漂卵石隧道自进式中空注浆锚杆力学性能测试分析

Field Test and Analysis of Mechanical Behaviors of the Self-drilling Hollow Grouting Anchor Bolt for the Tunnel in Sandy Pebble Stratum

  • 摘要: 为研究锚杆在漂卵石隧道中的支护效果,文章依托西藏某漂卵石隧道工程对锚杆进行了打入试验与拉拔试验。试验结果表明,原设计?25锚杆平均打入深度只有 1.50 m,为设计长度的 42.7%,打入到极限深度时发生扭转破坏或发生空转而无法继续钻进;原设计?51不带钻头锚杆的平均打入深度只有 1.15 m,为设计长度的 38.3%,均以无法继续钻进而终止;不带钻头的情况下?25锚杆打入深度较带钻头锚杆打入深度提高 23.1%,?51锚杆打入深度较带钻头锚杆打入深度提高 95.2%;?25锚杆拉拔力平均值接近设计值 50 kN,但却无法发挥锚固作用。依据锚杆测试结果,确定了 4项施工支护优化措施,包括:(1)取消系统锚杆,减小围岩扰动;(2)取消锚杆钻头,改为直接打入;(3)将锁脚锚杆由1组调整为2组,保证总体支撑深度;(4)超前锚杆由2.5 m长的?51锚杆调整为1.8 m长的?25锚杆。监测结果显示,方案调整后隧道收敛变形小幅增加,拱顶沉降明显减小,隧道施工速度明显加快,整体安全性得到提高。

     

    Abstract: In order to study the support effect of self-drilling hollow anchor bolt in sandy pebble stratum, a drilling test and pullout test were conducted based on a tunnel in sandy pebble stratum of Tibet. The tests show that the average drilling depth of ?25 anchor bolt is 1.50 m which is 42.7% of the designed length, torsion failure or idling occurs when it reaches the limit depth and drilling can′ t go further; the average drilling depth of ?51 bolt without drill bit is 1.15 m which is 38.3% of the designed length, and continuous drilling can′ t be fulfilled; the average drilling depth of ?25 anchor bolt increases by 23.1% when the drill bit is removed and the average drilling depth of ?51 bolt increases by 95.2% when the drill bit is removed; the average pullout force of ?25 bolt is close to the designed value of 50 kN, but the anchoring effect doesn′ t work. 4 optimization measures for construction support were determined based on the test results of anchor bolts, specifically systematic bolts is eliminated to reduce disturbance of sur? rounding rock; the drill bit is removed and the anchor bolt is drilled directly; the group number of feet-lock bolt is increased from 1 to 2 to ensure total support length; the ?25 advanced anchor bolt with a length of 1.8 m is selected instead of the ?51 anchor bolt with a length of 2.5 m. The monitoring data show that convergence deformation of the tunnel increases slightly after scheme adjustment while the crown settlement decreases obviously, the tunnel construction speed increases significantly and the safety is quite improved.

     

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