G. Heymann

Global search for critical failure surface in slope stability analysis

Soil slope stability problems in engineering works are often analyzed using limiting equilibrium methods. A number of methods are based on the method of vertical slices in which assumptions about the geometry of the failure surface are made. For homogeneous soils the assumed failure surface is often of a regular shape, but for a layered profile the shape of the failure surface is more complex, making it difficult to find the critical failure surface. This paper describes the use of a global optimization algorithm for determining the critical failure surface in slope stability analyses. An important feature of this new method it that no assumptions are required with regards to the geometry of the failure surface and no restrictions are placed on the positions of the initiation and termination point. As a result the solution is completely general. Janbus simplified method and Spencers method are used to demonstrate the new approach of formulating this programming problem.

Triaxial Ultra-Small Strain Measurements Using Laser Interferometry

This paper describes a prototype device for ultra-small strain triaxial stiffness measurement, using laser-optic interferometry, and based upon the Fabry-Perot principle. The results of a test on an intact specimen of weak rock are presented, and comparisons made between measurements using this device and a submersible LVDT system. The displacement resolution of the interferometer was 0.0006 m and the strain resolution 8 × 10%. It is shown that the measurement uncertainty of the instrument was low compared with the magnitude of the displacements measured and in addition it was sufficiently accurate to detect the linear stress-strain behavior of a weak rock.