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Overcoring method is used to determine in-situ stresses from a rock sample extracted from shallow depths, and released to expand freely. This method involves a sequence of steps illustrated in [[:File:GeoWikiWriteOff2021-Tayyib-Figure14.png|Figure 14]]. The process of cutting the hollow cylindrical rock, using the tool shown in figure 15, is called overcoring and the resulting change in shape is measured using a device called stressmeter. In general, the maximum expansion of the rock sample occurs in the direction of the maximum horizontal stress (σH).

Overcoring method is used to determine in-situ stresses from a rock sample extracted from shallow depths, and released to expand freely. This method involves a sequence of steps illustrated in [[:File:GeoWikiWriteOff2021-Tayyib-Figure14.png|Figure 14]]. The process of cutting the hollow cylindrical rock, using the tool shown in figure 15, is called overcoring and the resulting change in shape is measured using a device called stressmeter. In general, the maximum expansion of the rock sample occurs in the direction of the maximum horizontal stress (σH).

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File:GeoWikiWriteOff2021-Tayyib-Figure14.png|{{Figure number|14}}The sequence of overcoring method: (a) Drilling a large diameter hole. (b) Drilling a smaller pilot hole. (c) Placing the measuring device in the smaller hole. (d) Drilling the large diameter hole is resumed and the measuring device is overcored. (from Guo et al., 2013) [10]

File:GeoWikiWriteOff2021-Tayyib-Figure14.png|{{Figure number|14}}The sequence of overcoring method: (a) Drilling a large diameter hole. (b) Drilling a smaller pilot hole. (c) Placing the measuring device in the smaller hole. (d) Drilling the large diameter hole is resumed and the measuring device is overcored. (from Guo et al.<ref>Guo, Q., F. Ren, H.  Guo, L. Zhao, and Z. Yan, 2013, Strain sensors with temperature compensation employed for in situ stress monitor: TELKOMNIKA Indonesian Journal of Electrical Engineering, vol. 11, no. 11, p. 6296-6303.</ref>).

File:GeoWikiWriteOff2021-Tayyib-Figure15.png|{{Figure number|15}}Overcoring tool (from Hudson, 2003) [11]

File:GeoWikiWriteOff2021-Tayyib-Figure15.png|{{Figure number|15}}Overcoring tool (from Hudson<ref>Hudson, J., 2003, Strategy and tactics for rock stress estimation, ''in'' K. Sugawara, Y. Obara, and A. Sato, eds., Rock stress '03: Proceedings of the Second International Symposium on Rock Stress, Kumamoto, Japan, November 4-6, 2003, p. 3-21.</ref>).

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10 Guo, Q., Ren, F., Guo, H., Zhao, L., & Yan, Z. (2013). Strain sensors with temperature compensation employed for insitu stress monitor. TELKOMNIKA Indonesian Journal of Electrical Engineering, v. 11 no. 11 6296-6303. doi:10.11591/telkomnika.v11i11.2948.

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11 Hudson, J ,2003, Strategy and tactics for rock stress estimation. In: Sugawara, K., Obara, Y., & Sato, A. (Ed.). Rock stress '03: Proceedings of the Second International Symposium on Rock Stress Kumamoto, Japan,4-6 November 2003. (pp.3-21). AA Balkema Publishers. https://doi.org/10.1201/978100307889

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12 Kanduth, H., Corthesy, R., & Gill, D., 1991, Validation of borehole slotting as a method for, in situ stress measurements. Paper presented at the 7th ISRM Congress, Aachen, Germany, September 1991.

12 Kanduth, H., Corthesy, R., & Gill, D., 1991, Validation of borehole slotting as a method for, in situ stress measurements. Paper presented at the 7th ISRM Congress, Aachen, Germany, September 1991.