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摘要: 開口管樁由于其承載力高、質量可靠、施工方便等優點得到越來越廣泛的應用.土塞的生成使得開口管樁沉樁阻力不同于閉口管樁, 不僅包括樁外側摩阻力、樁端阻力, 樁內側摩阻力亦是其重要組成部分.針對開口管樁沉樁受力特性, 采用自主研發的大尺度模型試驗裝置, 進行不同樁靴形式下開口管樁的貫入試驗, 并與閉口管樁進行對比分析.研究表明, 開口管樁隨沉樁深度的增加趨于閉塞, 沉樁阻力隨沉樁過程基本呈線性增加, 樁內、外側單位摩阻力均存在"側阻退化"效應; 樁體貫入時樁周地表隆起量隨徑向距離增加逐漸減小, 隆起速率隨沉樁深度增加逐漸變緩, 樁周土影響范圍約為5~7倍樁徑; 樁靴對開口管樁土塞生成、沉樁阻力和擠土效應均有重要影響, 內30°樁靴土塞生成高度、樁內側摩阻力及其所占總沉樁阻力比例最大, 樁周土地表隆起量最小, 外30°樁靴與內30°樁靴情況相反, 直角樁靴居中; 閉口管樁沉樁阻力、外側摩阻力與擠土程度均大于開口管樁.Abstract: The open pipe pile is widely used because of its high bearing capacity, reliable quality, and convenient construction.The formation of the soil plug makes the total resistance of the open pipe pile different from that of the closed pipe pile. The bearing capacity of the open pipe pile includes three parts: the external friction of the pile, the pile end resistance, and the pile inside the friction. According to the stress characteristics of open pipe piles during installation, a self-developed large-scale laboratory test apparatus was used to test the penetration of open pipe piles under different forms of pile boots, and based on the results, the open pipe pile was compared with closed pipe pile. The results show that the open pipe pile tends to be occluded with the increase of pile depth. The resistance of pile increases linearly with the pile sinking process, while the frictional resistance inside and outside the pile has "lateral degeneration effect. "The influence range of surface displacement decreases with the increase of radial distance. The uplift rate gradually reduced with the increasing depth of pile sinking. The influence range of soil around pile is about 5 to 7 times of pile diameter. The pile shoe affects the height of the soil plug, pile resistance distribution, internal and external frictional resistance, and the effect ofpushing against soil. The pile of 30° inside pile boots has the largest height of soil plug formation, as well as the maximum friction resistance and the maximum proportion of total pile resistance. The amount of surface soil uplift around the pile is the smallest. The outer 30° pile boot is opposite to the inner 30° pile boot, while the right-angle pile boot is centered. The resistance, lateral friction, and soil compaction of closed-end pipe pile are greater than those of the open pipe pile.
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圖 5 內、外管實物圖. (a) 內管; (b) 外管
Figure 5. Picture of inner tube and outer tube: (a) inner tube; (b) outer tube
圖 9 各部分阻力隨沉樁的變化曲線. (a) PO-1; (b) PO-2; (c) PO-3; (d) PC
Figure 9. Variation of pile resistance during installation: (a) PO-1; (b) PO-2; (c) PO-3; (d) PC
圖 10 樁內側單位摩阻力沿深度分布曲線. (a) PO-1; (b) PO-2; (c) PO-3
Figure 10. Variation of internal unit friction with depth: (a) PO-1; (b) PO-2; (c) PO-3
圖 11 樁外側單位摩阻力沿深度分布曲線. (a) PO-1; (b) PO-2; (c) PO-3; (d) PC
Figure 11. Variation of external unit friction with depth: (a) PO-1; (b) PO-2; (c) PO-3; (d) PC
圖 12 地表隆起量隨樁體貫入深度的變化曲線. (a) PO-1; (b) PO-2; (c) PO-3; (d) PC
Figure 12. Development of surface displacement with penetration: (a) PO-1; (b) PO-2; (c) PO-3; (d) PC
表 1 砂樣物理參數指標
Table 1. Physical indices of testing sand
相對密度，Gs 最大孔隙比，emax 最小孔隙比，emin 平均粒徑，d50/mm 粒徑范圍/mm 內摩擦角，φ/(°) 2.65 0.52 0.30 0.72 0~15 42.8 
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表 2 試驗方案
Table 2. Testing program
試驗編號 砂樣相對密實度/% 加載方式 樁靴類型 PO-1 73 不間斷靜壓貫入 開口30°內傾角樁靴 PO-2 開口直角樁靴 PO-3 開口30°外傾角樁靴 PC 閉口直角樁靴
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表 3 各部分阻力及其所占的比例
Table 3. Resistance of each part and its proportion
試驗編號 沉樁深度/mm 貫入阻力/kN 樁內側摩阻力/kN (占比) 樁外側摩阻力/kN (占比) 樁(壁)端阻力/kN (占比) PO-1 110 10.79 0.23 (2.13%) 0.79 (7.32%) 9.77 (90.55%) 740 43.24 6.77 (15.66%) 8.99 (20.79%) 27.48 (63.55%) PO-2 110 9.69 0.05 (0.52%) 0.79 (8.15%) 8.85 (91.33%) 740 42.14 5.23 (12.41%) 9.28 (22.02%) 27.63 (65.57%) PO-3 110 9.42 0.02 (0.21%) 0.56 (5.95%) 8.84 (93.84%) 740 39.17 3.97 (10.14%) 10.04 (25.63%) 25.16 (64.23%) PC 110 16.54 1.15 (6.95%) 15.39 (93.05%) 740 59.17 14.60 (24.67%) 44.57 (75.33%)
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中文字幕在线观看表 4 沉樁深度為740 mm時距樁體不同徑向距離樁周地表隆起量
Table 4. Surface rise of piles at different radial distances from pile when the penetration depth of the pile is 740 mm
試驗編號 地表隆起量/mm 徑向距離100 mm 徑向距離200 mm 徑向距離300 mm 徑向距離400 mm 徑向距離500 mm PO-1 5.05 2.79 1.86 1.04 0.63 PO-2 6.43 3.64 2.89 1.52 0.84 PO-3 6.71 3.93 3.11 1.97 1.15 PC 8.60 6.18 3.87 2.45 1.47
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參考文獻
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