Stability of DPT hammer efficiency and relationships of blow-counts obtained by different DPT apparatuses
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摘要: 采用现场能量标定和试验的方法研究不同类型DPT锤击数之间的相关性,探讨DPT试验锤击能量的稳定性。分析结果显示：DPT试验是一种锤击能量稳定且锤击效率较好的现场测试方法,不同类型的DPT锤击能量传递率（ETR）均值均能超过80%,且落锤越重,探杆直径尺寸越大,能量传递率越高。通过能量传递率标定锤击数和现场试验的方法,分别获取了不同类型DPT锤击数之间的转化关系,且二者得到的不同类型DPT锤击数之间的转化系数较一致,重型DPT试验得到的锤击数约为超重型DPT试验锤击数2.5倍。能量测试仪获取的ETR实为锤击有效能量的传入率,经过探杆的能量损耗才是贯入的实际有效能量,而探头贯入能量测试是一项尚需解决的技术。Abstract: The blow counts of different DPT apparatuses and their relationships are analyzed by means of the energy-calibration method which uses a pile dynamic analyzer (PDA) energy measurement and the in-situ DPT tests. The stability of energy transmitted into penetration tips is discussed. The analytical results demonstrate that the DPT is a reliable site testing technique with good hammering efficiency. The energy transfer ratios (ETR) of different types of DPT are high with the average values more than 80%. The relationships of blow counts calibrated by ETR values are consistent well with those obtained by the in-situ tests. The blow counts of heavy DPT tests with a hammer of 63.5 kg is in average 2.5 times those obtained by super-heavy DPT with a hammer of 120 kg, and the influence of rod diameters can be neglected. The ETR values measure the energy transmitted into the rod through hammer drops, i.e., hammering efficiency. However, the actual energy transmitted into soil usually reduces due to the energy consuming of rods and should be measured at the tip. The technique is expected to be solved in the future.
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Keywords:
- dynamic penetration test /
- energy measurement /
- blow count /
- converting coefficient
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感谢东华理工大学侯龙清教授、桂林理工大学曹振中教授以及四川德阳金阳岩土工程有限公司对现场勘查工作提供的支持和帮助。
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图 1 成都平原现场动力触探试验点分布
Figure 1. Distribution map of selected sites with DPT tests conducted in Chengdu plains
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图 2 现场超重型动力触探试验
Figure 2. In-situ DPT apparatus with a donut hammer of 120 kg falling to anvil above PDA energy measurement
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图 3 现场DPT试验采用的穿心锤（63.5,120 kg）、探头和…探杆（直径为42,60 mm）
Figure 3. Donut hammers (63.5 and 120 kg), tips and rods (42 and 60 mm in diameter) used in DPT tests
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图 4 60 mm探杆和120 kg穿心锤现场试验实测ETR数据随深度的分布
Figure 4. Test data of ETR values varying with depth using a hammer of 120 kg and rods of 60 mm in diameter
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图 5 60 mm探杆和63.5 kg穿心锤现场试验实测ETR数据随深度的分布
Figure 5. Test data of ETR values varying with depth using a hammer of 63.5 kg and rods of 60 mm in diameter
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图 6 42 mm探杆和63.5 kg穿心锤现场试验实测ETR数据随深度的分布
Figure 6. Test data of ETR values varying with depth using a hammer of 63.5 kg and rods of 42 mm in diameter
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图 7 略平镇安平村DPT能量试验锤击数与能量传递率统计图
Figure 7. Histograms of numbers of hammer drops and ETR values conducted at Anping Village
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图 8 湔氐镇白虎头村DPT能量测试锤击数与能量传递率统计图
Figure 8. Histograms of numbers of hammer drops with ETR values conducted at Baihutou Village
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图 9 略平镇安平村DPT锤击数随深度的试验曲线
Figure 9. Curves of different DPT test blows varying with depth conducted at Anping Village
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图 10 湔氐镇白虎头村DPT锤击数随深度的试验曲线
Figure 10. Curves of different DPT test blows varying with depth conducted at Baihutou Village
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图 12 略平镇安平村不同类型DPT锤击数比值统计柱状图
Figure 12. Histograms of ERT ratios of different types of DPT tests conducted at Anping Village
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图 13 湔氐镇白虎头村不同类型DPT锤击数比值统计柱状图
Figure 13. Histograms of ERT ratios of different types of DPT tests conducted at Baihutou Village
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图 14 (N120)60与(N63.5)60的试验数据散点图
Figure 14. Scattering diagram of (N120)60 and (N63.5)60 data
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图 15 (N120)60与(N63.5)42的试验数据散点图
Figure 15. Scattering diagram of (N120)60 and (N63.5)42 data
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图 16 (N63.5)60与(N63.5)42的试验数据散点图
Figure 16. Scattering diagram of (N63.5)60 and (N63.5)42 data
表 1 采用120 kg穿心锤、60 mm探杆DPT试验实测能量传递率统计值
Table 1 ETR statistics of DPT tests with a hammer of 120 kg and rods of 60 mm in diameter
(%) 试验点 能量传递率（ETR） 均值 均值+标准差 均值-标准差 标准差 安平村 92.53 97.20 87.86 4.67 白虎头 87.65 92.82 82.48 5.17 天齐村 91.78 94.86 88.70 3.08 白江村 88.90 92.69 85.11 3.79 武都村 92.91 96.97 88.85 4.06 
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表 2 采用63.5 kg穿心锤、60 mm探杆DPT试验实测能量传递率统计值
Table 2 ETR statistics of DPT tests with a hammer of 63.5 kg and rods of 60 mm in diameter
(%) 试验点 能量传递率（ETR） 均值 均值+标准差 均值-标准差 标准差 安平村 88.88 96.16 81.60 7.28 白虎头 84.43 90.27 78.59 5.84 天齐村 94.51 100.80 88.22 6.29 白江村 89.32 93.64 85.00 4.32
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表 3 采用63.5 kg穿心锤、42 mm探杆DPT试验实测能量传递率统计值
Table 3 ETR statistics of DPT tests with a hammer of 63.5 kg and rods of 42 mm in diameter
(%) 试验点 能量传递率（ETR） 均值 均值+标准差 均值-标准差 标准差 安平村 76.96 81.45 72.47 4.49 白虎头 79.94 84.28 75.60 4.34 天齐村 92.94 99.30 86.58 6.36 武都村 82.52 86.76 78.28 4.24
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表 4 基于ETR标定的不同类型DPT试验锤击数比值
Table 4 ETR-calibrated blow-count ratios of different DPT tests with respect to (N120)60
试验点 DPT锤击数转化系数 (N63.5)60/(N120)60 (N63.5)42/(N120)60 (N63.5)42/(N63.5)60 安平村 2.63 3.03 1.15 白虎头 2.56 2.78 1.05 天齐村 2.44 2.44 1.02 白江村 2.50 — — 武都村 — 2.70 — 平均值 2.53 2.74 1.07
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表 5 现场实测不同类型DPT锤击数比值
Table 5 Blow-count ratios of different DPT with respect to (N120)60
试验点 试验锤击数的比值 (N63.5)60/(N120)60 (N63.5)42/(N120)60 (N63.5)42/(N63.5)60 安平村 2.33 3.29 1.44 白虎头 2.60 2.18 0.99 天齐村 2.91 2.67 0.98 白江村 2.03 — — 武都村 — 1.80 — 平均值 2.47 2.49 1.14
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