Characteristics and Calculation Method of Impact Load in Rockburst Tunnel
The hard and brittle surrounding rock in tunnels is prone to rockburst under high ground stress conditions.Currently,the support structure design for rockburst tunnels in China mainly adopts the engineering analogy method.In order to quantify the impact load of the rockburst on the support structure,the energy conversion relationship during the rockburst process was analyzed from an energy perspective.Then,the kinetic energy theorem and energy conservation principle were used to calculate the impact load.Combined with the loose pressure of the tunnel,a load calculation method for rockburst in tunnels was proposed.At the same time,the influence of different factors such as tunnel diameter on the range of rockburst action was explored.Finally,the rationality was verified based on the rockburst section of a high ground stress tunnel.The research results indicate that the dynamic load factor in the formula for rockburst impact load is positively correlated with the structural stiffness used for tunnel support.Under the same span and ground stress conditions,the rockburst depth of a circular tunnel is smaller than that of a horseshoe tunnel,and the lateral range of the rockburst is larger than that of a horseshoe tunnel.Under the same tunnel shape and ground stress conditions,as the tunnel span increases,the depth and lateral range of the rockburst also increase.Under the same tunnel shape and span conditions,a higher ground stress value indicates a greater depth and lateral range of the rockburst.The rockburst load of Grade Ⅱ surrounding rock in a single-track tunnel ranges from 12.02 kPa to 337.75 kPa,and that of Grade Ⅲ surrounding rock in a single-track tunnel ranges from 25.36 kPa to 352.12 kPa.Moreover,the rockburst load of Grade Ⅱ surrounding rock in a double-track tunnel ranges from 8.54 kPa to 288.55 kPa,and that of Grade Ⅲ surrounding rock in a double-track tunnel ranges from 33.11 kPa to 300.83 kPa.
high ground stressrockburst tunnelenergy methodimpact load
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