Stress-strain characteristics of Bangkok subsoils at low strain levels using bender elements | |
| Author | Sahabdeen, Mohamed Mohideen |
| Call Number | AIT Thesis no.GE-95-17 |
| Subject(s) | Strains and stresses Soils--Thailand--Bangkok--Testing |
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-95-17 |
| Abstract | Soil exhibits a non-linear elastic behaviour unlike metal, and it varies with strain levels. However, at very low strain levels, a linear elastic characteristics could be observed. The technique of analysing stress-strain characteristics at very low strain levels is by using Bender Elements where an electro-mechanical transducer converts the strains into electrical signals. Bender Elements originally developed by Norwegian Geotechnical Institute have been used in this research. Testings with the Bender Elements were carried out with conventional soil testing devices such as oedometer, triaxial testing device, togather with the appropriate accessories namely function generator, amplifier, and oscilloscope. In order to insert the Bender Elements, the conventional soil testing devices were modified and the testing program commenced with the oedometer. A series of reference tests were carried out to investigate the effects of using Bender Elements with soil samples and the effects were found to be insignificant. Moreover, the suitable dimensions of the samples were investigated by using different heights of samples, and varying the diameter to height ratios from 1.2 to 3.3, while maintaining the standard diameter of 63.Smm. From the relationship between height and shear modulus for a particular depth of sample, the suitable sample height that gave the constant shear modulus at a particular stress level was estimated and used for further analysis using the oedometer. The samples taken at different depths, ranging from 3.0 to 7 .Om were used to develop the initial shear modulus profile. This also includes the unconfined compression test, at two different strain rates of loading. The shear modulus obtained from the conventional observations was compared with the initial shear modulus obtained using Bender Elements at various depths. The test series was then proceeded to the triaxial (CIU) tests and similar comparison was made between the shear modulus observations with and without Bender Elem~nts. From this analysis it was observed that all tests gave similar order of initial shear modulus. The influence of factors such as the stress history , over consolidation ratio (OCR), the strain rate, the position of the state boundary surf ace, stress level and strain level of the devices and their suitability on the estimation of initial shear modulus, were also analysed in this study. |
| Year | 1995 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-95-17 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Balasubramaniam, A. S.; |
| Examination Committee(s) | Seah, T. H.;Noppadal Phien - Wej; |
| Scholarship Donor(s) | Japanese Government.; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 1995 |