Determination of the deformation modulus of dispersible-intercalated-jointed cherts using the Menard pressuremeter test

• We examine the deformation modulus (EMPT) of the dispersible cherts with pressuremeter test (MPT).
• We examine the EMPT of the cherts with geomechanical quality (UCS, basic RMR and GSI).
• The equations derived to estimate EMPT of the cherts yielded high coefficients of correlation.
• Due to the recommendations in the literature, dependency of EMPT to confining stress (P0) examined.
• Clear correlations were detected between the EMPT and the P0.

Due to the difficulties encountered during the preparation of representative cores from fragile/intercalated/weathered/jointed rock masses for laboratory-scale testing, various in-situ test methods, such as pressuremeter, dilatometer, plate loading, plate jacking, Goodman jacking, flat jack, cable jacking tests, etc., have been developed for determining the deformation modulus of rock masses. However, almost all of these in-situ tests require time-consuming procedures, have operational difficulties, and have high costs. Therefore, rock mass classification systems and empirical equations have been developed for estimation of parameters such as the deformation modulus. In this study, dispersible, fragile, intercalated and heavily jointed chert rock mass, supporting several large-scale structures under construction in Manisa (Turkey), was classified based on RMR, GSI, and UCS as input parameters for estimation of deformation modulus using some of well-known empirical equations. Three chert rock masses with different geomechanical qualities were identified. Point load tests were performed to determine the UCS of the cherts to characterize the rock masses. The deformation modulus obtained from the Menard pressuremeter tests was compared to the modulus estimated using empirical equations. In addition, an attempt also was made to examine the dependency of the deformation modulus of the studied chert rock masses to the confining stress. Empirical relationships and equations with high correlation were obtained for predicting the deformation modulus by using input parameters such as RMR, GSI, UCS, and confining stress.