季冻黄土地区框锚边坡预应力锚杆内力计算方法

冻融土体与锚杆之间相互作用机理研究的不足，导致工程实践中未能充分考虑土体冻融对锚杆内力的影响。针对该问题，基于西宁市季冻湿陷性黄土冻融循环三轴剪切试验，建立考虑冻融次数影响的湿陷性黄土黏聚力经验关系式；根据锚固体与周围土层的变形协调关系，推导冻融条件下框架预应力锚杆锚固段轴力和剪应力的解析式，将理论计算结果与现场试验结果进行对比验证，并分析冻融次数对锚固段轴力和剪应力的影响。结果表明：随冻融次数的增加，土体黏聚力呈指数型下降，锚固段轴力和剪应力在前3次冻融循环中急剧增大，冻融次数达到7次后趋于稳定；相较锚固段末端，锚固段始端轴力受冻融次数的影响更大，但锚固段始端至末端的剪应力随冻融次数的变化规律基本相同；现场试验结果验证了计算方法的合理性。

Calculation and analysis of internal forces of prestressed anchor on frame anchors supporting slope in the seasonal freeze-thaw loess area

Due to insufficient research on interaction mechanism between freeze-thaw soil and anchor, the influence of freeze-thaw of soil on the internal force of anchor cannot be fully considered in engineering practice. Therefore, development of an empirical relationship of collapsible loess cohesion considering the influence of freeze-thaw cycles based on the triaxial shear test on collapsible loess in Xining City is essential. Based on the deformation coordination relationship between the anchor body and the surrounding soil layer, the analytical formula of the axial force and shear stress of the anchorage section of the frame prestressed anchor under freeze-thaw conditions is deduced, and the results of the theoretical calculation are compared with field tests, and the influence is analyzed. Results show that the cohesion of the soil decreases exponentially with increase of freeze-thaw cycles, and the axial force and shear stress of the anchorage section increase sharply in the first 3 cycles, and then become stable after 7 cycles. The axial force at the anchorage front section is more influenced by freeze-thaw cycles than the back end. However, the variation pattem of shear stress along the anchorage with freeze-thaw cycles is same. Results of the field tests proved the rationality of the calculation method, which can provide a reference for design and calculation of frame supporting structure in such areas.