Showing papers on "Direct shear test published in 1979"

On the determination of stress state in the simple shear apparatus

Abstract: The simple shear apparatus is one of the few commonly available laboratory apparatus that permits the application of controlled rotations of the principal axes of stress and strain to soil samples. However, because of the boundary conditions in the apparatus the soil sample does not respond as a single element, and this should be reflected in the analysis of test results. In the Cambridge University simple shear apparatus, the sample is surrounded by an array of load cells (contact stress transducers) that measure the complete distribution of boundary stresses throughout a test. For simple shear test results to be presented in terms of useful stress parameters, a procedure for computing the stress state from the load cell measurements is required. Such a procedure is described, making use of the concept of an average stress tensor to determine a representative stress state in the central part of the sample, which is least influenced by the ends of the apparatus. Less complex and expensive apparatus exist that can only measure the average normal and shear stresses applied to the top and bottom horizontal boundaries of the sample. Patterns of soil response have been determined from tests on Leighton Buzzard sand in the more elaborately instrumented Cambridge apparatus, and a method is described for using these patterns to deduce the complete stress state in the less complex apparatus.

A New Direct Simple Shear Device

Abstract: Existing types of direct simple shear devices are discussed and a newly developed apparatus is presented. This apparatus uses a round specimen that is laterally covered by a rubber membrane and placed in a pressure cell in which vertical and horizontal normal stresses are applied as with triaxial test equipment. The shear stresses are transmitted to the specimen by a horizontally loaded top cap. Zero lateral strain during undrained shearing is achieved through an automatic measuring and regulating system. Procedures and results are described for an undrained cyclic simple shear test on sand and an undrained static strain-controlled test on an undisturbed normally consolidated clay.

Undrained Shear Tests on Clays

Abstract: The proposed model describes the anisotropic properties of rate-independent saturated clays under undrained loading conditions. The model is applied to relate the various undrained shear strengths measured in common soil tests, including laboratory triaxial, plane strain, simple shear, and in-situ pressuremeter tests. The model predictions are shown to agree very well with available experimental test results. It is shown that the disturbances caused by the installation of the pressuremeter probe affect the derived shear stress-strain curves significantly, and are responsible for both their strain-softening features and high shear strengths. It is shown that a simple correction allows the true material shear stress-strain curve to be obtained from pressuremeter test results.

Plastic fracture in poly(vinyl chloride)

Abstract: The strain fields around diamond-shaped cavities in cold-drawn rigid PVC have been determined by the application of fine grids to the specimen surface. An element of material adjacent to the diamond tip deforms predominantly in simple shear with a direction of strain parallel to the draw direction. Each element attains a maximum shear strain before the next element begins to shear. This process, possibly analogous to neck propagation in tensile tests, produces the characteristic diamond shape. Simple extension and simple shear tests on cold-drawn PVC confirm that under the stress system around a cavity, simple shear in the draw direction is a favourable mode of deformation.

Shear Strength of Concrete Masonry Joints

Abstract: The experimental results of 46 shear tests of ungrouted and grouted concrete block masonry are reported. The shear specimens were tested under shear along the bed joints. The influence of mortar type, grout strength, bed-joint reinforcement, and the level of compressive stress normal to the bed joints were studied. The results indicate that the mortar joint's strength characteristics do not have a major effect on the resistance of masonry joints to shear-slip failure. The grout strength and the normal compressive stress are the most significant parameters influencing the joint capacity. The relative contribution of grouting towards increasing the joint shear strength decreases as the level of precompression increases. A strong correlation between the shear strength and the normal compressive stress is shown to exist for both ungrouted and grouted masonry under low levels of precompression.

Static penetration resistance of soils

Abstract: In-situ tests play an important role in geotechnical investigations, particularly in situations where the problems of sample recovery and the consequent sample disturbance are severe limitations. -- This thesis is part of an ongoing research on penetrometers at Memorial University of Newfoundland. The results reported here are for two cone penetrometers, 35.6 mm and 76.2 mm diameter, which were used in a static mode. -- Different theoretical and experimental results are available in the literature to define the failure mechanism associated with the penetration resistance of cones into soils. -- Strength parameters and penetrometer interaction properties of fine sand and silty clay were determined using the conventional triaxial and direct shear tests. The results were then used as the basis for theoretical prediction of the penetration resistance after explicitly accounting for penetrometer base apex angle, penetrometer size and roughness. Comparison of unit penetration resistance values measured in controlled laboratory tests and predicted by theory subsequently permitted the suggestion of the most appropriate method for the penetration mechanism. -- Methods for evaluating in-situ shear strength of soils from measured cone penetration resistance are suggested. Values of shear strength parameters (C and o) are determined and compared with those of other investigators.

