Coffey International (Australia)

Structural data collection from drill core relies on the ability of the core to be accurately oriented. A number of methods are available for core orientation, but broken zones and core loss present difficulties in obtaining orientation data, which can result in a paucity of structural data for significant intervals of a drill hole. Where orientation is achieved, errors and uncertainties can result in significant scatter in the calculated structure orientation populations. Televiewer surveys, both optical and acoustic, provide a reliable and accurate alternative method of recording structural data. They are relatively quick to run, and allow data capture from vertical and inclined drill holes without the need for diamond coring. The Televiewer survey captures a downhole image of the internal drill hole walls. Structural data can be captured from the image by fitting sinusoids to discontinuity traces visible in the drill hole wall. Although structural data can be picked automatically, it is argued that data should be picked by experienced engineers who clearly understand the intended use of the resultant datasets, and the limitations of the surveys. In lieu of a procedure for the undertaking of Televiewer interpretation for structural orientation data for geotechnical purposes, the authors propose a set of guidelines and protocols that in their experience have proven useful.

Abstract REFRACT is an interactive seismic refraction interpretation software package, based on the Reciprocal and Intercept Time methods, developed by the Roads and Traffic Authority of New South Wales (Australia). REFRACT operates in graphic and spreadsheet displays on PCs and preserves much of the flexibility of manual methods. The power of REFRACT lies in its treatment of a seismic line as a single data set, combining overlapping segments and handling lateral velocity changes in all layers, and in its optimization of manual interpretation operations. After entry of first arrival times the T-X data may be checked and edited for shot depth and reciprocal times. Interpretation includes operations such as parallelism testing and layer labelling (Segmentation) on the T-X graph, Phantoming of overlapping segments, minus times Velocity Analysis, automatic Thickness Calculation and edits to the interpreted section. The interpretation stages employ a number of optimization routines that may be applied with default settings or may be reset and manipulated for close control of the interpretation process over part or all of the T-X data set. The Distance Range is a fundamental concept in REFRACT that controls the application of the Reciprocal and Intercept Time methods for the calculation of time depths, intercept times and harmonic mean velocities. REFRACT provides a new standard for seismic refraction interpretation.

Abstract Theoretical analyses have been carried out on five different pile types in two hypothetical soils representing offshore calcareous sediment profiles. It is demonstrated that both static and cyclic performance can be improved, over that of a conventional uniform pile, by altering the distribution of diameter and/or stiffness along the pile. To optimize performance under cyclic loading, a pile should be designed so that stress concentrations are minimized and the shape of the distribution of pile‐soil shear stress is the same as that of the limiting skin friction.