ROCKBURST RISK CONTROL FOR LARGE DIAMETER TBM BORING IN HIGH GEOSTRESS REGION

Water diversion tunnels #1 and #3 of Jinping II hydropower station are bored by tunnel boring machine(TBM).The rockburst risk is high in the middle alignment.For the purpose of establishing reasonable boring scheme and rockburst control measurement,based on previous researches,different numerical methods are used to evaluate different pilot boring schemes effects on reducing the rockburst risk,combining with actual situation.All these three pilot boring schemes can obviously reduce the rockburst risk.The selection of pilot boring schemes depends on the equipment and economic benefit factors.So,rockburst risk control measurements for large diameter TBM boring in high stress region are proposed.During TBM boring,the measurements of pilot,stress relieving blasting,assisting timely,systemic and high quality support are applied to reduce rockburst risk and ensure construction and structure safety.