Soil Testing Apparatus Research Articles

Research on the Mechanics Characteristics of Loess Tested by a New True Tri-Axial Apparatus

All true tri-axial experimental apparatuses are usually applied to test the mechanics characteristics of soils under complicated stress conditions. Because of the analysis of non-rationality of three kinds of chamber framework developed in past, a new true tri-axial apparatus with a new structural chamber is recently developed by the institute of geotechnical engineering, Xi’an University of Technology. The mechanical description of a new tri-axial apparatus for soil testing is presented herein. The design of new tri-axial apparatus took into the flexibility in adjusting sample size, convenience in assembling sample and easily controlling of three normal stress conditions. The stress-controlled and strain-controlled performance of experiments can be accomplished respectively in the new true tri-axial equipment, which is of a special chamber. The special chamber includes of four cells with bursa filling liquid, being corresponding to four lateral surfaces of cubic sample respectively, separated by steel clapboards. The steel clapboards can turn freely on the horizontal plane and flex in the radial direction so as to adapt to the displacement of sample corner. Through the true tri-axial testing of remolded loess and intact loess were executed on the new true tri-axial apparatus, and the characteristics of stress-strain curves for the true tri-axial tests of remolded loess and intact loess were analyzed under different intermediate principal stresses. The characteristics of the new true tri-axial apparatus are as following: structure is simple, and operation is well-suited, and stress state is real, and strain measurement is accurate, and testing process is controlled easily.

Dynamic behaviour of soils used for natural turf sports surfaces

The modulus and damping properties of soils in compression are a function of soil type, water content, stress history and loading rate. To model human–surface interaction with natural turf sports surfaces, stiffness and damping properties must be determined at dynamic loading rates. Two contrasting soil types, a Sand and a Clay Loam, commonly used in sports surfaces were loaded uniaxially to 2 kN at loading rates between 0.6 and 6 kN s−1 in modified dynamic soil testing apparatus. Soils were compacted prior to loading but initial cycles resulted in viscoplastic deformation, with strain accumulation with repeated cycles of loading. Ultimately a resilient, viscoelastic steady-state equilibrium with loading was established. Resilient modulus and damping ratio varied with soil type, water content, stress history and increased significantly with loading rate. The resilient modulus of the Sand soil, typical of modern free-draining sand construction natural turf sports surfaces, was significantly greater than that of a Clay Loam soil more characteristic of traditional natural turf surfaces; reducing water content caused an increase in modulus and a decrease in damping ratio in the Clay Loam soil. Determination of these properties provides initial data for the modelling natural turf surface behaviour in terms of both ball and human interactions, with further research required to determine the effect of both grass roots and leaves on mechanical behaviour.

The effect of shredding and test apparatus size on compressibility and strength parameters of degraded municipal solid waste

In many situations, MSW components are processed and shredded before use in laboratory experiments using conventional soil testing apparatus. However, shredding MSW material may affect the target property to be measured. The objective of this study is to contribute to the understanding of the effect of shredding of MSW on the measured compressibility and strength properties. It is hypothesized that measured properties can be correlated to an R-value, the ratio of waste particle size to apparatus size. Results from oedometer tests, conducted on 63.5 mm, 100 mm, 200 mm diameter apparatus, indicated the dependency of the compressibility parameters on R-value. The compressibility parameters are similar for the same R-value even though the apparatus size varies. The results using same apparatus size with variable R-values indicated that shredding of MSW mainly affects initial compression. Creep and biological strain rate of the tested MSW are not significantly affected by R-value. The shear strength is affected by shredding as the light-weight reinforcing materials are shredded into smaller pieces during specimen preparation. For example, the measured friction angles are 32 degrees and 27 degrees for maximum particle sizes of 50 mm and 25 mm, respectively. The larger MSW components in the specimen provide better reinforcing contribution. This conclusion is however dependent on comparing specimen at the same level of degradation since shear strength is also a function of extent of degradation.

A True Triaxial Apparatus for Soil Testing with Mixed Boundary Conditions

Abstract The mechanical description of a new true triaxial apparatus for soil testing is presented. The design took into consideration flexibility in accommodating different specimen sizes, easy assembly procedure, and well-controlled boundary conditions. The apparatus can perform stress-controlled and strain controlled experiments. It is well instrumented with load, displacement, and pressure sensors and has the capabilities to capture strain localization and shear band development. Verification experiments were conducted on F-75 Ottawa sand to study the influence of b-value (b = (σ2 − σ3)/(σ1 − σ3)) on stress-strain and volumetric behavior of sand. The results show that the specimen stiffness increases, and the amount of post-peak softening increases as b-value increases. The peak and critical state friction angles and the rate of dilation increase as b-value increases from 0 to 0.25, followed by a smaller increase in the friction angles and no change in the rate of dilation as b-value increases. Specimens failure is characterized by nonuniform deformations that initiate during the hardening regime before the peak stress; however, shear bands become visible on the specimen surface during the post peak softening at which specimens' volumetric strain changes from dilative behavior to the constant volume condition.

