MISCELLANEOUS PAPER S-71-9 Si CALCULATION …

1 \ I I Si MISCELLANEOUS PAPER S-71-9 CALCULATION OF stress AND strain FROM TRIAXIAL TEST DATA ON UNDRAINED soil SPECIMENS by J. Q. Ehrgott May 1971 Sponsored by Defense Atomic Support Agency Conducted by U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi ATIONALTECHNICAL APPROVED FOR PUBUC RELEASE; DISTRIBUTION UNLIMITED ^FORMATION SERVICE Va "151 mjmvmmmx . < , ,_ **- ** ^!.v - -V* *K f- ' Unclassified Socnritr CU ific tioo DOCUMENT CONTROL DATA -R&D (StcuHtr cUmtlllCMtm / llll . Zsdr ol mbmltmet mat InOmtlni mmatmtlim M farad AMI A* otwrafj il 0 I. ORIGINATING ACTIVITY fCofporaM mitoae) U. S. Amy Engineer Waterways Experiment Station Vicksburg, Miss. U, RtPOHT UCURirv CLASSIFICATION Unclassified I.

2 CROUP REPORT TITLE CALCULAUCH OF stress AMD strain FROM TRIAXIAL TEST DATA ON UNDRAINED soil SPECIMENS i. MIC IPTIVI MOTum (Trv ot report mud MclMll d*M*> Final report AUTH omiifTCn aw . aMtw in/(/ i, kiiiwg John Q. Ehrgott - .. OUT DATE May 1971 7 . TOTAL NO. OF PAGES 63 7b. MO- OF REFf ft. PROJECT HO. a. ORIGINATOR* REPORT NIHTICRIS) MISCELLANEOUS PAPER S-71-9 ft. OTHER REPORT NOI (Auf MB port) othmr wi ftirR star mm* ft mmmignmd 10. DISTRIBUTION STATEMENT Approved for public release; distribution unlimited. ii. SUPPLEMENTARY HOTEs PAPER presented at Eric C. Wan^ Symposium on Protective Structures Technology, Air Force Weapons Laboratory, Kirtlafrd AFB, N. Mex., 21-23 July 1970. 12. SPONSORING MILITARY ACTIVITY Defense Atomic Support Agency Washington, D.)

3 C. The formulation of constitutive relations for use in computerized analyses of free-field ground shock phenomena is based primarily on laboratory-determined material properties. These properties, as described by stress - strain relations, are not directly determined in the laboratory, but are derived through interpretation of load and deformation data measured by the experimenter. Throughout this PAPER , one laboratory test, the triaxial shear test, is used to illustrate the extent of inter- pretation required on raw data and the influence of this interpretation on recommended constitutive properties. Various techn. ques that have been developed to obtain stress - strain data from the triaxial test are reviewed along with current advances in measurement systems.

4 Typical raw data are presented and calculations of axial, lateral, and volumetric strains are made based on a variety of empirical and theoret- ical approaches.('The results demonstrate that research and development efforts are still required in the area of material proper by testing in order to establish adequate confidence in the formulation of constitutive relations for ground shock calculations. DD . LACES DO FORM UTS. I JAN M. MICH IS OMOL1TI re ARMY USE. 85 Unclassified ftcufity Classification Unclassified Security Classification Ground shock Shear tests soil stress - strain relations stress - strain measurement Triaxial tests 86 Unclassified Security Classification ** ,.i n* .< :^ -qpjpjfpj v w MUHMMMIMM MISCELLANEOUS PAPER S-71-9 CALCULATfON OF stress AND strain FROM TRIAX1AL TEST DATA ON UNDRAINED soil SPECIMENS by J.)

5 Q. Ehrgott May 1971 Sponsored by Defense Atomic Support Agency Conducted by U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi RMY-MRC VICKSBURG. MISS. APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED PlgrtgCH ! ABSTRACT The formulation of constitutive relations for use in computer- ized analyses of free-field ground shock phenomena is based primarily on laboratory-determined material properties. These properties, as described by stress - strain relations, are not directly determined in the laboratory, but are derived through interpretation of load and deformation data measured by the experimenter. Throughout this PAPER , one laboratory test, the triaxial shear test, is used to illustrate the extent of interpretation required on raw data and the influence of this interpretation on recommended constitutive properties.

