE COLLECTION AND LABELS

Rock samples and other material samples collected during drilling should be handled with care.

Depending on the volume, disturbed samples should be placed in 1-gallon airtight resealable bags (e.g., Ziploc), plastic jars with lids, plastic bulk sample bags, or 5-gallon buckets (with lids).

Rock should be cored using NQ- or, preferred, HQ-core-size barrels. Each core run should be:

1. Photographed in the steel sampler sleeve with a tape measure and placard or white board with the following information:

a. Exploration ID

b. Core Box Number

c. Depth Range (in tenths of feet)

2. Transferred to a wax-lined or corrugated plastic core box, following these procedures:

Exhibit 2.2–A EXAMPLE PROCESS FOR FILLING ROCK CORE BOX

a. Like reading a book, starting at the top and working from left to right and then down.

b. Place wood blocks at 1) core start, 2) between the beginning and end of individual core runs, and 3) core end.

c. Using a permanent marker, label each wood block with the core run number and depth (in feet with increments in tenths of feet, i.e., 12.5’ to 15.3’).

d. Using a permanent marker or paint stick, draw lines across fractures in the rock core, delineating discontinuities from mechanical breaks.

e. Once filled, photograph each core box including a tape measure and placard with the Exploration ID, Core Box Number, and Depth Range (in feet with increments in tenths of feet).

f. When coring moisture sensitive and/or soft rock materials (i.e., siltstone, mudstone, claystone, coal, etc.), carefully wrap the rock core in plastic wrap to maintain the natural moisture content.

g. Place the core box lid and secure with tape.

The outside of the core boxes should be labeled with permanent black marker and in clear penmanship with the following information:

1. FLH Project Name and FLH Project Number

2. Exploration ID

3. Box Number and Total Boxes per Boring (i.e., Box No. 2 of 8)

4. Rock core depth range (in feet with increments in tenths of feet) in box

5. Core run numbers in box

6. Collection date(s)

Note that protective measures, such as, bubble wrap, or removing and individually wrapping core and placing them in a padded containers for shipping may be required to preserve cored materials for laboratory testing. Guidance to Standard Practices for Preserving and Transporting Rock Core Samples is provided in ASTM D5079-08.

3 ROCK DESCRIPTION

The first step in classifying rock is to describe the intact properties, the rock type, strength, weathering grade, color, texture and grain size, and intact stratification.

3.1 ROCK TYPE

Rocks are divided into three categories based on origin: igneous rocks, sedimentary rocks, and metamorphic rocks. For additional information on identifying rocks and minerals, refer to FHWA’s publication entitled, Rock and Mineral Identification for Engineers (FHWA, 1991).

3.1.1 IGNEOUS ROCKS

Igneous rocks form by the solidification of molten or partially molten material. These rocks are classified based on mineralogy (as mafic or felsic) and source (as Intrusive or Extrusive), with the color and rock texture being the primary diagnostic indicators (shown in Exhibit 3.1.1–A):

• Mafic rocks are darker in color due to minerals such as pyroxene and olivine.

• Felsic rocks are lighter in color due minerals such as orthoclase, quartz, and feldspar

• Intrusive rocks have coarser-grained textures, with the magma solidifying before reaching the surface, allowing longer cooling periods;

• Extrusive (also called Volcanic) rocks have finer-grained textures, with the magma solidifying above or near the surface, causing rapid cooling. Extrusive rocks include pyroclastic rocks that weld together various lithic materials and glassy/amorphous rocks.

Exhibit 3.1.1–A COMMON INTRUSIVE AND EXTRUSIVE IGNEOUS ROCK

(Intrusive/Phaneritic)

(Extrusive/Aphanitic)

Although presented simplistically, no clear line separates intrusive and extrusive igneous rocks, and gradual transitions in rock textures occur between the two types.

Pyroclastic rocks are a common extrusive igneous rock derived from explosively or aerially ejected volcanic material from a volcanic vent. Pyroclastic textures refer to the igneous source of the tephra and clastic refers to the rock fragments that is usually recognized by the chaotic mix of crystals, angular glass shards, and rock fragments (Exhibit 3.1.1–B).

Exhibit 3.1.1–B COMMON PYROCLASTIC ROCKS

Rock Name Description

Pyroclastic Breccia Pyroclastic rocks comprised of (angular) volcanic blocks (> 2.5 inches [64 mm]) accounting for at least 75% of the rock by volume cemented in a fine-grained matrix.

Agglomerate Pyroclastic rocks comprised of (rounded) volcanic bombs (> 2.5 inches [64 mm]) accounting for at least 75% of the rock by volume cemented in a fine-grained matrix.

Tuff Breccia Pyroclastic rocks comprised of volcanic bombs and or blocks (>

2.5 inches [64 mm]) accounting for 25% to 75% of the rock by volume.

Lapilli Tuff

Consolidated pyroclastic rocks comprised of 1) volcanic bombs and/or blocks (> 2.5 inches [64 mm]) making up less than 25% of the rock by volume and 2) combined lapilli (0.08 to 2.5 inches [2 to 64 mm]) and ash less than 75%.

Ignimbrite Poorly sorted pyroclastic rocks or unconsolidated deposits made of mostly volcanic ash, some pumice, and a few scattered lithic fragments.

Ash Tuff / Welded Tuff

Pyroclastic rocks making up at least 75% volcanic ash (< 0.08 inches [2 mm]) of the rock by volume and other pyroclasts and materials making up to 25%.

