全长黏结岩石抗浮锚杆承载性能现场试验

抗浮锚杆具有地层适应能力强、锚固力高、造价低、工期短等优点,具有广阔的工程应用前景.开展了4组13根岩石抗浮锚杆的极限抗拔承载试验,在1根试验锚杆上安装光纤光栅应变传感器进行应力测试,所有试验锚杆均加载至极限破坏状态,从荷载-锚固体顶面位移曲线、锚筋轴力分布、锚筋剪应力分布规律及界面黏结强度等方面进行了分析.结果表明,抗浮锚杆主要出现锚筋-锚固体界面剪切滑移破坏、锚固体-周围岩体界面剪切滑移破坏及锚筋拔断3种破坏形态.试验条件下,黏结长度为2.0 m的抗浮锚杆其极限抗拔承载力为240 kN,黏结长度不小于3.0 m的抗浮锚杆其极限抗拔承载力不低于320 kN,承载力高、变形小,能够满足抗浮要求.锚筋轴力自上而下逐渐衰减,锚筋在距锚固体顶面3.0 m以下范围内不受力,建议中风化花岗岩中抗浮锚杆的黏结长度设计值取3.5～4.0 m.锚筋剪应力沿深度呈先增大后减小的趋势,在距锚固体顶面0.45 m的位置达到峰值,约为2.7 MPa.锚筋-锚固体界面平均黏结强度为1.14～1.36 MPa,锚固体-岩土体界面平均黏结强度为0.28～0.37 MPa.

Field testing study on bearing behavior of full-length bonding anti-floating anchor in rocks

Anti-floating anchors have a broad engineering application prospect, due to their excellent properties including good stratum adaption, high anchorage force, low energy consumption, and short construction period. Four sets of ultimate tensile load experiment for thirteen rock anti-floating anchors were conducted. One of the anchors was installed fiber grating strain sensors in order to monitor the anchor stress, and all of the anchors were loaded until the failure status. The aspects of load-anchor head displacement curve, axial and shear stress distribution of anchor rod, and interface bonding strength were analyzed. The experimental results show that there are three types of failure modes of test anchor, i.e. the shear-slip failure at the rod-anchorage body interface, the shear-slip failure at the anchorage body-surrounding rock interface, and the fracture failure of the anchor rod. Under the experiment conditions, the ultimate tensile load of the anti-floating anchors with a 2.0 m bonding length is 240 kN, and the ultimate load of the anchors with the bonding length exceeded 3.0 m is more than 320 kN. The properties of the experimental anchor including high bearing capacity and small deformation meet the engineering requirements. The axial force of the anchor rods reduces from the anchor head to anchor bottom, and the anchor rods bear tiny force after reaching the depth of three meters. Hence, the suggesting design value of the bonding length of anti-floating anchors embedded in moderately weathered granite is from 3.5 m to 4.0 m. The rod shear stress presents a trend of increasing firstly and then decreasing, the position of the maximum shear stress is located at the depth of 0.45 m and its value is approximate 2.7 MPa. In addition, the average bonding strengths of the rod-anchorage body interface and anchorage body-surrounding soil interface are 1.14-1.36 MPa and 0.28-0.37 MPa, respectively.