17M7972M_Geotechnical_Letter_of_Results_FS_622.pdf

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September 10, 2018 TPT Project 17M7972M

Martha Alunkal, PE

WSP USA

13530 Dulles Technology Drive, Suite 300

Herndon, Virginia 20171

Re: Letter of Results and Recommendations

DSR FS 622

Culvert Replacement and Roadway Reconstruction

Town of Spider Lake, Sawyer County, Wisconsin

Dear Ms. Alunkal:

This letter presents the results of our field exploration performed at the culvert crossing Forest Road

(FR) 622 at Lynch Creek in the Town of Spider Lake, Marengo County, Wisconsin. The site is located around 2,900 feet south of the intersection of FR 636 with FR 622.This work covers DSR FS 622 as part of the WI ERFO FS 2016-1(5) project.

Project

It is our understanding that WSP USA is in the design process for culvert replacement and roadway reconstruction at the above referenced site. It is our understanding that the culvert and roadway sustained damage from a large rain event in July 2016. It is our understanding that the replacement culvert will consist of an arch culvert; the dimensions of the culvert are unknown at the time of this report. As part of the design process geotechnical services were requested.

Our scope of services for this project consisted of performing one (1) Standard Penetration Test (SPT) boring to a depth of 20 feet below river bottom or refusal. We were authorized to proceed with the proposed scope of services in a signed subcontractor agreement dated February 26, 2018.

Field Exploration

Field procedures for this project were performed on May 16th, 2018 using our Geoprobe Systems

7822DT track mounted drill rig and hollow stem auger drilling methods. Boring FS 622 (West) was performed to the west of the existing culvert to a depth of 29 feet. Sand blowup was encountered at a depth of 29 feet and the boring was terminated at this depth. The boring location is shown on the

Boring Location Sketch attached to this letter. Surface elevations were recorded by our field crew using a surveyors level and rod and were referenced to a benchmark labeled 51251. It is our understanding that this benchmark has an elevation of 1402.3 feet.

1301 N 3 rd St. Superior WI 54880 715 - 392 - 7114 1 - 800 - 373 - 2562 F 715 - 392 - 7163 www.twinportstesting.com

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Laboratory Testing Results of the field testing and observed subsurface conditions were evaluated to develop a laboratory testing program. The final laboratory testing program included visual classification by a geotechnical engineer, water content testing, and sieve analysis testing.

Laboratory water content testing was performed in general accordance with ASTM D2216 on collected samples from the field exploration. Results of water content tests are shown on the borings logs in the

Appendix. In general water content ranged from four percent to 42 percent.

Sieve analysis testing was performed in general accordance with ASTM D422 procedures on one sample.

Test results for percent passing the #200 sieve are provided in Table 1 below and on the boring log in the Appendix.

Table 1: Summary of Sieve Analysis Results

Boring Depth

(feet)

Description of

Material

% Passing

#200

FS 622

(West)

0-2 SP-SM (Fill)

AASHTO A-2-4

10.5

*SP-SM = Poorly Graded Sand with silt

Subsurface Conditions - Soil

Fill soils consisting of poorly graded sand (AASHTO A-1-b) and silty sand (AASHTO A-2-4) were encountered at the surface to depths up to 18 feet. Fill soils generally contained gravel, ranged from fine to coarse grained, were brown to dark brown in color, and were moist to wet. Fill soils contained organics to a depth of 13 feet and trace roots and fibers to a depth of 18 feet.

Native poorly graded sand with silt soils (AASHTO A-1-b) were encountered below the fill soils to the boring termination depth of 29 feet. Poorly graded sand soils were generally fine to coarse grained, contained trace gravel, were brown in color, and were wet to waterbearing. Based upon results of SPT

N-values native silty sand soils appear to be generally very loose in relative density.

Subsurface Conditions - Groundwater

Groundwater was encountered in Boring FS 622 (West) at a depth of 13 feet while drilling and sampling at this site. Groundwater levels at this site are anticipated to correspond with the surface level of the adjacent Lynch Creek which had a surface elevation of 1395.8 feet during field procedures.

Design Considerations and Recommendations

Culverts bearing on aggregate bedding, spread footings, or driven timber piles appear to be the most economical options for this site. Alternative structure options for this site include bottomless arches or bridges bearing on spread footings or driven timber piles.