Pumice, scoria, and cinders are specific types of highly vesicular pyroclastic rocks. The vesicles form by the exsolution of gases from the magma upon eruption and can be spherical, lens-shaped, tubular, or highly irregular.

• Pumice: A light-colored, highly vesicular rock with closely-spaced vesicles separated by very thin walls of glass that forms in highly explosive pyroclastic eruptions. Pumice is typically rhyolitic in composition, but dacite or rhyodacite pumice may also form.

• Scoria: A dark-colored, highly vesicular rock with the volume of vesicles constituting the majority of the rock volume. Scoriaceous structure forms in lapilli and bombs in explosive mafic to intermediate composition eruptions and also in the rapidly cooled upper and lower surfaces of mafic lava flows.

• Cinder- A colloquial term for red or black highly vesicular lava that cooled in the air during flight after eruption from a vent and is roughly synonymous with scoria.

Obsidian is an extrusive volcanic glass that forms when molten rock material cools too rapidly for minerals to develop. Most obsidian has a composition similar to rhyolite and granite and can form from the same magma. Though obsidian is typically black, it can also be brown, tan, or green, and more rarely be blue, red, orange, or yellow.

3.1.2 SEDIMENTARY ROCKS

Sedimentary rocks form by the consolidation of sediments and are broadly described based on origin, composition, and grain-sizes. Sedimentary rocks origins include:

• Clastic – sediments such as gravels, sands, silts, and clays are deposited and lithified, or

• Non-Clastic – derived from the chemical precipitation from solutions (e.g., rock salt) or secretion from organisms (e.g., limestones).

Exhibit 3.1.2–A provides several common clastic rocks and the original sediment constituents.

Exhibit 3.1.2–A COMMON CLASTIC SEDIMENTARY ROCKS

Rock Type Grain Size Original Sediment Conglomerate Rounded Gravel, cobbles, and boulders in a sand, silt, and/or clay matrix Sand, Gravel, Cobbles, and

Boulders

Breccia Angular Gravel, cobbles, and boulders in a sand, silt, and/or clay matrix

Sand, Gravel, Cobbles, and Boulders

Sandstone Sand Sand

Siltstone Silt Silt

Claystone Clay Clay

Shale Clay Laminated Clay and Silt

A dilute mixture of hydrochloric acid (HCl) can be used to determine whether a rock contains calcium carbonate and help define the sedimentary, non-clastic rock type when similar in appearance.

Exhibit 3.1.2–B provides common non-clastic rocks and the primary mineral.

Exhibit 3.1.2–B COMMON NON-CLASTIC SEDIMENTARY ROCKS

Rock Type Grain Size Primary Mineral HCl Reaction Limestone Microscopic to very coarse Calcite Strong - violent reaction with bubbles forming immediately

Dolomite/Dolostone Fine to coarse grains Dolomite Weak - Some reaction with bubbles forming slowly

Chert Microscopic Quartz None - No visible reaction

Coal Clay Carbon None - No visible reaction

3.1.3 METAMORPHIC ROCKS

Metamorphic rocks form when minerals in pre-existing rocks recrystallize to new minerals in response to extreme changes in temperature and/or pressure. Metamorphic rocks are described based on two general categories:

• Foliated – contains laminated structures resulting from the segregation of different minerals into layers parallel to schistosity, and

• Non-Foliated – generally recrystallized and equigranular (non-laminated)

Exhibit 3.1.3–A provides common foliated metamorphic rocks and the likely original rock type.

Exhibit 3.1.3–A COMMON FOLIATED METAMORPHIC ROCKS

Rock Type Texture Formed From Primary Minerals

Slate Platy, fine grained Shale, Claystone Quartz & Mica

Phyllite Platy, fine grained with silky sheen

Shale, Claystone, Fine grained pyroclastic Quartz & Mica

Schist Medium grained with irregular layers

Sedimentary and Igneous Rocks

Mica, Quartz, Feldspar, and Amphibole

Gneiss Layered, medium to coarse grained

Sedimentary and Igneous Rocks

Mica, Quartz, Feldspar, and Amphibole

Exhibit 3.1.3–B provides common non-foliated metamorphic rocks and the original rock type.

Exhibit 3.1.3–B COMMON NON-FOLIATED METAMORPHIC ROCKS

Rock Type Texture Formed From Primary Minerals

Greenstone Crystalline Intermediate Volcanics & Mafic Igneous

Mica, Hornblende, and Epidote

Marble Crystalline Limestone & Dolomite Calcite & Dolomite

Quartzite Crystalline Sandstone & Chert Quartz

Amphibolite Crystalline Mafic Igneous &

Calcium-Iron Bearing Sediments

Hornblende & Plagioclase

3.2 ROCK STRENGTH

Rock strength is controlled by many factors including degree of induration, cementation, crystal bonding, degree of weathering or alteration, etc. Determining the relative rock strength can be estimated by simple field tests using a pocket knife and rock hammer, which can be refined through laboratory testing.

The relative rock strength should be determined based on intact specimens using the ISRM method outlined in Exhibit 3.2–A.

Exhibit 3.2–A RELATIVE INTACT ROCK STRENGTH (ISRM, 1978 and 1981)

Grade Description Field Identification

Approximate Uniaxial Compressive

Strength

R0 Extremely Weak Rock Specimen can be indented by thumbnail.

35 to 150 psi

250 to 1,000 kPa

R1 Very Weak Rock

Specimen crumbles under sharp blow with point of geological hammer, and can be peeled with a pocket knife.

