Cyclic Behavior of Transitional Fine-Grained Soils in Northern Willamette Valley

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Portland State University Portland State University

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Cyclic Behavior of Transitional Fine-Grained Soils in Cyclic Behavior of Transitional Fine-Grained Soils in Northern Willamette Valley Northern Willamette Valley

Frank E. Jarman Portland State University

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CYCLIC BEHAVIOR OF TRANSITIONAL FINE-GRAINED SOILS IN NORTHERN WILLAMETTE VALLEY

BY

FRANK JARMAN

A research project report submitted in partial fulfillment of the requirement for the degree of

MASTER OF SCIENCE IN

CIVIL AND ENVIRONMENTAL ENGINEERING

Project Advisor:

Arash Khosravifar

Portland State University

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ABSTRACT

As discussed within studies from Idriss and Boulanger (2008) and Bray and Sancio (2006), the undrained cyclic shear behavior of low-plasticity fine-grained soils will transition between liquefaction (sand-like behavior) to cyclic softening (clay-like behavior) over a narrow range of plasticity index (PI). Despite not being sufficiently understood, the cyclic behavior of low

plasticity silts has become an increasingly important field of study due to the significant impact it has on ground deformations and infrastructure failure in areas that are seismically active.

Laboratory tests were performed on soils by third party consultants on a site located in the northern Willamette Valley, and the results were provided to Portland State University for

further analysis. The soils in this study had PI values ranging from 4 to 15, and were classified as low plasticity silts and clays (ML, CL) using USCS classification. The cyclic behavior of these soils was analyzed and compared to the behavior of other Pacific Northwestern silt soils. The relationship between cyclic resistance ratio (CRR) and stress history (overconsolidation ratio) were explored in this study, as well as the relationship between post-cyclic strength degradation and excess porewater pressure during cyclic loading. The results of this study will improve our understanding of cyclic behavior of low plasticity silts in seismic evaluations of infrastructure in the Pacific Northwest.

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TABLE OF CONTENTS

1.0 INTRODUCTION ... 1

2.0 LABORATORY TESTING PROGRAM ... 2

3.0 TEST RESULTS ... 5

4.0 COMPARISON TO OTHER SILT SOILS IN PACIFIC NORTHWEST ... 18

5.0 CONCLUSIONS ... 21

6.0 REFERENCES ... 22

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LIST OF TABLES

Table 1. MDSS and CDSS testing parameters.

Table 2. Results of sieve analysis and Atterberg limits testing Table 3. Results of consolidation tests

Table 4. Undrained shear strength results Table 5. In situ strength results

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LIST OF FIGURES

Figure 1. Cyclic stress ratios compared to the recorded number of cycles to reach a shear strain amplitude of 3%

Figure 4. Stress-normalized post-cyclic DSS results for all 17 CDSS soil specimens

Figure 5. Undrained shear strength-normalized post-cyclic DSS results for all 17 CDSS soil specimens

Figure 6. Post-cyclic DSS results normalized by the soils’ associated static DSS results

Figure 7. Cyclic degradation vs maximum shear strain reached during cyclic loading for the 17 CDSS specimens

Figure 8. Cyclic degradation vs maximum pore pressure ratio during cyclic loading for the 17 CDSS specimens

Figure 9. CRR15 vs the range of qc1N values for the soils compared to the Idriss & Boulanger (2004, 2014) trendlines for cyclic and liquefaction behaviors

Figure 10. CRR15 vs the range of (N1)60 values for the soils compared to the Boulanger & Idriss (2014) trendline for liquefaction behavior

Figure 11. Cyclic resistance ratio at shear strain magnitude of 3% compared to overconsolidation ratios

Figure 12. OCR-normalized cyclic resistance ratios compared to plasticity index

Figure 13. Cyclic resistance ratios for a reference shear strain amplitude normalized to cyclic resistance ratios for a shear strain of 3%

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1.0 INTRODUCTION

In recent years, the geotechnical characterization of transitional soils, soils that are neither classified as purely coarse-grained or fine-grained, has become of increasing interest. Traditional methods of analyzing the cyclic behavior of soils were limited to classifications of clay-like materials, which are susceptible to cyclic softening, and sand-like materials, which are susceptible to liquefaction. Today, however, cyclic behavior of transitional soils is not clearly understood and consultants and researchers alike acknowledge the growing importance of determining the cyclic behavior of transitional soils such as non-plastic and low-plasticity sandy silts and silty sands.

