护盾式TBM施工隧洞豆砾石吹填过程模拟研究

豆砾石吹填是TBM施工中非常重要的一道工序,研究吹填过程对分析填充层质量和优化吹填工艺具有一定的工程应用价值。借助PFC在离散体研究方面的优势对豆砾石吹入过程进行多方案模拟,并进行豆砾石的受力运动分析,探究填充层内豆砾石的分布特征及其影响因素。结果表明:依次吹填管片环中部80°、上部160°、顶部180°(补吹)吹填孔,填充层呈4段分布,其中0°~45°和75°~135°区间,粒径不同的颗粒分层分布严重,大颗粒分别靠近管片侧和围岩侧,45°~75°区间存在局部颗粒分层分布现象,135°~180°区间存在吹填不密实的问题;分层分布现象受吹入豆砾石颗粒的粒径组合、表面摩擦系数、所受压力大小等因素的影响;通过改变吹填孔位置和新增吹填孔,控制各孔的填充范围,进而降低颗粒在该范围填充完成前受到的压力,再采用阶梯吹填法吹填,能显著缩小分层分布区且使颗粒分布更为规整。吹填孔的填充范围应控制在45°内,但顶部吹填孔易发生堵塞,不宜用做大量颗粒吹填,因此具体部位吹填孔的填充范围需进一步研究。此研究成果可为工程吹填方案设计提供一定的参考。

Simulation Study on Pea Gravel Filling Process of Shield TBM Construction Tunnel

Pea gravel filling is a very important process in TBM construction. The study of filling process has a certain engineering application value for analyzing the quality of filling layer and optimizing the filling process. Based on the advantages of PFC in the study of discrete bodies, this paper carries out multi-scheme simulations of the pea gravel filling process and analyzes the forced movement of the pea gravel particles to explore the distribution characteristics and its influencing factors. The results show that: fill the middle, upper, and top (Supplementary) of the segment ring in sequence, and the filling layer is distributed in four sections, among which particles with different particle sizes in the range of 0°~45° and 75°~135° are seriously distributed in layers, large particles are close to the side of the tube segment and the side of the surrounding rock respectively. In the range of 45°~75°, there is a phenomenon of local particle stratification. In the range of 135°~180°, there is a problem of insufficient filling. The layered distribution is affected by the particle size combination, surface friction coefficient and squeezing force of the filling pea gravel particles. By changing the position of filling holes and adding filling holes, the filling range of each hole is controlled, thereby reducing the squeezing force of the particles before the filling of the range is completed. And then the step-filling method was used, which can significantly reduce the layered distribution area and make the particle distribution more regular. The filling range of the filling holes should be controlled within 45°, but the top holes of the filling layer are prone to blockage, which is not suitable for filling a large number of particles. Therefore, the filling range of the filling holes in specific locations needs further study. This research result can provide a certain reference for the design of filling scheme.