Ground behaviour and support for mining and tunnelling

Abstract: The article presents the first part of the 14th Sir Julius Wernher Memorial Lecture Which discusses the behaviour of rock in relation to tunnelling and mining activities Rock behaviour is dominated by discontinuities represented as joints As the stress pattern in jointed rock is changed as a result of excavation so deformation will be determined initially by shearing movements at the joints As shear stresses increase new discontinuities develop and deformation is less controlled by the initial jointing pattern It is important to determine whether the problem is one of maintaining stability with the pre-existing jointing pattern or whether it is a problem of yielding rock mass A factor in determining soil or rock behaviour is that of the "competance" factor defined as the ratio of unconfined compressive strength under uniaxial load to effective pressure of the overburden at the tunnel level /TRRL/

Comparison of down-hole and laboratory shear wave velocities

Abstract: The method of down-hole seismic surveying is described. This method was successfully used to a depth of 50 m in a cased borehole and these results are presented. The method may be used to find the ...

Analysis of shear transfer in reinforced concrete with application to containment wall specimens

Abstract: In this report the shear transfer mechanism across continuous cracks penetrating through the thickness of a reinforced concrete element are investigated. The parameters influencing shear stiffness of the cracked sections are identified. Based on these parameters a mathematical model is developed for the prediction of the shear stiffness. This model is used to evaluate the shear rigidity of orthogonally reinforced concrete panels exhibiting parallel or orthogonal through cracks. The model is applicable to biaxially tensioned wall specimens subjected to monotonically increasing tangential shear stress. For two test specimens, the shear rigidity as predicted by the proposed model is implemented in a finite element computer program. Three dimensional finite element analysis is performed for these specimens to study the behavior of a containment wall portion under biaxial tension and tangential shear loading. The influence of the crack patterns and their stiffness on shear deformation and reinforcement stresses in the specimen is evaluated. The proposed model and analysis procedure predict shear rigidities and structural responses consistent with the observed behavior of the test specimens.

Properties of SMC Composites.

Abstract: : The mechanical properties of five glass fiber sheet molding compounds are investigated in this research program. The materials studied are SMC-25, SMC-3O, SMC-65, SMC-C20/R3o and XMC-3. The specific properties include the tensile, compressive and shear response, as well as the strain rate sensitivity, impact resistance, notch sensitivity, statistical strength properties and bolted joint characteristics. A discussion of experimental test methods includes an evaluation of three shear test methods and a description of non-destructive inspection techniques. The mechanical properties of five glass fiber sheet molding compounds are investigated in this research program. The materials studied are SMC-25, SMC-3O, SMC-65, sMC-C20/R3o and XMC-3. The specific properties include the tensile, compressive and shear response, as well as the strain rate sensitivity, impact resistance, notch sensitivity, statistical strength properties and bolted joint characteristics. A discussion of experimental test methods includes an evaluation of three shear test methods and a description of non-destructive inspection techniques. (MM)

Landslide in Claystone Derived Soil

Abstract: A landslide in a colluvial slope is described that occurred after excavation was made for the construction of a building. The geometry of the landslide mass before and after sliding was able to be established relatively well. Ground-water observations were made for a period 3 months after the slide occurred. The surface on which sliding probably occurred was established with reasonable confidence from observations and test-boring information. Large displacement reversal direct shear tests performed by the Pennsylvania Department of Transportation on samples of red clay soil obtained on or very near the failure plane yielded residual strength parameters. Stability analyses using the Morgenstern-Price method for non-circular failure surfaces indicate that the value of the angle of shear resistance in the field at failure probably was between 12? and 13? if it is assumed that the cohesion intercept is 0.

Shear Properties of Promising Adhesives for Bonded Joints in Composite Material Structures

Abstract: The results of an experimental program are given which provide quantitative and reproducible shear property data for many of the present and promising adhesives for use in bonded joints in composite material structures. The experiments employ a composite material test specimen in which the adhesive material is in a film configuration, typical of bonded joints, rather than measuring bulk adhesive properties. Because both the flexural and in-plane stiffnesses of the glass-epoxy adherends of the test piece are extremely large (> 106) compared to a parameter proportional to the shear and extensional modulus of the adhesive film, the adhesive film is virtually in a state of constant shear stress with negligible normal stresses. The details of the shear test piece have been published previously. The adhesives tested were those recommended by the major adhesive manufacturers, those selected by NASA Langley in the civil aviation program, and those utilized in the USAF PABST program. The data reported includes the ultimate shear stress, initial shear modulus, and elongation to failure, both mean values and standard deviations, for specimens made by the adhesive manufacturer and the University of Delaware.

