Laboratory Manual CEE121 Introduction to Civil and Environmental

Engineering Measurements

Carlton L. Ho, P.E. Department of Civil and Environmental Engineering

University of Massachusetts Amherst Amherst, MA 01003

Spring 2005

[Reference: University of Massachusetts Amherst (2005). Laboratory Manual CEE121 Introduction to Civil and Environmental Engineering Measurements. Dept. of Civil and Environmental Engineering, University of Massachusetts Amherst, Amherst, MA.]

molceseCross-Out

molceseCross-Out

molceseCross-Out

TABLE OF CONTENTS Page 1. INTRODUCTION 1.1 2. ENGINEERING UNITS 2.1

3. REPORTING ENGINEERING MEASUREMENTS 3.1

- Accuracy and Precision - Significant Figures - Rounding of Numbers

4. PREPARATION OF ENGINEERING LABORATORY REPORTS 4.1

- Report Grading - Report Guidelines - Model Report

1.0 INTRODUCTION Welcome to the CEE Measurements class. In this class you will learn how to conduct some common civil and environmental engineering measurements. This is a "hands-on" course. With the guidance of the course professor and teaching assistants you will conduct 10 sets of experiments that primarily cover basic laboratory measurements and surveying. This manual serves as a guide for preparation of your laboratory reports. It contains background information on engineering units, reporting engineering measurements, and guidelines on how to prepare a laboratory report. The format for preparation of your engineering reports is similar to that developed by the department for the junior year laboratory classes and also used in the CEE111 class.

molceseCross-Out

2.1

2.0 ENGINEERING UNITS We will conduct measurements in this course using both the traditional English system and Le Systme International d'Units (SI). However, the SI system is the preferred system of units for many of your CEE classes and you should know it well. The following is a guide to the SI system from the American Society for Testing and Materials.

ASTM (1999) Annual Book of ASTM Standards. ASTM, West Conshohocken, PA.

molceseCross-Out

3.1

3.0 REPORTING ENGINEERING MEASUREMENTS The document on the following pages from the American Society for Testing and Materials (ASTM 1999. Annual Book of ASTM Standards. ASTM, West Conshohocken, PA) is a guide for reporting engineering measurements including: difference between precision and accuracy, significant digits, and rounding numbers. There are two important issues regarding significant figures: 1. Conducting calculations with appropriate significant figures. See the following document for the rules to follow. 2. How to report laboratory data to the appropriate number of significant figures. When making laboratory measurements you must pay attention to the number of significant figures you record the data to. This depends on the accuracy and precision of your measurements. Once you decide this, all subsequent calculations with your measurements must follow the rules of significant figures.

4.1

4.0 PREPARATION OF ENGINEERING LABORATORY REPORTS There are many styles and formats for preparing engineering reports. The following are guidelines for preparing your CEE121 engineering laboratory reports. Also included in this section is the grading system that will be used to evaluate your reports. All reports must be prepared in their entirety using a personal computer, this includes using a word processor for text (e.g., Word, etc.), a graphics program for plotting data (e.g., Excel, SigmaPlot, etc.), a spreadsheet program for data reduction (e.g., Excel), and a drawing program for sketches (e.g., AutoCad, etc.). All text is to be doubled spaced (except where noted below) using a 12 point font (engineering reports are often single spaced but we need room to write comments). Most reports are prepared using Times New Roman font. Keep in mind that you are preparing a professional engineering report that must be of the highest quality both in terms of technical content and presentation. 4.1 LABORATORY REPORT GUIDELINES The following is to be used as a guide for preparing all laboratory reports in this course. The actual style of each report may vary depending on the specific assignment being conducted. See attached Model Report "Results of Direct Shear Tests Conducted on Ottawa Sand" as an example of a report prepared in general accordance with these instructions. Outline: 1. Cover Letter of Transmittal. The cover letter of transmittal is the official means of transmitting the report to your client. Describe what the report is for, indicate that the work was done in accordance to accepted engineering practices (in CEE121 that would be mostly in accordance to the instructions provided to you in the laboratory) and urge your client to contact you with any questions or concerns. All members of your group are to sign the letter. 2. Cover page. The cover page for each lab report should include the title of the report, the person, company or agency the report is prepared for and their address; the person, company or agency the report was prepared by and their address; and the date. This is page "i" of the report but do not put the number on this page.