Current methods assert that under cyclic loading, soils will transition from liquefaction (sand-like) to cyclic softening at a plasticity index (PI) ranging from 3 to 7 (Idriss & Boulanger, 2008), and that soils will transition from liquefiable to non-liquefiable behavior at a PI of 12-18 (Bray &

Sancio, 2006). To better understand the cyclic behavior and any associated soil parameter characterizations of these transitional soils, soils are often collected in the field using Shelby tube samplers and exposed to various lab testing.

This study was focused on transitional soils of Alluvial and Missoula Flood Deposit soils at an undisclosed site in Beaverton, Oregon. Results of lab testing including monotonic Direct Simple Shear (MDSS), Cyclic DSS (CDSS), and 1-D consolidation tests, were provided to Portland State University by third party consultants for an infrastructural project taking place over shallow alluvial soils and deeper Missoula Flood Deposits in the north Willamette Valley. Soils were collected using mud rotary drilling methods and Shelby tube sampling, and associated cone penetrometer probes (CPT) were advanced at the site near the soil boring explorations in order to achieve in situ strength and pore pressure profiles. The lab testing performed by third party consultants included MDSS, CDSS followed with post cyclic monotonic DSS tests, consolidations tests, Atterberg limits, and sieve analysis. The results of these tests were analyzed for soils including near-surface lean clay Alluvium, as well as underlying Missoula Flood Deposits that included sandy silt, low plasticity silt, and lean clay. Based on the results of the Atterberg limits tests, these soils can be classified as being susceptible to both liquefaction and cyclic softening behaviors per criteria from Idriss & Boulanger as well as Bray and Sancio.

The goal of this report is to discuss the cyclic behaviors of near surface transitional soils within a North Willamette site, and to compare these results to other data (Dickenson et al. 2021) that was published for similar transitional soils within the North Willamette region. The results of this study will be contributed to the growing body of data being collected for the formation of the Silt Database, a body of data aiding to the understanding of cyclic behaviors of transitional soils within the larger Pacific Northwestern region of the US.

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2.0 LABORATORY TESTING PROGRAM

To develop soil properties and distinguish expected cyclic behaviors for the silt and clay materials, a laboratory program was performed by the third-party consultants. The lab program included 4 constant rate of strain (CRS) consolidation tests to characterize the stress history, 5 monotonic direct simple shear tests to characterize static undrained shear strength, 17 stress-controlled cyclic direct simple shear tests to characterize the cyclic response and post-cyclic shear strengths, and various soil index testing such as sieve analysis and Atterberg limits.

All of the soils specimens that were subjected to DSS and CDSS tests as well as soil index lab testing were collected using SPT and Shelby tube samplers in accordance with ASTM standards D1586 and D1587, respectively. The soil specimens collected were classified in accordance with ASTM D2488 as fine-grained Alluvium, and fine-grained soils from the cataclysmic Missoula Flood Deposits. The Alluvium material was encountered in borings B-7 and B-8 at depths ranging from 15 to 35 feet below ground surface (bgs). This material consisted of lean-to fat clay, and all SPT samples within this soil unit had N-values of 0, indicating very soft consistency. The fine- grained Missoula Flood Deposits were encountered below the Alluvium material in all borings, and extended to depths ranging from 22 to 75 feet bgs. This material generally consisted of silt or silt with sand, with occasional lenses of lean clay. SPT N-values for this material ranged from 3 to 25, indicated a soft to very stiff consistency.

The CRS consolidation tests were performed in accordance with ASTM D4186 procedures on 4 samples (B3-S4, B5-S6, B7-S6, B8-S9) to obtain the stress history and overconsolidation ratios for each soil type. The stress histories obtained from the CRS testing for each soil were used to assign consolidation stresses and subsequent vertical confining stress to be applied to the CDSS samples prior to the cyclic stage of each CDSS tests in order to simulate the in-situ stress histories of the soil specimens.

