RECENT DEVELOPMENTS IN SITE INVESTIGATION AND TESTING FOR HARD ROCK TBM PROJECTS
For several recent TBM tunnel projects, unexpected ground conditions have been encountered, causing extra cost, considerable delay, and in some cases major claims. Undoubtedly, insufficient and/or irrelevant site investigation and testing are among the main causes of such incidents. The purpose of this paper is to review the main investigations and tests relevant for hard rock TBM projects, with particular emphasis on the considerable development that has taken place over the last few years. Also, guidelines for defining optimum scope and extent of site investigations and testing are discussed, as well as the importance of adjusting the investigations and tests according to complexity of the ground conditions and project type.
Csm Computer Model for Tbm Performance Prediction
The CSM model for TBM performance prediction was developed by the Earth Mechanics Institute (EMI) over a time period extending over 25 years. The development efforts on the CSM model began with a theoretical analysis of cutter penetration into the rock without any adjacent cuts or free-faces. As shown in Figure 1, this first step was crucial in understanding stress fields and the resultant fractures that are created beneath the penetrating edge of a disc cutter. Initially, the analysis focused on V-profile disc cutters, but later modified to include the constant-cross section discs as they became the industry standard. In this analysis, various previous theories derived from wedge indentation into rock were used as a guide. This analysis helped confirm the occurrence of a highly stressed crushed zone and the radial tension cracks during cutter penetration into the rock. Figure 1. Stress fields and the resultant fractures beneath the penetrating edge of a disc cutter
How Does the Keyword Method Affect Vocabulary Comprehension and Usage? Report from the project on Studies in Language: Reading and Communication. Working Paper No. 278.
THE KEYWORD METHOD of vocabulary learning involves forming a linkage between a to-be-learned vocabulary word and a familiar English word that sounds like part of the to-be-learned item (the keyword). Then the learner forms an interactive image between the keyword and definition referents. In previous research, the keyword method has been found to facilitate students' recall of definitions, given vocabulary items. In this study, use of the method was also shown to increase comprehension of English vocabulary in context, as well as usage of that vocabulary in a novel context.