Development of a visualization model for detecting fractures in Kuala Lumpur limestone for geological engineering purposes

The major geotechnical engineering problems confronted constructions and structure designs on Kuala Lumpur Limestone bedrock in Kuala Lumpur are: cavities, sinkholes, pinnacles, excavation collapses and irregular surface of limestone bedrock. To address these problems, a set of techniques were developed for (1) automatically detecting regional geological structures, (2) detecting geological structure intersections (dissolution zones) and their associated extreme karst features, and (3) visualizing geological structures and their associated karst features. These techniques include geological prediction model, hydro-morphological model and moropho-visualization model. These techniques were applied to Kuala Lumpur Limestone bedrock in Malaysia, by focusing on the adjacent mountainous areas and the geometries of ex-opencast mining ponds, depressions, major rivers and soil moisture. These features were spatially correlated and clarified by rose diagrams and semivariogram models.Visualizations technique was developed by applying percentile stretching and Soble filter with 10% threshold and equalization enhancement to the calculated thematic maps. Several new geological fractures (faults, joints and bedding plains) were detected, mapped and visualized for the first time using the modified methods. Their orientations are dominantly found in NE-SW, NW-SE, WNW-ESE and E-W directions and correspond well with regional tectonic zones of the South East Asia. The study revealed that the ridge which reflect footwall of fault zone and valley which reflect fault plain represent 47% and 41% respectively. In Kuala Lumpur city centre, the areas having very high probability occurrence of geotechnical engineering problems show an area of 2.66 km² (5%), whereas the areas characterized by low susceptibility for the occurrence of natural hazard is approximately 19 km2 (36.2 %) of total Kuala Lumpur area. However, the high probability occurrence of geotechnical engineering problems class occupies 6.1 km² (11.7%), while the moderate natural hazard susceptibility class occupies 9.49 km² (18%) of the map, indicating the overall low and moderate natural hazard susceptible of the Kuala Lumpur city center. In Seri Serdang area, the predictor map shows that the sites distributed on buried ex-open pit mining ponds, swamps and extensions of geological fractures have high probability for the occurrence of environmental and geotechnical engineering problems. These sites are in Serdang Lama (east) and Seri Serdang (west) and occupy an area of about 2.6 km2, which is 42.7% of the Serdang areas (6.5 km2). Results obtained using the developed techniques were compared to those of subsurface geological fractures reported by means of geophysical survey and field investigation. Results demonstrated the effectiveness of the modified techniques combined with integration of geophysical survey and field survey in detecting and visualizing subsurface geological structures and karst features precisely over multiscale. The modified techniques may be useful for mapping geological fractures in areas of high soil moisture where geophysical survey is difficult and/or not available and is also highly applicable in other parts of Malaysia or south East Asia, permitting a better understanding of the geotectonics and geotechnical engineering setting of the study area.

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