Butler James J, Healey John M, McCall G Wesley, Garnett Elizabeth J, Loheide Steven P
Kansas Geological Survey, University of Kansas, Lawrence 66047, USA.
Ground Water. 2002 Jan-Feb;40(1):25-36. doi: 10.1111/j.1745-6584.2002.tb02488.x.
The potential of direct-push technology for hydraulic characterization of saturated flow systems was investigated at a field site with a considerable degree of subsurface control. Direct-push installations were emplaced by attaching short lengths of screen (shielded and unshielded) to the bottom end of a tool string that was then advanced into the unconsolidated sediments. A series of constant-rate pumping tests were performed in a coarse sand and gravel aquifer using direct-push tool strings as observation wells. Very good agreement (within 4%) was found between hydraulic conductivity (K) estimates from direct-push installations and those from conventional wells. A program of slug tests was performed in direct-push installations using small-diameter adaptations of solid-slug and pneumatic methods. In a sandy silt interval of moderate hydraulic conductivity, K values from tests in a shielded screen tool were in excellent agreement (within 2%) with those from tests in a nearby well. In the coarse sand and gravel aquifer, K values were within 12% of those from multilevel slug tests at a nearby well. However, in the more permeable portions of the aquifer (K > 70 m/day), the smaller-diameter direct-push rods (0.016 m inner diameter [I.D.]) attenuated test responses, leading to an underprediction of K. In those conditions, use of larger-diameter rods (e.g., 0.038 m I.D.) is necessary to obtain kappa values representative of the formation. This investigation demonstrates that much valuable information can be obtained from hydraulic tests in direct-push installations. As with any type of hydraulic test, K estimates are critically dependent on use of appropriate emplacement and development procedures. In particular, driving an unshielded screen through a heterogeneous sequence will often lead to a buildup of low-K material that can be difficult to remove with standard development procedures.
在一个具有相当程度地下控制的现场，研究了直接推压技术用于饱和流系统水力特性表征的潜力。通过将短段筛管（屏蔽和非屏蔽）连接到钻具组合的底端，然后将其推进到未固结沉积物中，来进行直接推压安装。在粗砂和砾石含水层中，使用直接推压钻具组合作为观测井进行了一系列恒速抽水试验。发现直接推压安装估算的水力传导率（K）与传统井估算的水力传导率之间具有很好的一致性（在4%以内）。使用小直径的固体活塞和气动方法改进装置，在直接推压安装中进行了活塞试验计划。在水力传导率适中的粉砂质砂层中，屏蔽筛管工具试验得到的K值与附近井试验得到的K值非常吻合（在2%以内）。在粗砂和砾石含水层中，K值在附近井多级活塞试验得到的K值的12%以内。然而，在含水层渗透率较高的部分（K>70米/天），较小直径的直接推压杆（内径0.016米）会削弱试验响应，导致对K的预测偏低。在这些情况下，需要使用较大直径的杆（例如，内径0.038米）来获得代表地层的卡帕值。这项研究表明，在直接推压安装中进行水力试验可以获得很多有价值的信息。与任何类型的水力试验一样，K的估算严重依赖于使用适当的安装和洗井程序。特别是，将非屏蔽筛管打入非均质层序中，通常会导致低K物质的堆积，而用标准洗井程序很难清除这些物质。