6 Vari- ous techniques that have been developed to obtain stress - strain data from the triaxial test are reviewed along with current advances in measurement systems. Typical raw data are presented and calculations of axial, lat- eral, and volumetric strains are made based on a variety of empirical and theoretical approaches. The results demonstrate that- research and development efforts are still required in the area of material property testing in order to establish adequate confidence in the formulation of constitutive relations for ground shock calculations. ftmmwiWfiH * '**" * * !*S (ijj$ |8 g-^WW^w WP*l*>r?}>i*&Li Wf-gW,y^.JPfBHP ffWI^tl^J^tli^WVBfSFVWm? WW'HI' yn^yjmjwwji PREFACE This PAPER was prepared for presentation at the Eric H.)

7 Wang Symposium on Protective Structure Technology held at the Air Force Weapons Laboratory, Kirtland Air Force Base, New Mexico, 21-23 July 1970. The subject matter presented herein was primarily intended for those persons involved in the field of ground motion prediction, but not necessarily familiar with the area of material property determination. The laboratory equipment and techniques described in this re- port were developed in support of research on propagation of ground shock through soil and rock being conducted by personnel of the Soils Division, (J. S. Army Engineer Waterways Experiment Station (WES), for the Defense Atomic Support Agency (DASA). This report was prepared and presented by Mr. J.)

8 Q. Ehrgott, Impulse Loads Section, soil Dynamics Branch, Soils Division, WES. Helpful comments and guidance were provided by Mr. J. G. Jackson, Jr., Chief, Impulse Loads Section. Mr. R. W. Cunny was Chief of the soil Dynamics Branch and Mr. James P. Sale was Chief of the Soils Division. Directors of the WES were COL Levi A. Brown, CE, and COL Ernest D. Peixotto, CE. Technical Director was Mr. F. R. Brown. CONTENTS ABSTRACT 3 PREFACE h NOTATION -- 8 CONVERSION FACTORS, BRITISH TO METRIC UNITS OF MEASUREMENT 10 CHAPTER 1 INTRODUCTION - 11 CHAPTER 2 THE TRIAHAL TEST 13 Test Description 13 Measurement System 16 Measurement Errors 18 Typical Results 20 CHAPTER 3 INTERPRETATION OF RAW DATA 26 Determination of Volumetric strain 26 Method V-l 28 Method V-2 - 29 Method V-3 30 Method V-4- - 31 Method V-5 31 Method V-6 - 32 Summary 32 Determination of Deviator stress and strain 33 Method S-l - 35 Method S-2 - 36 Method S-3 36 Method S-k 37 Method S-5 - 38 Method S-6 39 Summary - 39 CHAPTER k DISCUSSION OF INTERPRETATION METHODS 58 ^.

9 1 Comparison for Hydrostatic Tests 58 Comparison for Shear Tests 62 CHAPTER 5 CONCLUSION - 73 REFERENCES - 75 FIGURES Data available from the triaxial test 22 Schematic of WES high-pressure triaxial test device 23 5 ! tu < > cf ftwflilh ' *' - $ygfc$si Typical constant p-type triaxLal test results for a sandy clay 24 Typical constant a -type triaxial test results for a siltstone 25 Deformed shapes of specimens during hydrostatic loading 4l Triaxial specimen of recompacted clayey silt after being subjected to 500-psi hydrostatic pressure, shape IC 42 Triaxial specimen of recompacted clayey silt after being subjected to 5 000-psi hydrostatic pressure, shape IC 43 Triaxial specimen of a silty clay with rock fragments after being subjected to 1,000-psi hydrostatic pressure, shape IIA > 44 Triaxial specimen of silty clay with rock fragments after being subjected to 5,000-psi hydrostatic pressure.

10 Shape IIA 45 Cross section of shapes considered in Method V-l 46 3-7 Cross section of assumed shape used in Method V-2 46 3-8 Cross section of assumed shape used in Method V-3 46 3-9 Assumed shape used in Method V-4 46 Summary of methods used to calculate volumetric strain i"f Shapes of failed specimens after shear test 48 Triaxial specimen of sandstone after shear failure during a dynamic constant p-type test, shape IIA 49 Triaxial specimen of recompacted clayey silt after being subjected to a small deviator stress while maintaining a confining pressure of 5>000 psi 50 Triaxial specimen of modeling clay prior to test 51 Triaxial specimen of modeling clay after application of a small deviator stress while a confining pressure of 5 000 psi is maintained 52 Triaxial specimen of modeling clay after application of a larger deviator stress while a confining pressure of 5,000 psi is maintained 53 Triaxial specimen of modeling clay after application of large (postyield)