Showing papers on "Direct shear test published in 1971"

A New Ring Shear Apparatus and Its Application to the Measurement of Residual Strength

Abstract: Synopsis This Paper describes both the design and principles of operation of a new ring shear apparatus, and its application to the measurement of the residual strength of undisturbed and remoulded samples. As the test results differ significantly from those obtained in multiple reversal direct shear box tests, a critical examination is made of all possible sources of error in both measurement and interpretation. The results of tests on five soils, blue London Clay, brown London Clay, Weald Clay, a Norwegian clay and the Cucaracha Shale from Panama, are presented and discussed in relation to other published residual strength data from tests on these materials. The factors controlling the brittleness of soils tested under drained conditions are examined. Cet article decrit a la fois la conception et les principes d'operation d'un nouvel appareil de mesure du cisaillement circulaire par torsion, et de son application a la mesure des resistances residuelles d'echantillons non pertubes et remoules. Comme les ...

Analysis of the Rail Shear Test-Applications and Limitations

Abstract: A detailed theoretical and experimental analysis of the rail shear test is presented. A Fourier series solution is obtained for the stresses in an idealized rail shear specimen. The theoretical results are quali tatively verified on fiber reinforced rubber composites. Rail shear data on the modulus and strength of current high-modulus rein forced composites is compared to predicted values obtained from lamination theory. Results show that, despite definite limitations, the rail shear test can be useful in the determination of the in-plane shear properties of a laminated composite.

The stamp-load bearing strength of rock an experimental and theoretical investigation

Abstract: The Stamp-Load Bearing Strength of Rock An Experimental and Theoretical Investigation Though the stamp-load bearing strength of rock is one of the more relevant rock properties in many mining problems it has been neglected in comparison with the efforts devoted to the strength of rock under uniform compression. As stamp-load bearing experiments offer a simple and effective means for studying the strength of rock under triaxial conditions the bearing strength of the rock has been investigated in detail. Using fundamental equations derived by Love and Sneddon the axisymmetric stress field induced by the indentation of a flat-ended circular stamp into a plane rock surface has been studied. In addition to the normal representation of a stress field by means of stress trajectories and lines of equal principal stresses, potential fracture zones have been calculated for a typical Witwatersrand quartzite. The theoretical analysis of the stampload bearing problem resulted in the acquisition of a deeper knowledge of the complexity of the induced stress field and the fracture mechanism. It has also been shown that there exist serious restrictions of the elastic treatment of this problem. In order to get a more detailed understanding of the actual failure mechanism and to establish the effects of the non-linear behaviour of rock near to failure some rock specimens were instrumented with strain gauges and cantilevers to measure surface strains and deflection outside the contact area of the stamp. From these experiments the conclusion can be drawn that lateral expansion of fractural rock is an integral part of the failure of rock under stamp loads. Based on these measurements a qualitative model of the failure process has been developed. The experimental work on the stamp-load bearing strength of rock has resulted in the following findings: 1. The load-displacement curve of the stamp-loading experiments is more sensitive to changes in rock properties than that obtained from compression tests. 2. The stamp-load bearing strength of rocks has been found to be affected by the size of the stamp. The size-dependent behaviour of rock is more obvious on brittle than on ductile rocks. It can be described by an experimental law of the formσ st =Q a a , withα being between 0 and −0.5 for ductile and brittle rocks respectively. At large stamp diameters the bearing strength tends towards a constant value of approximately four times the uniaxial compressive strength of rock. 3. A direct relation between the exponentα and the inelastic part of the lateral expansion of rock at failure has been found. This enables the determination of the lateral expansion of rock from stamp-loading experiments using different stamp sizes.

The adhesion of metal films to glass and magnesium oxide in tangential shear

Abstract: The adhesion of Au, Cu and Al films of thickness from 0·05 to 40 μm to glass and MgO single-crystal substrates was measured by a tangential shear test. For films deposited mainly at 10−7 to 10−8 Torr, the shear stress was found to be virtually independent of the film thickness, and had mean values of 3×105 N m−2 for Au, 8×105 N m−2 for Cu and 1·5×106 N m−2 for Al, for films on glass; these were increased by a factor of three for MgO substrates except for Al, for which the adhesion remained unaltered. These values are about 100 times smaller than those obtained in measurements where the force is applied normal to the substrate. Optical and Stereoscan micrographs indicate the basic features of the torn films after shear, in particular the formation of regularly shaped triangular tears in areas adjoining the adhesive junction, and the apical angle is found to vary systematically with the film thickness.