3. Executive Summary. On its own page, preceding the main body of the report, is an executive summary. This is one of the most important sections of a technical report. It offers the reader a summary of what is contained in the report. The executive summary should be concise (limit to one page) and should briefly summarize the objectives (why did you do the lab?), materials (what did you test?), methods (what standard methods were used? what modifications were made.), most important results and significance of the results.

molceseCross-Out

molceseCross-Out

molceseText BoxManuscrito en tinta

molceseLine

molceseLine

molceseText BoxCaratula del informe

molceseCross-Out

4.2

This is page "ii" of the report, numbered bottom center, using lowercase roman numerals in 12-point font. NOTE: you are NOT required to prepare an Executive Summary for CEE121. 4. Table of Contents. List each section title and the page it appears on. This is page "iii" of the report. Title heading is "TABLE OF CONTENTS", top center of the page. 5. List of Tables with page numbers. List of Table titles with the page number each table appears on. Tables are presented either in the main body of the report as close as possible after the first reference to the table or at the end of the main body of the report.

This is page "iv" of the report (or next number in sequence if Table of Contents is greater than 1 page). Title heading is "LIST OF TABLES", top center of the page. 6. List of Figures with page numbers. List of Figure titles with the page number each figure appears on. Figures are presented either in the main body of the report as close as possible after the first reference to the figure or at the end of the main body of the report following the figures.

This is page "v" of the report (or next number in sequence). Title heading is "LIST OF FIGURES", top center of the page. If the List of Tables and List of Figures are short they can be placed on one page. 7. List of Symbols. Alphabetical order, English first followed by Greek. Give definition and units.

This is page "vi" of the report (or next number in sequence). Title heading is "LIST OF SYMBOLS", top center of the page. Examples: T = temperature [C] u = pore water pressure [kPa] = angle [ or radians] = displacement [mm or m]

8. Introduction. The main body of the report begins with an introduction of 1-2 paragraphs. A proper introduction will present enough information so that the reader can understand the purpose of the report and the significance of the processes or phenomena being measured.

This is page 1 of the report, numbered bottom center, using Arabic numbers in 12-point font (with all previous pages being numbered using lower case roman numerals e.g., i, ii, iii, iv, v, etc.).

It is also section "1.0 INTRODUCTION", left justified, of the report. This and all subsequent pages do not contain a title. Instead, they will consist of sequentially numbered sections. See the format section for more details.

molceseCross-Out

4.3

9. Objectives/Purpose. The objectives define the purpose of the report. It states what you desire to accomplish and/or prove. Note that there is a difference between the Objective and the Method used to reach that objective. The objectives statement should be approximately one paragraph in length and be clear and concise. 10. Background. In some reports, a background section will be included to review such items as past work and/or relevant theory that the reader should note. NOTE: you are NOT required to prepare a Background section for CEE121. 11. Test Equipment and Samples Materials. If relevant, describe the equipment and sample(s) used for testing, how and when the samples were obtained, and how they were stored prior to testing. 12. Methods of Investigation. In your own words describe the general procedure for each test performed during the lab so that the reader understands what you did. Include technique, order of events, etc. Do not make this section too long. These should not be detailed instructions. The procedure summary should be concise and to the point. If a published standard (e.g., American Society for Testing and Materials) was used then reference the standard (give number and full title) followed by a summary of the major steps conducted for the procedure and note any variations from the standard. 13. Presentation of Results. Gives a description of the results. This is a factual presentation of the results, i.e., what did you measure, observe, calculate, etc. Include primary figures, tables, graphs and equations used for calculations. Refer to all figures and tables in the text. When appropriate, specific details should be included in a separate Appendix. Show sample calculations wherever necessary in an Appendix; this includes any data that was reduced using a spreadsheet. Ensure that the results are organized and presented in a logical sequence. Answer specific questions listed in the instructions for the laboratory. 14. Discussion of Results. This is your engineering interpretation of the results and their significance. It is an important part of the report. Discuss the results, i.e., do they seem reasonable, meet expectations, compare with published data whenever possible, etc. If problems were encountered during testing and/or the results appear to be incorrect, discuss what the problems were and their influence on the results. Answer specific questions listed in the instructions for the laboratory. 15. Summary and Conclusions. You should summarize what you did, why, how, and results obtained. The summary and conclusions is similar to the executive summary. 16. References. Provide citations for material borrowed from other authors. This includes background information, published standards and standard methods. In general you should avoid the use of direct quotes and put information in your own words. Stick with scientific journals and textbooks and avoid articles from the popular press. Make sure that internet sources are reputable (e.g. ASCE, EPA, professional organizations). Cite the material both where it appears in the text and in the references section. Make sure references are complete, i.e., author(s), date,

