Comparative Study of the Excavation Damage and Rockburst of the Deeply Buried Jinping II Diversion Tunnels Using a TBM and the Drilling-Blasting Method
Rockbursts occur sporadically in the surface layer of surrounding rock, generally affecting the depth of 0.1–0.3 m, which has little impact on the construction.
4–7
Medium rockburst (class II)
The phenomenon of surrounding rockbursts ejection is obvious, there is a bullet-like shooting clear burst sound with a certain duration, and the damage range is large with the general impact depth of 0.3–1 m, which has a certain impact on the construction.
2–4
Strong rockburst (class III)
Large bursts of surrounding rock occur, resulting in strong ejection with the phenomena of rock block catapulting and rock powder spraying and which lasts for a long time. The damage range and lumpiness are larger, generally affecting the depth of 1–3 meters, which has a great impact on the construction safety.
1–2
Extremely strong rockburst (class IV)
Rock burst occurred in the large area of the surrounding rock mass, and large rock brocks were ejected violently with strong vibration and crosstalk. The damage develops rapidly to the deep, which general influences more than 3 m, and even the whole tunnel is destroyed. This seriously affects the construction safety.
<1
Notes: is the rock mass strength/stress ratio, where is the saturated uniaxial compressive strength of rock mass and is the maximum stress in the surrounding rock mass.
