To analysis the correlation between the ratio of breakdown pressure (Pb) to horizontal minimum compression stress (Sh) and stability of surrounding rocks. Attempt to use the ratio to estimate the stability of surrounding rocks. The elementary results indicate: the higher the ratio, the more stable the wall rock. When Pb/Sh ≥1.8,the stability of surrounding rocks was well. When Pb/Sh ≤1.50, hard rock is potential to happen rock burst, soft rock is easy to convergent distort. When 1.8>Pb/Sh >1.50, the wall rock was in the critical condition of distortion. On the basic theory of hydraulic fracturing stress measurement, the definition of breakdown pressure (Pb) and instantaneous shut-in pressure (Ps) is explicit. The value is correctable, reliable and easy to acquire. The ratio reflects the effect of stress, intensity of tension resistance to stability of surrounding rocks. The method based on measurement of in-situ rock stresses and engineering information feedback, the stability of surrounding rocks is estimated in the engineering survey or preliminary design stage. All those may provide the basis data for the projects design and construction.


The hydraulic fracturing technique was introduced by the oil industry in 1948 for the purpose of oilwell production stimulation. The theoretical study have been carried out using the assumptions that rock behavior as a homogeneous, isotropic, elastic, continuous medium and that fluid is impermeable into the well. After decades of theoretical and experimental research, it is currently effective and practical method in deep stress measured (Hubbert and Wills1957, Mizuta 1984, Cornet 1992,Haimson 1993, Li, 2003). In the high stress region of deep hard rock, the accumulation of very high elastic strain energy, resource exploitation and tunnel excavation process, the secondary stress field formation due to internal stress adjustments in rock mass, generated stress concentration near the tunnel wall.

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