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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。
Faced with many large-scale, technical difficulty and high degree of risk of rock and soil engineering, compared with ordinary soil anchor, the expansion anchor can provide greater bearing capacity and solve complex engineering problems. Using the self-developed automatic bolt load-gauge, the vertical force in-wall model tests of tension-type and pressure-type expansion anchor were carried out respectively. The test results show that the damage of the model anchor rod is basically conical, and the diameter of the expansion section has a great influence on the diameter and ultimate bearing capacity of the failure cone. The length of the expansion section has little effect on the diameter and ultimate bearing capacity of the failure cone, With the increase of the diameter of the expansion segment, the ultimate bearing capacity of the model anchor decreases gradually, and the increase ratio of the unit cross-sectional area load changes from positive to negative. With the increase of the length of the expansion segment, Expansion length load increase ratio is negative. The Q-s hysteretic curves of the two types of rock bolts are parabolic. The elastic deformation curves of the two types of rock bolts are paralleled, and the plastic deformation curves are basically the same. The pressure-type expanded anchor can provide the restraining load more quickly. In engineering practice, the optimal design of the diameter and length of the extended section of the expanded anchor rod and the thickness of the overlying soil layer will help to improve the technical advantages and economic benefits of the expanded anchor rod.