Centrifugal model tests on CFG pile-net composite foundation under super-large loads
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摘要: CFG桩网复合地基广泛应用于处理软土地基。采用土工离心模型试验研究某码头堆场超大荷载下CFG桩网复合地基的变形和桩土应力特性,试验模拟了地基、CFG桩、树根桩、加筋垫层、防尘网和轨道梁基础、矿石堆载等,分析了超大荷载作用下复合地基表面变形、孔隙水压力、桩顶轴力、桩土应力比的变化规律。试验结果表明,复合地基的沉降速率在稳定控制标准之内,沉降量满足堆场使用要求,防尘网基础和轨道梁基础水平位移和沉降均很小,桩土应力比20~36。典型区CFG桩网复合地基在350 kPa荷载作用下是稳定安全的,达到了预期加固效果。
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关键词:
- CFG桩桩网复合地基 /
- 变形 /
- 桩土应力 /
- 超大荷载 /
- 离心模型试验
Abstract: CFG pile-net composite foundation is widely used to reinforce soft soil foundation. Geotechnical centrifuge model test was carried out to study the deformation and pile-soil stress characteristics of CFG pile-net composite foundation under super large load in the storage yard of a wharf. The foundation, CFG piles, root piles, reinforced cushions, dust nets, track beam foundation and ore loads are simulated. The variation laws of the surface deformations, pore water pressures and loads at the top of the CFG piles and the pile-soil stress ratio of the composite foundation are analyzed under super-large loads. The settlement rate of the composite foundation is within the stability control standard, and the settlement meets the requirements of the storage yard. The horizontal displacements and settlements of the dust net foundation and the track beam foundation are small. The pile-soil stress ratio is 20~36. The test results show that the CFG pile-net composite foundation in the typical zone is stable and safe under the load of 350 kPa, and the foundation reinforcement has achieved the expected effects. -
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表 1 土的物理力学性质指标
Table 1 Physical and mechanical properties of soils
土名 厚度/m 含水率/% 密度/(g·cm-3) 不排水强度/kPa 素填土①2 2.48 32.0 1.91 25 淤泥质黏土②1 6.20 50.8 1.72 31 粉质黏土③4 3.50 31.0 1.92 41 中粗砂③2 1.70 1.85 黏土④1、④2 42.3 1.77 51 表 2 复合地基表面变形特征值
Table 2 Surface deformations of composite foundation (mm)
测点 时间节点 堆载期 试堆期 恒载365 d 恒载408 d 沉降 Sa1 -22 -9 39 42 Sa2 50 82 175 181 Sa3 139 210 399 411 Sa4 149 208 366 375 Sa5 -20 -2 71 76 水平位移 Db1 -4 -9 -28 -30 Db5 0 11 44 45 表 3 复合地基孔隙水压力特征值
Table 3 Pore water pressures of composite foundation
时间节点 测点 U1 U4 孔压/kPa 孔压系数 孔压/kPa 孔压系数 堆载期 27 0.08 117 0.34 试堆期 48 0.14 180 0.51 峰值 50 0.14 205 0.59 (恒载32 d) (恒载85 d) 恒载365 d 33 0.09 198 0.57 恒载408 d 32 0.09 197 0.56 表 4 复合地基CFG桩顶轴力特征值
Table 4 Loads at top of CFG piles
测点 Tf1 Tf2 Tf3 Tf4 桩长、间距/m 10,1.8 14,1.8 16,1.8 16,1.65 上覆荷载/kPa 150 232 319 350 轴力/
kN堆载期 184 344 539 543 试堆期 185 349 522 528 恒载365 d 190 354 475 496 恒载408 d 191 353 474 495 表 5 复合地基桩土应力比特征值
Table 5 Pile-soil stress ratios of composite foundation
测点 Tf1 Tf2 Tf3 Tf4 堆载期 桩身应力/MPa 1.92 3.58 5.61 5.66 桩间土压力/kPa 96 130 157 156 桩土应力比 20 28 36 36 恒载408 d 桩身应力/MPa 1.99 3.68 4.94 5.16 桩间土压力/kPa 94 127 178 174 桩土应力比 21 29 28 29 -
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