The paper reviews the history of the punch penetration test (PPT) as a laboratory method that is conducted on intact sample to measure the rock brittleness (BI). Further, the interaction of rock brittleness and penetration rate of tunnel boring machine (TBM) has been examined and some relationship was developed between the BI and TBM penetration. For this aim, four tunnel projects having various rock types were studied and then four different dataset is examined and discussed herein. It is stated that the test via BI can be perfectly utilized for assessing the boreability of rocks. In conclusion, it is found that there is a relationship between the BI and TBMs penetration with correlation coefficient (r) ranging from 0.34-0.81 for hard rocks condition; however this correlation is quite low (0.34) for weathered and very weak sedimentary rocks categorized as extremely low brittle. The obtained results can be accepted for hard rocks but it should be used with care for weathered weak rocks that does not show brittleness behavior under the indentor.
Rock brittleness is one of the most significant properties of rock having a major impact not only on the failure process of intact rock but also on the response of rock mass to rock excavation. In fact, the brittleness is a combination of rock properties including not only the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) but also density and porosity of rocks. Due to that, the brittleness should be examined very carefully for any excavation projects, i.e., mechanized excavation, drilling and blasting. The aim of this paper is to compare the strength-based brittleness indices with both the rock brittleness index (BIo), directly obtained via punch penetration test (PPT) and also estimated via Yagiz’s approach (BI1) as a function of strengths and density of rocks. For the aim, database including more than 45 tunnel cases are used to compute common rock brittleness indices (BI2, BI3, BI4), different combination of UCS and BTS. Further, these indices are compared with both BIo and BI1 as well as each other. It is found that the BIo and BI1 have a significant relations (ranging of determination coefficients (r2) from 0.69 to 0.88 with strength-based brittleness indices commonly used in practice. Also, based on findings, several rock brittleness classifications are also revised herein.
Raise boring machines (RBMs) are commonly utilized for drilling of shaft and other inclined structures in mining and civil applications. This paper aim to introduce several empirical equations to estimate the performance and operational parameters of RBMs. For the aim, datasets having rock properties including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), brittleness (BI), rock quality designation (RQD), elastic modules (E) and Poisson ratio (v); and also RBMs operational parameters including Instantaneous penetration rate (IPR), Specific Energy (SE), Pushing Force (Fpush), reamerhead power (Pw) and rotational speed (RPM), were established from published case studies. After that, re-established dataset was utilized to develop multiple regression models to predict the performance and operational parameters of RBM. It is found that IPR, SE, Fpush, Pw and RPM could be estimated using several alternative rock properties with coefficients of determination ranging from 0.77 to 0.95. Based on utilized dataset, it is also concluded that RQD and BI are the most common rock properties for estimating the performance and operational parameters of RBMs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.