Rock joint spacing distribution analysis of granitic rocks in Hong Kong

Abstract

A study of rock joint spacing distribution analysis of granitic rocks in Hong Kong has been carried out so as to expand granitic rock database in Hong Kong. The objective of the study was to analyse the best-fit statistical models for representation of rock joint distribution of granites in Hong Kong with consolidation of results retrieved by Wong et al. (2018). The correlation of joint spacing and strength of granite in Hong Kong as well as the description of rock joint spacing in the current technical guideline (i.e. Geoguide 3, 2017 and Geoguide 4, 2018) published by the Geotechnical Engineering Office (GEO) have also been studied. The best-fit joint spacing models could provide not only the quantitative data of joint spacing analysis for future numerical modelling but also the mathematical description. The quantitative data could be beneficial for engineering design while the mathematical description could help the budget planning for tunnelling projects and provide prediction of boulder fall hazards in different locations in Hong Kong. Data has been obtained from rock joint mapping on five outcrops in Hong Kong and the paper of Wong et al. (2018). The data has been interpreted in relation to statistical approach with the use of Minitab 19 so as to obtain the best-fit statistical model for rock joint spacings of granites in Hong Kong. It is concluded that the rock joint spacings of granitic rocks in Hong Kong tends to follow 3-parameter Weibull distribution and exponential distribution based on the data collected from five selected outcrops in Hong Kong. With the consolidation of data retrieved from Wong et al. (2018), lognormal distribution was found to be the best-fit statistical model to represent the rock joint spacings of granitic rocks in Hong Kong.