Shallow foundations may not be the preferred foundation option due to deep fill soils encountered which extend below the water level of Lynch Creek. Performing a full depth soils correction will likely require an extensive dewatering program. Recommendations for both shallow foundations and driven piles are provided below.

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Site Preparation

Field explorations at this site encountered fill soils at the surface to depths of about 18 feet. The conditions and compactive effort under which fill soils were placed is unknown and it is possible that these soils would settle significantly when loaded.

Although soils beneath new construction are expected to experience little to no increase in net stresses, we do not recommend placing shallow foundations over uncontrolled fill soils. We recommend stripping all surface fill soils and any organic soils encountered within the footprint and influence area (1H:1V out from the outside edge of footings) of the proposed foundations and replacing with compacted engineered fill to reach design elevations. Excavations for the placement of culverts should be excavated to a minimum depth of one foot below the bottom of culvert elevation to insure the removal of any projections or boulders.

Minimum excavations for the removal of fill soils at this site are expected to be about 18 feet. If a full depth soils correction is not a feasible option at this site we recommend that culverts be designed to bear on driven timber piles. Recommendations for both shallow foundations and driven piles are provided below.

Shallow Foundations It appears that shallow foundations, consisting of spread footings or culverts bearing on aggregate bedding, may be used for foundation support when bearing on native sands or engineered fill over native sands. It is expected that culverts will be placed on a minimum of six inches of aggregate bedding overlying native soil. Recommendations for foundation design are provided below.

Net Allowable Bearing Stress

Results of the field and laboratory testing program were used to evaluate the net allowable bearing stress for shallow foundations. In our opinion, a net allowable bearing stress (with a minimum factor of safety of at least 2.5) of 3,000 psf (pounds per square foot) may be used to design footings placed on native soils or engineered fill over native soils.

Settlement Estimate

For foundations bearing on native soils or engineered fill over native soils and designed according to the net allowable bearing stresses outlined above, we estimate total settlement of less than one inch and differential settlements less than one-half inch.

Frost Protection We recommend that culvert foundations be placed at a minimum depth of six feet below finished exterior grade (surface of soil directly above foundation) to provide frost protection. We also recommend that the roadway surface be a minimum of five feet above the water table to minimize frost heave.

In areas where new culvert construction tie into existing roadways, we recommend that excavations extend from the bottom of culverts at a slope of 1:20 (Vertical:Horizontal) to provide frost differential protection.

Driven Timber Piles We evaluated two minimum timber pile tip diameters for this project; 8-inch and 12-inch diameter piles.

At a minimum, piles should meet the specifications of ASTM D25-12. Other types and sizes of driven piles can be evaluated upon request.

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Timber piles should be provided with end protection with the use of a metal boot or point to reduce the potential for damage during installation. If environmental restrictions will allow, timber piles should be treated with preservative treatments to reduce the risk of pile deterioration.

There are multiple methods of performing static analysis of pile resistance. Most methods are developed from empirical correlations with long term unit shaft and toe resistances being a function of effective stress. We strongly recommend that any static analysis be correlated with dynamic or static field tests in order to properly determine design effectiveness and assumptions.

Ultimate pile resistances for two pile sizes and associated lengths in Boring FS 622 (West) were estimated using the software AllPile developed by CivilTech Software. Field measured resistance depends on the control method used (dynamic formula, wave equation, Pile Dynamic Analyzer (PDA), or static load test).

LRFD Geotechnical Resistances: We used the computer program, AllPile, to estimate the geotechnical static resistances (Rη) of timber piles with minimum specified tip diameters of 8 inches and 12 inches.

Factored Geotechnical Capacities: Factored geotechnical pile resistances are determined by multiplying the pile driving resistance factor (Фdyn) by the total drive resistance (Rη). AASHTO recommends that

Фdyn be related to the degree of construction control. For situations where subsurface exploration and static calculations have been completed, we recommend factors for Фdyn as shown in the following table.

Table 2: Resistance Factors

Specified Field Control Method Фdyn

Dynamic Formula (Compression) 0.40

Wave Equation and Pile Driving Analyzer (PDA) 0.65

The following tables summarize estimated ultimate pile capacities based on depth and should be multiplied by the LRFD reduction factors outlined above for the appropriate method of field control.

Estimated ultimate resistances for two pile sizes, 8-inch and 12-inch diameter timber piles, are shown in

Table 3 for pile toe depths of 25 feet below existing grade, bearing in the loose sand soils encountered at this site. Depths are referenced from the surface of existing grade of our borings. We assumed piles will be cut-off at around elevation 1,403.0 feet.