150 to 725 psi

35 to 5,000 kPa

R2 Weak Rock Shallow cuts or scrapes can be made in a specimen with a pocket knife. A firm blow with a geological hammer point creates shallow indents.

725 to 3,500 psi

5,000 to – 25,000 kPa

R3 Medium Strong Rock

Specimen cannot be scraped or cut with a pocket knife. Specimen can be fractured with a single firm blow with a geologic hammer point.

3,500 to 7,250 psi

25,000 to 50,000 kPa

R4 Strong Rock Specimen requires more than one firm blow of the geologic hammer point to fracture.

7,250 to 14,500 psi

50,000 to 100,000 kPa

R5 Very Strong Rock

Specimen requires many firm blows from the hammer end of the geologic hammer to fracture.

14,500 to 36,250 psi

100,000 to 250,000 kPa

R6 Extremely Strong Rock

Specimen can only be chipped with firm blows from the hammer end of the geologic hammer.

>36,250 psi

>250,000 kPa

3.3 ROCK COLOR

Rock color is not a specific engineering property but may be an indicator of other significant geologic processes that may be occurring within the rock mass (i.e., water flow within fractures, weathering, alteration, etc.) and also aid in the correlation of rock units. Rock color should be determined as soon as the core has been recovered from the borehole while the core sample is wet.

Use basic color descriptions (i.e., brown, gray, black, green, white, yellow, red, etc.), using a dash to describe mixed colors by between two basic colors (e.g., gray-green). Describe different shades or tints of basic colors by adding the terms light or dark in front of the basic color, for example, light brown.

Use the 2009 Geological Society of America Munsell Rock Color Charts only when specified for a particular project.

3.4 WEATHERING

Weathering is the mechanical and/or chemical degradation of a rock mass through exposure to the elements (e.g., rain, wind, groundwater, ice, change in temperature, etc.). In general, the relative rock strength decreases as the weathering degree increases. In the earliest weathering stages, typically only discoloration and slight changes in texture has occurred. As weathering advances, changes in the rock mass physical properties will increase, until ultimately the rock is decomposed to residual soil.

The description of the weathered rock is based on six weathering classes (See Exhibit 3.3–A developed by the International Society of Rock Mechanics (ISRM, 1978 and 1981)).

Alteration is the process that applies specifically to the changes in the chemical or mineral composition of the rock due to hydrothermal or metamorphic activities. Alteration may occur in zones or pockets and can be found at depths far below that of normal weathering. Alteration does not strictly infer that there is a degradation of the rock mass or an associated loss in strength.

Where there has been a degradation of the rock mass due to alteration, the word altered should be substituted for weathered for Grade II through Grade V.

Exhibit 3.3–A WEATHERED ROCK STATE

Term Description Grade

Fresh No visible sign of rock material weathering; slight discoloration on major discontinuity surface is possible. I

Slightly Weathered

Discoloration indicates weathering of rock material and discontinuity surfaces. All rock material may be discolored by weathering and the external surface may be somewhat weaker than in its fresh condition.

II

Moderately Weathered

Less than half the rock material is decomposed and/or disintegrated to a soil.

Fresh or discolored rock is present either as a discontinuous framework or as corestones. A minimum 2 inch (50 mm) diameter sample cannot be broken readily by hand across the rock fabric.

III

Highly Weathered

More than half of the rock is decomposed and/or disintegrated to soil. Fresh or discolored rock is present either as a discontinuous framework or as corestones. A minimum 2 inch (50 mm) diameter sample can be broken readily by hand across the rock fabric.

IV

Completely Weathered

All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact. Material can be granulated by hand. If rock is considered to be completely weathered, use FLH Soil Description and Identification Guidelines to describe the residual soil material.

V

Residual Soil

All rock material is converted to soil. The mass structure and material fabric are destroyed but the apparent structure remains intact. There may be a large change in volume, but the soil has not been significantly transported.

Material can be easily broken-down by hand. If rock is considered to be residual soil, use FLH Soil Description and Identification Guidelines to describe the residual soil material.

VI

3.5 GRAIN SIZE AND SHAPE

Grain size is defined as the size of the particles or mineral crystals that make up the intact portion of the rock.

The description of crystalline size for igneous rocks should follow the criteria as set forth in Exhibit 3.5–A.

Exhibit 3.5–A IGNEOUS ROCK MINERAL/GRAIN SIZES

Grain Size Range Description

Extrusive (Aphanitic) Rocks

No grains present Glassy

Less than 0.04 inches (< 1 mm) Very Fine

Intrusive (Phaneritic) Rocks

Less than 0.04 inches (< 1 mm) Fine

0.04 to 0.2 inches (1 to 5 mm) Medium

0.2 to 0.75 inches (5 mm to 2 cm) Coarse

Greater than 0.75 inches (> 2 cm) Very coarse, pegmatic

Pyroclastic Rocks

Less than 0.002 inches (< 0.06 mm) Fine ash

0.002 to 0.08 inches (0.06 mm to 2 mm) Coarse ash

0.08 to 2.5 inches (2 mm to 64 mm) Lapilli

2.5 to 10 inches (64 mm to 2.6 cm) Fine blocks and bombs

Greater than 10 inches (> 2.6 cm) Coarse blocks and bombs

The description of grain size for sedimentary rocks should follow the criteria as set forth in Exhibit 3.5–B.

Exhibit 3.5–B SEDIMENTARY ROCK GRAIN SIZES

Grain Size Description Criteria

Less than 0.003 inches (<0.075 mm)

Very fine grained Cannot be distinguished by unaided eye. Few to no mineral grains are visible with a hand lens.