The 5 monotonic DSS tests were performed using ASTM D6528 procedures to obtain the static undrained shear strengths (Su) of soil specimens within Shelby tubes B3-S4, B5-S6, B7-S6, and B8-S9. The Su values obtained from the monotonic DSS tests is interpreted as the measured shear stress at 10% shear strain. The Su values for the DSS tests performed were normalized against their confining stresses at which the samples were sheared, and these results were plotted against each sample’s OCR values. This resulted in a SHANSEP correlation in the form of Su ratio = 0.266 x OCR^0.7, which was used in the analysis to estimate the Su values for select silt specimens between 5 and 55 feet bgs.

The third-party consultants performed a total of 17 stress-controlled CDSS tests to characterize the cyclic behavior of the fine-grained materials and their associated post-cyclic strength loss. These tests were performed in general accordance with ASTM D8296-19 procedures. The cyclic resistances and associated excess pore pressure ratios were recorded against the triggering of defined levels of 3%, 5% and 7% shear strain by recording the number of loading cycles to reach the respective levels of shear strain. The number of cycles to reach each defined magnitude of shear strain were compared to cyclic stress ratio (CSR) values to find cyclic resistance ratios (CRR) at those respective magnitudes of shear strain. This was ultimately used to find relationships between CSR, CRR, stress history, and soil index properties. Post cyclic DSS tests were performed in accordance with ASTM D6528 to record the post cyclic undrained shear strengths at 10% shear strain, which were compared to pre-cyclic undrained shear strengths to generate values of cyclic

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degradation, and then compared with values of maximum cyclic shear strain and excess pore pressure ratios to further understand each soil’s cyclic softening behavior. Testing parameters for the MDSS and CDSS tests are presented in Table 1.

Table 1. MDSS and CDSS testing parameters.

Specimen ID

Depth of Sample (ft)

Max Consol.

Vertical Stress (psf)

Vertical Stress Prior

to Shear (psf)

CSR (at 0.1 Hz Loading)