Table 3: Estimated Ultimate Axial Resistance – 8-inch diameter Timber Pile

Pile

Diameter

(in)

Assumed Pile

Cutoff Elevation

(feet)

Estimated

Minimum Pile

Length (feet)

Toe

Elevation

(feet)

Estimated

Ultimate

Resistance

(kips)

8 1403.0 25 1378.0 42

12 1403.0 25 1378.0 75

Graphs depicting estimated ultimate pile resistance vs. pile depth for each pile type and location are included in the Appendix. The estimated resistances assume that piles will by protected from scour.

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Factored Tensile Capacities: Geotechnical capacities for tension are dependent upon the shaft resistance of a pile. A reduction factor (Фdyn) of 0.3 is common when using the dynamic formula control method. We do not anticipate that tensile pile capacity will be a limiting factor in design. If necessary, tensile capacity can be estimated using skin friction values from the bearing capacity charts in the Appendix and applying the desired reduction factor.

Settlement Using the estimated pile capacities presented above with the appropriate reduction factors, we anticipate total and differential deformation at the pile heads will be less than one inch.

Drag Load and Downdrag

Drag load is the integration of the unit negative skin friction and usually benefits foundation performance by prestressing the pile (assuming adequate structural strength is provided). Downdrag refers to settlement from soils above the neutral plane “hanging” on the pile and pulling it down. Where piles are driven into a very dense soil layer or bedrock, drag load is maximized and downdrag is minimal.

Downdrag is of most concern for shallow, predominately “shaft-bearing” piles where outside influences

(fill loads, groundwater table changes, adjacent foundations, etc.) cause settlement of the soils above the neutral plane.

Bridge abutment elevations are assumed to be at existing grade plus no more than two feet. As such, embankment induced settlement and associated drag load are expected to be minimal. We do not recommend reducing loads or increasing pile lengths to account for drag load in geotechnical design.

This practice effectively increases the factor of safety and typically results in an less economical design.

Lateral Design Parameters

Lateral earth pressures are an important aspect of designing underground structures including driven piles, sheet piles, and abutment walls. Lateral earth pressures are generally calculated for three modes of soil stress referred to as the at-rest condition, active condition, and the passive condition. For cohesionless soils or cohesive soils under long term loading, lateral earth pressures for each of the three conditions are calculated based upon soil friction angle and the respective earth pressure coefficients

(Ko, Ka, and Kp) using an effective stress analysis. Estimated lateral earth pressure coefficients and soil parameters for use in LPILE or GROUP software are shown in the Tables 4 and 5 below.

Table 4: Coefficients of Lateral Earth Pressure

Depth (feet) Ko Kp Ka

0-18 0.45 3.4 0.30

18-29 0.45 3.4 0.30

Table 5: LPILE/GROUP Estimated Design Parameters

Depth

(ft) p-y Curve Soil Model

Effective/Dry

Unit Weight (pcf) φ' (deg)

Cu (psf)

Kh (pci) E50

0-18 Sand (Reese) 57.6/120 33 - 25 -

18-29 Sand (Reese) 57.6/120 33 - 20 -

We recommend providing drainage behind abutment walls to reduce the potential for water collecting behind the walls.

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As part of determining lateral parameters we estimated the depth of fixity of driven timber piles. Depth of fixity will be dependent upon the design lateral loads of the structure and pile size. Based upon the pile sizes discussed above and assumed lateral loads of 5 kips, we estimate that the depth of fixity of timber piles will be located 6 feet to 8 feet below the ground surface.

Uplift Driven piles may be designed to resist uplift using the dead weight of the pile section and the frictional resistance along the pile shaft. We recommend that a resistance factor of 0.3 be used to determine the factored resistance of piles in uplift.

Structural Pile Strength

After pile diameters, lengths, and design loads have been determined, an analysis of structural strength should be performed. We recommend limiting the maximum load (dead load + drag load at the neutral plane) to 50% of the pile axial strength.

Pile Spacing

We recommend minimum pile spacing based on the following equation:

c/c = 2.5b+0.02D where c/c = minimum center to center spacing b = pile diameter

D = pile embedment length

If piles are spaced closer than outlined above, we should be consulted to evaluate group effects.

