Abstract
The paper deals with comparison of tangent moduli Gs of kaolin from Tuowice obtained from cyclic triaxial tests on the basis of external and internal reading in the small strains range (10 -5 ÷10 -3 ). The tests were carried out on a modernised test bed, enabling full saturation of specimens using the back pressure method as well as a precise internal measurement of strains by means of contactless microdisplacements sensors. The value of linearity factor L is one of adopted quality criteria for two measuring methods. Maintaining a constant deformation rate the influence of various cyclic process parameters (deviator stress amplitude - constant or variable; high or low; initial level of stress and strain, at which the unloading and reloading cycles were started; overconsolidation ratio OCR as well as cycles' number and arrangement) on the shear modulus - axial strain characteristic was studied. The obtained values of Gint and Gext (or Lint and Lext) clearly show an underestimation (even 5 times) of Gs value within the range 10 -5 ÷10 -3 when using an external measurement. In addition, the differences between Gint and Gext, which develop differently depending on specified cyclic process parameters, gradually decrease with increasing axial strains.
Highlights
A reliable determination of relationships between stress and strain is the foundation of safe designing of service states
Issues related to the influence of measurement type in undrained triaxial tests on the value of Young’s modulus E may be found inter alia in Rampello’s paper [4]
Results obtained by Rampello confirmed previous results obtained by Rampello and Pane [5], Georgiannou et al [6], Costafilho [7], Daramola [8], namely that the stiffness – in undrained triaxial conditions – from internal measurements is always higher, but the differences diminish with increasing axial strains
Summary
A reliable determination of relationships between stress and strain is the foundation of safe designing of service states The accomplishment of this task in the case of soils on the basis of laboratory tests results should proceed under full control of boundary conditions for fields of effective strain and stress and conditions of pore drainage. EPJ Web of Conferences particular when the pressure from the foundation on the soil is relatively small, what usually happens in the case of buildings of extensive plans (Kriegel and Weisner, [1]; Burland, [2]). Higher discrepancies were observed in turn in the case of tests without consolidation and undrained (UU) In their case external measurements give erroneous indications of linear behaviour of soils in the area of small strains.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