Total Number

of Cycles

Post- Cyclic

Test Method

B5-S6 (DSS) 26.5 7128 3240 - - -

B5-S6-1 26.3 7128 3240 0.38 4 MDSS

B5-S6-2 25-27.2 7128 3240 0.31 10 MDSS

B5-S6-3 25-27.2 7128 3240 0.27 65 MDSS

B3-S4 (DSS) 10 11960 1150 - - -

B3-S4-1 10 11960 1150 0.6 100 MDSS

B3-S4-2 11.2 11960 1150 0.82 142 MDSS

B7-S6 (DSS) 17-19 15075 2010 - - -

B7-S6 (DSS) 17-19 15000 15000 - - -

B7-S6-1 17-19 15075 2010 0.52 200 MDSS

B7-S6-2 17-19 15075 2010 0.7 200 MDSS

B7-S6-3 17-19 15000 15000 0.15 100 MDSS

B8-S9 (DSS) 27.8 14000 2800 - - -

B8-S9-1 27-29 14000 2800 0.5 17 MDSS

B8-S9-2 27-29 14000 2800 0.4 17 MDSS

B8-S9-3 27-29 14000 2800 0.28 100 MDSS

KGJ-B1-S5-1 13.6 4344 1498 0.3 12 MDSS

KGJ-B1-S5-2 13.2 4344 1498 0.5 1 MDSS

KGJ-B1-S5-3 13.5 8985 2995 0.15 200 MDSS

KGJ-B1-S9-1 27-29 6456 3398 0.38 1 MDSS

KGJ-B1-S9-2 27-29 16200 6480 0.25 56 MDSS

KGJ-B1-S9-3 27-29 6456 3398 0.15 23 MDSS

In addition to the CRS, DSS and CDSS tests performed on the selected Shelby tube samples and corresponding soil specimens, the third-party consultants performed soil index tests on various other soil samples. These tests included sieve analysis and Atterberg limits tests using ASTM D6913 and D4318 procedures, respectively. Due to the lack of index testing performed on the same Shelby tube samples used for the CRS, DSS and CDSS tests, the results of the soil index testing on the various collection of soil samples was compared to the provided soil explorations logs and corresponding soil types and geologic units to estimate fines content and plasticity indices (PI) for the soil specimens taken from the above-mentioned Shelby tube samples. Soil samples that received sieve analysis and Atterberg limits testing were separated into their respective geologic units and USCS soil types, and results were averaged over all of these soil samples with the same soil classification and geologic unit, with the average fines content and PI values being

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subsequently assigned to the target soil specimens with the same respective soil classifications and geologic units. If there were Atterberg tests performed on soil samples that were within close range of depth to the target soil specimen within the same soil boring, soil classification, and geologic unit, the Atterberg results for that nearby soil sample were assigned to the target soil specimen.

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3.0 TEST RESULTS

Soil Index Properties. Table 2 below presents the results of the fines content, PI values, USCS soil type and geologic unit assigned to each soil specimen. Most soil specimens were classified as low plasticity silt or clay, with the soil specimens from one Shelby tube being classified as sandy silt. The low plasticity silt and clay specimens were assigned fines contents of 95% (average values of all sieve samples of the same soil classification and geologic unit), and the sandy silt specimens were given a fines content of 60%, which is the average value of fines for a soil classified as sandy silt. The silt and sandy silt soil specimens had PI values ranging from 4 to 7, and the clay specimens had PI values ranging from 8 to 15. Most of the soil specimens with the exception of Shelby tube B5-S6, borrowed Atterberg results from soil samples within the same boring, soil class, geologic unit, and within a nearby range of depth. Since there were not any reliable soil samples within a close range of depth that had Atterberg results, the specimens within B5-S6 were assigned Atterberg results from the average of all Atterberg results for Missoula Flood silts.

Table 2. Results of sieve analysis and Atterberg limits testing

Specimen ID

Fines

Content (%) Plasticity Index USCS Soil Type Geologic Unit

B5-S6-1 95 4 Silt (ML) Missoula Flood Deposits

B3-S4-1 95 15 Lean Clay (CL) Missoula Flood Deposits

B3-S4-2 95 15 Lean Clay (CL) Missoula Flood Deposits

B7-S6-1 95 8 Lean Clay (CL) Alluvium

KGJ-B1-S5-1 60 5 Sandy Silt (ML) Missoula Flood Deposits

KGJ-B1-S9-1 95 7 Silt (ML) Missoula Flood Deposits

Stress History and Overconsolidation Ratio. The results of the CRS consolidation tests can be shown in Table 3. As presented, the OCR values for the soil specimens ranged from 2.2 to 10.5 for the Missoula Flood Deposits, and from 3.4 to 7.5 for the Alluvium material.

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Table 3. Results of consolidation tests

Specimen ID

Vertical Effective Stress (psf)

Maximum Past

Pressure (psf) OCR

USCS Soil

Type Geologic Unit

B5-S6 1800 4000 2.2 Silt (ML) Missoula Flood Deposits

B3-S4 800 8400 10.5 Lean Clay

(CL) Missoula Flood Deposits

B7-S6 1260 9400 7.5 Lean Clay

(CL) Alluvium

B8-S9 1750 6000 3.4 Lean Clay

(CL) Alluvium

Undrained Shear Strengths. Table 4 shows the Su values that were retrieved from the MDSS tests and subsequently applied to the related soil specimens from the same Shelby tube. As shown by Table 4, some of the soil specimens had Su values assigned to them which were generated using the SHANSEP relationship that was developed using the OCR and Su values from the soil samples that were exposed to CRS and MDSS tests.

