Showing papers on "Direct shear test published in 1969"

Strength of Discontinuous Rocks in Direct Shear

Abstract: Synopsis The strength of discontinuous rocks under direct shear loading is examined analytically and experimentally. In the direct shear test a homogeneous and isotropic block of rock may fail by three mechanisms: failure in tension, failure in shear and failure at ultimate strength. The strength parameters include the tensile strength, fundamental shear strength (cohesion), angle of internal friction, the angle of friction at ultimate strength and the normal stress on plane of enforced shear. The direct shear strength of planes of weakness, orientated in the plane of enforced shear, is derived from two sources: strength of solid rock where no separation exists and joint friction along the separated parts of the shear surface. Maximum shear strength develops only if solid strength and joint friction are mobilized simultaneously, that is at the same deformation. On examine analytiquement et experimentalement la resistance de roches discontinues soumises a une charge de cisaillement direct. Dans un essai de...

Dynamic Interaction of a Shear Wall with the Soil

Abstract: An analysis is presented of the interaction between a shear wall, placed on a rigid foundation, and soil when the soil is subjected to a plane shear wave. Due to the particular symmetry of the model adopted an exact closed-form solution is obtained for the steady state response. The base displacements and base shear forces are compared with the corresponding values obtained neglecting the interaction. It is shown that the base displacements are zero for the fixed-base natural frequencies of the shear wall.

Mechanics of Second Order Faults and Tension Gashes

Abstract: The origin of en echelon second order shear fractures and tension gashes associated with first order, or primary, faults is examined analytically and experimentally. It is postulated that en echelon second order structures form under the influence of a stress mechanism similar to the one occurring in the direct shear test. The direct shear or modified direct shear state of stress could develop at certain points along a forming primary fault as a result of a local reduction in the normal stress acting on planes perpendicular to the displacement direction. It is argued that in most en echelon arrays the orientation of the individual fractures reflects the existence of a local state of stress, and cannot directly be correlated with the regional (primary) stress field. The zone in which they occur, however, may represent planes of high effective shear stress within the regional framework. The direct shear model (full relief of transverse normal stress) offers a stress mechanism which can explain the origin of not only en echelon tension gashes but also second order faults. For a given set of strength parameters, the type of en echelon fractures that will develop depends on the normal stress acting in the primary fault plane. In general, tension fractures form at low normal stress, shear fractures at intermediate values of normal stress, and at high normal stress a crush or shear zone is produced. If the state of stress is one of modified direct shear (only partial relief of transverse normal stress), the development of second order faults is favored.

Engineering Classification of In-Situ Rock

Abstract: : An engineering classification for in-situ rock is proposed which is based upon the results of field exploration and laboratory testing. The field program included a study of more than fifteen construction projects from which data were obtained from geophysical testing, borehole photography, water pressure testing, and geologic mapping. Laboratory analyses of 530 samples taken from these projects included physical and mineralogical descriptions, unit weights, absorption, strength, modulus of elasticity, and sonic velocities (saturated and dry). The rock types investigated included granite and basalt, gneiss, schist, sandstone, limestone, and siltstone. Geologic discontinuities such as joints, faults, and weathered rock are of major importance in an engineering evaluation of in-situ rock because of their effect upon the deformability, shear strength, and permeability of the mass.

Effect of temperature on strength behavior of cohesive soil

Abstract: THE OBJECTIVE OF THIS STUDY WAS TO DETERMINE THE EFFECT OF TEMPERATURE ON PEAK SHEARING STRENGTH AND CREEP BEHAVIOR OF TWO COHESIVE SOILS AND THUS TO CHARACTERIZE THEIR BEHAVIOR IN TERMS OF MORE FUNDAMENTAL PARAMETERS THAN IS THE CURRENT GENERAL PRACTICE. A SIMPLE MODEL FOR SOIL BASED ON BONDS AT INTERPARTICLE CONTACTS AND AN EQUATION FOR RATE OF DEFORMATION OF A STRESSED SOIL MASS ARE PROPOSED AND SHOWN TO BE CONSISTENT WITH OBSERVED SOIL BEHAVIOR. THE SAME MODEL AND EQUATION WERE FOUND TO APPLY TO SOIL BEHAVIOR IN BOTH DIRECT SHEAR AND CREEP TESTS. THE STUDY WAS CONDUCTED ON REMOLDED, STATICALLY COMPACTED SPECIMENS OF A HIGHLY PLASTIC CLAY AND A LOW-PLASTICITY SILT USING A DIRECT SHEAR MACHINE. THE MACHINE WAS MODIFIED TO PERMIT CONTROL OF SPECIMEN TEMPERATURE AND FOR USE AS A CONTROLLED STRESS APPARATUS AS WELL AS CONTROLLED RATE OF DEFORMATION. /AUTHOR/

The Solid-Rod Torsion Test for the Determination of Unidirectional Composite Shear Properties1:

Abstract: The primary requirements of a desirable shear test method include the ability to introduce a well-defined state of stress in the specimen, capability of determining both shear modulus and shear str...

