What is Q-value in rock?
It expresses the quality of the rock mass in the so-called Q-value, on which are based design and support recommendations for underground excavations. A multiplication of the three terms results in the Q parameter, which can range between 0.001 for an exceptionally poor to 1000 for an exceptionally good rock mass.
What does rock mass rating mean?
RMR combines the most significant geologic parameters of influence and represents them with one overall comprehensive index of rock mass quality, which is used for the design and construction of excavations in rock, such as tunnels, mines, slopes, and foundations. …
What are the properties of rock mass?
Parameters for Rock Mass Classification Strength and deformability of intact rock. Rock Quality Designation (RQD) which considers the intensity of fracturing in a drill core. Rock fractures parameters (spacing, orientation, width, roughness, weathering, etc.) Groundwater pressure and flow.
How is rock mass rating calculated?
RQD is determined from rock cores or volumetric joint count; it is the percentage of rock cores in one meter of drill run. On the basis of RMR values for a given engineering structure, the rock mass is sorted into five classes: very good (RMR 100–81), good (80–61), fair (60–41), poor (40–21), and very poor (<20).
What is RMR value & Q-value and its difference?
Weakness zones are characterized differently in the three systems. In the RMR, no special parameter is used; the Q applies a classification based on composition and depth of the zone; in the RMi the size of the zone is used.
Why Q-system is appropriate in Nepal?
The Khimti 1 Hydropower Project (KHP) is the first project applying Q-system in Nepali Himalayan Rock. The method was found to be appropriate for drill and blast tunnels in jointed, fractured and sheared rock, which tend to overbreak.
What is Q-system in geology?
The Q-system is a classification system for rock masses with respect to stability of underground openings. Based on estimation of six rock mass parameters, a Q-value for a rock mass can be calculated. This value gives a description of the rock mass quality.
What are engineering properties of rock?
Common engineering properties typically obtained from laboratory tests include specific gravity, point load strength, compressive strength, tensile strength, shear strength, modulus, and durability. Rock mass properties are determined by visual examination and description of discontinuities within the rock mass.
What is engineering property of rock?
Engineering properties of rocks is a collective nomenclature which includes all such properties of rocks that are relevant to engineering application after their extraction from natural beds or without extraction i.e. insitu conditions.
What is RQD soil investigation?
Rock quality designation (RQD) is a standard technique in the mining industry for the qualitative and quantitative assessment of rock quality and degree of jointing, fracturing, and shearing in a rock mass.
What is rock quality designation explain in brief?
Rock-quality designation (RQD) is a rough measure of the degree of jointing or fracture in a rock mass, measured as a percentage of the drill core in lengths of 10 cm or more. High-quality rock has an RQD of more than 75%, low quality of less than 50%.
What is Q-system in rock Mechanics?
What is the rock mass quality q value?
(a) Rock Mass Number, N Rock Mass Number (N) is the rock mass quality Q value when SRF is set at 1 (i.e., normal condition, stress reduction is not considered). N can be computed as, N = (RQD/Jn) (Jr/Ja) (Jw)
What is rock mass properties and classifications (RQD)?
For tunnel boring machine and roadheader excavated tunnel, Hpfor Classes II to VI reduces 20-25%. Chapter 6 Rock Mass Properties and Classifications 4 6.1.4 Rock Quality Designation (RQD) (Deere 1964) Rock quality designation (RQD) was introduced in 1960s, as an attempt to quantify rock mass quality.
Does rock mass quality affect rock mass classification?
Rock mass classification systems, including RMR and Q, when developed, were intended to classify rock mass quality to arrive a suitable support design. The systems were not meant for the design of excavation methodology. In general, with increasing of rock mass quality, penetration decreases. However, very poor rock mass does not facilitate
What is rock mass rating (RMR)?
The rock mass rating (RMR) system is a rock mass quality classification developed by South African Council for Scientific and Industrial Research (CSIR), close associated with excavation for the mining industry (Bieniawski 1973). Originally, this geomechanics classification system incorporated eight parameters.