Hypothesis for Shear Failure of Brickwork

Abstract: The validity of the concept that the shear strength of brickwork depends on a combination of the bond shear strength and frictional resistance in the mortar layers is questioned on account of inconsistencies revealed by earlier series of experiments. As an alternative approach the writers suggest that the shear strength may be dependent on the tensile strength of the mortar layers. Assuming that failure occurs when the principal tensile stress in the mortar equals its tensile strength, finite element stress analyses are conducted to determine the maximum principal tensile stresses in brickwork triplets resulting from applied shear and normal compressive forces. Failure curves are constructted relating the theoretical shear strength and normal compressive stress on the triplet for different modular ratios. Experimental results of shear tests on brickwork triplets, with varying normal compressive stress, are compared with the corresponding theoretical curve to provide support for the writers' proposition.

Influence of strain rate on the residual strength of a kaolinitic clay

Abstract: DIFFERENCES IN THE RESIDUAL STRENGTH OF CLAY MAY ARISE FROM THE VARIOUS METHODS USED TO TEST IT BECAUSE OF THE LIMITATIONS OF EACH. THE CURRENT LITERATURE REVEALS THAT THE RESIDUAL STRENGTH OF NATURAL CLAYS OR CLAY MINERALS MAY DEPEND ON A NUMBER OF FACTORS AMONG THEM STRAIN RATE. IN THE INVESTIGATION DESCRIBED IN THIS TECHNICAL NOTE, THE STRAIN RATE INFLUENCE WAS STUDIED BY ADOPTING A MODIFIED PROCEDURE OF HUTCHINSON. DETAILS ARE GIVEN OF THE ATTERBERG LIMITS. GRAIN SIZE DISTRIBUTION, SPECIFIC GRAVITY, ACTIVITY AND ORGANIC CONTENT OF THE KAOLINITIC CLAY SAMPLES FROM BANGALORE INDIA, WERE USED IN THE INVESTIGATION. THE CONSOLIDATED SAMPLES WERE MOUNTED IN A DIRECT SHEAR BOX ALLOWED TO SATURATE UNDER NORMAL LOAD, AND TESTED UNDER NORMALLY CONSOLIDATED CONDITIONS. DURING THE FIRST FORWARD START, A LOW RATE OF STRAIN WAS APPLIED; THIS ALLOWED FOR COMPLETE PORE PRESSURE DISSIPATION AND BROUGHT THE PARTICLES AT THE EFFECTIVE STRESS STAGE. THE STRUCTURE AT THE RESIDUAL STAGE WAS STUDIED BY THE SHRINKAGE RATIO TECHNIQUE, THE SHRINKAGE RATIO WAS ALSO DETERMINED AT PEAK STAGE. /TRRL/

The clay content and the shear strength in sand clay mixtures

Abstract: DIRECT SHEAR TESTS WERE CARRIED OUT ON ARTIFICIAL MIXTURES WITH INCREASING PROPORTIONS OF CLAY, COMPRISING TWO TYPES OF LAND (FINE AND COARSE) AND A MONTMORILLONITIC CLAY FROM THE SAME REGION (LUANDA, ANGOLA). THE SHEAR TESTS, SLOW CONSOLIDATED TYPE, WERE CARRIED OUT AFTER STANDARD COMPACTION (AASHO T99). AN APPRECIATION IS MADE OF THE EFFECT OF CONSOLIDATION AND DENSITY OF THE SAMPLES RELATIVE TO THE CRITICAL VOID RATIO. THE VERTICAL AND HORIZONTAL SHEAR DEFORMATIONS ARE ANALYSED RELATIVE TO MAXIMUM AND LIMIT SHEAR STRESS. THREE ZONES OF BEHAVIOR (INCOHERENT, TRANSITION, AND COHERENT) ARE FOUND AND THE PERCENTAGES OF CLAY TO WHICH THEY CORRESPOND ARE INDICATED. /AUTHOR/

Direct shear testing of marine sediment

Abstract: Traditionally, the methods used to determine the mechanical properties of marine sediments were those used in the field of soil mechanics. These methods are generally acceptable wiien the sediment tested is plastic or at water contents below the liquid limit. However, for predicting in-situ conditions, that is for sediment at water contents above the liquid limit, the problem is complex. Specifically, the determination of shear strength of an unconsolidated-undrained sample by the direct shear method was found to exhibit an angle of internal friction ranging from 19 degrees to 23.5 degrees. This indicates that the shear strength of the sediments is dependent on the normal load applied to it.