Cyclic behaviour of clays for offshore type of loading | |
| Author | Handali, Samuel |
| Call Number | AIT Diss. no. GT-86-02 |
| Subject(s) | Clay--Testing Strains and stresses |
| Note | A dissertation submitted in partial fulfilment of the requirements for the Degree of Doctor of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | A series of static and cyclic triaxial tests were carried out on undisturbed samples of soft Bangkok c lay to study the pore pressure developments, stress-strain behaviour and strength characteristics of the soil under offshore type of loading. Samples were consolidated along different constant stress ratio paths and were subsequently sheared under monotonic loading, cyclic loading and post-cyclic monotonic loading conditions. The interpretation of the test results is mainly given by the pore pressure - stress ratio relationship through which important aspects on the pore pressure development under the different types of loading emerged . Of particular significance is the behaviour of isotropically consolidated samples in the normally consolidated state, showing a linear variation between the pore pressure and the stress ratio under monotonic loading conditions. Patterns on the same p lot were also established for other clays such as Kaol in , Drammen c l ay and Boston Blue clay and it appears that linear variation is normally observed in clays having liquid limits greater than 50%. A comparative study on the available data of Bangkok clay also revealed that under different strain rates, the linearity of the pore pressure - stress ratio relationship persists but the gradient of the line decreases with the increase in strain rate . Overconsolidated samples and post -cyclic samples showed bi-linear variation on the same plot. Similarly, anisotropically consolidated samples having various initial conditions (normally consolidated, overconsolidated and post-cyclic conditions) also showed bi-linear variations. The gradient of the first linear sect ion is a function of the initial mean normal stress while t he second linear section is parallel to t hat of the isotropically consolidated sample in t he normally consolidated state having t he same void ratio as that particular sample. By means of a suitable shifting procedure applied on the bi-linear lines, the second linear sections merged onto the path of t he isotropically consolidated sample in the normally consolidated state . The position of the latter a s a state boundary for the other samples is thus strongly depicted . The results of stress- controlled cyclic loading tests on isotropically and anisotropically consolidated samples also s howed linear variation between the pore pressure and the stress ratio for each loading pat h beyond the deviator stress corresponding to the consolidation stress . These gradients can be expressed in terms of the initial mean normal stress in a similar form as that of samples under monotonic loading and post-cyclic monotonic loading. The linear/bi-linear variation in the pore pressure - stress ratio relationship was further used to develop simple formulae of the undrained stress paths for different initial conditions of the sample sand loading types by means of one or two material parameters . |
| Year | 1986 |
| Type | Dissertation |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Geotechnical and Transportation Engineering (GT) |
| Chairperson(s) | Balasubramaniam, A.S. |
| Examination Committee(s) | Karasudhi, Pisidhi ;Chandra, Sarvesh ;Bergado, Dennes T ;Towhata, Ikuo |
| Scholarship Donor(s) | Government of Japan |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1986 |