# New Method to Estimate Rock Mass Deformation Modulus Based on BQ System
###### Abstract  
The rock mass deformation modulus is one of the most important design parameters in a range of rock engineering applications. Its value is usually obtained directly through in situ testing or estimated indirectly on the basis of a rock mass quality classification system. Because in situ testing is generally costly, time-consuming, and presents operational difficulties, it cannot be carried out extensively, and many researchers have concentrated on developing indirect procedures to obtain information on the modulus of deformation, such as the RMR method, Q method, and GSI method. The purpose of this paper is to present a new system for estimating the rock mass deformation modulus called the BQ method, which is based on the BQ (basic quality) system. In this paper, the BQ system is first briefly reviewed, and then more than 60 in situ measurements from three large hydropower stations in China are used to develop a new relationship between BQ and the deformation modulus, based on a power function relationship. The paper also derives correlations based on the existing estimation formula and the relationship between BQ and other classification schemes, resulting in several recommended formulas for estimating the deformation modulus of a rock mass using the BQ method.  
deformation modulus; the BQ system; rock mass engineering classification 2024202420242024202420242  
certain point, so many researchers and geological engineers have tended towards the use of empirical methods to provide information on the modulus of deformation.  
Empirical estimation is performed using a variety of methods, most of which establish a correlation between various rock mass classifications or a single geological index and the deformation modulus [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13]. These correlations are useful for practical applications. Importantly, these rock mass classifications and geological indicators are readily available in the field.  
Among the commonly used rock mass quality grading systems, the RMR and Q systems are mainly used in underground engineering. The BQ (basic quality) system is the Chinese standard for engineering classification of rock masses [14] and is applicable in various rock engineering operations. Similar to the RMR method, this system classifies rock mass quality through two steps. Firstly, the basic quality of the rock mass is assessed using the geological index of uniaxial compressive strength (UCS) and the rock intactness index (K\({}_{\rm v}\)). Both of these are quantitative indexes that can be obtained through laboratory or in situ testing, thus reducing the influence of subjective factors relating to the geological engineer. Secondly, the final rating for the rock mass is obtained by adjusting this value considering the groundwater, ground stress, and discontinuities according to different rock engineering operations, for example, a dam foundation, slope, or tunnel. This paper first introduces the BQ method, and then proposes a new relationship between the BQ method and the deformation modulus of rock masses based on data from in situ measurements from three large hydropower stations in China.