季节冻土对土钉支护的影响

川藏交通廊道规划路线沿线滑坡锚固工程在全生命周期内将不可避免受到季节性冻土冻胀融缩的不利影响。为减缓此不利影响，本文提出基于多个挤压摩擦型屈服套的屈服装置、消能蓄能型碟簧系统，形成可双向调节预应力的锚索新结构。并对该锚索进行室内张拉试验、极限承载力试验及工作机理研究，成功研制吨位500 kN级、行程100 mm的双向调节预应力锚索。室内试验证实，单个挤压摩擦型屈服套起始屈服力为120~135 kN，平稳行程可达255 mm；屈服装置由4个挤压摩擦型屈服套及P锚组成，起始屈服力为420~450 kN，行程可达到100 mm以上；碟簧系统可实现耗能(冻胀时可抵消约60%的预应力增长)与蓄能(融缩时可抵消约40%的预应力损失)的目的。屈服行程完结后，双向调节预应力锚索极限承载力为1050kN，与传统锚索极限承载力相当。该新型锚索起始屈服力及行程具有较好的可拓展性，性能参数优于市场同类产品，可用于冻融环境及地震、大变形情形下的滑坡边坡加固，为川藏交通廊道沿线季节性冻土区滑坡、边坡防护提供了一种新的解决方案。

Soil nailing under the influence of the seasonal frozen soil

The Sichuan-Tibet traffic corridor passes through the frozen soil area of the Qinghai-Tibet Plateau. During its life cycle,the slope protection projects would inevitably and adversely be affected by frozen soil. Some prevention and control projects nearby were damaged during the freeze-thaw cycles. To mitigate the adverse effects,we proposed a new anchor cable. The new anchor cable was mainly composed of the disc spring system and yield device. We made and tested 7 groups of yield sets with different lengths,different contact methods and different outer diameters. And we found some samples that could provide sufficient yield force and stroke. Then we proposed a calculation method for the key parameters of the yield set. We developed a yield device which consists of 4 yield sets. Each yield set could provide resistance force 120~135 kN. The total initial yield strength was 420~450 kN. The yield stroke can reach more than 100 mm. We performed the tension test of the disc spring anchor cable in the laboratory. The laboratory test results showed that the growth of the force was reduced by 60% during the frost heave process. And the loss of the force was reduced by about 40% during the melting process. We analyzed the working principle of disc springs on the basis of experiments. We combined the yielding device and the disc spring to form a new anchor cable and tested it under tension. The laboratory tests showed that it could adjust the prestress in both directions effectively. After the end of the yield stroke,we carried out the ultimate bearing capacity tests of the anchor cables. The ultimate bearing capacity of the anchor cable was 1050 kN. The initial yield force and the stroke of the anchor cable could be extended as needed. The performance of the new anchor cable was better than similar products in the market. It could be used for landslide protection in seasonal frozen soil areas along the Sichuan-Tibet traffic corridor.