Sample size effects using the ngi (norwegian geotechnical institute) direct simple shear apparatus

Abstract: To improve the use and the interpretation of results of the Norwegian Geotechnical Institute (NGI) direct simple shear device modified for cyclic loading, tests were conducted using undisturbed soil samples of Gulf of Alaska and Gulf of Mexico clays. The effects of variations in sample size are quantified. The parameters which varied were sample cross section and sample height. Two cross-sectional sizes and three heights were compared. Equipment used in the investigation, testing procedures, and soil characteristics are discussed. Test data include lateral strain measurements from which horizontal normal stresses and subsequently the initial lateral stress ratio values were calculated. These calcultions and results are discussed as affected by sample size, with special attention to the initial lateral stress ratio. Step-by-step instructions on the use of the use of the NGI direct simple shear device in both static and cyclic functions are explained. The use of the NGI sample trimming apparatus and methods for calibrating the NGI reinforced membrances using calibration cylinders are detailed.

Internal Friction Factor of Powder by A Double-Cylinder Rotary Shear Tester

Abstract: A double-cylinder rotary shear tester has been developed which can measure the shearing torque exerted on the inner rotating cylinder and the side wall pressure distribution on the outer stationary cylinder simultaneously. Various powders were tested by changing the powder bed height, the outer cylinder radius and the rotational speed of the inner cylinder.The torque was shown to be proportional to the square of the powder bed height. The stress normal to the shearing plane at the inner cylinder was estimated from the relation of the side wall pressure distribution to the outer cylinder radius and the internal friction factor was evaluated without introducing Rankine's passive powder pressure coefficient.The internal friction factors thus obtained for some of the powders tested were in good agreement with those measured by a direct shear tester.

Shear Tests of Deep Beams with Flanges

Abstract: It is well known that the shear strength of deep reinforced concrete beams in higher than that of slender beams. Even without shear reinforcement, directly loaded deep beams exhibit reserve strength in shear above the shear force causing the diagonal tension cracks whereas the formation of diagonal tension cracks almost immediately leads to shear failure in slender reinforced concrete beams with no shear reinforcement.

Analysis of graphite/polyimide rail shear specimens subjected to mechanical and thermal loading

Abstract: A two-dimensional, linear-elastic, finite element analysis of selected graphite/polyimide rail shear test specimens was made to determine the mechanical loading and the effect of heating the specimen to a uniform temperature. The presence of specimen free edges and their influence on the accuracy of the rail shear test is discussed. Parameters include the length-to-width ratio of the specimen and the ply layup for symmetric, balanced laminates. Results presented include shear and normal stress distributions and the deflection behavior of various specimens caused by the mechanical loading and elevated temperature.

Coefficients of Friction between Calcareous Sands and Some Building Materials, and Their Significance.

Abstract: : Friction tests of a coralline and an oolitic sand and a foraminiferal sand-silt against smooth and rough steel and concrete surfaces were run in a modified soils direct shear machine. Friction test results for these calcareous materials did not differ markedly from the results for a quartz sand. These results indicate that there is nothing inherently different in the capability of these calcareous materials to develop frictional forces on typical building material surfaces - when compared to quartz-predominant sands - except that some calcareous materials experience large volume decreases during shear. These large volume decreases would impair the development of high effective normal stresses against the building material surface, resulting in low friction forces on piles, some anchors, and penetrometers in calcareous materials. This latter hypothesis is stated, but not directly addressed in this reported work. (Author)

Trafficability studies on wet clay

Abstract: A laboratory study was undertaken upon two clays, London clay and Cheshire clay, at a range of typical moisture contents encountered in the UK. Soil-rubber and soil-soil shear tests were undertaken using a direct shear box. The results of these tests are related to work undertaken on soil-rubber wheel shear using a simple experimental test facility in which the soil was moved into the instrumented wheel. Conclusions have been drawn regarding the mobility characteristics of wheels on London clay and the leaner Cheshire clay. (TRRL)

Stress conditions within simple

Abstract: The second method is based on the assumption that the directions of the principal stress axes during simple shear are known. The differences between the two methods are discussed, and the undrained 'shear strength values of normally consolidated clays measured in the simple shear test are compared with those measured in the triaxial compression test on an equal basis.