molceseCross-Out

4.4

title, full name of journal or book, Volume #, pages, etc. Make this section single spaced. There are several formats for listing references. The method that is used by the American Society of Civil Engineers is shown below:

Example citations in text:

One author: (Babcock 1995)

Two authors: (Babcock and Wilson 1995)

Three or more authors: (Babcock et al. 1995)

Example reference formats:

For your lab manual:

University of Massachusetts Amherst (2004). Laboratory Manual CEE121 Introduction to Civil and Environmental Engineering Measurements. Dept. of Civil and Environmental Engineering, University of Massachusetts Amherst, Amherst, MA.

For internet articles:

Author/editor (year) Title of Electronic Work. Online. Information supplier, site/path/file. Access date.

For a book:

Knudsen, J.G. and Katz, D.L. (1958). Fluid Dynamics and Heat Transfer, McGraw Hill. New York, NY.

For a journal article:

Norris, R.H. and Streid, D.D. (1940). Laminar Flow Heat Transfer Coefficients for Ducts. Trans. Am. Soc. Mechanical Engineers, 5, 525.

17. Appendices. When relevant include sample calculations, detailed data tables and figures, raw data sheets, etc. Additional Notes: 1. Data sheets that are completed during lab session and those that involve simple calculations may be completed in pencil and should appear in an appendix. 2. Number all sections consecutively starting with the Introduction as follows-

1.0 MAJOR SECTION TITLE -- all caps + bold 1.1 FIRST SUBSECTION -- all caps + bold 1.1.1 Second Subsection -- first letter cap, underline text + bold

3. Number pages bottom center using 12-point font. 4. When using tables and figures that are cut and paste from other publications make sure to clearly identify the reference in the figure or table title as either (from xxxx - means you copied the figure directly out of the reference) or (after xxxx - means you took the figure from the reference but made some modifications). When taking other information from publications make

molceseCross-OutManuscrito en tinta

molceseText BoxManuscrito en tinta

4.5

sure to reference the material. If you directly quote material from the literature then it must be presented in quotations, i.e., " .". 5. The axes of graphs should be scaled such that the curve(s) extend over the complete area of the graph for greatest definition. All measured data points should appear as symbols on the graph regardless of whether a line is fit to the data. Make proper use of legends, units, symbols, scale, etc., in graphs. Keep all axes titles, tick labels etc. in 12 pt font size. Use Portrait layout as often as possible. Note: default settings in Excel make for poor quality graphs (in terms of presentation). See attached for example of a poor quality Excel graph versus a good quality Excel graph, which can be made with only a few changes to the default Excel settings. 6. Headings and data entries in tables should be of the same style and font size as that used for the main text of the report (typically 12-point Times New Roman). 7. All tables and figures must have titles numbered in sequential order of how they are referenced in the text (e.g., Table 1, Table 2, etc.). All table titles should be centered above the table or below the figure in bold 12-point font size and of the same style font used for the main text of the report (e.g., most often this is Times New Roman). For example, Table 1. Summary of dimensions measured for aluminum part 1 - table follows title- - figure followed by title- Figure 1. Schematic of aluminum part 1 8. Equations should be numbered sequentially and all variables fully described including units directly after the equation and in the list of symbols. k = q/iA (1) where: k = hydraulic conductivity (m/s) q = flow rate (m3/s) i = hydraulic gradient (m/m) A = area of specimen (m2)

