Laboratory Pull-Out Test Study of Basalt Fiber Reinforced Polymer Bolt for Strengthening Mixed Soil
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摘要:
玄武岩纤维增强复合材料（BFRP）质量轻、强度高、耐久性好，将该材料用作锚杆可有效解决传统钢筋锚杆的腐蚀问题，在恶劣环境下的工程建设中具有广阔的应用前景. 本文以广泛存在于西南山区的崩坡积混合土为对象，通过室内拉拔试验研究了锚杆类型、锚杆直径、锚固长度以及灌浆体直径等因素对极限拉拔荷载和界面剪应力的影响，并对锚固体系的破坏模式以及应力分布规律进行了分析. 研究结果表明：混合土中BFRP锚杆破坏模式均为沿灌浆体与土体界面的剪切破坏，BFRP锚杆与钢筋锚杆的抗拔承载性能基本一致，实际工程可以使用BFRP锚杆直接替代钢筋锚杆；BFRP锚杆拉拔荷载位移曲线呈三阶段形式，弹性临界荷载为极限荷载的20% ~ 28%，试验条件下锚杆的极限承载力与锚固长度、灌浆体直径成正比关系；灌浆体环向裂缝使锚杆的轴向应力沿杆体呈单峰形式分布，同时使锚固段前部的应力集中程度降低；混合土中灌浆体直径越大则界面强度越低，直径从90 mm增大为110 mm，界面强度降低约8%.
Abstract:Basalt fiber reinforced polymer (BFRP) has the advantages of light weight, high strength and good durability. Using the material as anchor can effectively solve the corrosion problem of traditional steel bar anchor and has a broad application prospect in engineering construction in harsh environment. Taking the collapse alluvial mixed soil which widely exists in the southwest mountainous area as the object, through the indoor pull-out test, the effects of anchor type, anchor diameter, anchorage length and grouting diameter on the ultimate pullout load and interface shear stress are studied. The failure mode and stress distribution law of the anchoring system are analyzed. The results show that the failure mode of BFRP anchor in mixed soil is shear failure along the interface between grouting body and soil, and the pull-out bearing capacity of BFRP anchor is basically the same as that of reinforced anchor, so BFRP anchor can be used to replace reinforced anchor directly in practical engineering. The pullout load-displacement curve of BFRP anchor is in the form of three stages, and the elastic critical load is 20%−28% of the ultimate load. Under the test condition, the ultimate bearing capacity of the bolt is proportional to the anchoring length and the diameter of the grout. And the circumferential crack in the grouting body makes the axial stress of the bolt in the form of a single peak and reduces the stress concentration in the front of the anchoring section. The larger the diameter of the grouting body in the mixed soil is, the lower the interface strength is, the diameter increases from 90 mm to 110 mm, and the interface strength decreases by about 8%.
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Key words:
- BFRP bolt /
- talus mixed soil /
- pull-out test /
- the interfacial mechanical behaviors
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表 1 锚杆力学参数
Table 1. Mechanical parameters of bolts
类别 直径/
mm弹模/
GPa密度/
（kg·m−3）抗拉强度/
GPa极限
应变/%钢筋 16 200 7850 0.4 >10.0 BFRP 12 50 1940 1.1 2.20 BFRP 16 48 2050 1.0 2.08 BFRP 20 45 2020 0.9 2.08 
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表 2 物理力学参数
Table 2. Physical and mechanical parameters
类别 密度/
（kg·m−3）黏聚力/kPa 摩擦角/（º） 含水率/% 原状土 ① 1840 24.9 38.9 20.2 原状土 ② 1810 23.1 39.9 16.8 原状土 ③ 1800 31.8 35.0 16.6 试验土 1850 20.5 40.4 8.0
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表 3 试件方案参数
Table 3. Specimen parameters
杆型 方案 杆名 锚杆
直径
/mm锚固
长度
/m锚杆
总长
/m灌浆体
直径
/mmBFRP 1 B12A0.8G90 12 0.8 1.2 90 2 B12A1.2G90 12 1.2 1.6 90 3 B12A1.6G90 12 1.6 2.0 90 4 B16A0.8G90 16 0.8 1.2 90 5 B16A1.2G70 16 1.2 1.6 70 6 B16A1.2G90 16 1.2 1.6 90 7 B16A1.2G110 16 1.2 1.6 110 8 B16A1.6G90 16 1.6 2.0 90 9 B20A0.8G90 20 0.8 1.2 90 10 B20A1.2G90 20 1.2 1.6 90 11 B20A1.6G90 20 1.6 2.0 90 钢 12 S16A1.2G90 16 1.2 1.6 90
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表 4 拉拔试验结果
Table 4. Experimental results of pullout test
杆名 极限拉拔
荷载/kN第一界面平均
剪应力/kPa第二界面平均
黏结强度/kPaB12A0.8G90 3.0 100.6 13.4 B12A1.2G90 4.0 88.7 11.8 B12A1.6G90 4.9 81.2 10.8 B16A0.8G90 3.1 77.9 13.9 B16A1.2G90 3.9 64.9 11.5 B16A1.2G70 3.3 55.2 12.6 B16A1.2G110 4.4 73.1 10.6 B16A1.6G90 4.6 57.2 10.2 B20A0.8G90 3.3 66.2 14.7 B20A1.2G90 4.2 55.8 12.4 B20A1.6G90 4.5 44.8 10.0 S16A1.2G90 4.1 68.2 12.1
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表 5 锚杆类型的影响
Table 5. Influence of anchor type
锚杆类型 平均黏结
强度/kPa极限拉拔
荷载/kN第一界面
剪应力/kPaB16 11.54 3.92 64.92 S16 12.12 4.11 68.17
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表 6 极限拉拔荷载增幅
Table 6. Increasing range of ultimate pullout load
% 荷载 B12G90 B16G90 B20G90 A0.8 → A1.2 A1.2 → A1.6 A0.8 → A1.2 A1.2 → A1.6 A0.8 → A1.2 A1.2 → A1.6 增幅 32.3 21.9 25.0 17.5 26.5 7.0
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表 7 灌浆体直径的影响
Table 7. Influence of grouting body diameter
灌浆体直径 平均黏结
强度/kPa极限拉拔
荷载/kN第一界面
剪应力/kPaG70 12.61 3.33 55.19 G90 11.54 3.92 64.92 G110 10.62 4.41 73.05
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