The Q system is a widely used rock mass classification system that was developed by Barton, Lien, and Lunde in 1974. The Q system is based on a quantitative assessment of the rock mass quality and is widely used in rock engineering projects such as tunneling, mining, and slope stability analysis.

The Q system is based on six parameters that describe the quality of the rock mass. These parameters are:

RQD (Rock Quality Designation): This parameter describes the degree of intactness of the rock mass. It is expressed as a percentage of the drilled core length that is recovered in pieces longer than 100 mm.

Jn (Joint set number): This parameter describes the number of joint sets present in the rock mass.

Jr (Joint roughness coefficient): This parameter describes the roughness of the joints in the rock mass.

Ja (Joint alteration factor): This parameter describes the degree of alteration of the joints in the rock mass.

SRF (Stress reduction factor): This parameter describes the degree to which the rock mass has been subjected to stress changes.

GSI (Geological Strength Index): This parameter is a qualitative estimate of the rock mass strength based on its lithology, structure, and degree of weathering.

Each of these parameters is assigned a weighting factor based on its relative importance to the overall quality of the rock mass. The Q value is then calculated by summing the weighted values of each parameter.

The Q system has been widely used in rock engineering projects to assess the quality of the rock mass and to design appropriate support systems. The system has been adapted and modified for specific applications, and several variants of the Q system have been developed over the years. Despite its limitations, the Q system remains a valuable tool for rock mass classification and engineering design.

The Q system is a rock mass classification system that was developed by Swedish engineer and geologist Johan Gunnar Qvist in the 1960s. The system is used to evaluate the stability of rock slopes and underground excavations in mining, civil engineering, and other industries. The Q system takes into account various factors that affect the strength and behavior of rock masses, such as geological structure, rock quality, joint spacing and orientation, groundwater conditions, and stress distribution. The Q system assigns a numerical value (Q-value) to a rock mass based on its characteristics, which can range from 0 to 100. The higher the Q-value, the more stable the rock mass is considered to be. The Q system uses six parameters to calculate the Q-value: 1. RQD (Rock Quality Designation): This parameter measures the continuity of intact rock pieces in a core sample. The higher the RQD value, the better the quality of the rock. 2. Jn (Joint Set Number): This parameter measures the number of joint sets in a rock mass. Joint sets are planes of weakness that can affect the stability of a slope or excavation. 3. Jr (Joint Roughness): This parameter measures the roughness of joint surfaces in a rock mass. Rougher surfaces provide better frictional resistance and increase stability. 4. Ja (Joint Alteration): This parameter measures the degree of weathering or alteration of joint surfaces in a rock mass. More altered joints are weaker and reduce stability. 5. SRF (Stress Reduction Factor): This parameter measures how much stress relief occurs when a rock mass is excavated. Excavation can cause stress redistribution that affects stability. 6. GSI (Geological Strength Index): This parameter combines all the above factors into a single index that reflects the overall strength of a rock mass.