The Louisiana Plane Strain Apparatus for Soil Testing

Abstract The mechanical description of a new plane strain (biaxial) apparatus for soil testing is presented. The design took into consideration flexibility in accomodating different specimen sizes, easy assembly procedure, and well-controlled boundary conditions. The apparatus is well instrumented with load, displacement, and pressure sensors and has the capabilities to capture localization and shear band development. A comparison between two experiments that were conducted on F-75 Ottawa sand is presented and the effect of inhibiting lateral movement of bottom end platen is presented and discussed. It has been found that restraining lateral movement of bottom end platen has resulted in higher peak and residual load values.

The Danish Rigid Boundary True Triaxial Apparatus for Soil Testing

Abstract The intermediate principal stress plays an important role for the stress-strain behavior of soils. The effect of the intermediate stress cannot be examined in the conventional triaxial apparatus since axisymmetric stress states are prescribed in it. Thus, other testing devices capable of producing asymmetric stress states are necessary for more accurate determination of the stress-strain behavior. This paper describes the Danish rigid boundary true triaxial apparatus developed at Aalborg University and the techniques employed to prepare and test specimens of clay and sand for effects of the intermediate stress. Three series of true triaxial tests are presented together with various conventional triaxial tests to illustrate the capabilities of the apparatus. The first series of tests was carried out on cross-anisotropic specimens from a natural clay deposit. The other two series were carried out on air-pluviated (frozen and unfrozen) specimens of sand that also showed cross-anisotropic behavior.

A Multiple Purpose Soil Testing Apparatus

Abstract A relatively compact soil testing system that is capable of performing monotonic/cyclic triaxial and torsional simple shear tests has been developed. A high-torque direct-drive, servo/stepper motor is used to provide the driving force. Under the servo mode, the motor could be controlled to provide a constant torque, which is used in stress-controlled tests. Strain-controlled tests are conducted using the stepper control mode. To perform triaxial tests, the rotational motion of the motor is transformed into linear motion using a preloaded ball screw shaft. A preloaded ball spline shaft directly attached to the motor is used to perform torsional simple shear tests. Because there are no gears in the driving system, there is no backlash during reversals of loading directions. The motor is equipped with an encoder and an indexer. The extremely rigid driving system and high resolution of the encoder enable the linear and rotational displacement to be monitored through the encoder/indexer system. Test control and data logging are fully automated using a personal computer. This paper provides details of the apparatus. A set of strain-controlled test data are presented to demonstrate capabilities of the new apparatus.

Microcomputer-based laboratory apparatus for soil testing : Shen, C K; Li, X S; Chan, C K; Wang, Z Proc 12th International Conference on Soil Mechanics and Foundation Engineering, Rio de Janeiro, 13–18 August 1989V1, P119–122. Publ Rotterdam: A A Balkema, 1989

Microcomputer-based laboratory apparatus for soil testing : Shen, C K; Li, X S; Chan, C K; Wang, Z Proc 12th International Conference on Soil Mechanics and Foundation Engineering, Rio de Janeiro, 13–18 August 1989V1, P119–122. Publ Rotterdam: A A Balkema, 1989

Cubical triaxial apparatus for soil testing : Lade, P V Geotech Test J, V1, N2, June 1978, P93–101

Cubical triaxial apparatus for soil testing : Lade, P V Geotech Test J, V1, N2, June 1978, P93–101

A New Soil Testing Apparatus

A New Soil Testing Apparatus

A New Soil Testing Apparatus

Synopsis The design and construction of a soil test box, capable of applying any combination of three principal stresses to a cubical soil specimen, is described. The principal stresses can be varied independently or by means of a stress control device which is a mechanical-hydraulic analog of an octahedral plane in the principal stress space. The three principal strains are measured, together with an independent measurement of the volume change of the soil sample. The behaviour of a medium dense Ottawa sand in an axial compression test at constant octahedral stress in the equipment is compared withthat of the same material in a conventional triaxial apparatus. On décrit la conception et la construction d'une boite d'essais de sol permettant d'appliquer n'importe quelle combinaison de trois contraintes principales à un échantillon de sol cubique. Les contraintes principales peuvent être variées indépendamment ou au moyen-d'un appareil de contrôle de contrainte qui est mécaniquement-hydrauliquement analogue à un plan octaédrique dans l'espace de contrainte principale. On a fait la mesure de trois déformations principales ainsi qu'une mesure indépendante de chargement volumétrique de l'echantillon de sol. On-compare le comportement d'un sable d'ottawa moyennement dense dans un essai de compression axial sous une contrainte octaédrique constante dans l'appareil avec celui du même matériel dans un appareil triaxial conventionnel.

A new soil testing apparatus: H.Y. Ko and R.F. Scott.Geotechnique17, No. 1, 1967

A new soil testing apparatus: H.Y. Ko and R.F. Scott.Geotechnique17, No. 1, 1967