Automatic Mapping of Discontinuity Persistence on Rock Masses Using 3D Point Clouds

Finding new ways to quantify discontinuity persistence values in rock masses in an automatic or semi-automatic manner is a considerable challenge, as an alternative to the use of traditional methods based on measuring patches or traces with tapes. Remote sensing techniques potentially provide new ways of analysing visible data from the rock mass. This work presents a methodology for the automatic mapping of discontinuity persistence on rock masses, using 3D point clouds. The method proposed herein starts by clustering points that belong to patches of a given discontinuity. Coplanar clusters are then merged into a single group of points. Persistence is measured in the directions of the dip and strike for each coplanar set of points, resulting in the extraction of the length of the maximum chord and the area of the convex hull. The proposed approach is implemented in a graphic interface with open source software. Three case studies are utilized to illustrate the methodology: (1) small-scale laboratory setup consisting of a regular distribution of cubes with similar dimensions, (2) more complex geometry consisting of a real rock mass surface in an excavated cavern and (3) slope with persistent sub-vertical discontinuities. Results presented good agreement with field measurements, validating the methodology. Complexities and difficulties related to the method (e.g. natural discontinuity waviness) are reported and discussed. An assessment on the applicability of the method to the 3D point cloud is also presented. Utilization of remote sensing data for a more objective characterization of the persistence of planar discontinuities affecting rock masses is highlighted herein

Students and teacher responses to a unit of student-designed games

Background: Despite the support in primary education that student-designed games enhance student contextualisation of skills and tactics, there has been little support in secondary education, nor any empirical research exploring these claims. This paper attempts to rekindle these beliefs and explores the use of student-designed games in an English secondary school. Aim: To provide a detailed account of classes of secondary students designing their own games, and to investigate their responses to the games-making process. Method: Two classes of boys (aged 14–16) at a school in England participated in the study. Each class was divided into three teacher-selected teams and attended one lesson per week, each lasting 40 minutes, for seven weeks. Lessons were adapted to give students four phases of development: a 2-week library-based planning and wiki construction phase; a 1-week outdoor modification and wiki update phase; three weeks of trials of the games with a wiki refinement phase; and a 1-week game and wiki finalization phase. In this time frame the pupils involved were challenged to design an invasion game that would be played in a subsequent unit. Data consisted of: teacher post-teaching reflections, interviews between a professor-researcher and the on-site participants, observations and analysis of wikis. Data analysis occurred on three levels. The first aspect was immediate and ongoing by the teacher-researcher to meet the ‘on the spot’ learning needs of his students. Secondly, the professor-researcher aided the teacher-researcher in systematic collection, organisation and analyses. Thirdly, peer debriefing occurred in which the research team analysed and critiqued the data during the collection and writing processes. Results: We found that students ‘bought into’ the process of games-making, were afforded an inclusive voice and worked as teams. Furthermore they engaged in immediate searches for innovation which were influenced by popular media, and shared ideas and learning with others to a degree that allowed them to exclude problematic skills. However, there was student frustration induced by watching others failing to properly play these games. Conclusions: We concluded that student-designed games ‘freed’ children to define competition at their own developmental level. This paper shows that by trusting pupils and supporting them to be creative in the games that they play it is possible to gain an insight into the processes by which students apply their knowledge about physical education