Frost Protection

If a concrete pile cap is used, we recommend that frost protection be provided. To provide frost protection, we recommend that a minimum of 6 feet of soil cover be provided above bottom of pile cap

(BOPC) elevation. If pile caps are placed at shallower depths, we recommend providing frost protection as outlined in ASCE 32-01 Design and Construction of Frost-Protected Shallow Foundations. Timber piles extending above the ground surface do not require frost protection.

Backfill and Fill A wide variety of materials can be considered as suitable for engineered backfill placed in a controlled manner or for general fill soils at non-structural locations. The choice of materials is a function of structural requirements, water table conditions, seasonal construction constraints, placement and compaction methods, and other site or project specific needs. Soils which classify as SP, SP-SM, or SM in the Unified Soil Classification System (ASTM D2487) or AASHTO A-1 and AASHTO A-2 in the AASHTO Soil Classification System are usually the most available suitable soils for engineered backfill and fill.

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For this project, we recommend that Aggregate Bedding meeting the gradation outlined below for direct culvert support/bedding.

Table 6: Gradation for the entire sample

Sieve Percent Passing by Weight (%)

1 ¼ inch 100

No. 4 25-100

Table 7: Gradation for the portion of the sample passing the No. 4 sieve, conform to the following limits

Sieve Percent Passing by Weight (%)

No. 4 100

No. 40 --

No. 100 0-30

No. 200 0-15

Other gradations for backfill of over excavations or embankment construction may also be suitable as approved by the project geotechnical engineer. Existing fill and native soils may be suitable for re-use, but should be verified through sieve analysis of representative bulk samples.

We recommend that a geotextile fabric (WisDOT Type SAS or equivalent) be placed between native soils and engineered fill/aggregate bedding to promote drainage and provide separation.

Compaction Standard We recommend using ASTM D698 - Standard Proctor as the laboratory compaction standard.

Density

We recommend compacting each lift to a minimum of the following percentage of the above compaction standard for the respective types of fill materials:

Table 8: Compaction Recommendation

Type of Engineered Fill % Minimum Compaction

Foundation Structural Backfill 98%

Aggregate Bedding 98%

Non-structural Foundation Backfill 95%

Within 3 Feet of Pavement or Aggregate Base Section 100%

Lift Thickness Place engineered backfill and fill materials in lifts not to exceed eight inches in a loose condition, unless the contractor can demonstrate satisfactory results when placing thicker lifts. Maximum compacted lift thickness should not exceed 12 inches in a loose condition.

Moisture In general, granular fill materials should be place and compacted within two percent of optimum moisture content, as determined by the above referenced compaction standard. When the moisture content of fill materials is not in this range, compaction to the required density may be difficult if not impossible. The excavating contractor is responsible for controlling and adjusting moisture content of backfill materials.

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Scour and Riprap We recommend the use of concrete end treatments (headwalls and wingwalls) combined with riprap to prevent the erosion of embankment soils and to provide protection against scour. Culvert foundations should be placed at an adequate depth to avoid scour. A detailed scour analysis was not included in our scope of work.

Dewatering Groundwater was observed in Boring FS 622 (West) at a depth of 13 feet during drilling and sampling at this site. Groundwater within excavations for construction of the proposed culvert is expected to be directly related to the levels of the adjacent Lynch Creek which had a surface elevation of 1395.8 feet during field procedures. If excavations extend below the groundwater surface and dewatering is necessary for construction, a large scale dewatering plan will be required. Dewatering options include diverting the Lynch Creek around the excavations or installing temporary sheet pile cofferdams with sumps and pumps.

Over Sizing Excavations for the placement of engineered backfill should extend horizontally at least a minimum of one foot beyond the bottom edge of footing for every one foot of over excavation depth required below the footing.

Temporary Shoring Temporary shoring of excavations may be required for this project. Any temporary shoring systems should be designed by a registered professional engineer.

Frozen Materials If construction occurs during temperatures below freezing, the base of all excavations and backfill materials should be protected from freezing. Excavated surfaces which become frozen should be completely thawed prior to placing backfill, concrete, or pavements. If freezing has loosened and reduced the bearing capacity of the excavation surface, remove the frozen material to the undisturbed surface. Frozen material should not be used as backfill.

Wave Equation Analysis

A wave equation driveability analysis should be performed to evaluate the contractor’s proposed driven pile installation method. A wave equation analysis will also help to determine a restrike criteria for field evaluation of pile resistance and can be used in combination with high-strain dynamic pile testing.

