目前国内对松散岩层多半采用锤击法,或无泵钻进工艺。我队从1978年起,开始用双管双动取心器钻进砂土层。几年来,经过50多个钻孔的试验,对取心器进行几次改进,岩心采取率由1978年的58％,提高到74％。1981—1982年施工的6个取心率较高的钻孔,第四纪地层岩心采取率平均达92％, At present, most of the loose rock strata are peening or drilling without drilling. Since 1978, our team started drilling the sand layer with a double pipe double action taker. In the past few years, after more than 50 drilling tests, several improvements have been made to the coring device. The core adoption rate has risen from 58% in 1978 to 74%. Six well-bored boreholes were constructed in 1981-1982 and the average core-recovery rate of Quaternary strata reached 92%