The application of static expansion rock fracturing technology has shown that drilling holes with sharp corners significantly enhances the fracturing effect due to the pronounced stress concentration effect. Therefore

it is of great significance to study the directional fracturing mechanism of static rock fracturing using quadrilateral holes with multiple sharp corners and to propose criteria for quantitatively analyzing the fracturing effectiveness. To this end

soft rock specimens with varying fractured rock areas

numbers

and shapes of drill holes were designed to conduct static expansion tests. The fracture processes and dynamic fracture mechanics behaviors of the specimens were monitored and analyzed using particle image velocimetry (PIV) technology and strain rosettes. Secondly

to quantitatively assess the fracturing effectiveness of the specimens

dimensionless parameters such as the average energy utilization rate

fracture time efficiency ratio

stress ratio

and fracture area ratio coefficient were introduced. The fracture coefficient was proposed as a comprehensive evaluation criterion. The results indicate that each specimen developed two main cracks along the angular bisectors of the quadrilateral’s sharp corners. As the cracks propagated

the peak stress and total energy decreased sequentially

while the fracture time lagged. For single-hole fracturing

the stress concentration effect of trapezoidal holes was 13.75% higher than that of rhombic holes

resulting in a better fracturing effect. For dual-hole interaction fracturing

the stress concentration effect of rhombic holes was 16.67% higher than that of trapezoidal holes

and the stress decay was slower. Among the combinations

the square-rhombic hole configuration had the highest average energy utilization rate at 62.66%. The fracturing effectiveness of the rhombic-trapezoidal hole combination was not significantly improved

with a fracture coefficient only 6.67% higher than that of a single trapezoidal hole. The square-trapezoidal hole combination exhibited the best fracturing effect

with a fracture coefficient of 1.15.