Premium
Hydraulic Tests with Direct‐Push Equipment
Author(s) -
Butler James J.,
Healey John M.,
McCall G. Wesley,
Garnett Elizabeth J.,
Loheide Steven P.
Publication year - 2002
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.2002.tb02488.x
Subject(s) - slug test , hydraulic conductivity , aquifer , silt , shielded cable , geotechnical engineering , rod , core (optical fiber) , geology , soil science , materials science , engineering , groundwater , electrical engineering , geomorphology , composite material , soil water , medicine , alternative medicine , pathology
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 K 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.