囊式扩体锚杆现场试验分析及承载力计算模式研究

发布时间：2018-05-16 08:01

本文选题：囊式扩体锚杆 + 拉拔试验　；参考：《郑州大学》2017年硕士论文

【摘要】：囊式扩体锚杆是基于传统锚杆在杆体的端部通过增加橡胶囊袋而形成的一种新型扩体锚固技术。橡胶囊袋气密性好、承载力高且抗摩擦、耐腐蚀能力强,通过注浆膨胀可以形成高质量的锚固体,能够克服传统锚杆锚固体强度低、施工质量差的缺点。该新型锚杆自从被研究出来以后,由于其承载力高、成本低、应用范围广且施工简便的特点,已在国内许多工程中得到成功的应用,然而目前关于该新型锚杆的研究仍比较匮乏,理论认知远落后于工程应用。因此有必要对囊式扩体锚杆继续展开深入地研究。采用现场试验监测与有限元分析相结合的方法,在变化扩体段高喷压力和囊袋注浆压力情况下,对囊式扩体锚杆的受力机理、轴力和侧摩阻力分布进行了研究;通过改变不同的参数,探讨得出囊式扩体锚杆极限承载力的主要影响因素;同时在现场试验和有限元模拟基础上,对比分析了囊式扩体锚杆不同承载力计算模式及其适用条件。主要的研究成果及结论如下:(1)囊式扩体锚杆极限承载力与扩体段高喷压力和囊袋注浆压力呈线性增加关系,在其他参数相同的情况下,注浆压力超过1.5MPa后,极限承载力提高效果并不显著;与传统无囊式扩体锚杆相比,新型锚杆增加预制囊袋,承载力提高幅度在27%~43%。(2)粉质黏土中深埋型囊式扩体锚杆的最终破坏形式为扩体段端承面土体发生局部剪切破坏。当拉拔荷载较小时,锚杆主要靠侧摩阻力提供抗拔力,超过500kN后端承力开始发挥作用,且端承作用越来越明显而侧摩阻力趋于稳定;荷载达到625kN时扩体段端承面土体开始出现塑性应变,且随着荷载增大塑性区域不断向外扩张,达到极限荷载时塑性区域呈现蝴蝶翅状。(3)囊袋膨胀压力对锚周土体的挤压作用有限,超过一定值后继续增大膨胀压力,承载力不发生变化。在膨胀挤压作用下囊袋呈现上大下小的倒锥台状,不规则的扩体段形状及膨胀后的土体特性对承载力均有显著影响;通过分析不同参数对承载力的影响,认为囊袋长度、扩体段直径和扩体段埋深对极限承载力的影响最为显著,土体参数和囊袋注浆压力次之,扩体段长度对承载力的影响最小。(4)通过囊式扩体锚杆不同承载力计算模式对比分析,认为土重法计算的极限承载力最符合真实情况,规范法计算简便且具有较大安全贮备,弹性理论法在土体参数较少时可以采用,计算结果虽然偏于保守但可满足安全性要求,岩土锚固法和Boussinesq位移法适用于对浅埋式扩体锚杆极限承载力进行估算。
[Abstract]:A new type of expansion anchoring technique is formed by adding rubber bag to the end of the bolt. Rubber bag has good air tightness, high bearing capacity, high friction resistance and strong corrosion resistance. High quality anchors can be formed by grouting expansion, which can overcome the shortcomings of low strength and poor construction quality of traditional anchors. Because of its high bearing capacity, low cost, wide range of application and easy construction, the new bolt has been successfully applied in many domestic projects since it was studied. However, the research on the new bolt is still scarce, and the theoretical cognition lags far behind the engineering application. Therefore, it is necessary to carry out further research on the burlap-expanded anchor rod. With the combination of field test monitoring and finite element analysis, the stress mechanism, axial force and lateral friction distribution of the bolted bolt are studied under the condition of varying high pressure of spray and grouting pressure of bag. By changing different parameters, the main factors influencing the ultimate bearing capacity of the bolting are discussed, and on the basis of field test and finite element simulation, the different calculation modes of the bearing capacity of the bolting and their applicable conditions are compared and analyzed. The main research results and conclusions are as follows: (1) the ultimate bearing capacity of the bolt is linearly increased with the high spray pressure and the grouting pressure of the bag. When other parameters are the same, the grouting pressure exceeds the 1.5MPa. The improvement of ultimate bearing capacity is not significant. Compared with the traditional non-cystic bolting, the new type of anchor increases the prefabricated bag. In silty clay, the ultimate failure form of deep burying type expansion bolt is local shear failure of soil on the end bearing surface of the expansion section. When the drawing load is small, the anchor rod mainly depends on the side friction to provide the pull-out force, which starts to play a role beyond the 500kN back end bearing force, and the end bearing effect is more and more obvious, and the side friction resistance tends to be stable. When the load reaches 625kN, the soil on the end face of the expansion section begins to appear plastic strain, and the plastic region expands outward with the increase of load. When the ultimate load is reached, the plastic region presents a butterfly wing shape. 3) the expansion pressure of the bag has a limited effect on the soil around the anchor, but the expansion pressure will continue to increase after a certain value, but the bearing capacity will not change. Under the action of expansion and extrusion, the bag presents the shape of inverted cone, the shape of irregular expansion section and the characteristics of soil after expansion have significant influence on the bearing capacity, and through the analysis of the influence of different parameters on the bearing capacity, it is considered that the length of the bag, the shape of the dilated body and the characteristics of the soil after expansion have a significant effect on the bearing capacity. The influence of the diameter of the expansion section and the depth of the expansion section on the ultimate bearing capacity is most significant, followed by the soil parameters and the grouting pressure of the bag, and the influence of the length of the expansion section on the bearing capacity is the least. It is considered that the ultimate bearing capacity calculated by the soil weight method is the most suitable for the real situation, the calculation of the standard method is simple and has a large safe reserve, the elastic theory method can be used when the soil parameters are less, and the calculation results are conservative but can meet the safety requirements. The geotechnical anchoring method and Boussinesq displacement method are suitable for estimating the ultimate bearing capacity of shallow-buried anchor bolts.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU476

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