0.003 to 0.02 inches (0.075 to 0.425 mm)

Fine grained Few crystal boundaries are visible; grains can be distinguished with difficulty by the unaided eye but can be somewhat distinguished by hand lens.

0.02 to 0.08 inches (0.425 to 2 mm)

Medium grained Most crystal boundaries are visible; grains distinguishable by eye and with the aid of a hand lens.

0.08 to 0.2 inches (2 to 4.75 mm).

Coarse grained Crystal boundaries are visible; grains distinguishable with the naked eye and hand lens.

>0.2 inches (>4.75 mm)

Very coarse grained Crystal boundaries are clearly visible; grains are distinguishable with the naked eye.

The description for grain shape of sedimentary rocks should follow the criteria as set forth in Exhibit 3.5–C.

Exhibit 3.5–C SEDIMENTARY ROCK GRAIN SHAPES

Description Characteristic

Angular Showing very little evidence of wear. Grain edges and corners are sharp.

Secondary corners are numerous and sharp.

Subangular Showing definite effects of wear. Grain edges and corners are slightly rounded off. Secondary corners are slightly less numerous and slightly less sharp than in angular grains.

Subrounded Showing considerable wear. Grain edges and corners are rounded to smooth curves. Secondary corners are reduced greatly in number and highly rounded.

Rounded Showing extreme wear. Grain edges and corners are smoothed off the broad curves. Secondary corner are few in number and rounded.

Well-rounded Completely worn. Grain edges or corners are not present. No secondary edges or corners are present.

The description of crystalline size for metamorphic rocks should follow the criteria as set summarized in Exhibit 3.5–D.

Exhibit 3.5–D METAMORPHIC ROCK MINERAL/GRAIN SIZES

Grain Size Range Description Less than 0.01 inches (< 0.25 mm) Fine

0.01 to 0.04 inches (0.25 to 1 mm) Medium

0.04 to 0.8 inches (1 mm to 2 mm) Coarse Greater than 0.8 inches (> 2 mm) Very coarse

3.6 STRATIFICATION AND DIP ANGLE

As applicable, describe the bedding thickness or spacing in the sedimentary or igneous extrusive (volcanic) rock, as set summarized in Exhibit 3.6–A.

Exhibit 3.6–A BEDDING SPACING (After USBR, 2001)

Description Thickness / Spacing Massive Greater than 10 feet

Very Thickly Bedded 3 to10 feet Thickly Bedded 1 to 3 feet

Moderately Bedded 4 inches to 1 foot Thinly Bedded 1 to 4 inches

Very Thinly Bedded ¼ to 1 inch Laminated Less than ¼ inches

The angles and orientations of the bedding spacing should be measured using a goniometer, like the one shown in Exhibit 3.3-B, or a see-through compass and recorded on the boring logs.

Exhibit 3.6–B….EXAMPLE OF A GONIOMETER

Exhibit 3.6–C BEDDING ANGLE RANGES

Description Degrees(a) Horizontal 0 to 20 Dipping 21 to 50 Vertical 50 to 90

Notes: a – from assumed horizontal

3.7 SLAKING

Slaking is the disintegration of a rock when exposed to wetting and drying, or to air. This behavior is primarily related to the chemical composition of the rock and is identified in the field if samples shrink and crack, or otherwise degrade over several hours. Rocks prone to slaking include shale, siltstone, claystone, weakly welded tuff, and highly weathered crystalline igneous and metamorphic rocks.

If degradation of the rock sample occurs, and slaking is suspected; an air dried sample may be placed in clean water to observe a reaction. The greater the tendency for slaking the more rapid the reaction will be when immersed in water and can be rated using the Jar Slake Index, Ij, as described in Exhibit 3.7–A.

Exhibit 3.7–A RATE OF SLAKING (After AIR FORCE MANUAL)

Description Behavior 1 Degrades to a pile of small particles or fragments.

2 Breaks rapidly and forms many fragments 3 Breaks slowly and forms few fragments 4 Breaks rapidly and develops several fractures 5 Breaks slowly and develops few fractures 6 No change to condition of the rock fragment

3.8 VESICULARTY

The degree of vesicularity in an igneous extrusive (volcanic) rock should be reported by estimating the vesicle area percent in relationship to the total sample area (Exhibit 3.8–A).

Exhibit 3.8-A DEGREE OF VESICULARITY

Descriptor Percentage of Total Sample (by volume) Slightly Vesicular 5 to 10 Percent

Moderately Vesicular 10 to 25 Percent

Highly Vesicular 25 to 50 Percent

Scoriaceous Greater than 50 Percent

4 DISCONTINUITY PROPERTIES DECSRIPTION

The discontinuity properties in a rock are based on the engineering properties of the bounding structure. Structure refers to large-scale (megascopic), planar features which separate intact rock blocks, and impact the overall strength, permeability, and breakage characteristics.

4.1 DISCONTINUITY TYPES AND DESCRIPTIONS

Common planar features (collectively called discontinuities) within a rock include joints, beds, shears, faults, fracture zones, and mechanical breaks (Exhibit 4.1–A).

Exhibit 4.1–A TYPICAL DISCONTINUITY TYPES AND DESCRIPTIONS

Discontinuity Type Description Joint / Fracture Relatively planar fracture that has little or no shearing displacement Fracture Zone Numerous, very closely intersecting fractures

Bedding Separation along bedding planes in sedimentary rocks or igneous extrusive (volcanic) rocks due to stress relief or slaking

Shear / Fault Structural break with differential movement along surface or zone characterized by polish surfaces, striations, slickensides, gouge, breccia, etc. Faults are shears that can be correlated between observation locations

Mechanical Breaks Break from drilling or handling. Absent of oxidation, stains, or mineral fillings

Exhibit 4.1–B illustrates the discontinuity properties in a typical rock mass or core.