4.6

5.2 REPORT GRADING SYSTEM 5.2.1. Laboratory Reports Laboratory report grades will be based on technical content, presentation, and overall impression of the report. Presentation is how well the report is prepared in terms of writing and editorial issues including using proper format for page layout, figures, text, equations, pagination, references, margins, grammar, spelling, etc. Technical content refers to the accuracy and completeness of the material presented including proper description of methods of investigation, reduction of data, equations and assumptions, discussion of results, conclusions from data, evaluation of accuracy of results, etc. Overall impression is our assessment of the overall quality of the report. Breakdown of the grading system is as follows (maximum = 20 pts): 1. Technical 60% (12 pts): Introduction and Objectives - 1 pt. Materials and Methods - 2 pts. Presentation and Discussion of Results - 7 pts Summary and Conclusions - 2 pts. Score: __________ 2. Presentation 30% (6 pts): Cover letter Spelling and grammar Quality of writing Page layout Layout of graphs and Tables Table of Contents, List of Tables, List of Figures, and pagination References format List of symbols Format of equations Correct use of units and significant figures Score: __________ 3. Overall Impression 10% (2 pts) Final assessment of overall quality of report. Score: __________ ========= Total Score: __________

molceseCross-Out

4.7

5.2.2 Interpretation of Grades The following describes each number grade based on grades from 0 to 100%.

Number Grade (%)

Rating Description of Grade

90 - 100 Excellent Outstanding report in all respects 80 - 89 Very good High quality report in nearly all respects 70 - 79 Good A quality report but with some deficiencies

60 - 69 Fair Report lacking in several critical aspects; some key issues were not addressed 59 and less Poor Report has serious deficiencies

Due Dates and Late Policy: Reports are due at the beginning of your laboratory section one week after the last laboratory period unless otherwise instructed. Any report handed in after the start of laboratory on the due date but before 5:00 p.m. will have 25% deduced from the grade. Any report handed in after 5:00 p.m. on the due date will have 50% deducted from the grade. No exceptions will be given without a valid (e.g., medical emergency) and substantiated excuse. Attendance for all laboratories is mandatory. Failure to attend a laboratory session without prior approval or a valid emergency will result in a grade of zero for that lab.

molceseCross-Out

MMOODDEELL RREEPPOORRTT

Thursday Morning Laboratory Section CEE121 CEE Measurements

Dept. of Civil and Environmental Engineering University of Massachusetts Amherst Amherst, MA 01003 January 28, 2004

Professor Don J. DeGroot CEE121 CEE Measurements Dept. of Civil and Environmental Engineering University of Massachusetts Amherst Amherst, MA 01003 Dear Professor DeGroot: We are pleased to submit herewith our Report Results of Direct Shear Tests Conducted on Ottawa Sand. This note summarizes the results of the direct shear tests we conducted on the samples of Ottawa Sand you provided us. All tests were conducted in general accordance with the American Society for Testing and Materials standards. This report completes our work for this laboratory. Should you have any questions please do not hesitate to contact us. Sincerely yours, Maurice Richard Project Engineer Henri Richard Project Engineer Enclosure (1)

molceseCross-Out

molceseCross-Out

MMOODDEELL RREEPPOORRTT

Results of Direct Shear Tests Conducted on Ottawa Sand

Prepared for

Don J. DeGroot CEE121 Civil and Environmental Engineering Measurements

Department of Civil and Environmental Engineering University of Massachusetts Amherst

Amherst, MA 01003

Prepared by

Maurice Richard and Henri Richard Thursday Morning Laboratory Section

CEE121 Civil and Environmental Engineering Measurements Department of Civil and Environmental Engineering

