Effect Of Rock Mass Structure On Rockburst In Underground Engineering

Rockburst which has obvious dynamic characteristics is a geological disaster often take place in underground engineering.And rockburst also is a dynamic instability failure with a sudden release of energy.In recent years as the underground project continues towards deeper the phenomenon such as high ground stress and high osmotic pressure become more common,the increase of these phenomenon lead to the possibility of rockburst also rise,therefore the urge of rockburst research growing faster than ever before.Although problems such as mechanism of rockburst,ruckburst influencing factors,rockburst forecast,rockburst control have been well studies by scholars,the research which focus on the influence of structural plane on rockburst is short.This paper which base on the existing research results of domestic and foreign scholars on the structure-type rockburst use discrete element method to simulate the project of Qamchiq tunnel.The main research contents and conclusions are as follows:(1)This paper meant to discuss the influence of strike-dip structural surfaces on straight wall semicircle arch tunnel and circle tunnel under the condition of single group structural plane.Analysis the most danger area of tunnel and the dip of structural plane which most easily evoked rockburst.From the final simulation results:When the lateral pressure coefficient is greater than 1,the straight wall semicircle arch tunnel vault,circular tunnel vault and arch bottom is the place where most likely to happen rockburst;Under the condition of single group structural rockburst is mainly concentrated in the position where the angle of structural plane is steep,and when the angle of structural plane is gentle rockburst basically does not occur;The structural plane can also affect the failure mode of rockburst,the rock near the structural plane has a strong extrusion to structural plane which make the rock block between structural plane easily collapse and become strong rockburst after excacation unloading;Compare straight wall semicircle arch tunnel and circular tunnel,straight wall semicircle arch tunnel is more easily form rockburst when they affected by the same structure.(2)The spacing and location structural plane also have great impact on surrounding rockburst.This paper analysis how the change of spacing and location of structural plane effect the surrounding rockburst.Simulation results are as follows:The structural plane near the boundary of the excavation has the biggest influence on surrounding rockburst,with the increase of the distance from excavation boundary the influence of structural plane on surrounding rock stress state is gradually reduced;the structural plane more closer to the excavation boundary higher the stress around the tunnel would be;Except the distance between excavation boundary and structural plane the change of structural plane spacing also influence the fragmentation degree of surrounding rock,when the distance between structural plane and excavation boundary maintain the same,the higher structural plane spacing is the greater the stress state will get and the more energy surrounding rock will accumulate to induced rockburst.This paper focuses on the affect of structural plane on rockburst,analysis which kind of structural plane can easily trigger rockburst.The results of this paper will contribute to project location,rockburst forecast and rockburst control.