Application of pore pressure measurements to shear strength of cohesive soils

Abstract: AN ACCURATE METHOD OF MEASURING PORE PRESSURE IN SOILS IS NECESSARY FOR DETERMINING STRESS WHEN DESIGNING SOIL STRUCTURES. THE BUREAU OF RECLAMATION HAS MADE THE FOLLOWING ADVANCES IN MEASURING NEGATIVE PORE PRESSURES. IN THE EXPOSED END PLATE METHOD OF MEASURING THE INITIAL NEGATIVE PORE PRESSURE OF SOILS, THE NEGATIVE PORE PRESSURE CAN BE DETERMINED ON A ROUTINE LABORATORY TESTING BASIS ON SPECIMENS WITHOUT DAMAGING THEM FOR FURTHER TESTING. CAPILLARY PRESSURE IS MEASURED THROUGHOUT THE VOLUME CHANGE RANGE AS THE UNDRAINED (SEALED) SPECIMENS ARE COMPRESSED FROM INITIAL NEGATIVE PORE PRESSURE TO THE POINT WHERE THE CAPILLARY PRESSURE BECOMES ZERO AT SATURATION. RESULTS OF THIS TEST CONDUCTED ON ONE OF A SERIES OF SPECIMENS, TOGHETHER WITH RESULTS OF THE EXPOSED END PLATE TEST ON EACH SPECIMEN OF THE SERIES ARE APPLIED IN THE ANALYSIS OF SOIL STRENGTH FROM SHEAR TEST RESULTS. IMPROVED ACCURACY IS ACHIEVED IN MEASURING PORE AIR PRESSURE BY SEPARATING THE WATER FILM IN THE SOIL FROM THE END PLATE MEASURING DEVICE AND CONTROLLING THE END PLATE SO THAT WATER IS NOT DRAWN INTO OR FROM THE SOIL. VARIABLE SOIL STRESS CONCITIONS THAT WOULD BE INTRODUCED BY CHANGING SOIL MOISTURE CONDITIONS ARE ELIMINATED. /AUTHOR/

A comparison of the test results of vane and direct shear tests made on recent marine sediments

Abstract: : Shear strength envelopes calculated from consolidated-undrained direct shear tests (hereafter called direct-shear lines) were compared to strength envelopes calculated from vane shear tests (hereafter called vane-shear lines) made throughout the length of a sediment core These comparisons were made on shear strength measurements from seven recent marine sediment cores The seven sediment cores used for this study were obtained from the upper San Diego Trough slope in water depths of 249 to 291 meters by Lockheed's submersible DEEP QUEST The materials tested were classified primarily in the clayey silt to silty clay range based upon grain size distribution (Author)

Investigation of Joints in Advanced Fibrous Composites for Aircraft Structures. Joint and Attachment Investigation. Volume 2. Test Results

Abstract: : Engineering drawings, experimental data, and quality control data are presented in this volume for specimens that were tested in an investigation of joints and attachments in advanced fibrous composites for aircraft structures. Engineering drawings are presented showing design details and parametric variations for each specimen. Test fixture and instrumentation details are shown for a trosion ring adhesive shear test apparatus designed to measure stress- strain characteristics of adhesives in pure shear without the stress concentrations of conventional lap shear specimens. Experimental plots or test data tabulations are presented for basic laminate and adhesive properties and for static and fatigue strength tests on bonded and bolted joint specimens. Test results are summarized for six adhesives. Static test results are given for adhesive joint specimens and for single-fastener, bolted joint specimens. Test results are tabulated for selected joint concepts under constant-amplitude fatigue test conditions. Quality control specifications, incoming inspection records, and resin and void content determinations are presented. The vacuum pyrolysis method of determining the resin content of boron-epoxy laminates is described.

Shear strength of coarse fragmental soils

Abstract: 1. The construction of high earth and rock dams requires that investigators obtain exact data on the shear resistance and deformative properties of coarse-fragmental soils. 2. Investigations carried out in recent years here and abroad have made it possible to establish the following: a) The angle of internal friction of coarse-fragmental soils largely depends on the density of packing, soil stresses, and size of the particles composing the soil; b) The angle of internal friction of coarse-fragmental soil can exceed numerically its angle of repose and is within limits up to 54° and sometimes higher; c) Investigations of shear strength can be conducted both by shear instruments and by consolidometers, provided Dinst/dfrac≥5; d) One should try to investigate coarse-fragmental soils of natural granular composition using field instruments. 3. The angle of internal friction of coarse-fragmental materials decreases with an increase of normal stresses and to a greater degree for rock than for gravel in the same range of stresses. 4. Further investigations of the shear strength of coarse-fragmental soils should be aimed at perfecting large devices (preference should be given to consolidometers) and methods of investigation.