Rock Type

Discontinui ty Orientation

Aperture Opening

Discontinui ty Spacing

Discontinui ty Roughness

Discontinui ty Type

Aperture Opening In�lling & Type

Discontinui ty Set #’s

Exhibit 4.1–B Illustration of Discontinuity Features in a Rock Mass

When defining the properties of discontinuities within the rock, the recovered rock core from the borehole is examined, and the following information is recorded:

1. Discontinuity Spacing

2. Discontinuity Condition

3. Discontinuity Angle Range and Orientation

4. Discontinuity Separation and Aperture

a. Separation Opening Width

b. Separation Infilling Amount

c. Aperture Infilling Type

5. Discontinuity Roughness Quality

6. Joint Roughness Coefficient (JRC)

4.2 DISCONTINUITY SPACING

Discontinuity spacing is the distance between natural discontinuities as measured along the borehole. An evaluation of discontinuity spacing within each core run should be made, and reported on the field logs in conformance with the ISRM criteria in Exhibit 4.2–A. Mechanical breaks caused by drilling or handling are not included, and should be identified on the core sample with an “X” marking across the break.

Exhibit 4.2–A Discontinuity Spacing Ranges

Description Spacing Range Extremely Widely Spaced >20 feet (> 6 m)

Very Widely Spaced ~6 to 20 feet (2 to 6 m)

Widely Spaced ~2 to 6 feet (600 mm to 2 m)

Moderately Spaced ~8 inches to 2 feet (200 to 600 mm)

Closely Spaced ~2 to 8 inches (60 to 200 mm)

Very Closely Spaced ~3/4 to 2 inches (20 to 60 mm)

Extremely Closely Spaced <3/4 inches (<20 mm)

4.3 DISCONTINUITY CONDITION

The least favorable condition of these three descriptors should determine the selection of the discontinuity condition. For example, the condition of the discontinuity is very rough, the separation is greater than 0.04 inches (1 mm), and with a hard discontinuity wall, the discontinuity would be “Fair Condition” due to the aperture separation.

The discontinuity condition description in Exhibit 4.3–A summaries the roughness, the amount of separation and infilling in the apertures, and the discontinuity wall strength (estimated R value).

Exhibit 4.3–A Discontinuity Condition (ISRM, 1978 & 1981)

Condition Description Excellent Condition Very rough surfaces, no separation, hard discontinuity wall (>R2).

Good Condition Slightly rough surfaces, separation less than ~0.04 inches (1 mm), hard discontinuity wall (>R2).

Fair Condition Slightly rough surface, separation greater than ~0.04 inches (1 mm), soft discontinuity wall (<R3).

Poor Condition Slickensided surfaces, or soft gouge less than ~0.2 inches (5 mm) thick, or open discontinuities between ~0.04 and 0.2 inches (1 to 5 mm).

Very Poor Condition Soft gouge greater than ~0.2 inches (5 mm), or open discontinuities greater than ~0.2 inches (5 mm).

4.4 DISCONTINUITY ANGLE RANGE AND ORIENTATION

The angles and orientations of the discontinuities should be measured in the same manner as the intact stratification using a goniometeror a see-through compass and recorded on the boring logs.

Exhibit 4.4–B DISCONTINUITY ANGLE RANGES

Description Degrees(a) Horizontal 0 to 20 Dipping 21 to 50 Vertical 50 to 90

Notes: a – from assumed horizontal

4.5 DISCONTINUITY SEPARATION AND APERTURE

Separation is the maximum distance between two joint walls. The separation is generally small, mainly less than a millimeter, except for filled discontinuities. The size of the joint is often proportional to the thickness or separation of the joint.

Aperture is the perpendicular distance separating the adjacent rock walls of an open discontinuity, in which the intervening space is air or water filled. Aperture is thereby distinguished from the width of a filled discontinuity (ISRM, 1978).

The separation width should be measured and classified, as shown in Exhibit 4.5-A, Exhibit 4.5–A CLASSIFICATION OF DISCONTINUITY SEPARATION

Description Width

Very Tight Less than 0.004 inches

Tight 0.004 to 0.02 inches

Moderately Open 0.02 to 0.10 inches

Open 0.10 to 0.40 inches

Wide Greater than 0.40 inches

The amount and type of infilling within the discontinuity separation should also be noted, as shown in Exhibits 4.5-B and 4.5-C.

Exhibit 4.5–B INFILLING AMOUNTS Exhibit 4.5–C INFILLING TYPES

Amount Common Types Surface Staining Clay / Clay Gouge

Spotty Sand Partially Filled Silt

Filled Calcium Carbonate None Quartz

Areas of prominent soil infilling within the discontinuities should be qualitatively tested as described Exhibit 4.5–D.

Exhibit 4.5–D DISCONTINUITY SOIL INFILLING DESCRIPTION

Grade Description Field Identification S1 Very soft Easily penetrated several inches by fist S2 Soft Easily penetrated several inches by thumb

S3 Firm Can be penetrated several inches by thumb with moderate effort

S4 Stiff Readily indented by thumb but penetrated only with great effort

S5 Very Stiff Readily indented by thumbnail S6 Hard Indented with difficulty by thumbnail

The soils should be placed in a plastic bag and sealed for moisture content and additional laboratory testing.

