3. A horizontal circular cavity with a diameter of 2R,=6m is excavated in the rock mass at a depth of 400m below the sur

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3 A Horizontal Circular Cavity With A Diameter Of 2r 6m Is Excavated In The Rock Mass At A Depth Of 400m Below The Sur 1 (44.4 KiB) Viewed 9 times

3. A horizontal circular cavity with a diameter of 2R,=6m is excavated in the rock mass at a depth of 400m below the surface. It is assumed that the natural stress of the rock mass is hydrostatic pressure state, and the natural density of the rock mass is p=2.7g/cm'. Please calculate: (20 points) (1) The redistributed stress on the wall and 2 times of the radius of the cavity (2) If the strength parameters of the surrounding rock are Cm = 0.4MPa, m = 30°, please discuss the stability of the cavity (3) If the cavity is not stable, please calculate the radius of the plastic ring (R1) = >