Table 4. Undrained shear strength results

Specimen ID

Consolidation Stress (psf)

Vertical Effective Stress (psf)

Su at 10%

Shear Strain (psf)

Testing Method

B5-S6-1 7128 3240 1528 DSS

B5-S6-2 7128 3240 1528 DSS

B5-S6-3 7128 3240 1528 DSS

B3-S4-1 11960 1150 1612 DSS

B3-S4-2 11960 1150 1612 DSS

B7-S6-1 15075 2010 2222 DSS

B7-S6-2 15075 2010 2222 DSS

B7-S6-3 15000 15000 3899 DSS

B8-S9-1 14000 2800 2222 DSS

B8-S9-2 14000 2800 2222 DSS

B8-S9-3 14000 2800 2222 DSS

KGJ-B1-S5-1 4344 1498 852 SHANSEP*

KGJ-B1-S5-2 4344 1498 852 SHANSEP*

KGJ-B1-S5-3 8985 2995 1745 SHANSEP*

KGJ-B1-S9-1 6456 3398 1438 SHANSEP*

KGJ-B1-S9-2 16200 6480 3323 SHANSEP*

KGJ-B1-S9-3 6456 3398 1438 SHANSEP*

*The undrained shear strengths at 10% shear strain were retrieved using SHANSEP constant of 0.266 and an exponent of 0.7.

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Cyclic Direct Simple Shear. The plots shown in Figures 1 through 3 present the values of CSR vs number of cycles for shear stress values of 3%, 5%, and 7%. These plots separated the soils by their respective soil types and associated values of OCR, and generated their respective trendlines.

Since there was not sufficient cyclic testing performed for the Alluvium clay and Missoula Flood clay materials, a trendline could not be accurately defined for these materials. Because of this, the exponent value for the trendline of the Missoula Flood materials was assigned to the other materials and the “a” constant and CRR15 values were solved for using the known exponent value, or “b-value”. These plots show that higher CSR and CRR15 values tend to correlate with higher OCR values.

Figure 1. Cyclic stress ratios compared to the recorded number of cycles to reach a shear strain amplitude of 3%

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Post Cyclic Direct Simple Shear. The results for the 17 post-cyclic DSS tests can be seen on Figures 4 through 8. Figures 4 and 5 present the stress-normalized and shear strength-normalized post cyclic results, and Figure 6 presents post cyclic DSS results that are normalized against the monotonic DSS results. In Figures 7 and 8, the cyclic degradation values (Supost-cyc /Sustatic) were plotted against the maximum level of shear strain and maximum pore pressure ratios (Ru) during cyclic loading. These show that samples that reached higher levels of maximum shear strain and maximum Ru had lower levels of Supost-cyc, resulting in more pronounced levels of cyclic degradation.

Figure 4. Stress-normalized post-cyclic DSS results for all 17 CDSS soil specimens

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Figure 5. Undrained shear strength-normalized post-cyclic DSS results for all 17 CDSS soil specimens

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Figure 6. Post-cyclic DSS results normalized by the soils’ associated static DSS results

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Figure 7. Cyclic degradation vs maximum shear strain reached during cyclic loading for the 17 CDSS specimens

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Figure 8. Cyclic degradation vs maximum pore pressure ratio during cyclic loading for the 17 CDSS specimens

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In Situ Strengths. Table 5 shows the (N1)60 and qc1N values that were assigned to the soil specimens. The (N1)60 values were achieved by assigning the SPT N-values from SPT samples that were either directly above or directly below each respective Shelby tube sample, assigning correction factors for energy ratios, borehole diameter, rod length, and sampler liners to convert to values of N60, followed by the Boulanger & Idriss (2014) methods of converting N60 values to (N1)60. The values of qc1N were calculated by using Boulanger & Idriss (2014) methods, followed by assigning the 50% quartile of qc1N values within a close range of depth surrounding the depths of the Shelby tube samples. The Missoula Flood silt materials had (N1)60 values ranging from 6 to 9 and qc1N values ranging from 40.8 to 73.8 tsf. The Missoula Flood clay material had (N1)60 values of 5 and qc1N values of 24 tsf. The Alluvium clay material had (N1)60 values of 0 and qc1N values of 18.6 to 40 tsf.

Table 5. In situ strength results

Specimen ID

Depth of Sample

(ft)

SPT (N1)60

CPT

qc1N USCS Soil Type Geologic Unit

B5-S6-1 26.3 7 52.3 Silt (ML) Missoula Flood Deposits

B5-S6-2 25-27.2 7 52.3 Silt (ML) Missoula Flood Deposits B5-S6-3 25-27.2 7 52.3 Silt (ML) Missoula Flood Deposits B3-S4-1 10 5 24 Lean Clay (CL) Missoula Flood Deposits B3-S4-2 11.2 5 24 Lean Clay (CL) Missoula Flood Deposits

B7-S6-1 17-19 0 18.6 Lean Clay (CL) Alluvium

B8-S9-1 27-29 0 40 Lean Clay (CL) Alluvium

KGJ-B1-S5-1 13.6 6 40.8 Sandy Silt (ML) Missoula Flood Deposits KGJ-B1-S5-2 13.2 6 40.8 Sandy Silt (ML) Missoula Flood Deposits KGJ-B1-S5-3 13.5 6 40.8 Sandy Silt (ML) Missoula Flood Deposits KGJ-B1-S9-1 27-29 9 73.8 Silt (ML) Missoula Flood Deposits KGJ-B1-S9-2 27-29 9 73.8 Silt (ML) Missoula Flood Deposits KGJ-B1-S9-3 27-29 9 73.8 Silt (ML) Missoula Flood Deposits

The range of in-situ strengths were plotted against the values of CRR for the Missoula Flood silt, Missoula Flood clay, and Alluvium clay materials, and then compared to liquefaction and cyclic softening behavior trendlines developed by Boulanger & Idriss (2004, 2014) as shown in Figures 9 and 10. These figures show that the Missoula Flood clay materials plots closer to the trendline for cyclic softening behavior, the Missoula Flood silt materials plot closer to the trendline for liquefaction behavior, and that the Alluvium clay plots in between the two types of soil behavior.

Please note that the clay behavior trendline for the (N1)60 – CRR plot was generated by converting

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the qc1N values from the I&B04 clay behavior trendline to (N1)60 values for their associated CRR values.

Figure 9. CRR15 vs the range of qc1N values for the soils compared to the Idriss &

Boulanger (2004, 2014) trendlines for clay and liquefaction behaviors

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Figure 10. CRR15 vs the range of (N1)60 values for the soils compared to the Boulanger &

Idriss (2014) trendline for liquefaction behavior

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4.0 COMPARISON TO OTHER SILT SOILS IN PACIFIC NORTHWEST

Figure 11 below displays the relationship between stress history and CRR of the soils on the study site (Beaverton, OR) and compares its trendline to the lines developed from other studies performed on silts in the Pacific Northwest. Although the trendline for the soils that were analyzed in this study present a fairly consistent relationship between OCR and CRR, the slope for the presented curve is slightly lower compared to the slopes for the silts analyzed in the other studies.

Figure 11. Cyclic resistance ratio at shear strain magnitude of 3% compared to overconsolidation ratios

In Figure 12 on the following page, the values CRR for a shear strain of 3% were normalized with respect to each soils’ value of OCR^0.8, and then plotted against their PI values. As shown in the plot, the soils in this study have relatively low values of CRR/OCR^0.8 compared to the values of PNW silt soils from other studies that were included in this plot. When the CRR values were instead normalized to their OCR values with a respective exponent value of 0.6 instead of 0.8, the soils in this study plotted considerably closer to the other Pacific Northwestern silt soils and the associated trendline.

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Figure 12. OCR-normalized cyclic resistance ratios compared to plasticity index values

Figure 13 on the following page displays the values of CRR/CRRγ=3% plotted against the reference amplitude shear strains for the soils that received CDSS testing. The soils analyzed in this study show that the values of CRR/CRRγ=3% increase directly with shear strain amplitudes, and that these soils plot within close range of other Pacific Northwestern silt soils analyzed in other studies.

CRR/CRRγ=3% values for the soils in this study range from 1.0 to 1.16.

