砂卵石地层盾构微扰动施工及掘进控制研究

Research on the Micro-disturbance Construction and Tunneling Parameters Control of Earth Pressure Balance Shield Machine in Sandy Cobble Stratum

研究目的:针对北京地铁8号线天桥~永定门外区间右线隧道试验段1~160环掘进施工,结合地层条件分析掘进参数和地表变形间的关系,并对土压平衡盾构微扰动施工控制进行初步探索,以期为砂卵石地层盾构隧道的设计与施工提供借鉴和参考。研究结论:(1)相对于粉质黏土与砂卵石组成的复合地层,盾构施工在砂卵石地层引起的沉降更大,对地层的扰动也更大;(2)盾构在砂卵石地层中掘进时,按照太沙基松动土压力理论计算得到的开挖面支护压力更加贴合现场实际情况;(3)千斤顶推进速度与螺旋机转速对于调节开挖面支护压力至关重要;(4)盾构在砂卵石地层中掘进所需的推力和扭矩要高于粉质黏土与砂卵石组成的复合地层中的相应值;(5)由于砂卵石土孔隙率较大,故需要及时调整注浆压力以保证注浆量,从而控制地表沉降;(6)对于砂卵石地层中的盾构施工,通过合理控制盾构掘进参数,可以较好地减小地表沉降和地层损失。

Research purposes: Combining with the construction of the 1 st to 160 th ring of the interval tunnel from Tianqiao station to Yongdingmenwai station of Beijing Metro Line 8,the relationship between the shield machine tunneling parameters and the surface deformation was studied based on the analysis of the ground geologic conditions,and the preliminary exploration was also carried out on the micro-disturbance construction control of the earth pressure balance shield machine,to provide reference for the design and construction of shield tunnel in sandy cobble stratum.Research conclusions:( 1) The settlement caused by tunneling in sand cobble layer is larger than that in other layers,and the disturbance to the stratum is also greater;( 2) When the shield tunnels in the sandy cobble layer,the support pressure on excavation face calculated according to the Terzaghi’ s loose earth pressure theory is more suitable for the actual situation on site;( 3) The pushing speed of jack and the rotation speed of screw are crucial to adjust the support pressure of excavation face;( 4) The jack thrust and cutterhead torque required for the shield tunneling in the sand cobble stratum is higher than the corresponding value in the composite stratum consisting of silty clay and sand cobble;( 5) Due to the large porosity of the sandy cobble soil,it is necessary to adjust the grouting pressure in time to ensure the of grouting amount and thus control the surface settlement;( 6) For the shield construction in sandy cobble stratum,ground surface settlement and stratum loss can be better reduced by reasonable controlling the shield tunneling parameters.