Correlation of hardened concrete test methods and results

Abstract: A LABORATORY INVESTIGATION WAS CONDUCTED TO DETERMINE COMPRESSIVE, TENSILE, AND SHEAR STRENGTH PARAMETERS OF SEVERAL CONCRETE MIXTURES, TO EVALUATE THE TEST METHODS UTILIZED, AND TO CORRELATE THE RESULTS OBTAINED. SIX-BY TWELVE-IN. CONCRETE TEST SPECIMENS WERE CAST FROM FOUR DIFFERENT CONCRETE MIXTURES USING TWO TYPES OF AGGREGATE (LIMESTONE AND NATURAL) AND TWO CEMENT FACTORS (4 AND 6 BAGS PER CU. YD.). COMPRESSIVE, TENSILE (DIAMETRAL COMPRESSION), AND THREE TYPES OF DIRECT SHEAR STRENGTH TESTS WERE CONDUCTED ON AIR-DRIED SPECIMENS, AND TRIAXIAL TESTS WERE CONDUCTED ON SPECIMENS REPRESENTING THREE DIFFERENT MOISTURE CONDITIONS. THE SHEAR STRENGTH DETERMINED BY THE MOHR ENVELOPE OF FAILURE FOR THE TRIAXIAL TESTS MOST CLOSELY APPROXIMATES THE PURE SHEAR STRENGTH OF CONCRETE. THE DIRECT SHEAR TESTS HAVE INHERENT DISCREPANCIES IN THE METHODS AND EQUIPMENT THAT CAST DOUBTS ON THE RESULTS OBTAINED THROUGH THEIR USE. THE STRENGTH OF CONCRETE KEPT MOIST UNTIL TIME OF TEST IS LOWER THAN THAT OF CONCRETE THAT HAS BEEN ALLOWED TO AIR-DRY. THE BENEFICIAL EFFECTS OF ANGULAR AGGREGATE AS COMPARED TO ROUNDED AGGREGATE BALANCE THE DETRIMENTAL EFFECT OF THE HIGHER WATER-CEMENT RATIOS REQUIRED FOR EQUAL CONSISTENCY. /AUTHOR/

Closure on waco dam slide

Abstract: AN INTERESTING CORRELATION WAS PRESENTED BY LITTLE BETWEEN THE EFFECTIVE RESIDUAL SHEARING RESISTANCE AND THE CLAY FRACTION PERCENTAGE FOR CLAY FROM THE MANGLA DAM SITE. INVESTIGATIONS OF PROJECTS OF THE CORPS OF ENGINEERS INVOLVING CLAY SHALES HAVE SHOWN LOWER RESIDUAL FRICTION ANGLES WITH HIGHER LIQUID LIMITS AND PLASTICITY INDICES WITHIN A GIVEN GEOLOGIC FORMATION. HOWEVER, THE CORRELATION CURVE FOR ONE FORMATION CANNOT NECESSARILY BE USED IN A DIFFERENT FORMATION. FURTHER STUDIES ARE BEING MADE OF RESIDUAL SHEAR STRENGTH AND REPEATED REVERSALS OF DIRECT SHEAR ON SQUARE SPECIMENS AND ROTATIONAL DIRECT SHEAR ON ANNULAR SPECIMENS WILL BE USED. THE PIEZOMETERS AND REFERENCE MARKS HAVE BEEN OBSERVED PERIODICALLY SINCE COMPLETION OF THE EMBANKMENT AND IMPOUNDMENT OF THE RESERVOIR. NO SIGNIFICANT DEFORMATIONS IN THE EMBANKMENT OR ITS FOUNDATION HAVE BEEN OBSERVED. THE PORE PRESSURES IN THE PEPPER AND AT THE PEPPER-DEL RIO CONTACT ARE STILL 90 PERCENT TO 95 PERCENT OF THE PORE PRESSURES THAT EXISTED AT THE END OF CONSTRUCTION. DELAYS IN CONSTRUCTION TO PERMIT DISSIPATION OF PORE PRESSURE ARE OF NO BENEFIT IN CLAY SHALES OF THIS TYPE. REFERENCES: WACO DAM SLIDE, RALPH R BEENE, ASCE PROCEEDINGS PAPER 5306, JULY, 1967.