| Author | Prapas Wanthong |
| Call Number | AIT Thesis no.GE-07-17 |
| Subject(s) | Vertical drains--Forecasting
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| Note | A thesis proposal submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-07-17 |
| Abstract | The study aims to examine the effect of vacuum loading in accelerating the consolidation of vertical drains improved in soft Bangkok clay. The laboratory test were conducted in large scale consolidomter diameter of 305 mm and 500 mm height with reconstituted specimens using PYD with and without vacuum pressure, In addition the field data was collected from Second Bangkok International Airport (SBIA) site improved by PYD with and without vacuum. Analyses were carried out to compare the compressibility parameters by back-calculation of laboratory and field settlements using Asaoka (1978) and Hansbo (1979) methods as well as sensitivity analyses of numerical experiments by using PYDCON software. From the laboratory tests have found that the Ch value from reconstituted specimens were 1.05 and 2.20 m²/yr for PYD without and with vacuum pressure, respectively. In addition kh/ks were 1.50 for normal PYD and 1.45 for vacuum PYD The horizontal coefficient of consolidation of PYD with vacuum pressure was higher than only PYD improvement. After the improvement the water content was reduced which leads to increasing of undrained shear strength. The field data analysis based from back-calculated results showed that the kh/ks are 4 for both PYD with and without vacuum. The Ch values is about 4.18 m²/yr and 5.52 m²/yr from the normal PYD and vacuum PYD, respectively. The time to reach 90% degree of consolidation of vacuum PYD was shorter than normal PYD by about one-third because of higher Chvalue. By this reason, vacuum PYD is one good method for soft ground improvement to reduce the construction time. The settlement predictions by Asaoka (1978) graphical method agreed with the observed values. The settlement predictions using PYDCON software was less than observed values at the first stage of consolidation but agreed with the observed values at the final stage. From sensitivity analysis by PYDCON software, increasing of kh/ks and OCR values resulted in lower settlement values. From the sensitivity analysis, for PYD only, the appropriate OCR was found to be 1.2 to 1.3 with kh/ks of 4 to 6 and Ch=2Cv. For PYD with vacuum pressure at -60 kPa, the appropriate OCR was found to be 1.2 to 1.3 with kh/ks of 4 to 6 and Ch=3Cv where Cv = 1.58 m²/year. Thus, the addition of vacuum pressure leads to increase of the horizontal coefficient of consolidation which shortened the time of preloading |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-07-17 |
| 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) | Noppadol Phien-wej;Pham Huy Giao; |
| Scholarship Donor(s) | Royal Thai Government; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2007 |