A reanalysis of the Nong Ngoo Hao test excavation | |
| Author | Ho, Wing-on |
| Call Number | AIT Thesis no. 905 |
| Subject(s) | Soils--Thailand--Nong Ngoo Hao--Testing Soil mechanics |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of Asian Institute of Technology, Bangkok Thailand. |
| Publisher | Asian Institute of Technology |
| Abstract | This thesis is concerned with a detailed study of the stability analysis of the trial excavation built to failure at Nang Ngoo Hao . It is an extension of the work carried out by ESSA (1974) but emphasis is made in carrying out additional laboratory tests which when incorporated with the existing data would be adequate to give an accurate analysis. The total stress analysis employed the undrained shear strength from the common field and laboratory tests. The effective stress analysis employed the CIU, CK0U, CK0D effective strength parameters from triaxial tests. A complete series of consolidated drained (CK0D) tests were performed at the same depth with the existing CK0 U tests in order to compare the effective strength parameters from the two types of tests. From the results of the experiments, the same effective strength envelope is observed. The total stress approach (ยข = 0 analysis) is determined by both Stability Chart and Swedish Methods. The effective stress approach (c, analysis) is determined by both Swedish and Bishop's method. The safety factors at failure obtained from the analysis by different methods are not the same, however, each of them show a logical figure indicating the safety conditions in the excavation. This shows that each method of analysis has its own .merits and all can be used to describe the stability of an excavation provided an appropriate correction factor is used to balance the effects of uncertainties in the shear strength obtained. The actual slip surface appears to be circular from field measurement and is within the range of the critical failure surfaces found theoretically. The consideration of tension cracks with hydrostatic pressure acting on it is found to be closer to the real situation in the field. Pore pressure prediction by Elastic method appears to be quite consistent with the measured pore pressure and the safety factors obtained from the measured and predicted pore pressures agree closely. The stability analysis by both Bishop and Swedish method shows that CKoU effective strength parameters can be used for CK0D parameters since they give practically the same values of safety factors. A simplified design procedure is suggested which involves the use of a factor of safety of 2.0 together with Bjerrum's correction factor. The result of the analysis shows that a depth of 2.5 m can be adopted for a 1:2.5 excavation in Nang Ngoo Hao to stand permanently. |
| Year | 1976 |
| Type | Thesis |
| School | Student Research Before 1980 |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Thesis (Year <=1979) |
| Chairperson(s) | Balasubramaniam, A.S. |
| Examination Committee(s) | Brand, E.W. ;Brenner, R.P |
| Scholarship Donor(s) | The Canadian Government |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 1976 |