| Author | Nattavut Theramast |
| Call Number | AIT Thesis no. GE-97-12 |
| Subject(s) | Shear strength of soils--Testing
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | A series of bender element tests and constant volume direct shear box tests were carried out on soft and stiff clay samples collected from Suthisan site, Bangkok, as to characterize the initial shear modulus and undrained shear strength of Bangkok subsoil, respectively. The very small strain shear modulus (G111aJ was determined by using a relatively new laboratory technique known as bender element test. The initial shear modulus (G111aJ was plugged into an appropriate empirical expression incorporating new void ratio function which described the variation of Gmax with current state in terms of current stresses and OCR. The effect of OCR was found negligibly small with the exponent k close to zero for a sedimentation of soil showing OCR close to unity. The newly proposed void ratio function, the term f( e) = (1 +e y4 · 1 5 ' was considered to represent the Gmax variation. It was found applicable and very well minimize OCR effect on the initial shear modulus. An empirical equation to estimate pseudo-elastic shear modulus of ground with shear strains less than 0.001 % is proposed in this thesis. The Gmax profile with depth of Bangkok subsoil was successfully made from available borehole data. The exponent expressing the stress level dependency (n) of undisturbed sample ranges approximately from 0.41 to 0.49 whereas reconstituted clay sample shows the constant value 9f about 0.48. The soil structure effect on Gmax was found vary with depth. The non-dimensional material constant reflecting current soil structure (Sv11) seems to increase with depth. Series of constant volume direct shear box tests were performed in an attempt to determine the shear strength parameters and to evaluate the aging and soil structure effects on shear strength. First, undisturbed clay samples were sheared with the vertical consolidated stress equal to those experience in the field. Second, undisturbed clay samples were sheared with consolidated pressure far beyond the maximum past pressure. Third, reconstituted samples were consolidated into normally consolidated state prior to shear. It was found that the ~·d s and ~'cu of soft clay are 21.3 ° and 19.8 ° whereas those of stiff clay are 27.5° and 24.7°, respectively. Higher shear strength gain due to aging effect developed by chemical bonding was found 3.58 kPa for soft clay. The k value, indicated the degree of secondary compression, shows the value about 1.05. At vertical consolidation stress higher than 320 kPa the soil structure was found no longer influence the shear strength. |
| Year | 1998 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Shibuya, Satoru;Lin, Der Guey (Co-Chairperson); |
| Examination Committee(s) | Balasubramaniam, A.S.;Noppadol Phien-wej; |
| Scholarship Donor(s) | Asian Institute of Technology Partial Scholarship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology |