For hard rocks as granite, rock mass class is mostly associated with discontinuities.

花岗岩这样的硬质岩石，其岩体质量与结构面关系极为密切。

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The test and popularization results of the method of putting in stalk through pulling apart core by Using the long core barrel in Sichuan hard rocks are simply presented in this article.

本文简要介绍了拨断岩心接单根方法在四川硬地层长筒取心中的试验和推广效果。

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Studying the variety laws of the plastic failure, distortion and stress of soft and hard rocks alternate-layered roof with the constant vertical stress only the horizontal stress changing.

在垂直应力不变，不断改变水平应力的条件下，分析各类软硬岩互层项板的应力、变形、破坏规律。

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Hydraulic fracturing, also known as fracking, involves drilling down and creating tiny explosions to crack the hard shale rocks to release the gas inside.

BBC: Drilling for gas

Hydraulic fracturing or "fracking" is a process of forcing water mixed with chemicals through deep wells to shatter and crack hard shale rocks to release the gas inside.

BBC: Hydraulic fracturing

That leaves Turkey trapped between rocks and hard places, belonging fully to neither.

FORBES: Turkey, Between Rocks and Hard Places