High-Strain Dynamic Pile Testing

We recommend that high-strain dynamic pile testing (HSDPT) with a Pile Driving Analyzer (PDA) be performed in accordance with ASTM D4945 on at least two piles at the project site. HSDPT provides an evaluation of pile hammer performance, pile integrity, pile stresses during driving, and pile resistance.

CAPWAP

CAPWAP analysis of PDA data is an essential part of HSDPT and should be performed on each test pile.

CAPWAP provides an estimate of soil resistance distribution along the pile and is correlated with static analysis to provide verification of design assumptions.

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Restrikes

Restrikes should be performed on at least one production pile to confirm estimates of long-term capacity from static analysis, HSDPT, and CAPWAP data.

Observation - Excavations Excavation bottoms and engineered fill operations should be observed by a geotechnical engineer or a designated representative to assure that the recommendations in this report are being followed. In-place density testing should be performed to document that project specifications are met.

Observation - Foundations Installation of foundations should be observed and documented by a qualified technician or engineer.

We recommend that at a minimum, concrete be tested for air content, temperature, slump, and compressive strength.

Observation Driven Piles An experienced engineering technician working under the supervision of the geotechnical engineer or experienced technician should observe the installation of driven piles in general accordance with Timber

Pile Design and Construction Manual prepared by APWI. The engineering technician should record pile information such as lengths, elevations, and driving resistances.

Frequency of Testing

For this project, we recommend a minimum density testing frequency of one test per 1,000 square feet of backfill area per lift. If the project area is smaller than this, we recommend a minimum of one test per lift. For isolated locations or questionable areas, we recommend a minimum of one test per occasion.

General

If you have any questions regarding our results, or if we may be of further service on this project, please call us at 715.392.7114.

Twin Ports Testing II, Inc.

Brett Carlson, PE

Project Engineer

Martin L. Halvorson, PE

Senior Engineer

Attachments:

Boring Location Sketch (1 Page)

Boring Logs (2 Pages)

Pile Capacity Graphs (2 Pages)

Boring Log Notes (2 Pages)

N

Approximate Boring Location

DRAWN BY: CHECKED BY:

DATE: SCALE:

DRAWING NO:

TPT PROJECT NO:

DRAWING NO:

1/1

REV:

DCS BMC

7/13/2018 N/A

17M7972M-01

17M7972M

A

BORING LOCATION SKETCH

Culvert Replacement and Roadway Reconstruction

FS 622

Bayfield County, Wisconsin

T win

P orts

T esting

FS 622 WEST

SS

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

SS

HSA

8.0

13.0

18.0

29.0

(FILL) Poorly Graded Sand with silt and gravel, fine to coarse grained, brown, moist *Sieve analysis of % passing #200 sieve test performed at 1 foot = 10.5

(FILL) Silty Sand with gravel, trace organics, fine to coarse grained, brown to dark brown, wet

(FILL) Poorly Graded Sand with silt, trace gravel, trace roots and fibers, fine to coarse grained, dark brown, waterbearing

(SP-SM) POORLY GRADED SAND with Silt, trace gravel, fine to coarse grained, brown, waterbearing, very loose (AASHTO A-1-b)

*Sand blowup at 29 feet

Boring then Backfilled with Bentonite

End of Boring

CLIENT:

DSR FS 622

PROJECT:

5/21/18

13 ft WD

River Elev 1395.8 ft

Autohammer

CAVE IN LEVELWATER LEVEL

SITE LOCATION:

WSP USA

RIGSPT HAMMER

5 ft ACR

BORING STARTED

CREW CHIEF

MLH

WATER LEVEL

WSP USA Spider Lake, Sawyer County, Wisconsin

ARCHITECT - ENGINEER:

THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES

IN-SITU, THE TRANSITION MAY BE GRADUAL.

05/16/18 05/16/18

REPORT DATE:

WATER LEVEL BORING COMPLETED ABBREVIATIONS: ACR-After Casing Removal, BCR-Before Casing Removal, AB-After Boring, WD-While Drilling, WS-While Sampling, NE-None Encountered, DB-Diamond Bit, HSA-Hollow Stem Auger, RB-Rock Bit, SS-Split Spoon, ST-Shelby Tube, PA-Power Auger, MR-Mud Rotary, CS-Continuous, RP-Rock Probe, PH-Percussion Hammer, WL-Water Level, WOH-Weight of Hammer, EIL-Exceeds Instrument Level, TS-Topsoil, PP-Pocket Penetrometer

