Field Comparative Experiments of Pipe Pile Composite Foundation with Different Cushion Layers
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摘要: 为比较管桩+钢筋混凝土板复合地基、管桩+桩帽+土工格室复合地基、管桩+桩帽+土工格栅复合地基的受力和沉降控制效果，开展了3种复合地基处理深厚软土路基的现场试验，分析研究了不同垫层条件下管桩复合地基受力和变形规律，结果表明：路堤荷载作用下，桩顶和桩间土应力由路基中心向路肩、坡脚处逐渐减少，土工格栅垫层时桩土应力比为2.47~5.42，土工格室垫层加固桩土应力比为2.30~6.25；钢筋混凝土板垫层时桩土应力比为8.05~14.81；随着路基填土荷载的增大，土工格栅、土工格室拉力逐渐增大，路肩位置拉力最大，相同荷载作用下土工格室所受拉力大于土工格栅；3种复合地基加固措施中管桩+钢筋混凝土板对路基沉降的加固效果最好，稳定后地基面沉降分别为土工格栅和土工格室桩网复合地基地基面沉降的68.46%和72.56%.Abstract: In order to compare the stress and evaluate the ability to control deep soft soil settlement of three kinds of composite foundations, field experiments were carried out. Each pipe pile composite had a different cushion layer; a reinforced concrete slab, a geocell, and a geogrid, respectively. For the geocell and geogrid composites, a pile cap was added.Both the stress response, and the settlement, of the pipe pile composite foundations, under different cushion layers, were analyzed. The results show that the stress of both the pile's top surface and the soil between the piles was gradually reduced, from the subgrade center to the shoulder. The pile-soil stress ratios were 2.47-5.42, 2.30-6.25, 8.05-14.81 for the geogrid-reinforced cushion layer, the geocell-reinforced cushion layer, and the reinforced concrete slab cushion layer, respectively. As the load of the subgrade filling increased, the tensile strength of both the geogrid and the geocell gradually increased, and maximum tension occurred at the shoulder. The tensile strength of the geocell was greater than that of the geogrid, under the same load. The composite foundation of a pipe pile, plus a reinforced concrete slab is the best for controlling the settlement of the subgrade filling, and the settlement of the ground surface contributes 68.46% and 72.56% of entire settlement of the pipe pile-pile cap-geogrid and the pipe pile-pile cap-geocell composite foundations, respectively.
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Key words:
- geocell /
- geogrid /
- pipe pile composite foundation /
- settlement /
- pile-soil stress ratio
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图 1 地基剖面及测试元器件布置图(单位:m)
Figure 1. Foundation profile and test component layout (unit: m)
图 7 管桩不同结构复合地基地基面沉降曲线
Figure 7. Surface settlement curves of the pipe-pile composite foundation with different types of cushion layer
表 1 管桩区填土完毕桩土应力
Table 1. Pile-soil stress ratios at the pipe pile area, after soil filling
分析对象 桩板 土工格栅 土工格室 路基中心 路肩 坡脚 路基中心 路肩 坡脚 路基中心 路肩 坡脚 桩顶土压力/kPa 604.3 520.5 178.0 233.1 198.2 73.0 288.6 238.6 67.2 桩间土土压力/kPa 40.8 38.6 22.1 43.0 39.0 29.5 46.2 41.3 29.2 桩土应力比 14.81 13.48 8.05 5.42 5.08 2.47 6.25 5.78 2.30 
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表 2 土工格栅、土工格室拉力
Table 2. The tension of the geocell and geogrid
加筋材料 尺寸 设计抗拉强度
/(kN·m-1)拉力/kN 路基中心 距路基中心3.3m 路肩处 靠近坡脚处 土工格栅 2.5 cm×2.5 cm 250 0.461 0.922 0.653 0.250 土工格室 40 cm×40 cm×5 cm 200 1.080 2.800 3.870 1.910
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