4.6 DISCONTINUITY SURFACE ROUGHNESS AND JRC

Provide qualitative and quantitative estimates for the discontinuity surface roughness.

The qualitative estimate should be described as shown in Exhibits 4.6-A.

Exhibit 4.6–A DISCONTINUITY SURFACE ROUGHNESS (After Bieniawski 1989)

Description Roughness Very Rough Near vertical ridges evident

Rough Some ridges; surface abrasion Slightly Rough Asperities on surface can be felt

Smooth No asperities, smooth to the touch Slickensided Visible polishing / striated surface

In addition, assign a quantitative estimate of the surface roughness using the Joint Roughness Coefficient (JRC). Generally, very rough discontinuity surfaces have JRC greater than 10. To estimate the JRC, use the roughness profiles in Exhibit 4.6–B.

Exhibit 4.6–B JRC RANGES (ISRM, 1978 & 1981)

To estimate discontinuity wall hardness, ISRM (1978 & 1981) suggests using the knife and geologic hammer rebound tests described in Exhibit 3.2-A for the relative strength of intact rock specimens.

5 OTHER PROPERTY DESCRIPTORS

Guidelines for additional rock coring measurements and descriptions are provided in this Section.

Include remarks on the performance of the drill or comments made by the driller when the conditions change between samples as described in Section 5.6.

5.1 ROCK CORE RECOVERY

Core recovery (CR) should be recorded on the field logs for each core run and is defined as the ratio of core recovered to the run length expressed as a percentage:

𝑪𝑪𝑪𝑪 (%) = (𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳 𝒐𝒐𝒐𝒐 𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪 𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹 ÷ 𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳 𝒐𝒐𝒐𝒐 𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪 𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹𝑹) × 𝟏𝟏𝟏𝟏𝟏𝟏

5.2 ROCK QUALITY DESIGNATION

The Rock Quality Designation (RQD) provides a subjective estimate of rock mass quality based on a modified core recovery percentage from a double or triple tube diamond core barrel. The RQD is defined as the percentage of “sound,” intact rock core recovered in pieces of 4 inches (100 mm) or more in length through the length of a core run. The soundness of a piece of rock core is qualitative and is typically a measure of the degree of weathering or hydrothermal weathering of the intact pieces. ASTM defines sound core as any core that is fresh to moderately weathered and has sufficient strength to resist hand breakage. Lengths should be measured along the centerline of the core piece and in accordance with ASTM D 6032. Mechanical breaks caused by drilling or handling, lengths of core that are not “sound”, and vertical fractures should not be included in the RQD calculation.

𝑹𝑹𝑹𝑹𝑹𝑹 (%) = �

𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳 𝒐𝒐𝒐𝒐 𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺 𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪 𝒊𝒊𝒊𝒊 𝒑𝒑𝒑𝒑𝒑𝒑𝒑𝒑𝒑𝒑𝒑𝒑 > 𝟒𝟒 𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊𝒊 (𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏)

𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳𝑳 𝒐𝒐𝒐𝒐 𝑪𝑪𝑪𝑪𝑪𝑪𝑪𝑪 𝑹𝑹𝑹𝑹𝑹𝑹

� × 𝟏𝟏𝟏𝟏𝟏𝟏

An example for measuring RQD is presented in Exhibit 5.2-A. It provides the hole logger with a good example for measuring and calculating RQD.

Exhibit 5.2-A EXAMPLE OF RQD FROM ROCK CORE (USBR, 1998)

The RQD values should be described as shown in Exhibits 5.2-B.

Exhibit 5.2–B ROCK QUALITY DESIGNATION PERCENT RANGES

Description Ranges Very Poor 0 to 25

Poor 26 to 50 Fair 51 to 75

Good 76 to 90 Excellent 91 to 100

5.3 FRACTURE FREQUENCY

Fracture frequency (FF) is defined as the number of natural fractures per unit length of core recovered. The fracture frequency is measured for each core run, and recorded on the field logs as fractures per foot (300 mm). Therefore, 𝑭𝑭𝑭𝑭 =

𝑵𝑵𝑵𝑵𝑵𝑵𝑵𝑵𝑵𝑵𝑵𝑵 𝒐𝒐𝒐𝒐 𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏𝒏 𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇

𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻𝑻 𝒍𝒍𝒍𝒍𝒍𝒍𝒍𝒍𝒍𝒍𝒍𝒍 𝒐𝒐𝒐𝒐 𝒄𝒄𝒄𝒄𝒄𝒄𝒄𝒄 𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓𝒓 (𝒇𝒇𝒇𝒇𝒇𝒇𝒇𝒇)

Mechanical breaks caused by drilling or handling should not be included in the fracture frequency count. In addition, vertical fractures in the core should not be utilized in the fracture frequency determination. If significant changes are observed in the natural fracture patterns or a change in materials within a core run, two fracture frequencies should be reported for the differing characteristics of the rock.

5.4 ROCK CORING RUN TIME

The time it takes to core a run of rock, known as the rock coring time (RCT), can provide valuable information to the designer and contractor regarding penetration rates of the rock units with the drilling methods being utilized. Time for each coring run should be indicated on the field logs.

Significant changes in penetration rate within a core run should be noted.

5.5 VOIDS

Voids are important subsurface conditions to note in the field logs and are defined as relatively large open spaces within the rock mass often caused by chemical dissolution or the action of subterranean water within the rock mass or the result of subsurface mining activities. Voids, when encountered, should be recorded on the field logs. Attempts should be made to determine the size of the void by drilling action, water loss, etc.

