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摘要: 通过单桩及复合地基静载荷试验、静力触探、低应变动力测试、沉降观测等现场测试技术, 研究了低置换率CFG (CementFlyashGravel) 桩处理软土地基的加固效果, 阐述了设计方法和施工技术措施。研究显示, 处理后的复合地基承载力比天然地基承载力提高了1 4~2 0倍; 低置换率CFG桩对桩间土无挤密作用; 保证工后沉降为50mm的所需固结时间, 短桩段复合地基不超过0 5a, 长桩段不超过1 0a, 且短桩段地基固结速率大于长桩段。结果表明, 低置换率CFG桩能满足软土路基承载力和工后沉降要求。Abstract: This paper studied CFG pile strengthening effect of soft ground, which has low replacement ratio, with multiple field-testing techniques, such as static cone penetration test, plate loading test, low strain dynamic testing and settlement observation. The design method and construction technology of CFG pile were also represented concisely. It is pointed that the bearing capacity of composite foundation after treatment is 1.4~2.0 bold that of natural ground, CFG pile can not compact the soil between piles, in order to guarantee the consolidation time of settlement (50 mm) after projection, it needs no more than 0.5 year to reach the specified settlement for the zone used short piles, and no more than 1.0 year for the zone used long piles, and the rate of consolidation in the zone used short piles is higher than in the zone used long piles. The results indicate that this kind of CFG pile can guarantee bearing capacity and settlement after projection criterion of soft ground.
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Key words:
- geotechnical engineering /
- soft ground /
- CFG pile /
- settlement after projection
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表 1 土的物理力学指标
Table 1. Physical and mechanical indices of soil
地层名称 描述 层厚/m 土性指标 ①*粘土 褐黄色, 软塑, 局部偏硬塑, 属中等压缩性土 2.30~2.70 ω=31.4%, γ=19.2 kN/m3, e=0.87, cu=14.3 kPa, φu=15.4°, a1-2=0.44 MPa-1, E1-2=5.0 MPa, Ps=1.2~1.5 MPa ②2淤泥质粉质粘土 灰色, 流塑 0.65~1.10 ω=41.6%, γ=17.9 kN/m3, e=1.17, cu=2 kPa, φu=17.9°, a1-2=0.81 MPa-1, Ps=0.4~0.8 MPa ②3粉土 局部粉砂, 灰色, 松散, 饱和, 属中等压缩性土 0.60~1.00 ω=41.7%, γ=18.4 kN/m3, e=1.1, cu=12 kPa, φu=9.9°, a1-2=0.37 MPa-1, Ps=0.66~1.32 MPa ③淤泥质粉质粘土 灰色, 流塑, 含少量腐植物, 具有低强度, 高触变性特点 11.20~12.60 ω=39.2%, γ=18.3 kN/m3, e=1.07, cu=7.21 kPa, φu=4.9°, a1-2=0.81 MPa-1, E1-2=2.6 MPa, Ps=0.4~0.8 MPa ④淤泥质粘土 9.40~11.00 ω=37.6%, γ=18.2 kN/m3, e=1.06, cu=8.64 kPa, φu=5.4°, a1-2=0.62 MPa-1, E1-2=2.6 MPa, Ps=0.6~1.0 MPa ⑤2粉土 灰色, 中密, 饱和, 中等压缩性土 0~1.90 ω=31.4%, γ=18.3 kN/m3, e=0.94, cu=15 kPa, φu=25.8°, a1-2=0.25 MPa-1, Ps=4.06~6.77 MPa ⑤3粉质粘土 灰色, 软塑, 属中、高等压缩性土 未穿透 ω=34%, γ=18.3 kN/m3, e=0.99, cu=11.2 kPa, φu=14.1°, a1-2=0.36 MPa-1, E1-2=5.5 MPa, Ps=1.30~1.70 MPa 
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表 2 最终沉降量及后期沉降预测值
Table 2. Forecast values of last settlement and later period settlement
最终沉降量/mm 保证工后沉降50 mm所需时间/d 1 a后剩余沉降/mm 2 a后剩余沉降/mm 3 a后剩余沉降/mm 短桩段 541.0 150 1.23 / / 长桩段 393.0 260 26.00 2.8 0.3
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