涨壳式预应力中空锚杆支护效果及注浆工艺改进研究

为了研究涨壳式预应力中空锚杆对深埋隧道的支护效果,并对现有注浆工艺提出改进措施,依托中兰铁路香山隧道工程,采用有限差分数值分析软件FLAC3D,对比分析了普通砂浆锚杆和涨壳式预应力中空锚杆支护作用下的隧道围岩变形及应力状态变化情况; 开展现场锚固试验研究,分析了锚杆长度和注浆体龄期对锚杆锚固效果的影响; 进行现场注浆试验研究,分析了注浆方式和注浆压力对涨壳式预应力中空锚杆注浆密实度的影响,并对现有注浆工艺提出了改进措施。结果表明:与普通砂浆锚杆相比,涨壳式预应力中空锚杆控制围岩变形、改善围岩应力状态等的效果更佳,其中围岩变形可减小约40%; 相比于锚固长度,注浆体养护龄期对涨壳式预应力中空锚杆的支护效果影响更为显著,当养护龄期为28 d时,支护效果可提升50.12%; 采用中空杆体内注浆方式时,注浆压力需大于0.8 MPa方可达到最佳效果,且该注浆方式适用于涨壳式预应力中空锚杆水平或向下安装; 采用中空杆体外注浆方式时,宜采用更大的注浆压力,且该注浆方式适用于锚杆向上安装; 改进后的锚杆注浆口可以有效防止漏浆,保证了注浆的密实度,对保护锚杆和加强锚杆与地层联结均有积极作用。

Study on supporting effect of expansion-shell pre-stressed hollow anchor and improvement of grouting technology

In order to study the supporting effect of expansion-shell pre-stressed hollow anchor on deep-buried tunnels and put forward improvement measures for the existing grouting technology, based on the Xiangshan Tunnel project of Zhongwei-Lanzhou Railway, the finite difference numerical analysis software FLAC3D was used to compare and analyze the deformation and stress state of tunnel surrounding rock under the support of ordinary mortar anchor and expansion-shell pre-stressed hollow anchor. The influence of anchor length and grouting age on the anchoring effect was analyzed by field anchoring test. Based on the field grouting test, the influence of grouting method and grouting pressure on the grouting compactness of expansion-shell pre-stressed hollow anchor was analyzed, and the improvement measures for the existing grouting technology were put forward. The results show that compared with the ordinary mortar anchor, the expansion-shell pre-stressed hollow anchor has better effect on controlling the deformation and stress state of the surrounding rock, and the deformation of surrounding rock can be reduced by about 40%. Compared with the anchorage length, the curing age of grouting has a more significant effect on the supporting effect of expansion-shell pre-stressed hollow anchor. When the curing age is 28 d, the supporting effect can be improved by 50.12%. When the internal grouting of anchor is adopted, the grouting pressure needs to be greater than 0.8 MPa to achieve the best effect, and the grouting method is suitable for the horizontal and downward installation of the expansion-shell pre-stressed hollow anchor. When the external grouting of anchor is adopted, the greater grouting pressure should be adopted, and the grouting method is suitable for the upward installation of the anchor. The improved grouting port of anchor can effectively prevent slurry leakage and ensure the compactness of grouting, which plays a positive role in protecting anchor and strengthening the connection between anchor and stratum.