# Estimating RMR Values for Underground Excavations in a Rock Mass

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## Abstract

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## 1. Introduction

## 2. Methodology

- for each RMR value observed at the current excavation face (n), RMR values are estimated for the next five advances (n + 1, ..., n + 5);
- with these RMR values recorded for subsequent advances, the sample mean and standard deviation are calculated;
- Results for each RMR value (n) at the face and for each of the following excavation advances (n + 1, ..., n + 5) are computed to assess all the inherent probability functions, assuming a normal distribution;
- for each of these probability functions, the probability of occurrence of each RMR value on a scale of 1–100 for subsequent advances (n + 1, ..., n + 5) is calculated; and,
- the resulting probabilities are presented as percentages in graphical form as a probability map of each RMR value of the current face (n) and the associated probabilities of all the RMR values occurring for the next advances (n + 1, ..., n + 5) are presented.

## 3. Case Studies

## 4. Results and Discussion

## 5. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 1.**Scheme of the methodology used (adapted from [21]).

**Figure 2.**Infographics of the six case studies superimposed on an image of the geological map of Portugal (1:1,000,000) (adapted from [30]).

**Figure 3.**Infographics of geological settings at AHVNII and AHVNIII (adapted from [33]).

**Figure 4.**Infographics of geological settings at Picote II (AHP) and Bemposta II (AHB) (adapted from [34]).

**Figure 5.**Infographics of the geological settings of Alqueva II (AHA) (adapted from [37]).

**Figure 6.**Infographics of the geological settings of Marão tunneling (TM) (adapted from [40]).

**Figure 7.**Distribution of rock mass rating (RMR) values observed in the six case studies: Kolmogorov-Smirnov and P-Plot tests.

**Figure 8.**RMR values observed in the following excavation advances considering the RMR value at the current excavation face (n): (

**a**) for the n + 1 excavation advance; (

**b**) for the n + 2 excavation advance; (

**c**) for the n + 3 excavation advance; (

**d**) for the n + 4 excavation advance; and, (

**e**) for the n + 5 excavation advance.

**Figure 9.**Probability of occurrence of RMR values on the following fronts according to that observed at the current face (n): (

**a**) for the n + 1 excavation advance; (

**b**) for the n + 2 excavation advance; (

**c**) for the n + 3 excavation advance; (

**d**) for the n + 4 excavation advance; and, (

**e**) for the n + 5 excavation advance.

Case Study | Rock Mass | Tunnel Length (m) | Cross Section Minimum–Maximum (m²) | Number of Recorded Excavation Advances |
---|---|---|---|---|

AHVNII | Granite | 5897 | 10–80 | 1127 |

AHVNIII | 7978 | 26–113 | 1896 | |

AHP | 1894 | 14.5–113 | 572 | |

AHB | Metasedimentary | 491 | 87–113 | 140 |

AHA | 811 | 37–71 | 247 | |

TM | 10,317 | 105 | 2330 | |

Total | 27,388 | 10–113 | 6312 |

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**MDPI and ACS Style**

Santos, V.; Da Silva, P.F.; Brito, M.G.
Estimating RMR Values for Underground Excavations in a Rock Mass. *Minerals* **2018**, *8*, 78.
https://doi.org/10.3390/min8030078

**AMA Style**

Santos V, Da Silva PF, Brito MG.
Estimating RMR Values for Underground Excavations in a Rock Mass. *Minerals*. 2018; 8(3):78.
https://doi.org/10.3390/min8030078

**Chicago/Turabian Style**

Santos, Vítor, Paula F. Da Silva, and M. Graça Brito.
2018. "Estimating RMR Values for Underground Excavations in a Rock Mass" *Minerals* 8, no. 3: 78.
https://doi.org/10.3390/min8030078