			Home About us Contact

Back Analysis (back + analysis)

Distribution by Scientific Domains

Engineering	80%

Selected Abstracts

Back analysis of model parameters in geotechnical engineering by means of soft computing

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2003
B. Pichler
Abstract In this paper, a parameter identification (PI) method for determination of unknown model parameters in geotechnical engineering is proposed. It is based on measurement data provided by the construction site. Model parameters for finite element (FE) analyses are identified such that the results of these calculations agree with the available measurement data as well as possible. For determination of the unknown model parameters, use of an artificial neural network (ANN) is proposed. The network is trained to approximate the results of FE simulations. A genetic algorithm (GA) uses the trained ANN to provide an estimate of optimal model parameters which, finally, has to be assessed by an additional FE analysis. The presented mode of PI renders back analysis of model parameters feasible even for large-scale models as used in geotechnical engineering. The advantages of theoretical developments concerning both the structure and the training of the ANN are illustrated by the identification of material properties from experimental data. Finally, the performance of the proposed PI method is demonstrated by two problems taken from geotechnical engineering. The impact of back analysis on the actual construction process is outlined. Copyright © 2003 John Wiley & Sons, Ltd. [source]

A numerical method for the study of shear band propagation in soft rocks

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2009
Marta Castelli
Abstract This paper investigates the possibility of interpreting progressive shear failure in hard soils and soft rocks as the result of shear propagation of a pre-existing natural defect. This is done through the application of the principles of fracture mechanics, a slip-weakening model (SWM) being used to simulate the non-linear zone at the tips of the discontinuity. A numerical implementation of the SWM in a computation method based on the boundary element technique of the displacement discontinuity method (DDM) is presented. The crack and the non-linear zone at the advancing tip are represented through a set of elements, where the displacement discontinuity (DD) in the tangential direction is determined on the basis of a friction law. A residual friction angle is assumed on the crack elements. Shear resistance decreases on elements in the non-linear zone from a peak value at the tip, which is characteristic of intact material, to the residual value. The simulation of a uniaxial compressive test in plane strain conditions is carried out to exemplify the numerical methodology. The results emphasize the role played by the critical DD on the mechanical behaviour of the specimen. A validation of the model is shown through the back analysis of some experimental observations. The results of this back analysis show that a non-linear fracture mechanics approach seems very promising to simulate experimental results, in particular with regards to the shear band evolution pattern. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Inextensible reinforcement on non-linear elasto-plastic subgrade under oblique pull

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 18 2008
J. T. Shahu
Abstract In this paper, a rational analysis of pullout resistance of inextensible sheet reinforcement subjected to oblique end force has been presented considering a non-linear (hyperbolic), elasto-plastic, normal stress,displacement relationship of the subgrade. Under an oblique pull, high normal stresses develop on stronger subgrades, thus mobilizing high shearing resistance at the reinforcement,soil interface. The higher the bearing resistance of the subgrade, the higher the horizontal component of pullout force and the lower the end displacement of the reinforcement. On the other hand, the end displacement at pullout can become very high for weaker subgrades especially at high values of the angle of obliquity. Also, the pullout capacity under oblique loading for weaker subgrades may approach or even fall below the axial pullout capacity at high values of the angle of obliquity. These adverse pullout responses owing to a low value of bearing resistance of subgrade are magnified when the subgrade stiffness is also small. On weaker subgrades, improvement in angle of interface shear is not advisable as this leads to further reduction in the pullout force and increase in the end displacement. Results are compared with back analysis of published test data on model reinforced soil walls. The comparison suggests that the present model leads to a more rational and better prediction of the pullout failure. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Back analysis of model parameters in geotechnical engineering by means of soft computing

Clarification of regional and local in situ stresses using the compact conical-ended borehole overcoring technique and numerical analysis

ISLAND ARC, Issue 3 2003
Seong-Seung Kang
Abstract Stress measurement is performed to estimate the states of in situ rock stress at the Torigata open-pit limestone mine in Japan using the compact conical-ended borehole overcoring (CCBO) technique. A set of back and forward analyses are then carried out to evaluate the states of regional and local in situ rock stresses and the mine-induced rock slope stability using a 3-D finite element model. The maximum horizontal local in situ rock stress measured by the CCBO technique acts in the northeast,southwest direction. The horizontal regional tectonic stresses obtained by the back analysis are in good agreement with those of the horizontal local in situ rock stress measured by the CCBO technique. However, the horizontal regional tectonic stress is more compressive than the horizontal local in situ rock stress. This is because the horizontal regional stress due to gravity is not considered in the back-analyzed horizontal regional tectonic stress, but it is included in the local in situ rock stress measured by the CCBO technique. The local stress obtained by the forward analysis, especially its horizontal components, is in good agreement with the horizontal local in situ rock stress measured by the CCBO technique, and the magnitude of the vertical normal stress increases more rapidly than those of the horizontal normal stresses with depth. As a result, the ratio of the horizontal normal stress to the vertical normal stress is largest at the nearest excavation level and decreases with depth. This means that the stress field within the mine-induced rock slope is affected by the horizontal components of the local in situ rock stress. [source]