A Rigid-Flexible Boundary True Triaxial Apparatus for Testing Soils in a Three-Dimensional Stress State PDF Download

Author: Jian-Hua Yin
Publisher:
ISBN:
Category : Friction
Languages : en
Pages : 8

View

Book Description
In this paper, a new true triaxial loading device with mixed rigid and flexible boundaries and its setup are described. The main features of the new true triaxial loading device are four sliding rigid plates acting on the soil specimen enclosed in a rubber membrane, which solves the corner contact interference problem. Measures for reducing friction on the specimen are also presented. All forces and sources of friction on the soil specimen applied by this loading device and their influence on the distribution of strains and stresses in the specimen are analysed and discussed. The true triaxial apparatus with this new loading device has been used to study the stress-strain behaviour of a completely decomposed granite (CDG) soil in Hong Kong. Typical test results are presented and discussed. Based on the description, test results, and discussion, it is found that this new true loading device has a number of merits, especially for testing soils under large strains without corner interferences. It is also found that the stress-strain behaviour of the CDG is dependent on the b-value and the Lade-Duncan failure criterion is more suitable for the CDG in a three-dimensional stress state.

Author: S. Shao
Publisher:
ISBN:
Category : Failure strength
Languages : en
Pages : 10

View

Book Description
Several kinds of true triaxial apparatuses have been devised and applied to obtaining the strength and deformability behavior of soils under different stress paths. However, for these true triaxial apparatuses with flexible loading boundaries boundary interference is still not solved. This paper presents a new type of true triaxial apparatus, with rigid-flexible-flexible boundaries, which addresses the boundary interference using four division strip-platens. This apparatus applies three principal stresses on a 70-mm cuboidal specimen from two rigid platens along the vertical direction and four hydraulic rubber bags around four side faces of the cuboidal specimen. The rigid platens and hydraulic rubber bags were assembled in a true triaxial chamber and driven by three servo-hydraulic cylinders. Four division strip-platens are installed along the lateral edges of the confining side wall of the chamber to separate adjacent rubber hydraulic bags and can adjust themselves to accommodate dimensional changes in the deforming specimen. Therefore, this apparatus does not only allow independent control of stresses applied in three dimensions to a cuboidal specimen but also resolve the boundary interferences. The effectiveness of this apparatus was confirmed by tests on remolded loess under five stress paths with the intermediate principal stress parameter b = 0, 0.25, 0.5, 0.75, and 1. The test results show that the stress-strain relationship, volume strain, and failure strength of remolded loess depend on the stress path.

Author: L. Bo Ibsen
Publisher:
ISBN:
Category : Clay
Languages : en
Pages : 12

View

Book Description
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.

Author: KA. Alshibli
Publisher:
ISBN:
Category : Boundary conditions
Languages : en
Pages : 10

View

Book Description
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 = (?2 − ?3)/(?1 − ?3)) 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.

Author: KR. Reddy
Publisher:
ISBN:
Category : Cementation
Languages : en
Pages : 17

View

Book Description
A stress-controlled, flexible boundary, true (or cubical) triaxial apparatus has been developed to investigate the behavior of cemented sand under various stress paths which are not achievable using conventional axisymmetric triaxial apparatus. The apparatus components, specimen preparation, and test procedure are described. Tests were performed on cemented sand along different stress paths which included hydrostatic compression, conventional triaxial compression, and along different directions on octahedral planes. The test results indicate that stress-strain and volumetric response of cemented sand depends on stress path.

Author: Changho Choi
Publisher:
ISBN:
Category : Coarse-grained soil
Languages : en
Pages : 13

View

Book Description
This paper presents a recently developed true triaxial apparatus and a series of verification studies. The apparatus is capable of handling 241-mm cubical specimens providing the means for testing specimens under a wide variety of stress paths under drained and undrained conditions. It uses flexible boundaries to apply three independently controlled principal stresses with back pressure. The apparatus also uses a fully computer-controlled electro-pneumatic loading system with advanced technology for data control. A testing program is presented for the purpose of verification. Pea-gravel specimens with D50=6.6 mm were tested under fully stress-controlled loading conditions. Stress paths used in this verification study include undrained and drained constant total mean stress paths and conventional triaxial compression and extension stress paths. Results from this study indicate that the newly developed apparatus is capable of capturing the stress-strain characteristics of coarse-grained soils.

Author:
Publisher:
ISBN:
Category : Engineering geology
Languages : en
Pages : 758

View

Book Description

Author: Lyesse Laloui
Publisher: Springer Science & Business Media
ISBN: 3642324924
Category : Science
Languages : en
Pages : 331

View

Book Description
Significant advancements in the experimental analysis of soils and shales have been achieved during the last few decades. Outstanding progress in the field has led to the theoretical development of geomechanical theories and important engineering applications. This book provides the reader with an overview of recent advances in a variety of advanced experimental techniques and results for the analysis of the behaviour of geomaterials under multiphysical testing conditions. Modern trends in experimental geomechanics for soils and shales are discussed, including testing materials in variably saturated conditions, non-isothermal experiments, micro-scale investigations and image analysis techniques. Six theme papers from leading researchers in experimental geomechanics are also included. This book is intended for postgraduate students, researchers and practitioners in fields where multiphysical testing of soils and shales plays a fundamental role, such as unsaturated soil and rock mechanics, petroleum engineering, nuclear waste storage engineering, unconventional energy resources and CO2 geological sequestration.

Author: Jae Hyun Park
Publisher:
ISBN: 9780542226946
Category : Civil engineering
Languages : en
Pages :

View

Book Description
A stress-controlled, flexible boundary, true triaxial (cubical) testing apparatus has been developed to test 3-inch cubical specimen of partially saturated soil under different moisture contents and for a wide range of multiaxial stress paths. A series of HC, CTC, TC, TE, and SS tests were conducted in order to perform a thorough performance and check-out verification testing of the newly developed device by investigating the multiaxial stress-strain response of partially saturated silty sand specimens artificially prepared in the laboratory. The development of the apparatus, specimen preparation process, test procedure, and the corresponding validation of its suitability for testing partially saturated sandy soils are described. In this work, specimens were prepared using a dual-mesh pluviation technique at four different moisture contents: w = 2.0, 4.5, 5.3, and 6.1%. In all cases, initial total soil suction was induced and found to exert a paramount influence on the stress-strain-strength behavior of partially saturated silty sand.

Author: Robert T. Donaghe
Publisher: ASTM International
ISBN: 0803109830
Category : Anisotropy
Languages : en
Pages : 896

View

Book Description
"Although the triaxial compression test is presently the most widely used procedure for determining strength and stress-deformation properties of soils, there have been no books published on triaxial testing since the 1962 second edition of the landmark work The Measurement of Soil Properties in the Triaxial Test by Bishop and Henkel. It is apparent there is a need to document advances made in triaxial testing since publication of Bishop and Henkel's book and to examine the current state of the art in a forum devoted solely to triaxial testing. Because of increasing versatility brought about by recent developments in testing techniques and equipment, it is also important that the geotechnical profession be provided with an up-to-date awareness of potential uses for the triaxial test."--Overview.