A free, simple Q-system rock mass classification calculator for evaluating underground excavation stability in jointed rock masses.
Download a CSV template with the required data format
The Q-value is calculated using the following equation:
Q = (RQD/Jn) × (Jr/Ja) × (Jw/SRF)
RQD = Rock Quality Designation
Jn = Joint Set Number
Jr = Joint Roughness Number
Ja = Joint Alteration Number
Jw = Joint Water Reduction Factor
SRF = Stress Reduction Factor
Represents the block size and degree of jointing
Represents the shear strength of joints
Represents the active stress environment
The Q-system is a widely recognised method for classifying the stability of underground excavations in jointed rock masses. It distils a handful of geotechnical parameters—such as joint set count, roughness, and water inflow—into a single Q-value that captures the overall quality of the rock mass. A higher Q-value points to more stable rock conditions, while a lower Q-value flags areas that might need extra support or design adjustments.
The Q-system suits everything from tunnelling to building caverns, helping you quickly get a grip on rock quality and make decisions on support. Whether you're designing a new excavation or keeping tabs on changing ground conditions in an active project, the Q-system streamlines a lot of technical data into one straightforward metric. This lets engineers, geologists, and planners compare sites, monitor developments over time, and stay one step ahead of any stability issues.
Our free Q-system calculator brings all this to your screen with just a few clicks. Input some basic rock mass details—like joint spacing and groundwater conditions—and the tool does the maths. You'll get a clear Q-value that reflects how strong or weak the rock mass might be, along with insights on what that means for reinforcement or excavation design. It's an ideal tool if you want practical, no-fuss evaluations without burying yourself in complex software or manual calculations.
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