University of Massachusetts Amherst Amherst, MA 01003

28 January 2004

molceseCross-Out

molceseText BoxNombres de los integrantes del grupo

ii

TABLE OF CONTENTS Page TABLE OF CONTENTS ............................................................................................... ii LIST OF TABLES ......................................................................................................... iii LIST OF FIGURES ....................................................................................................... iii LIST OF SYMBOLS ..................................................................................................... iv 1.0 INTRODUCTION..................................................................................................... 1 2.0 OBJECTIVES ........................................................................................................... 1 3.0 TEST MATERIALS ................................................................................................. 1 4.0 METHODS OF INVESTIGATION ........................................................................ 2 5.0 PRESENTATION OF RESULTS ........................................................................... 3 6.0 DISCUSSON OF RESULTS .................................................................................... 5 7.0 SUMMARY AND CONCLUSIONS ....................................................................... 6 REFERENCES................................................................................................................ 7 Appendix A Tabulated Test Results and Sample Calculation ....................................... 11 Appendix B Original Data Sheets.................................................................................. 22

[Note: the Appendices are not included in this model report]

iii

LIST OF TABLES

Page Table 1 Specimen Parameters and Test Results.......................................................... 8

LIST OF FIGURES Figure 1 Shear Stress versus Horizontal Displacement................................................ 9 Figure 2 Volume Change versus Horizontal Displacement ......................................... 9 Figure 3 Peak Horizontal Shear Stress versus Vertical Consolidation Stress ............ 10

iv

LIST OF SYMBOLS

ENGLISH

Dr = relative density (%)

eo = initial void ratio (-)

ec = void ratio at the end of consolidation (-)

emax = maximum void ratio (-)

emin = minimum void ratio (-)

Vv = volume of voids (cm3)

Vs = volume of solids (cm3)

GREEK

Xh = change in horizontal displacement (mm) Xv = change in vertical displacement (mm) v = vertical strain (%) ' = friction angle () s = density of solids (Mg/m3) 'vc = vertical consolidation stress (kPa) h = horizontal shear stress (kPa)

1

1.0 INTRODUCTION

This report presents and discusses results of three direct shear tests conducted on

reconstituted samples of Ottawa sand. The tests were performed on 28 January 2004 at the

University of Massachusetts Amherst, Geotechnical Engineering Laboratories. The Ottawa sand

specimens were prepared to a dense condition, consolidated and then sheared with drained

conditions. The direct shear test forces a shear failure to occur on a horizontal plane in a soil

specimen contained in a split box, by sliding the two halves of the box relative to each other. The

test data measured in this laboratory were used to estimate the shear strength of the soil in terms

of the friction angle.

This report presents a summary of the test program and measured results. The report

includes information on the objectives, methods of investigation, and presentation and discussion

of test results.

2.0 OBJECTIVES

The purpose of this report is to evaluate the results of drained direct shear tests to

determine the shear strength parameters (' and c') of Ottawa sand. The objective of the experiment was to measure the relationship between shear stress and vertical effective stress for

several specimens of reconstituted dense Ottawa Sand under drained conditions using a direct

shear apparatus.

3.0 TEST MATERIALS

The direct shear tests were conducted on a sample of uniformly graded Ottawa sand. The

sand was supplied in an air dry condition by the Ottawa Sand Co., Ottawa, Illinois in a 22.7 kg

2

bag. The manufacturer's data sheet lists the nominal gradation to be: 100 % passing a #40 sieve

and 100 % retained on a #200 sieve.

4.0 METHODS OF INVESTIGATION

The direct shear tests were conducted on Ottawa sand in general accordance with

American Society for Testing and Materials (ASTM) D3080 Standard Test Method for Direct

Shear Test of Soils Under Consolidated Drained Conditions (ASTM 1998) using an ELE Ltd.

Model DX-4 direct shear device. The basic test procedure consists of placing a soil specimen in a

square shear box, applying a vertical (normal) consolidation stress and subsequently shearing the

specimen by application of a horizontal shear force at a constant rate of deformation. The shear

box is split horizontally, forming a plane that allows for the top of the specimen to be displaced

relative to the bottom. During shear, measurements of the vertical displacement, horizontal

displacement, and horizontal shear force are made.

Key features of the specimen preparation and test procedures used for the three tests

conducted for this project are as follows:

1. The Ottawa sand was placed into the 60 mm square direct shear box by allowing the

particles to free fall, from a height of about 15 cm. This "raining" technique was used to

obtain dense specimens. The final target height of each specimen was approximately 26

mm.

