Geotechnical parameters

Particular attention should be paid to the following issues in the design and design review of structures  

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Koliopoulos, T.C., Kolhas, V, KoUias, P, and Koliopoulou, G. 2007d. Evaluation of geotechnical parameters for effective landfill design and risk assessment. In Geotechnics Related to the Environment, Sarsby, R.W. and Felton, A.J. (eds.), pp. 49-57. UK Taylor Francis Group. 

Lee, H.J., and Clausner, J.E. 1979. Seafloor Soil Sampling and Geotechnical Parameter Determination— Handbook, Technical Report R873, US Navy Civil Engineering Laboratory, Port Hueneme, CA,... 

Hutchinson, J.N. 1988. General Report Morphological and geotechnical parameters of landslides in relation to geology and hydrogeology. Proceedings, 5th International Symposium on Landslides, Balkema, Rotterdam, 1 3-35. 

Figure 1. Workflow for obtaining of equivalent geotechnical parameters from deformation based back analysis. 

Sakurai (1997) presented a procedure for assessment of the structure stability. It can be extended for deformation prediction and slope stability analysis, which is shown in Figure 1. Given the deformation results, the mathematic model for obtaining equivalent geotechnical parameters can be described as follows ... 

M1 Samples preparation Orthogonal design and normalization of geotechnical parameters within parametric domain need to be implemented. The map from parameters to deformation need to be created via forward FEM calculation. It is presented in step 1 and 2. M2 Configuration of neural network One hidden layer and four hidden neurons were set up. Three input neurons and two output neurons were set up, which is subject to the number of displacement observation nodes and parameters to be inversed. In this case, the three input neurons are the detected deformations of three groups, and the two output neurons are the unloading modulus of clay and sand layers of the slope. 

M3 Training and testing Calculated deformation is deemed as input, and corresponding geotechnical parameter as target. The big proportion of samples is used to train a net, while the rest of them to test the net. It is identical with step 3. 

M4 Determination of parameters Monitored deformation is input to the net. The outputs are the geotechnical parameters. It is accomplished by step 4, 5, 6, and 7. The quality of outputs needs to be assessedthrough an iteration process, which runs from step 3 to step 7. 

Geotechnical parameters which can be easily ascertained by empirical approaches or experiments are fixed prior to determination of E. Equivalent geotechnical parameters (Table 3) m e FEM forward simulation more agreed with monitored deformation. To verify the reliability of E, the calculated deformation based on the fixed parameters should be compared with the detected deformation. The maximum discrepancy of both is 3.33% (Table 4),... 

Based on the concept of equivalent geotechnical model, back propagation neural networks was applied to determinesome geotechnical parameters, which are difficult to be ascertained. Verification through comparing detected deformation and calculated deformation qualifies equivalent geotechnical model for FEM assessment of slope stabihty. 

The selection of soil properties, frequencies and strain dependences should be adequately documented. Methods of investigation and testing procedures are discussed in Ref. [3]. In this design context, a range of variation in soil properties should be defined to take account of uncertainties in geotechnical parameters, as suggested in Ref. [3]. The effect of such variation may envelop the variation in structural properties (e.g. due to a cracked section) this aspect should be explicitly addressed in the safety evaluation. 

As stated earlier, the nominal resistance in LRFD is synonymous with the ultimate capacity in WSD. Therefore, ultimate capacities and nominal resistances are used interchangeably in this section and applicable to both WSD and LRFD. Distinctions in other geotechnical parameters, when necessary, are clearly noted. 

ANS 2.11 Guidelines for elevating site-related geotechnical parameters at power reactor sites... 

Euroeode 7, Part 1 (2004) states in this respect cautious estimate of the mean value is a selection of the mean value of the limited set of geotechnical parameter values, with a confidence level of 95% where local failure is concerned, a cautious estimate of the low value is a 5% fractile. ... 

Because density is a mass property that correlates well with many other geotechnical parameters, it is an important parameter when constructing hydraulic fills. For a definition of the density, reference is made to section 8.3.1. Density of cohesive materials can easily be determined by undisturbed sampling. The in-situ density of cohesionless material can only be determined by specific tests (see Appendix B) for fill present above the ground water table. A problem with land reclamation projects, however, is that a considerable part of the fill may be present below the water table. That means that these speeifie tests which measure the in-situ density in dry circumstances cannot be used, and therefore one has to rely on correlations to determine the in-situ density. Recent developments of the nuclear density probe show promising results to measure the in-situ density direetly. The in-situ density is continuously recorded during the penetration of the probe. The principle of the nuclear density probe is described in Appendix B. 

Define the geotechnical parameters of the fill e, and y) and the maximum value of the pore pressure parameter, r = max[M(z)/y z], where (z) = pore pressure at depth z below... 

To evaluate geotechnical parameters to be used in the design of the foundation. 

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