Geostatistical assessment of unconfined compressive strength of rocks in Northeast Jeddah, Saudi Arabia

The determination of rock strength holds paramount importance in the field of engineering geology. In this study, we conduct a comprehensive geostatistical evaluation of the unconfined compressive strength (UCS) within a 100 km2 area situated in northeast Jeddah, Saudi Arabia. The UCS values were indirectly estimated using an empirical equation based on the Schmidt hammer rebound method, resulting in a range of strengths from 9.2 to 198.4 MPa. The corresponding mean UCS values vary between 60.3 to 81.7 MPa, with standard deviations ranging from 18.6 to 45.3 MPa. The analysis revealed that, among the sites examined, a specific location exhibited the highest median UCS value of 72.2 MPa, while another site recorded the lowest value of 56.2 MPa. Based on the distribution of UCS values, the study area was classified into five distinct strength categories: very low, low, medium, high, and very high. Notably, the majority of variability in UCS values was confined within the middle 50% range, as evident from the interquartile range (IQR) below 30 MPa. Additionally, certain sites displayed a tighter cluster of UCS values, while an IQR of DEFJ≥60 indicated a more widespread distribution of strength values. Furthermore, two locations were identified as representing the minimum and maximum UCS values within a 95% confidence interval. The UCS in location A was estimated at 60.25±9.14 MPa, whereas in location B, it was 81.72±8.50 MPa. These findings offer valuable insights into the rock strength characteristics of the designated area, providing essential data for engineering and geotechnical applications.