5.6 REMARKS

Include remarks on the performance of the drill or comments made by the driller when the conditions change between samples, such as water color or fluid circulation, binding, caving or sloughing, difficulty in coring, etc.

Loss of coring fluid can indicate a major discontinuity, change in materials, or void in the drill hole.

Note the depth, time, and approximate amount of fluid loss when the driller loses circulation of drilling fluids.

Examples of additional remarks that may be included are:

driller remarks core barrels binding from 16 to 18 feet driller remarks loss of water circulation from 18 to 20 feet

5.7 GROUNDWATER OBSERVATIONS

Groundwater observations are not a specific rock sample descriptor; however, the water table is an important consideration in almost any type of geotechnical design and therefore, it should be sought out in any type of geotechnical investigation.

As a general rule of thumb, water levels and borehole cave-in depths should be checked and recorded in the remarks section of the log in the following cases, as applicable:

• when advancing the borehole after wet soil samples are encountered, stop the drilling and measure the depth to groundwater and wait for it to equilibrate in the boring (e.g., water level observed at 16 feet while drilling).

• if borehole is stopped at the end of the work shift, and before resuming drilling (e.g., water level observed at 17 feet and casing is at 20.5 feet at end of work shift on 9/2/15, water level observed at 16.5 feet before resuming drilling on 9/3/15).

• after reaching the bottom of the borehole before pulling the augers/casing out of the ground (e.g., water level observed at 18 feet upon completion of boring with augers in).

• and after pulling the augers/casing out of the ground (e.g., water level observed at 17.5 feet immediately after withdrawal of augers).

• at a set time after completion of the hole (e.g., water level observed at 15 feet 24 hours after withdrawal of augers).

When drilling fluids are introduced or groundwater instrumentation is being installed in the boring, the borehole should be baled to develop the hole. The groundwater will need to be allowed to recharge to measure the static water level following baling. In fine-grained soils, recharge to the static water level may take up to 24 hours and, in these cases, the borehole should be left open overnight and covered at the surface to allow this measurement the following day. However, in this absence of baling the drilling fluids, the groundwater should not be recorded to avoid collecting erroneous data.

6 FIELD: ROCK EXPLORATION LOGS

This section describes the linework to use and when to delineate stratigraphic changes and the order and content to include on the Field Rock Exploration Logs.

6.1 DEFINING AND DELINEATING STRATIFICATION

Most often in a boring where rock coring occurs, the stratigraphy will transition from soil to rock, requiring initial documentation following FHWA’s Soil Description and Identification Guidelines using a soil field log prior to switching to a rock core field log. The depth where rock coring begins should be clearly marked on both logs and the appropriate project, borehole, and drilling details denoted.

As appropriate, indicate the thickness and type of groundcover encountered at the boring location.

For example, the uppermost layer may be described as follows:

Asphalt Concrete (3.25 inches thick) over ¾-inch-minus base course aggregate (8 inches thick) Topsoil (5 inches thick) Duff/leaf litter (3 inches thick) Aggregate Roadway Surfacing (6 inches thick)

For borings through paved surfaces, record asphalt concrete pavement (ACP) or Portland cement concrete (PCC) pavement thickness to the nearest ¼ inch, and base course thickness, when present, to the nearest 1 inch.

For the rock core descriptions:

• For the intact rock properties, in the first sample of every stratum, provide a full description as described under Section 6.3 Order of Descriptors – Intact Rock Properties.

On subsequent samples, list changes from the first sample in that layer, if applicable (e.g., Becomes very strong (R5), moderately vesicular).

• For the in-situ discontinuity properties, provide full descriptions for each individual discontinuity, with the exceptions of intensely fractured zones and mechanical breaks, as described under Section 6.3 Order of Descriptors – Discontinuity Properties. Mechanical breaks should be clearly denoted on the rock core logs.

Use a stratification line to separate adjacent layers on the field logs where the Soil Group Name changes and where the geological origin of the material changes. Stratification lines may also be used if more than two of the descriptors change between samples. Use:

• A solid horizontal line when a stratigraphic change is observed within a sample.

• A dashed horizontal line when a change occurs between samples and is not observed, or when the driller notes a change in drilling behavior between samples. Place the dashed line midway between samples if the location of the change is unknown by drilling behavior.

Geologic origin or unit may be added if the information is available from geologic maps or the unit can be identified based on known area geology. When samples are interpreted as fill materials, or the geologic origin or unit is known, add a note at the end of the sample description with parentheses around the interpretation, e.g., (Fill), (Grand Ronde Basalt), or (Chuckanut Formation).

Groundwater observations must also be recorded on the boring logs. See Section 5.7 for guidance on recording groundwater.

6.2 POORLY INDURATED AND TRANSITIONAL MATERIALS

Poorly indurated formational materials such as siltstone, claystone, weakly cemented sandstone etc., which display both rock-like and soil-like properties, regardless of the degree of weathering, should be dually classified with full descriptions for 1) as a soil in accordance with Federal Lands Highway Soil Description, Interpretation, and Reporting Guidelines Manual (2025) and 2) as a rock in accordance with this manual.

6.3 ORDER OF DESCRIPTORS

Field Rock Core Log sheet title blocks should be completed in their entirety, including subsequent sheets for explorations that span multiple pages. In addition to the rock core descriptions, relevant notes should be recorded on changes in drill action, fluid losses, complications, artesian flow rates, and other possible indicators of in situ subsurface conditions.

The protocol for field identification of rock is to describe the intact rock properties in the following order, separating each numbered descriptor using either a comma or semi-colon:

1. ROCK TYPE;

2. relative rock strength (R-value),

3. color a;

4. weathered rock state (Grade),

5. (as appropriate) texture / grain size range, shape of primary or groundmass minerals or clasts;

6. (as appropriate) texture / grain size range, shape of larger or secondary minerals or clasts;

7. (as appropriate) intact stratification and dip angle;

8. (as appropriate) slaking, vesicularity.

9. (GEOLOGIC UNIT).

Notes:

*Drilling notes would be placed at or near the relevant depths where observed and not in the rock description.

a – Use basic color descriptions (i.e., brown, gray, black, green, white, yellow, red, etc., NO tan, olive, grey). Describe mixed colors by using a dash between the two basic colors (e.g., gray-green, NO ishes). Describe different shades or tints of basic colors by adding the terms light or dark in front of the basic color, for example, light brown)

Beginning on a new line, the protocol for field identification of rock is to describe the in-situ discontinuity properties in the following order, separating each numbered descriptor using either a semi-colon:

1. DISCONTINUITIES (SET #)a:

2. discontinuity spacing;

3. discontinuity condition;

4. discontinuity angle and orientation;

5. discontinuity separation / aperture width, infilling amount, infilling type;

6. discontinuity surface roughness, JRC;

Notes:

a – Add set # if more than one pattern is apparent

6.4 ROCK CORE LOGGING EXAMPLES

SANDSTONE; very weak to moderately weak (R1 to R2), yellow brown, moderately to highly weathered (Grade III to IV); fine to medium grained sand; moderately bedded, horizontal (0 to 20 degrees);

interbedded with laminated SILTSTONE, dipping (21 to 50 degrees). (CHUMSTICK FORMATION)

DISCONTINUITIES (SET#1): closely to moderately spaced; good condition; horizontal (0 to 20 degrees);

tight to moderately open separation (0.004 to 0.10 inches), spotty infilling with sand; slightly rough to rough surface, JRC = 8 to 10.

DISCONTINUITIES (SET#2): extremely closely spaced; poor condition; dipping (21 to 50 degrees); very tight separation (less than 0.004 inches), filled with silt; slickensided surfaces, JRC = 0 to 2.

BASALT; strong to extremely strong (R4 to R5), gray, fresh to slightly weathered (Grade I to II); very fine grained with medium grained olivine phenocrysts (0.04 to 0.2 in); highly vesicular (25 to 50 percent);

sulfur odor. (GRANDE RONDE BASALT)

DISCONTINUITIES: widely spaced; poor condition; vertical (50 to 90 degrees); open separation (0.10 to

0.40 inches); partially filled with S2 clay; rough surface, JRC 12 to 14.

POORLY INDURATED AND TRANSISTIONAL MATERIALS

Poorly-graded sand with silt; very dense, gray-brown, moist; non-plastic; fine to coarse sand; stratified, dipping (21 to 50 degrees); moderate cementation, weak to moderate HCl reaction, slightly micaceous.

(POORLY INDURATED SANDSTONE)

SANDSTONE; extremely weak (R0), gray-brown, fresh to slightly weathered (Grade I to II); fine to coarse grained; very thinly to thinly bedded, dipping (21 to 50 degrees).

DISCONTINUITIES (SET#2): closely spaced; poor condition; dipping (21 to 50 degrees); very tight separation (less than 0.004 inches), filled with sand; slightly rough surfaces, JRC = 6 to 8.

7 REPORT: ROCK EXPLORATION LOGS

This section describes examples of key interpretations and modifications to the Field Rock Exploration Logs when digitizing and generating the Report Rock Exploration Logs.

7.1 DATA AND SAMPLE REVIEW AND LABORATORY TESTS

When creating the Report Rock Exploration Logs, the responsible geotechnical engineer or engineering geologist should interpret the Field Rock Exploration Logs, based on:

• Review of published geologic information and previous work

• Further visual examinations of the field collected data and materials

• After completing a laboratory testing program on representative samples

• Professional experience and judgment

7.2 FIELD ROCK EXPLORATION LOG MODIFICATIONS

The Report Rock Exploration Logs should be modified, with ongoing interpretations and iterations being made, as details are entered into the digital boring software and reviews, including:

• Coalescing or removing general information and diagnostic behavior notes once the rock descriptions have been translated from the field exploration logs to the digital report logs.

However, some field drill notes (i.e., fluid circulation losses, caving, barrel binding, etc.)

should always be included on the Report Rock Exploration Log at the depth these events were observed.

• Rock classifications should be corrected based on the various laboratory test results, and these corrections should be applied to the interpreted common stratigraphy in adjacent borings. For example, if a correlatable rock layer is a Moderately Weak Rock (R2) in the field exploration log and the Unconfined Compression Strength test determines the material is a Moderately Strong Rock (R3), the nearby borings should be assessed, and similar layers should also be reclassified.

• In the event of poor rock recovery during coring, the stratigraphic contact depths and geologic unit names should be adjusted based on observations during drilling and sample reviews that may indicate when a layer or unit changes between samples.

For example, a field drill note of “coring went from smooth to chatter at 12 feet bgs” and the sample collected at 15 feet contains cemented gravel/gravel-sized constituents the change likely indicates the conglomerate layer begins at 12 feet bgs. The stratigraphic line on the borings should be placed at 12 feet bgs and the field drill note can be removed.

If no drilling condition changes were noted, the stratigraphic line should be placed at the depth…