17M7972M

SA

M

PL

E

N O

D

EP

TH

(f t)

EL

EV

AT

IO

N

(f t)

0.0

10.0

20.0

30.0

1405.0

1395.0

1385.0

1375.0

SA

M

PL

E

D

IS

TA

N

C E

PLASTIC

LIMIT %

TPT Project No.:

UNCONFINED COMPRESSIVE STRENGTH (TONS/FT2)

PERCENT PASSING #200 SIEVE

10 20 30 40 50

1 2 3 4 5

10 20 30 40 50

FS 622 (West)

See Boring Location Sketch

R

EC

O

VE

R Y

10 20 30 40 50

DESCRIPTION OF MATERIAL

WATER

CONTENT %

LIQUID

LIMIT %

W

AT

ER

L

EV

EL

SA

M

PL

E

TY

PE

BORING LOCATION:

BORING LOG

STANDARD PENETRATION TEST N-VALUE

BOREHOLE LOG 17M7972M DSR FS 622.GPJ TWINPORT.GDT 7/16/18

G R

AP

H

IC

L

O G

SURFACE ELEVATION:

1404.95 ftST

R

AT

A C

H

AN

G E

D

EP

TH

0 0

5 5

10 10

15 15

20 20

25 25

30 30

35 35

40 40

45 45

50 50

0 03 36 69 912 1215 1518 1821 2124 2427 2730 30

Foundation Depth, L -ft Foundation Depth, L -ft

C o m p re s s io n C a p a c it y

Q d w k p

U p li ft

C a p a c it y

Q u p k p

ULTIMATE CAPACITY vs FOUNDATION DEPTH

ALL-PILE CivilTech Software www.civiltech.com Licensed to

Twin Ports Testing Project # 17M7972M FS 622 Figure 1

DSR FS 622 (West) 8 inch diameter pile

0 0

8 8

16 16

24 24

32 32

40 40

48 48

56 56

64 64

72 72

80 80

0 03 36 69 912 1215 1518 1821 2124 2427 2730 30

Foundation Depth, L -ft Foundation Depth, L -ft

C o m p re s s io n C a p a c it y

Q d w k p

U p li ft

C a p a c it y

Q u p k p

ULTIMATE CAPACITY vs FOUNDATION DEPTH

ALL-PILE CivilTech Software www.civiltech.com Licensed to

Twin Ports Testing Project # 17M7972M FS 622 Figure 1

DSR FS 622 (West) 12 inch diameter pile

BORING LOG NOTES

Water Level Water levels indicated on the boring logs are as measured at stated times. In clean sand soils, the elevations indicated are considered relatively reliable levels. However, in less permeable soils, even after several days of monitoring, accurate determinations may not be possible. Therefore, additional/alternative methods of groundwater elevation monitoring should be sought.

Commonly Used Moisture Conditions of Soils Term Meaning Dry Requires the addition of considerable moisture to attain optimum for compaction Moist Near optimum moisture for compaction Wet Requires drying to attain optimum moisture for compaction Waterbearing Saturated granular soils

Gradation Description and Terminology Soil Type Particle Name Size Range Coarse Grained Soils Boulders Over 12”

Cobbles 3”-12” Gravels #4-3” Gravels – Coarse ¾”-3” Gravels – Fine #4-¾” Sands #200-#4 Sands – Coarse #10-#4 Sands – Medium #40-#10 Sands – Fine #200-#40

Fine Grained Soils Silt 0.005 mm-#200 Clay Less than 0.005 mm

Descriptive Terms of Components Present in Sample (other than ASTM D 2487) Term Percent of Dry Weight Trace 1-5% With 5-12% Some 12-30% And 30-50%

Relative Density of Granular Soils N-Value (SPT) Relative Density Standard “N” Penetration 0-4 Very Loose Blows per foot of a 140 pound hammer 5-10 Loose falling 30” on a 2” outside diameter 11-30 Medium Dense split barrel sampler 31-50 Dense Over 50 Very Dense

Consistency of Cohesive Soils N-Value (SPT) Consistency (Q, tsf or kg/cm2) 0-2 Very Soft Less than 0.25 3-4 Soft 0.25-0.50 5-8 Medium 0.50-1.00 9-15 Stiff 1.00-2.00 16-30 Very Stiff 2.00-4.00 Over 30 Hard 4.00-8.00

UNIFIED SOIL CLASSIFICATION SYSTEM – ASTM D 2487