扩体锚杆承载特性的模型试验研究

Model Test Research on Bearing Capacity of Underreamed Ground Anchor

面对许多规模宏大、技术难度与风险程度高的岩土工程,与普通土层锚杆相比,扩体锚杆能够提供更大的承载能力并解决复杂工程问题。利用自行研制的自动化锚杆载荷仪,分别进行了拉力型与压力型扩体锚杆竖向力室内模型试验。试验结果表明,模型锚杆的破坏基本呈锥形,扩体段直径对破坏圆锥体的直径和极限承载力影响较大,扩体段长度对破坏锥体的直径和极限承载力影响较小,随扩体段直径的增大,模型锚杆的极限承载力增大幅度逐渐减缓,单位横截面积荷载提高比由正变负,随扩体段长度的增大,单位侧周面积荷载与单位扩体长度荷载提高比均为负值。两类锚杆的Q-s滞回曲线呈抛物线状,在相同对比条件下的弹性变形曲线十分相似,塑性变形曲线也基本一致,压力型扩体锚杆能更快的提供约束荷载。在工程实践中,对扩体锚杆的扩体段直径与长度以及上覆土层的厚度进行优化设计,有助于提高扩体锚杆的技术优势和经济效益。

Facing many large-scale, high degree of technical difficulties and risks of geotechnical engineering, compared with the ordinary soil anchors, the expanded anchor can provide higher capacity and solution of many these complex problems. Using the self-developed automatic load equipment, the model tests of compression and tension types of anchors were carried on, Test results showed that the failure mode of test anchor was a cone shape, the diameter of the expanded part had more influence on the failure cone and ultimate bearing capacity, the length of the expanded part had less. With the increasing of the fixed end diameter, the increscent range of ultimate bearing capacity of the model anchor gradually reduced, and the increased proportion of bearing capacity of unit cross sectional area varied from positive to negative. With the increasing of the length of underreamed body, the increased proportion of bearing capacity of unit side area and unit length were always negative. The Q - s hysteretic curves were paraboliones, and the elastic deformation was basically coincident with the plastic deformation in the same conditions. The