Composite interface strength between DMM pile and surrounding soil | |
| Author | Tran Chi Vi |
| Call Number | AIT Thesis no.GE-02-18 |
| Subject(s) | Soil cement Strains and stresses Shear strength of soils |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Masters of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-02-18 |
| Abstract | The strength and deformation characteristics of unit cell of end bearing DMM piles improved ground has been simulated in the laboratory by conducting a series of CIU tests of composite cylindrical specimen, which is composed of varying diameter of cement treated clay core that is mixed at the center of undisturbed clay specimen. The possible improvement of surrounding clay due to migration of diffusing cement ions from the soil cement paste composing the DMM pile has also been investigated in the laboratory by conducting laboratory vane shear test on prepared miniature of DMM pile unit cell. In addition, the increase in interface strength between DMM pile and the surrounding soil was also investigated by conducting direct shear test on specimen, prepared in a specified manner. Twenty-eight days curing time was utilized in all test specimens. The results of CIU test of composite specimen revealed that the stress-strain curve of composite soil , those with spacing ratio (n) higher than 2 and with cement content ranging from 7% to 23%, demonstrated yielding at failure but without necessarily undergoing strain softening. For n=2, however, only composite specimen with cement content higher than 20% shows strain softening at failure. In practice, where n may range from 2.5 to 3.0 and cement content may range from 10% to 15%, the composite foundation (DMM piles improved ground) is most likely to behave plastically and not brittle failure. Moreover, some of the cement ions in clay-cement paste composing the DMM piles could possibly diffused into the surrounding clay and, thereby, stabilized the surrounding soil. Based on the results of laboratory vane shear test of miniature unit cell of soil-cement pile, the surrounding soft clay has increased its strength to 2 to 3.2 times the strength of untreated clay within a distance of 0.5 to 1.5 times the radius of pile from the edge of soil-cement pile, respectively, for all practical values of cement content. This possible improvement of the surrounding soil would further prevent the soil-cement pile from experiencing sudden collapse at failure. Furthermore, it has been found from direct shear test of interfacing undisturbed clay and cement-admixed clay that the undrained cohesion, c, and the undrained friction angle, ¢, at the interface of soil-cement pile and surrounding clay can be taken as 25 kPa to 35 kPa and 15°, respectively, for cement content from 10% to 15% which is normally employed in practice. |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-02-18 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Bergado, Dennes T.; |
| Examination Committee(s) | Glawe, Ulrich;Park, Kyung Ho ; |
| Scholarship Donor(s) | Asian Institute of Technology- Partial Fellowship.; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2003 |