全断面细砂地层暗挖隧道施工存在塌方失稳的工程风险。本研究通过开展室内试验、现场原位浆液渗透注浆加固试验和现场原位注浆开挖试验,对改性水玻璃浆液在细砂层内部的扩散特征、固砂性能及隧道开挖稳定性开展了一系列工作。结果表明:当改性水玻璃浆液凝结时间控制在1~4 h时,可有效改善低应力条件下粉细砂的抗剪强度,无侧限抗压强度可达到140~170 kPa;在0.3~0.5 MPa注浆压力作用下,改性水玻璃浆液在小导管周边形成了60~80 cm厚的固砂体,有效抑制了砂层塌落,为暗挖隧道的稳定开挖提供保障,现场实测地表变形量控制在25 mm以内; 细砂层暗挖隧道超前小导管布孔间距控制在30~50 cm以内,改性水玻璃浆液合理配比宜通过室内试验初选、现场浆液渗透注浆加固试验验证和现场开挖效果反馈等多种手段进行综合确定。
In the fine sand layer, frequent loosening and falling accidents occur during the construction of bored tunnels. A series of research work was carried out on diffusion characteristics, sand fixation performance, and tunnel excavation stability of modified water glass slurry inside the fine sand layer through indoor experiments, field infiltration grouting reinforcement experiments, and field grouting excavation experiments. The results indicated that: When the setting time of modified water glass slurry is controlled within 1~4 hours, it can effectively improve the shear strength of fine sand under low-stress conditions, and the unconfined compressive strength can reach 140~170 kPa. At a grouting pressure of 0.3~0.5 MPa, the modified water glass slurry formed a 60~80 cm thick sand consolidation body around the small conduit. This successfully suppressed the loosening and falling of the fine sand layer and provided a stable environment for bored tunnel excavation. The spacing between advanced ductile in the fine sand layer underground tunnel excavation should be controlled within 30~50 cm. The reasonable ratio of modified water glass slurry should be determined comprehensively through various methods such as indoor test selection, field slurry penetration grouting reinforcement test verification, and field excavation effect feedback.
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