Soft ground improvement by prefabricated vertical drain (PVD) at elevated temperatures (Thermo-PVD) | |
| Author | Chanidnun Phothiraksanont |
| Call Number | AIT Diss. no.GE-09-02 |
| Subject(s) | Vertical drains--Thailand--Bangkok Clay soils--Thailand--Bangkok |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Geotechnical and Geoenvironmental Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. GE-09-02 |
| Abstract | This study is focused on the performance of Thermo-PVD in the laboratory and the field conditions. The installation of PVDs using a mandrel causes disturbed or smeared zone around the PVDs. The extent of this zone depends on the size of the mandel. The permeability of this zone is reduced. Consequently, the smear zone acts as barrier against pore water drainage into the PVDs. One way to achieve faster rate of primary settlement of the clay subsoil is to increase its temperature up to 90oC. This study not only consists of laboratory investigations using small and large scale consolidometer tests but also the field investigations of conventional PVDs and Thermo-PVDs (with heat preloading). Laboratory model tests were performed on small and large scale consolidometers with undisturbed and reconstituted samples. To investigate flow parameters in terms of the horizontal coefficient of consolidation (Ch) and the ratio between the horizontal permeability in undisturbed zone (Kh) to the horizontal permeability in smear zone (Ks) or (Kh/Ks) using Hansbo (1979) method based on the final settlement by Asaoka (1978) method. For small scale consolidometers, the increased permeability in the smear zone of Thermo-PVD undisturbed sample resulted in the decrease in Kh/Ks of about 20% and increase in Ch by 10% as well as increase in horizontal permeability in the smear zone by 1.38 times. The increased permeability in the smear zone of Thermo-PVD reconstituted sample resulted in the decrease in Kh/Ks of about 14.28% and increase in Ch by 15.74% as well as increase in horizontal permeability in the smear zone by 1.35 times. The back-calculated Ch values for reconstituted sample improved with Thermo-PVD in the large consolidometer was 3.0 m²/yr and the corresponding Kh/Ks value was 1.50. For the field tests, two identical full scale embankments improved without and with heat using a combination of solar eletric powers were constructed on improved soft ground with dimensions of 11 m x 11 m at the bottom and 3 m x 3 m at the top with 6 m height. The increased permeability in the smear zone of Thermo-PVD resulted in the decrease in Kh/Ks of about 125% and increase in Ch by 45.45% as well as increase in horizontal permeability in the smear zone by 3.27 times. The permeability of the smear zone increased due to the increase in temperature which caused the reduction of viscosity in the pore water. Consequently, the Kh/Ks values slightly decreased while the coefficient of horizontal consolidation, Ch, increased |
| Year | 2010 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. GE-09-02 |
| Type | Dissertation |
| 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) | Noppadol Phien-wej ;Kunnawee Kanitpong ; |
| Scholarship Donor(s) | The Royal Thai Government; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2009 |