2. The tests were conducted in an open container that was used as a water bath for the

specimens. After application of the seating load, the zero reading on the vertical

molceseCross-Out

molceseText BoxNTP

3

displacement dial gauge was recorded and thereafter Town of Amherst tap water was

added to the water bath.

3. The three tests were conducted at different final vertical (normal) consolidation stresses

of 100 kPa for Test DS-1, 200 kPa for Test DS-2, and 400 kPa for Test DS-3. The

consolidation stresses were applied in one increment. During consolidation, changes in

the height of the specimens were measured using the vertical displacement dial gauge.

Approximately 15 minutes was allowed to elapse between application of the vertical

consolidation stress and start of shear.

4. All specimens were sheared at a constant rate of horizontal deformation equal to 0.25

mm/min. Free drainage was allowed to occur during shear. Periodic readings of vertical

displacement, horizontal displacement (using a dial gauge) and horizontal shear force

(using a proving ring) were recorded during shear. The tests were allowed to continue

until a definite peak horizontal shear resistance was reached.

5. At the end of shear, the apparatus was disassembled and the specimen was collected and

placed in an oven to measure the mass of solids.

5.0 PRESENTATION OF RESULTS

Table 1 presents a summary of the results for the three tests. Tabulated data for the shear

portion of each test are in Appendix A. Original data sheets are in Appendix B.

The initial void ratio of each specimen was computed as

eo = Vv/Vs (5.1)

where

eo = initial void ratio (-)

4

Vv = volume of voids (cm3)

Vs = volume of solids (cm3)

The volume of solids was computed using the oven dry mass of solids and an assumed density of

solids s = 2.65 Mg/m3 (Holtz and Kovacs 1981). The volume of voids was computed as the difference between the measured total specimen volume and the computed volume of solids. The

initial void ratio for the specimens ranged from 0.544 to 0.561 which corresponds to initial

relative densities of 85 and 80 percent using a minimum void ratio emin = 0.5 and a maximum

void ratio emax = 0.8 (Lambe and Whitman 1969). The void ratio at the end of consolidation (ec)

was computed using the measured vertical deformation of the specimen at the end of

consolidation.

Figure 1 plots the measured shear stress versus horizontal displacement and Figure 2

plots the volume change versus horizontal displacement for the three tests. The data show an

increase in the shear stress with increasing horizontal displacement until the peak shear stress is

reached. Thereafter, the specimens exhibit a strain softening response. The increase in shear

resistance to the peak shear stress and subsequent strain softening response is more pronounced

with an increase in the consolidation stress. In terms of volume change, all three specimens

display an initial contraction followed by significant dilation that continues until the end of the

test. The magnitude of dilation tends to increase with a decrease in the consolidation stress while

the maximum rate of dilation appears to coincide with the peak shear resistance for all three

specimens.

Since the complete state of stress is not known in the direct shear device, i.e., only the

shear and normal stress on the horizontal plane is known, there is not enough information to

compute the Mohr circle of stress for the failure condition. It is therefore common to assume that

5

the horizontal plane is the failure plane (Lambe and Whitman 1969). With this assumption, it is

possible to compute the friction angle of the specimen as

' = tan-1(h/'vc)max (5.2) where

' = friction angle () h = horizontal shear stress (kPa) 'vc = vertical consolidation stress (kPa)

Table 1 presents the values of (h)max for the three tests and the corresponding values of ' which range from 42.7 to 43.8. These results are plotted in Figure 3 together with a best fit

linear line to the three data points using an assumed cohesion intercept = 0. This line corresponds

to a friction angle of 43.

6.0 DISCUSSION OF RESULTS

The initial relative densities of the three specimens vary somewhat (80 to 85%) but all

three specimens have a sufficiently high enough relative density to be considered a dense to very

dense sand (Lambe and Whitman 1969). The corresponding shear data, presented in Section 5,

show characteristics expected of a dense sand: (1) shear stress versus horizontal displacement

curves that display a distinct peak shear stress followed by strain softening; (2) an increase in the

consolidation stress results in a corresponding increase in the peak shear stress; and (3) initial

contraction followed by significant dilation during shear.

