Year: 2026
Type: article
Abstract: Pre-excavation grouting in jointed rock masses depends partly on whether grout holes intersect hydraulically significant discontinuities at favourable angles, because poor geometric alignment may limit access to targeted joint set. In this study, this geometric compatibility is described by hit rate, with higher values representing more favourable borehole–joint intersection angles. Existing CAD-based assessments require manual construction and measurement of borehole–joint geometry, making repeated evaluation of multiple boreholes and joint sets less practical. This study therefore develops and assesses an explicit vector-based workflow for calculating hit rate. Tunnel alignment, borehole-fan geometry, and joint-set orientation are represented in a common three-dimensional coordinate system, enabling direct calculation from borehole direction vectors and joint-plane normal vectors. The workflow is applied to the Haga Station section of the West Link railway tunnel and evaluated against CAD-based results. It reproduces the spatial distribution of reported hit rates for Joint Set 1 (SG-1) and identifies similar favourable and unfavourable sectors, although moderate differences remain in magnitude. Application to Joint Set 2 (SG-2) and Joint Set 3 (SG-3) shows that joint-set orientation strongly influences hit-rate magnitude and spatial distribution. In a reorientation scenario targeting SG-1, selected boreholes were redirected, increasing hit rate by up to 12 percentage points. Incorporating borehole length and representative joint spacing also enables estimation of the expected number of borehole–joint intersections. The proposed method provides a transparent and reproducible framework for screening grouting fans, comparing alternative borehole directions, and assessing multiple joint-set orientations without repeated manual construction of three-dimensional CAD models.
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,290
OpenAlex ID: W7170090495