不同类型DPT试验锤击能量稳定性及锤击数转化关系探讨

Stability of DPT hammer efficiency and relationships of blow-counts obtained by different DPT apparatuses

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。

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.