The principal parameter desired in strength testing of sands is the friction angle, which

defines the Mohr-Coulomb failure criteria. In this test program, the same method was used to

6

prepare all of the samples and, as desired, approximately the same initial void ratio (and relative

density) was achieved for all of the tests (Table 1). For the same initial density, the friction angle

should be approximately the same for different consolidation stresses. Table 1 and Figure 3 show

that this is the case for the three tests giving an average friction angle of about 43. The friction

angle of 43 is typical for dense sands as reported in the literature (e.g., Lambe and Whitman

1969, Holtz and Kovacs 1981).

7.0 SUMMARY AND CONCLUSIONS

This report presents the results of three direct shear tests conducted on reconstituted

samples of Ottawa Sand. The tests were conducted at the Geotechnical Engineering Laboratories,

University of Massachusetts Amherst, on 28 January 2004. The tests used a standard 60 mm

square direct shear apparatus and were conducted in general accordance with ASTM D3080

Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions

(ASTM 1998). The three specimens were prepared for testing by allowing the sand to free fall

from a height of 15 cm into the direct shear box to achieve a high initial relative density. The

specimens were then consolidated to a different preshear vertical consolidation stress for each

test equal to 100, 200, and 400 kPa. Direct shear was conducted at a constant rate of strain of

0.25 mm/min until the specimens sheared beyond their peak horizontal shear resistance.

The initial void ratio for the three specimens ranged from 0.544 to 0.561, which

corresponds to initial relative densities of approximately 85 and 80 percent (Table 1). The

measured shear behavior for all three specimens is typical of that for dense sands, i.e., shear

stress versus horizontal displacement curves with a distinct peak shear stress followed by strain

softening (Figure 1) and initial contraction followed by significant dilation (Figure 2). Using the

molceseCross-Out

molceseText BoxNTP

7

assumption that the horizontal plane is the failure plane, the three tests give similar friction

angles ranging from 42.7 to 43.8 (Table 1). The best linear fit to the data, assuming a zero

cohesion intercept, is approximately 43 (Figure 3). This friction angle is consistent with that

reported in the literature (Lambe and Whitman 1969).

REFERENCES

ASTM. (1998). 1998 Annual Book of ASTM Standards, Volume 04.08 Soil and Rock (I): D420 - D4914, West Conshohocken, Pennsylvania. Holtz, R.D. and Kovacs, W.D. (1981). An Introduction to Geotechnical Engineering. Prentice-Hall, Inc., Englewood Cliffs, New Jersey. Lambe, T.W. and Whitman, R.V. (1969). Soil Mechanics. John Wiley & Sons, Inc., New York.

molceseText BoxNTP

molceseCross-Out

8

Table 1 Specimen Parameters and Test Results

Initial State Consolidation At Peak Horizontal Shear Stress Test

No. eo Dr

(%) 'vc

(kPa) v

(%) ec Xh

(mm) Xv

(mm) h

(kPa) ' ()

DS-1 0.559 80 100 0.36 0.553 1.56 0.234 93.1 43.0

DS-2 0.561 80 200 0.47 0.554 1.50 0.131 184.6 42.7

DS-3 0.544 85 400 0.73 0.533 1.70 0.144 383.0 43.8 Notes: 1. Dr computed using assumed emax = 0.8 and emin = 0.5

9

Horizontal Displacement, Xh (mm)0 1 2 3

She

ar S

tress

, h (k

Pa)

0

100

200

300

400

DS-1DS-2DS-3

Horizontal Displacement, Xh (mm)0 1 2 3

Volu

me

Cha

nge,

Vol

(mm

3 )

-500

0

500

1000

1500

DS-1DS-2DS-3

Figure 1. Shear Sstress versus horizontal displacement

Figure 2. Volume change versus horizontal displacement

dilation

contraction

10

Vertical Consolidation Stress, 'vc (kPa)0 100 200 300 400 500

Pea

k S

hear

Stre

ss, (

h)m

ax (k

Pa)

0

100

200

300

400

500

DS-1DS-2DS-3

Figure 3. Peak horizontal shear stress versus vertical consolidation stress

' = 43 degrees