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Figure 13. Cyclic resistance ratios for a reference shear strain amplitude normalized to cyclic resistance ratios for a shear strain of 3%

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5.0 CONCLUSIONS

A series of lab testing including soil index testing, constant rate of strain consolidation tests, monotonic direct simple shear, and cyclic direct simple shear were performed on a collection of Missoula Flood silt and clay and Alluvium clay soils in the northern Willamette Valley. Using the in-situ strength data along with the results of the cyclic tests and each soil’s estimates of plasticity indices, these soils demonstrated a mixture of transitional and clay-like behavior when filtered through screening methods from Idriss and Boulanger (2004, 2008, 2014), and can be classified as susceptible to moderately susceptible to liquefaction when considering screening methods from Bray and Sancio (2006). The relationship between the soils’ CRR and OCR values demonstrate a fairly consistent correlation. However, when generating plots of the soils’ CRR and OCR values, the OCR values present a slope exponent of approximately 0.6, which is slightly lower compared to the slope exponent of approximately 0.8 for other silty soils in the Pacific Northwest. As the CRR15/OCR^0.8 values are plotted against the corresponding PI values for each respective soil type and then compared to the values of other Pacific Northwestern silts, the soils in this study show relatively low values of CRR15/OCR^0.8. However, if the CRR values are normalized to an OCR with a corresponding exponent of 0.6 instead of 0.8, these soils plot within close range to the trendline generated from studies performed on various Pacific Northwestern silts. In summary, the soils in this study fall within the boundaries of expected “sand-like” and “clay-like” behavior, but exhibit their own distinct behavior, especially when considering the relationship between cyclic strengths and stress histories.

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6.0 REFERENCES

ASTM. 2000. Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils.

ASTM D4318. West Conshohocken, PA: ASTM

ASTM. 2019. Standard Test Methods for Standard Penetration Test (SPT) and Split-Barrel Sampling of Soils. ASTM D1586. West Conshohocken, PA: ASTM.

ASTM. 2017. Standard Practice for Thin-Walled Tube Sampling of Soils for Geotechnical Purposes. ASTM D1587. West Conshohocken, PA: ASTM.

ASTM. 2017. Standard Test Method for Consolidated Undrained Direct Simple Shear Testing of Fine Grain Soils. ASTM D6528. West Conshohocken, PA: ASTM.

ASTM. 2019.Standard Test Method for Consolidated Undrained Cyclic Direct Simple Shear Test Under Constant Volume with Load Control or Displacement Control. ASTM D8296-19.

West Conshohocken, PA: ASTM.

ASTM. 2017. Standard Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis. ASTM D6913-17. West Conshohocken, PA: ASTM.

ASTM. 2020. Standard Test Methods for One-Dimensional Consolidation Properties of Saturated Cohesive Soils Using Strain-Controlled Loading. ASTM D4186. West Conshohocken, PA: ASTM

Bray, Jonathan D., and R. B. Sancio. Assessment of the liquefaction susceptibility of fine-grained soils. Journal of geotechnical and geoenvironmental engineering 132.9 (2006): 1165- 1177.

Dickenson, S. E., Khosravifar, A., Beaty, M. H., Bock, J., Moug, D., Schlechter, S. M., and Six, J. (2021). “Cyclic and Post-Cyclic Behavior of Silt-Rich, Transitional Soils of the Pacific Northwest; A Database for Geoprofessionals in Practice and Research,” Data report prepared for the Oregon Department of Transportation, Bridge Engineering Section, Salem, Oregon, by New Albion Geotechnical, Inc., Reno, NV

Boulanger, R.W., & Idriss, I.M. (2014). CPT and SPT Based Liquefaction Triggering Procedures.

Department of Civil and Environmental Engineering, University of California at Davis.

Report No. UCD/CGM-14/01.

Idriss, I.M., & Boulanger, R.W. (2004). Evaluating the Potential for Liquefaction or Cyclic Failure of Silts and Clays. Department of Civil and Environmental Engineering, University of California at Davis. Report No. UCD/CGM-04/01.

Idriss, I. M., & Boulanger, R. W. (2008). Soil Liquefaction During Earthquakes. Earthquake Engineering Research Institute.